DOE-STD-1020-2002, Natural Phenomena Hazards Design and Evaluation Criteria for Department of Energy Facilities

NOT MEASUREMENT SENSITIVE DOE-STD-1020-2002 January 2002 Superseding DOE-STD-1020-94 April 1994 DOE STANDARD NATURAL PHENOMENA HAZARDS DESIGN AND EVALUATION CRITERIA FOR DEPARTMENT OF ENERGY FACILITIES U.S. Department of Energy AREA NPHZ Washington, D.C. 20585 DISTRIBUTION STATEMENT A. Approved for public release; distribution is unlimited. TS This document has been reproduced from the best available copy. Available to DOE and DOE contractors from ES&H Technical Information Services, U.S. Department of Energy, (800) 473-4375, fax: (301) 903-9823. Available to the public from the U.S. Department of Commerce, Technology Administration, National Technical Information Service, Springfield, VA 22161; (703) 605-6000. DOE-STD-1020-2002 iii Foreword This revision provides information to help meet the requirements of 10 CFR Part 830, “Nuclear Safety Management,” (for Nuclear Facilities), DOE O 420.1 and its associated Guides, accounting for cancellation of DOE O 6430.1A and updating this standard to most current references. This standard has also been brought up-to-date to match the requirements of current model building codes such as IBC 2000 and current industry standards. Since the publication of DOE-STD-1020-94 several new documents have been published which made the seismic design standards of DOE-1020-94 outdated. � The 1997 NEHRP Recommended Provisions for Seismic Regulations for New Buildings and Other Structures Parts 1 and 2 introduced new seismic maps for evaluating the seismic hazard. � The three model building codes UBC, BOCA, and SBCCI were replaced by the International Building Code (IBC 2000), which adopted the 1997 NEHRP seismic provisions. � DOE Order 420.1 and the associated guide, DOE G 420.1-2, were approved and adopted the use of IBC 2000 for PC-1 and PC-2 facilities. Since DOE-STD-1020-94 adopted the UBC for the seismic design and evaluation of PC-1 and PC-2 structures, it was necessary to accommodate the use of the IBC 2000 instead of the UBC for DOE facilities. The seismic hazard in the IBC 2000 is provided by maps that define the seismic hazard in terms of the Maximum Considered Earthquake (MCE) ground motions. Except for locations on or near very active known faults, the maps contain accelerations that are associated with a 2500-year return period earthquake. The ground motions associated with MCE ground motions as modified by the site conditions are used for the design and evaluation of PC-1 and PC-2 structures in this revised DOE standard. The graded approach is maintained by applying a 2/3 factor for PC-1 facilities, and a factor of unity for PC-2 facilities. At the same time PC-3 design ground motions have been adjusted from a 2,000 year return period to a 2,500 year return period. This differs from DOE-STD-1020-94 where different return periods of 500, 1000, 2000 (1000)1 , and 10,000 (5000)11 years were used for PC-1, PC-2, PC-3, and PC-4, respectively. Also, specific performance goals were established for each performance category (PC-1 thru PC-4). These performance goals (in terms of a mean annual probability of failure) were based on a combination of the seismic hazard exceedance levels and accounting for the level of conservatism used in the design/evaluation. In this revised standard the performance goals for PC-1 and PC-2 facilities are not explicitly calculated but are consistent with those of the IBC 1 Numbers in parenthesis are for locations near tectonic plate boundaries.

DOE-STD-1020-2002 iv 2000 for Seismic Use Group I and III, respectively2. For PC-3 SSCs there is no change to the performance goal when compared to the previous version of this standard. This was accomplished by making a slight adjustment to the PC-3 scale factor. Thus, it is not the intent of this revision to alter the methodology for evaluating PC-3 facilities nor to increase the performance goal of PC-3 facilities by increasing return period for the PC-3 DBE from a 2000- year earthquake to a 2500-year earthquake. Rather, the intention is more for convenience to provide a linkage from the NEHRP maps and DOE Standards. All PC-3 SSCs which have been evaluated for compliance with the previous version of this standard do not require any re- evaluation considering that the PC-3 level of performance has not changed. Major revisions to DOE-STD-1020-94 were not attempted because of ongoing efforts to develop an ASCE standard for seismic design criteria for Nuclear Facilities. Referring the design of PC- 1 and PC-2 facilities to building codes (such as the IBC 2000) is consistent with design criteria in the proposed ASCE standard. Some of the major impacts of the above changes are identified below: 1. Use of IBC 2000, International Building Code for PC-1 to be designed as Seismic Use Group I and PC-2 to be designed as Seismic Use Group III. 2. Use of seismic hazard exceedance probability of 4x10-4 in place of 5x10-4 in current STD for PC-3 facilities. 3. Use of wind advisory for design of SSCs for straight wind referenced in DOE G 420.1-2. In addition tornados wind speeds should be based on the tornado hazards methodology of LLNL (Ref. 3-14). For steel structures, guidance per SAC (see Chapter I) should be followed based on Northridge experience. For existing buildings evaluation and upgrades, RP-6 is minimum criteria. In addition, the references in Chapter 1 have been updated for current use. There is an established hierarchy in the set of documents that specify NPH requirements. In this hierarchy, 10 CFR Part 830 (for Nuclear Facilities only) has the highest authority followed by DOE O 420.1 and the associated Guides DOE G 420.1-1 and DOE G 420.1-2. The four NPH standards (DOE-STDS-1020, 1021, 1022, 1023) are the last set of documents in this hierarchy. In the event of conflicts in the information provided, the document of higher authority should be utilized (e.g., the definitions provided in the Guides should be utilized even though corresponding definitions are provided in the NPH standards). The Department of Energy (DOE) has issued DOE O 420.1 which establishes policy for its facilities in the event of natural phenomena hazards (NPH) along with associated NPH mitigation requirements. This DOE Standard gives design and evaluation criteria for NPH effects as guidance for implementing the NPH mitigation requirements of DOE O 420.1 and the associated Guides. These are intended to be consistent design and evaluation criteria for 2 Refer to the 1997 NEHRP Provisions for a description of the performance goals associated with Seismic Use Groups. DOE-STD-1020-2002 v

protection against natural phenomena hazards at DOE sites throughout the United States. The goal of these criteria is to assure that DOE facilities can withstand the effects of natural phenomena such as earthquakes, extreme winds, tornadoes, and flooding. These criteria apply to the design of new facilities and the evaluation of existing facilities. They may also be used for modification and upgrading of existing facilities as appropriate. It is recognized that it is likely not cost-effective to upgrade existing facilities which do not meet these criteria by a small margin. Hence, flexibility in the criteria for existing facilities is provided by permitting limited relief from the criteria for new design. The intended audience is primarily the civil/structural or mechanical engineers familiar with building code methods who are conducting the design or evaluation of DOE facilities. The design and evaluation criteria presented herein control the level of conservatism introduced in the design/evaluation process such that earthquake, wind, and flood hazards are treated on a consistent basis. These criteria also employ a graded approach to ensure that the level of conservatism and rigor in design/evaluation is appropriate for facility characteristics such as importance, hazards to people on and off site, and threat to the environment. For each natural phenomena hazard covered, these criteria consist of the following: 1. Performance Categories and target performance goals as specified in the Appendices B and C of this standard. 2. Specified probability levels from which natural phenomena hazard loading on structures, equipment, and systems is developed. 3. Design and evaluation procedures to evaluate response to NPH loads and criteria to assess whether or not computed response is permissible. . DOE-STD-1020-2002 vi Intentionally Blank DOE-STD-1020-2002 vii Table of Contents Foreword................................................................................................................................... iii Table of Contents ..................................................................................................................... vi 1.0 Introduction ..................................................................................................................... 1-1 1.1 Overview of DOE Natural Phenomena Hazards Order, Standards, and Guidance ..................................................................................... 1-1 1.2 Overview of the NPH Design and Evaluation Criteria............................................ 1-5 1.3 Evaluation of Existing Facilities ............................................................................. 1-6 1.4 Quality Assurance and Peer Review .................................................................... 1-7 1.5 References ........................................................................................................... 1-8

2.0 Earthquake Design and Evaluation Criteria.................................................................... 2-1 2.1 Introduction ............................................................................................................ 2-1 2.2 General Approach for Seismic Design and Evaluation ........................................ 2-1 2.3 Seismic Design and Evaluation of Structures, Systems, and Components............................................................................................................. 2-6 2.3.1 Performance Category 1 and 2 Structures, Systems, and Components................................................................................................. 2-9 2.3.2 Performance Category 3 and 4 Structures, Systems, and Components .............................................................................................. 2-11 2.3.3 Damping Values for Performance Category 3 and 4 Structures, Systems, and Components ...................................................................... 2-14 2.4 Additional Requirements ...................................................................................... 2-18 2.4.1 Equipment and Distribution Systems ....................................................... 2-18 2.4.2 Evaluation of Existing Facilities.................................................................. 2-21 2.4.3 Basic Intention of Dynamic Analysis Based Deterministic Seismic Evaluation and Acceptance Criteria .......................................................... 2-24 2.5 Summary of Seismic Provisions ........................................................................... 2-25 2.6 References............................................................................................................. 2-27 DOE-STD-1020-2002 viii 3.0 Wind Design and Evaluation Criteria .............................................................................. 3-1 3.1 Introduction ........................................................................................................... 3-1 3.2 Wind Design Criteria ............................................................................................. 3-2 3.2.1 Performance Category 1 ......................................................................... 3-5 3.2.2 Performance Category 2 ......................................................................... 3-6 3.2.3 Performance Category 3 ......................................................................... 3-6 3.2.4 Performance Category 4 ......................................................................... 3-11 3.2.5 Design Guidelines ................................................................................... 3-13 3.3 Evaluation of Existing SSCs ................................................................................. 3-13 3.3.1 Data Collection ........................................................................................ 3-14 3.3.2 Analysis of Element Failures ................................................................... 3-14 3.3.3 Postulation of Failure Sequence .............................................................. 3-14 3.3.4 Comparison of Postulated Failures with Performance Goals .................. 3-15 3.4 References ........................................................................................................... 3-16

4.0 Flood Design and Evaluation Criteria ............................................................................ 4-1 4.1 Flood Design Overview ......................................................................................... 4-1 4.1.1 Design Basis Flood (DBFL) ....................................................................... 4-2 4.1.2 Flood Evaluation Process ......................................................................... 4-4 4.1.3 Flood Design Strategies ............................................................................ 4-7 4.2 Flood Design Criteria ............................................................................................ 4-9 4.2.1 Performance Category 1 ........................................................................... 4-9 4.2.2 Performance Category 2 ........................................................................... 4-10 4.2.3 Performance Category 3 ............................................................................ 4-10 4.2.4 Performance Category 4 ........................................................................... 4-11 4.3 Flood Design Practice for SSCs Below the DBFL Elevation ................................. 4-11 4.3.1 Flood Loads .............................................................................................. 4-11 4.3.2 Design Requirements ................................................................................ 4-12 4.3.2.1 Performance Categories 1 and 2.................................................. 4-12 4.3.2.2 Performance Categories 3 and 4.................................................. 4-12 4.3.3 Site Drainage and Roof Design ................................................................. 4-12 4.3.4 Flood Protection and Emergency Operations Plans ................................. 4-13 DOE-STD-1020-2002 ix 4.4 Considerations for Existing Construction .............................................................. 4-14 4.5 Probabilistic Flood Risk Assessment .................................................................... 4-15 4.6 References ........................................................................................................... 4-15 Appendix A Terminology and Definitions ............................................................................... A-1 Appendix B Commentary on General NPH Design and Evaluation Criteria ......................... B-1 B.1 NPH Design and Evaluation Philosophy................................................................ B-1 B.2 Graded Approach, Performance Goals, and Performance Categories ................. B-3 B.3 Evaluation of Existing Facilities ............................................................................. B-7 B.4 References ........................................................................................................... B-10

Appendix C Commentary on Earthquake Design and Evaluation Criteria ............................. C-1 C.1 Introduction ........................................................................................................... C-1 C.2 Basic Approach for Earthquake Design and Evaluation and Meeting Target Performance Goals .................................................................................... C-4 C.2.1 Overall Approach for DOE Seismic Criteria .............................................. C-4 C.2.2 Influence of Seismic Scale Factor ............................................................ C-8 C.3 Seismic Design/Evaluation Input ............................................................................ C-11 C.3.1 Earthquake Hazard Annual Exceedance Probabilities .............................. C-14 C.3.2 Earthquake Ground Motion Response Spectra ......................................... C-15 C.3.2.1 DBE Response Spectra at High Frequencies ........................... C-16 C.3.3 Effective Peak Ground Motion .................................................................. C-18 C.4 Evaluation of Seismic Demand (Response) .......................................................... C-18 C.4.1 Dynamic Seismic Analysis ........................................................................ C-21 C.4.2 Static Force Method of Seismic Analysis .................................................. C-23 C.4.3 Soil-Structure Interaction............................................................................ C-23 C.4.4 Analytical Treatment of Energy Dissipation and Absorption ..................... C-28 C.4.4.1 Damping .................................................................................... C-28 C.4.4.2 Inelastic Behavior ...................................................................... C-29 C.4.4.3 Guidance on Estimating the Inelastic Energy Absorption Factor Fµ .................................................................................. C-34 C.5 Capacities ............................................................................................................. C-40 C.5.1 Capacity Approach .................................................................................... C-40 DOE-STD-1020-2002 x C.5.2 Seismic Design and Detailing ................................................................... C-41 C.6 Special Considerations for Systems and Components.......................................... C-45 C.6.1 General ..................................................................................................... C-45 C.6.2 Seismic Interaction .................................................................................... C-48 C.7 Special Considerations for Existing Facilities ........................................................ C-49 C.8 Quality Assurance and Peer Review .................................................................... C-51 C.9 Alternate Seismic Mitigation Measures ................................................................. C-53 C.10 References ............................................................................................................ C-55

Appendix D Commentary on Wind Design and Evaluation Criteria........................................ D-1 D.1 Wind Design Criteria ............................................................................................. D-1 D.2 Tornado Hazard Assessment ............................................................................... D-2 D.3 Load Combinations ................................................................................................ D-3 D.4 Windborne Missiles ................................................................................................ D-6 D.5 References ............................................................................................................. D-8 Appendix E Effects of Natural Phenomena Hazards ............................................................... E-1 E.1 Effects of Earthquakes .......................................................................................... E-1 E.2 Effects of Wind ................................................................................................... E-4 E.2.1 Wind Pressures ......................................................................................... E-5 E.2.2 Additional Adverse Effects of Tornadoes .................................................. E-7 E.2.3 Effects on Structures, Systems, and Components .................................... E-7 E.3 Effects of Flooding ................................................................................................ E-8 E.3.1 Causes and Sources of Flooding and Flood Hazards................................ E-8 E.3.2 Flooding Damage ...................................................................................... E-10 E.4 References .......................................................................................................... E-12 DOE-STD-1020-2002 1-1 Chapter 1 Introduction 1.1 Overview of DOE Natural Phenomena Hazards Order, Standards, and Guidance It is the policy of the Department of Energy (DOE) to design, construct, and operate DOE facilities so that workers, the general public, and the environment are protected from the impacts of natural phenomena hazards on DOE facilities. NPH safety requirements are briefly described in 10 CFR Part 830, Nuclear Safety Management, (Ref.1-13) and DOE O 420.1,“Facility Safety” (Ref.1-1). The associated Guides,“Guide for the Mitigation of Natural Phenomena Hazards for DOE Nuclear Facilities and Non-nuclear Facilities” (Ref. 1-2), “Guide for Nonreactor Nuclear Safety Design Criteria and Explosives Safety Criteria” (Ref. 1-3), and “Implementation Guide for use with DOE Orders 420.1 and 440.1 Fire Safety Program” (Ref. 1-4) describe acceptable methods to meet these requirements in a consistent manner throughout DOE which include: (1) providing safe work place; (2) protecting against property loss and damage; (3) maintaining operation of essential facilities; and (4) protecting against exposure to hazardous materials during and after occurrences of natural phenomena hazards. There is an established hierarchy in the set of documents that specify NPH requirements. In this hierarchy,10 CFR Part 830 is the highest authority (for Nuclear Facilities only), followed by DOE 0 420.1. The next set of controlling documents are the associated Guides followed by the set of NPH standards (DOE- STDS-1020-1023). The NPH requirements have been developed to provide the necessary information that assess the NPH safety basis for DOE facilities, which is documented in Safety Analysis Reports (SARs), if available. 10 CFR Part 830 (Ref. 1-13), DOE O 5480.23 (Ref. 1-5) and the guidance provided in the associated Standard, DOE-STD-3009-94 (Ref. 1-6) prescribe the use of a graded approach for the effort to be expended in safety analysis and the level of detail required to be presented in the associated documentation. DOE NPH mitigation requirements are also consistent with the National Earthquake Hazards Reduction Program (NEHRP) and Executive Order 12699 (Ref. 1-7) and 12941 (Ref. 1-8).

The overall approach for NPH mitigation is consistent with the graded approach embodied in the facility SAR. The application of NPH design requirements to structures, systems, and components (SSCs) is based on the life-safety or the safety classifications for the SSCs as established by safety analysis. The application of the most rigorous design requirements should be limited to those SSCs classified by safety analysis as Safety-Class or Safety-Significant consistent with DOE-STD-3009-94. Although DOE-STD-3009-94 is specifically applicable to non-reactor nuclear facilities, it is DOE’s intention to apply DOE-STD- 3009-94 definitions for “Safety-Class” and “Safety-Significant” to all nuclear non-reactor and other hazardous facilities, and this broader approach is applied here. Mission importance and economic considerations should also be used to categorize SSCs which require NPH design. Once the SSCs have been classified, DOE O 420.1 and the associated Guides specify the NPH requirements to ensure that the SSCs are adequately designed to resist NPH. The NPH requirements utilize a graded approach in order to provide a reasonable level of NPH protection for the wide variety of DOE facilities. A graded approach is one in which various levels of NPH DOE-STD-1020-2002 1-2 design, evaluation and construction requirements of varying conservatism and rigor are established ranging from common practice for conventional facilities to practices used for more hazardous critical facilities. Four DOE Standards (DOE-STDS-1020, 1021, 1022, 1023) have been developed to provide specific acceptance criteria for various aspects of NPH to meet the requirements of DOE O 420.1 and the associated Guides. These NPH standards should be used in conjunction with other pertinent documents which provide more detailed methods on specific NPH design and evaluation subjects such as DOE guidance documents, consensus national standards, model building codes, and industry accepted codes and specifications. Figure 1-1 presents a conceptual NPH design frame work which identifies how the DOE standards are used to assess NPH design requirements. The following national consensus codes and standards should be referred to with this standard: ACI 318 Building Code Requirements for Reinforced Concrete ACI 349 Code Requirements for Nuclear Safety-Related Concrete Structures ACI 530 Building Code Requirements for Masonry Structures AISC N690 Nuclear Facilities - Steel Safety Related Structures for Design, Fabrication, and Erection AISC (LRFD) Manual of Steel Construction, Load & Resistance Factor Design AISC (ASD) Manual of Steel Construction, Allowable Stress Design AISC Seismic Provisions SAC Guidance Documents FEMA 350, 351, 352, 353 (2000) ASCE 4 Seismic Analysis of Safety-Related Nuclear Structures and Commentary ASCE 7 Minimum Design Loads for Buildings and Other Structures ASME B31.4-95 Boilers and Pressure Vessels Code ASME B 31.1-98 Power Piping ASME QME-1 Qualification of Active Mechanical Equipment used in Nuclear Facilities IEEE 344 IEEE Recommended Practice for Seismic Qualification of Class IE Equipment for Nuclear Power Generating Stations NFPA 13-96 Installation of Sprinkler Systems IBC 2000 International Building Code DOE-STD-1020-2002 1-3 FEMA 302, 303 NEHRP Recommended Provisions for (368, 369 – in print) Seismic Regulations for New Buildings and other structures, Part 1,2 ICSSC RP6 Standards of Seismic Safety for Existing Federally Owned or

Leased Buildings and Commentary FEMA 310 NEHRP handbook for the Seismic Evaluation of Existing Buildings – A Prestandard FEMA 356 Prestandard and commentary for the Seismic Rehabilitation of Buildings AISI Design Specification for Design of Cold-Formed Steel Structural Members Manual DOE-STD-1020-2002 1-4 10 CFR PART 830, DOE ORDER 5480.23 PROCESS DOE ORDER 420.1 & NPH GUIDE PROCESS Facility SAR (if available) NPH Hazard Characterization DOE-STD-1022 DOE-STD-1020 DOE-STD-1027 Potential Accident (Scenarios) NPH Design Input DOE-STD-1023 DOE G 420.1-2 DOE-STD-3009 NPH Design Criteria FACILITY NPH SAFETY DOCUMENTED AS PART OF SAR SSCs Identified Life Safety (All Facilities) Safety Significant Safety Class DOE-STD-1021 NPH Performance Categorization of SSCs Figure 1-1 Natural Phenomena Design Input Conceptual Framework (Nuclear and Hazardous/Facilities) DOE-STD-1020-2002 1-5 The NPH Guide DOE G 420.1-2 has established Performance Categories. Performance goals as described in Appendices B and C are expressed as the mean annual probability of exceedance of acceptable behavior limits of structures and equipment due to the effects of natural phenomena. Five Performance Categories (PC) have been established in this NPH Guide of DOE O 420.1. Performance Categories and performance goals range from those for conventional buildings to those for facilities with hazardous materials for operations. The selection of NPH Performance Categories for SSCs is dependent on several factors including the overall risk of facility operation and the assigned function to the SSC. An SSC’s safety classification is based on its function in accident prevention or mitigation as determined by safety analysis. The safety classification should be applied to specific SSCs on a case-by-case basis and need not apply to an entire facility (see DOE-STD-1021). 1.2 Overview of the NPH Design and Evaluation Criteria This natural phenomena hazard standard (DOE-STD-1020), developed from UCRL- 15910 (Ref. 1-9), provides criteria for design of new SSCs and for evaluation, modification, or upgrade of existing SSCs so that Department of Energy (DOE) facilities safely withstand the effects of natural phenomena hazards (NPHs) such as earthquakes, extreme winds, and flooding. DOE-STD-1020 provides consistent criteria for all DOE sites across the United States. These criteria are provided as the means of implementing DOE O 420.1 and the associated Guides, and Executive Orders 12699 and 12941 for earthquakes. The design and evaluation criteria presented in this document provide relatively straightforward procedures to evaluate, modify, or upgrade existing facilities or to design new facilities for the effects of NPHs. The intent is to control the level of conservatism in the design/evaluation process such that: (1) the hazards are treated consistently; and (2) the level of conservatism is appropriate for structure, system, and component characteristics related to safety, environmental protection, importance, and cost. The requirements for each hazard are presented in subsequent chapters. Terminology, guidelines, and commentary material are included in appendices which follow the requirement chapters.

Prior to applying these criteria, SSCs will have been placed in one of five Performance Categories ranging from PC-0 to PC-4. No special considerations for NPH are needed for PC-0; therefore, no guidance is provided. Different criteria are provided for the remaining four Performance Categories, each with a specified performance goal. Design and evaluation criteria aimed at target probabilistic performance goals require probabilistic natural phenomena hazard assessments. NPH loads are developed from such assessments by specifying natural phenomena hazard mean annual probabilities of exceedance. Performance goals may then be achieved by using the resulting loads combined with deterministic design and evaluation procedures that provide a consistent and appropriate level of conservatism. Design/evaluation procedures conform closely to industry practices using national consensus codes and standards so that the procedures will be easily understood by most engineers. Structures, systems, and components comprising a DOE facility are to be assigned to a Performance Category utilizing the approach described in the DOE Guide 420.1-2 (Ref.1-2) and performance categorization standard (Ref. 1- 10). These design and evaluation criteria (DOE-STD-1020) are the specific provisions to be DOE-STD-1020-2002 1-6 followed such that the performance goal associated with the Performance Category of the SSC under consideration is achieved. For each category, the criteria include the following steps: 1. NPH loads are determined at specified NPH probabilities as per DOE- STD-1023 (Ref. 1-11). 2. Design and evaluation procedures are used to evaluate SSC response to NPH loads. 3. Criteria are used to assess whether or not computed response in combination with other design loads is permissible. 4. Design detailing provisions are implemented so that the expected performance during a potential NPH occurrence will be achieved. 5. Quality assurance and peer review are applied using a graded approach. For each Performance Category, target performance goals are provided in the Appendices B and C in terms of mean annual probability of exceedance of acceptable behavior limits. In Item 1, the annual probability of exceedance of an NPH parameter such as ground acceleration, wind speed, or water elevation is specified. The level of conservatism in Items 2, 3, 4, and 5 above is controlled such that sufficient risk reduction from the specified NPH probability is achieved so that the target performance goal probability is met. DOE-STD-1020 provides an integrated approach combining definition of loading due to natural phenomena hazards, response evaluation methods, acceptance criteria, and design detailing requirements. Performance goals and NPH levels are expressed in probabilistic terms; design and evaluation procedures are presented deterministically. Design/evaluation procedures specified in this document conform closely to common standard practices so that most engineers will readily understand them. The intended audience for these criteria is the civil/structural or mechanical engineer conducting the design or evaluation of facilities. These NPH design and evaluation criteria do not preclude the use of probabilistic or alternative design or evaluation approaches if these approaches meet the specified performance goals. 1.3 Evaluation of Existing Facilities

Evaluations of existing SSCs must follow or, at least, be measured against the NPH criteria provided in this document. For SSCs not meeting these criteria and which cannot be easily remedied, budgets and schedule for required strengthening must be established on a prioritized basis. A back-fit analysis should be conducted. Priorities should be established on the basis of Performance Category, cost of strengthening, and margin between as-is SSC capacity and the capacity required by the criteria. For SSCs which are close to meeting criteria, it is probably not cost effective to strengthen the SSC in order to obtain a small reduction in risk. As a result, some relief in the criteria is allowed for evaluation of existing SSCs. It is permissible to perform such evaluations using natural phenomena hazard exceedance probability of twice the value specified for new design. For example, if the natural phenomena hazard DOE-STD-1020-2002 1-7 annual probability of exceedance for the SSC under consideration was 10-4, it would be acceptable to reconsider the SSC at hazard annual probability of exceedance of 2x10-4. This would have the effect of slightly reducing the seismic, wind, and flood loads in the SSC evaluation by about 10% to 20%. This amount of relief is within the tolerance of meeting the target performance goals and is only a minor adjustment of the corresponding NPH design and evaluation criteria. In addition, it is consistent with the intent of the Federal Program (Ref. 1-8) developed by the Interagency Committee on Seismic Safety in Construction. When upgrading becomes necessary, the design should be based on the current design criteria in the standard for the new facility. The DOE G 420.1-2 Guide provides guidance for facilities with a remaining service life of less that 5 years. 1.4 Quality Assurance and Peer Review All DOE structures, systems, and components must be designed or evaluated utilizing a formal quality assurance plan as required by 10 CFR Part 830. (Ref.1-13) and DOE O 414.1 (CHG 1) (Ref.1-12). The QA and peer review should be conducted within the framework of a graded approach with increasing level of rigor employed from Performance Category 1 to 4. Specific details about a formal quality assurance plan for NPH design and evaluation should be similar to the seismic plan described in the Commentary, Appendix C. The major features of a thorough quality assurance plan for design or evaluation for natural phenomena hazards are described below. In general, it is good practice for a formal quality assurance plan to include the following requirements. On the design drawings or evaluation calculations, the engineer must describe the NPH design basis including (1) description of the system resisting NPH effects and (2) definition of the NPH loading used for the design or evaluation. Design or evaluation calculations should be checked for numerical accuracy and for theory and assumptions. For new construction, the engineer should specify a program to test materials and inspect construction. In addition, the engineer should review all testing and inspection reports and visit the site periodically to observe compliance with plans and specifications.

For Performance Categories 2, 3, and 4, NPH design or evaluation must include independent peer review. The peer review is to be performed by independent, qualified personnel. The peer reviewer must not have been involved in the original design or evaluation. If the peer reviewer is from the same company/organization as the designer/evaluator, he must not be part of the same program where he could be influenced by cost and schedule consideration. Individuals performing peer reviews must be degreed civil/mechanical engineers or qualified professionals in the field of review with 5 or more years of experience in NPH evaluation. Section 2.3 of RP-6 provides good guidance about the qualifications of designers and reviewers. DOE-STD-1020-2002 1-8 1.5 References 1-1. U. S. Department of Energy, Facility Safety, DOE Order 420.1, Washington, D. C., October 13, 1995. 1-2. U. S. Department of Energy, (DOE G 420.1-2), Guide for the Mitigation of Natural Phenomena Hazards for DOE Nuclear Facilities and Non-nuclear Facilities, Washington, D. C., March 28, 2000. 1-3. U. S. Department of Energy, (DOE G 420.1-1), Guide for Nonreactor Nuclear Safety Design Criteria and Explosives Safety Criteria, Washington, D. C., March 28, 2000. 1-4. U. S. Department of Energy, Implementation Guide (DOE G 440.1-5) for use with DOE Orders 420.1 and 440.1 Fire Safety Program, Washington, D. C., May 21,1996. 1-5. U. S. Department of Energy, Nuclear Safety Analysis Reports, DOE Order 5480.23, Washington, D. C., April 30, 1992. 1-6. U. S. Department of Energy, Preparation Guide For U. S. Department of Energy Nonreactor Nuclear Facility Safety Analysis Reports, DOE-STD-3009-94, Washington, D. C., July 1994. 1-7. Seismic Safety of Federal and Federally Assisted or Regulated New Building Construction, Executive Order 12699, Washington, D.C., January 5, 1990. 1-8. Seismic Safety of Existing Federally Owned or Leased Buildings, Executive Order 12941, Washington, D. C., December 1, 1994. 1-9. Kennedy, R.P., S.A. Short, J.R. McDonald, M.W. McCann, R.C. Murray, J.R. Hill, Design and Evaluation Guidelines for Department of Energy Facilities Subjected to Natural Phenomena Hazards, UCRL-15910, Lawrence Livermore national Laboratory, Livermore, California, June 1990. 1-10. U.S. Department of Energy, Performance Categorization Criteria for Structures, Systems, and Components at DOE Facilities Subjected to Natural Phenomena Hazards, DOE-STD-1021-93, Washington, D.C., July 1993. 1-11. U. S. Department of Energy, Natural Phenomena Hazards Assessment Criteria, DOE- STD-1023-95, Washington, D. C., September 1995. 1-12. U. S. Department of Energy, Quality Assurance, U.S. Government Printing Office, Washington, D. C., DOE O 414.1 (CHG 1), July 2001. 1-13. U.S. Department of Energy, Nuclear Safety Management, U.S. Government Printing Office, Washington, D.C. 10 CFR Part 830. DOE-STD-1020-2002 1-9 1-14 U. S. Department of Energy, Natural Phenomena Hazards Site Characterization Criteria, DOE-STD-1022-94, Washington, D. C., March 1994. 1-15 U.S. Department of Energy, Hazard Categorization and Accident Analysis Techniques for Compliance with DOE Order 5480.23, Nuclear Safety Analysis Reports, DOE-STD- 1027. DOE-STD-1020-2002 1-10 Intentionally Blank DOE-STD-1020-2002 2-1 Chapter 2 Earthquake Design and Evaluation Criteria 2.1 Introduction

This chapter describes requirements for the design or evaluation of all classes (i.e. safety class, safety significant) of structures, systems, and components (SSCs) comprising DOE facilities for earthquake ground shaking. These classes of SSCs include safety class and safety significant SSCs per DOE-STD-3009-94 (Ref. 1-6) and all SSCs per the International Building Code 2000 (IBC 2000) and other codes with seismic provisions comparable to NEHRP provisions. This material deals with how to establish Design/Evaluation Basis Earthquake (DBE) loads on various classes of SSCs; how to evaluate the response of SSCs to these loads; and how to determine whether that response is acceptable. This chapter also covers the importance of design details and quality assurance to earthquake safety. These earthquake design and evaluation provisions are equally applicable to buildings and to items contained within the building, such as equipment and distribution systems. These provisions are intended to cover all classes of SSCs for both new construction and existing facilities. These design and evaluation criteria have been developed such that the target performance goals listed in Appendices B and C are achieved. For more explanation see the Commentary (Appendix C) herein and the Basis Document (Ref. 2-1). 2.2 General Approach for Seismic Design and Evaluation This section presents the approach upon which the specific seismic force and story drift provisions (as applicable) for seismic design and evaluation of structures, systems, and components in each Performance Category (as described in Section 2.3) is based. These provisions include the following steps: 1. Selection of earthquake loading 2. Evaluation of earthquake response 3. Specification of seismic capacity and applicable drift limits, (acceptance criteria) 4. Ductile detailing requirements for buildings It is important to note that the above four elements taken together comprise the earthquake design and evaluation criteria. Acceptable performance (i.e., achieving performance goals) can only be reached by consistent specification of all design criteria elements as shown in Figure 2-1. In order to achieve the target performance goals, these seismic design and evaluation criteria specify seismic loading in probabilistic terms. The remaining elements of the criteria (see Fig. 2-1) are deterministic design rules which are familiar to design engineers and which have a controlled level of conservatism. This level of conservatism combined with the specification of seismic loading, leads to performance goal achievement. DOE-STD-1020-2002 2-2 M e e t P e r f o r m a n ce Go a l ( c o n s i s t e n t wit h DO E S a f e t y P o l i c y ) R e a s o n a b l e L e v e l o f H a z a r d S e l e c t L o a d R e s p o n s e E va l u a t i o n Conservatism Added Detailing Requirements D e t e r m i n i s t i c P ro c e du re B a s e d o n I n d u s t ry C o de s a n d S t a n dards P r o b a b i l i s t i c B a s i s ( w i t h h i s t o r i c c h e c k ) Permissible Response Level Figure 2-1. DOE-STD-1020 Combines Probabilistic and Deterministic Methods to Achieve Performance Goals Criteria are provided for each of the four Performance Categories 1 to 4 as defined in

DOE O 420.1, the accompanying Guide DOE G 420.1-2 (Ref. 1-2 ) and DOE-STD-1021 (Ref. 1- 10). The criteria for Performance Categories 1 and 2 are similar to those from model building codes. Criteria for PC-3 are similar to those for Department of Defense Essential Facilities (Ref. C-5) Tri-Services Manual. Criteria for PC-4 approach the provisions for commercial nuclear power plants. Seismic loading is defined in terms of a site-specific design response spectrum (the Design/Evaluation Basis Earthquake, [DBE]). Either a site-specific design response spectrum developed for the site, or a generic design response spectrum that is appropriate or conservative for the site may be used. Seismic hazard estimates are used to establish the DBE per DOE-STD- 1023 (REF. 2-22). For each Performance Category, a mean annual exceedance probability for the DBE, PH is specified from which the maximum ground acceleration (and/or velocity) may be determined from probabilistic seismic hazard curves, see Table 2-1. Evaluating maximum ground acceleration from a specified mean annual probability of exceedance is illustrated in Figure 2-2a. Earthquake input excitation to be used for design and evaluation by these provisions is defined by a median amplification smoothed and broadened design/evaluation response spectrum shape such as that shown in Figure 2-2b (from Ref. 2-2). Such spectra are determined in accordance with DOE-STD-1023 (Ref. 2-19). DOE-STD-1020-2002 2-3 For PC-1 and PC-2 facilities IBC/USGS maps should be used for ground motion unless there are special reasons to conduct site-specific studies. However, use of any site specific results shall conform to the limits established in the IBC 2000. It should be understood that the spectra shown in Figure 2-2 or in-structure spectra developed from them represent inertial effects. They do not include differential support motions, typically called seismic anchor motion (SAM), of structures, equipment, or distribution systems supported at two or more points. While SAM is not usually applicable to building design, it might have a significant effect on seismic adequacy of equipment or distribution systems. Figure 2-2. Earthquake Input Excitation is Defined by Maximum Ground Acceleration Anchoring Site-Specific Response Spectra. DOE-STD-1020-2002 2-4 Table 2-1 Seismic Performance Categories and Seismic Hazard Exceedance Levels Performance Category Mean Seismic Hazard Exceedance Levels, PH Remarks 0 No Requirements 1 Follow IBC 2000 in its Entirety* Use IBC 2000 Seismic Use Group I Criteria-2/3 MCE Ground Motion 2 Follow IBC 2000 in its Entirety* Use IBC 2000 Seismic Use Group III Criteria 2/3 MCE Ground Motion with Importance Factor of 1.5 3 4x10-4 (1x10-3 ) 1 Establish DBE Per DOE-STD-1023 Analysis Per DOE-Std. 1020 4 1x10-4 (2x10-4) 1 Establish DBE Per DOE-STD-1023 Analysis Per DOE-Std. 1020 * Based on Maximum Considered Earthquake (MCE) Ground Motion – generally 2% Exceedance Probability in 50 years from the seismic hazard maps, modified to account for site effects. PH = 4x10-4 1 For sites such as LLNL, SNL-Livermore, SLAC, LBNL, and ETEC, which are near tectonic plate boundaries.

Performance Category 2 and lower SSCs may be designed or evaluated using the approaches specified in IBC 2000 seismic provisions. Common cause effects and interaction effects per DOE- STD-1021 should be taken into account. However, for Performance Category 3 or higher, the seismic evaluation must be performed by a dynamic analysis approach. A dynamic analysis approach requires that: 1. The input to the SSC model be defined by either a design response spectrum, or a compatible time history input motion. 2. The important natural frequencies of the SSC be estimated, or the peak of the design response spectrum be used as input. Multi-mode effects must be considered. DOE-STD-1020-2002 2-5 3. The resulting seismic induced inertial forces be appropriately distributed and a load path evaluation (see Section C.4.2) for structural adequacy be performed. A "dynamic analysis approach" does not imply that complex dynamic models must be used in the evaluation. Often equivalent static analysis models are sufficient if the above listed three factors are incorporated. However, use of such simplified models for structures in Performance Category 3 or higher must be justified and approved by DOE. This dynamic analysis approach should comply with the seismic response analysis provisions of ASCE 4 (Ref. 2-3) except where specific exceptions are noted. The maximum ground acceleration and ground response spectra are used in the appropriate terms of the IBC code equation for base shear. The maximum ground acceleration is also used in the IBC code equation for seismic forces on equipment and non-structural components. Use of modern site-specific earthquake ground motion data and the IBC 2000 requirements based on NEHRP provisions (Reference 2-6) maps are considered to be preferable to the general seismic zonation maps from the previous codes and should be applied according to the guidance provided in DOE-STD-1023 (Ref. 2-22). For structures, the IBC code provisions require a static or dynamic analysis approach in which loadings are scaled to the base shear equation value. In the base shear equation, inelastic energy absorption capacity of structures is accounted for by the parameter, R. Elastically computed seismic response is reduced by R values ranging from 1¼ to 8 as a means of accounting for inelastic energy absorption capability in the IBC code provisions and by these criteria for Performance Category 2 and lower SSCs. This reduced seismic response is combined with non-seismic concurrent loads and then compared to code allowable response limits (or code ultimate limits combined with code specified load factors). For concrete structures, the design detailing provisions from the IBC 2000 (for PC 1& 2) and ACI-349 (for PC-3 & 4) which provide ductility, toughness, and redundancy, are also required such that SSCs can fully achieve potential inelastic energy absorption capability. For structures constructed of other materials follow the relevant codes and standards specified in Chapter 1. Normally, relative seismic anchor motion (SAM) is not considered explicitly by model building code seismic provisions. However, SAM should be considered for PC-3 and PC-4 SSCs. Executive Order 12699 (Ref. 1-7) establishes the minimum seismic requirements for new

Federal buildings. NEHRP updates the provisions required to meet these requirements every 3 years. The Interagency Committee on Seismic Safety in Construction (ICSSC) compares model building codes with the NEHRP provisions. Designers must consider the NEHRP provisions and ICSSC comparisons to ensure the use of the proper model building code in their design and evaluation. Currently the IBC 2000 and ASCE 7-98 meet the requirements of the NEHRP provisions. While using the IBC 2000 or successor documents, designers must consider the Seismic Use Group and Seismic Design Category. The seismic provisions in the IBC 2000 have been specified for PC-1 and PC-2 because it is the only current model code meeting NEHRP provisions. The Interagency Committee on Seismic Safety in Construction has concluded that the following seismic provisions are equivalent for a given DBE the and latest NEHRP provisions: DOE-STD-1020-2002 2-6 1. International Building Code 2000 2. ASCE 7-98 The seismic provisions in the Uniform Building Code (UBC) 1997 have not been found to be equivalent to the 1997 NEHRP provisions. However, this code may be used on case by case basis as long as the intent of the seismic provisions in this standard are met (Based on IBC 2000/1997 NEHRP provisions). The seismic design maps associated with 1997 UBC are generally out of date (over 20 years old) and at a minimum the MCE ground motion maps in IBC 2000 should be consulted to ensure that DBE ground motion are adequate and conservative. Other model building codes may be followed provided site-specific ground motion data is incorporated into the development of the earthquake loading in a manner consistent with DOE- STD-1023, and the NEHRP provisions. For PC-3 and PC-4 SSCs, these seismic design and evaluation criteria specify that seismic evaluation be accomplished by dynamic analysis. The recommended approach is to perform an elastic response spectrum dynamic analysis to evaluate the elastic seismic demand on SSCs. Inelastic energy absorption capability is allowed by permitting limited inelastic behavior. By these provisions, the inelastic energy absorption capacity of structures is accounted for by the parameter, Fµ. However, strength and ductile detailing for the entire load path should be assured. Elastically computed seismic response is reduced by Fµ values ranging from 1 to 3 as a means of accounting for inelastic energy absorption capability. The same Fµ values are specified for both Performance Categories of 3 and 4. In order to achieve the conservatism appropriate for the different Performance Categories, the reduced seismic forces are multiplied by a scale factor. Scale factors are specified for Performance Category 3 and 4. The resulting factored seismic forces are combined with non-seismic concurrent loads and then compared to code ultimate response limits. Alternatively for PC-3 and PC-4 SSCs, non-linear static (push- over analysis) may be adequate, and in extreme cases a non-linear dynamic analysis may be used, if justified. Fµ factors should not be used when performing non linear analysis. For concrete structures, the design detailing provisions from the ACI 349 which provide ductility, toughness, and redundancy, are also required such that SSCs can fully achieve potential inelastic energy absorption capability (for other materials, follow relevant codes listed in Chapter 1). Also, explicit consideration of relative seismic anchor motion (SAM) effects is required for PC- 3 and PC-4 SSCs.

The overall DOE Seismic Design and Evaluation Procedure is shown in Figure 2-3. In addition to the general provisions described in this chapter, the topics discussed in Appendix C should be considered before commencing design or evaluation. 2.3 Seismic Design and Evaluation of Structures, Systems, and Components � Select Performance Categories of structure, system, or component based on DOE G 420.1-2 (Ref. 1-2) and DOE-STD-1021 (Ref. 1-10). DOE-STD-1020-2002 2-7 � For sites with PC-3 or PC-4 SSCs, obtain or develop a seismic hazard curve and design response spectra in accordance with DOE-STD-1023 (Ref. 2-19) for all performance categories based on site characterization discussed in DOE-STD-1022 (Ref. 1-14). � Establish design basis earthquake from PH, (see Table 2-1) mean seismic hazard curve, and median response spectra. � For sites with only PC-1 and PC-2 SSCs, and no site-specific seismic hazard curve, obtain seismic coefficients from model building codes which are based on national seismic hazard maps prepared by the United States Geological Survey. If available, site specific data can be used for these categories but with limitations imposed in the IBC 2000. DOE-STD-1020-2002 2-8 Figure 2-3. DOE Seismic Design and Evaluation Procedure DOE-STD-1020-2002 2-9 2.3.1 Performance Category 1 and 2 Structures, Systems, and Components. Seismic design or evaluation of PC-1 and PC-2 SSCs is based on model building code seismic provisions. In these criteria, the current version of the International Building Code shall be followed. Alternatively, the other equivalent model building codes may be used as discussed in Section 2.2. All of the IBC 2000 seismic provisions shall be followed for Performance Category 1 and PC-2 SSCs Load combinations to be used for PC-1 and PC-2 will be based on the provisions in the IBC 2000. Use of site specific data will be limited per provisions of IBC 2000. Post-Northridge earthquake SAC recommendations should be taken into consideration for steel structures. The steps in the procedure for PC-1 and PC-2 SSCs are as follows: • Evaluate element forces for non-seismic loads, DNS, expected to be acting concurrently with an earthquake. • Evaluate element forces, DSI, for earthquake loads. a. Static force method, where V is applied as a load distributed over the height of the structure for regular facilities, or dynamic force method for irregular facilities as described in the IBC 2000. b. In either case, the total base shear is given in the IBC 2000 where the parameters are evaluated as follows: - Use Seismic Use Group I for design of PC-1 SSCs - Use Seismic Use Group III for design of PC-2 SSCs which essentially results in a multiplier of 1.5 to forces for PC-1 The seismic design categories per IBC 2000 must also be taken into consideration. DOE-STD-1020-2002 2-10 Figure 2-4. Example Design/Evaluation Earthquake Ground Motion Response Spectrum For systems and components, seismic design forces are accounted as per the IBC 2000 provisions. If a recent site-specific seismic hazard assessment is available, it can be used subject to limitations imposed in the IBC 2000. For evaluation of SSCs using site specific hazard analysis, the design shall be based on 5% critical damping as recommended by the IBC 2000. Final earthquake loads are subject to approval by DOE. For structures, response modification coefficients, R, and for systems and components RP are given in IBC 2000

• Combine responses from various loadings (DNS and DSI) to evaluate demand, DTI, by code specified load combination rules (e.g., load factors for ultimate strength design or applicable load factors for allowable stress design). DOE-STD-1020-2002 2-11 • Evaluate capacities of SSCs, CC, from code ultimate values when strength design is used (e.g., IBC for reinforced concrete or LRFD for steel) or from allowable stress levels (with one-third increase) when allowable stress design is used. Minimum specified or 95% non-exceedance in-situ population values statistically adjusted for sample size, for material strengths should be used for capacity estimation. • Compare demand, DTI, with capacity, CC, for all SSCs. If DTI is less than or equal to CC, the facility satisfies the seismic force requirements. If DTI is greater than CC, the facility has inadequate seismic resistance. • Evaluate story drifts (i.e., the displacement of one level of the structure relative to the level above or below due to the design seismic forces), including both translation and torsion. Calculated story drifts should not exceed the limitations in IBC 2000. • Elements of the facility shall be checked to assure that all detailing requirements IBC 2000 provisions are met keeping into consideration the seismic design category of the building. • A quality assurance program consistent with model building code requirements shall be implemented for SSCs in Performance Categories 1 and 2. In addition, peer review shall be conducted for Performance Category 2 SSCs. 2.3.2 Performance Category 3 and 4 Structures, Systems, and Components The steps in the procedure for PC-3 and PC-4 SSCs are as follows: • Evaluate element forces, DNS, for the non-seismic loads expected to be acting concurrently with an earthquake. • Calculate the elastic seismic response to the DBE, Ds, using a dynamic analysis approach and appropriate damping values from Table 2-2. Response Level 3 is to be used only for justifying the adequacy of existing SSCs with adequate ductile detailing. Note that for evaluation of systems and components supported by the structure, in-structure response spectra are used. For PC-3 and PC-4 SSCs, the dynamic analysis must consider 3 orthogonal components of earthquake ground motion (two horizontal and one vertical). Responses from the various direction components shall be combined in accordance with ASCE 4. Include, as appropriate, the contribution from seismic anchor motion. To determine response of SSCs DOE-STD-1020-2002 2-12 which use Fµ > 1, the maximum spectral acceleration should be used for fundamental periods lower than the period at which the maximum spectral amplification occurs (See Figure 2-4). For higher modes, the actual spectral accelerations should be used. Calculate the inelastic seismic demand element forces, DSI, as SID = SF SD µF (2-1) where: Fµ = Inelastic energy absorption factor from Table 2-3 for the appropriate structural system and elements having adequate ductile detailing SF = Scale factor related to Performance Category = 1.25 for PC-4 = 0.9 for PC-3 Variable scale factors, based on the slope of site-specific hazard curves are

discussed in Appendix C, to result in improved achievement of performance goals. Site specific scale factors for low seismicity sites should be quantified to ensure that use of S.F = 0.9 is adequately conservative. SF is applied for evaluation of structures, systems, and components. At this time, Fµ values are not provided for systems and components. It is recognized that many systems and components exhibit ductile behavior for which Fµ values greater than unity would be appropriate (see Section C.4.4.2). Low Fµ values in Table 2-3 are intentionally specified to avoid brittle failure modes. • Evaluate the total inelastic-factored demand DTI as the sum of DSI and DNS (the best-estimate of all non-seismic demands expected to occur concurrently with the DBE). DTI = DNS + DSI (2-2) • Evaluate capacities of elements, CC, from code ultimate or yield values Reinforced Concrete Use IBC 2000, ACI 318 & ACI-349 Steel Use IBC 2000 and AISC - LRFD provisions, or DOE-STD-1020-2002 2-13 - Plastic Design provisions, or - Allowable Stress Design provision scaled by 1.4 for shear in members and bolts and 1.7 for all other stresses. Refer to References 2-9 and 2-10 for related industry standards. Note that strength reduction factors, φ , are retained. Minimum specified or 95% nonexceedence in-situ values for material strengths should be used to estimate capacities. • The seismic capacity is adequate when CC exceeds DTI, i.e.: CC > DTI (2-3) • Evaluate story drifts due to lateral forces, including both translation and torsion. It may be assumed that inelastic drifts are adequately approximated by elastic analyses (note that lateral seismic forces are not reduced by Fµ when computing story drifts). Calculated story drifts should not exceed 0.010 times the story height for structures with contribution to distortion from both shear and flexure. For structures in which shear distortion is the primary contributer to drift, such as those with low rise shear walls or concentric braced-frames, the calculated story drift should not exceed 0.004 times the story height. These drift limits may be exceeded when acceptable performance of both the structure and nonstructural elements can be demonstrated at greater drift. • Check elements to assure that good detailing practice has been followed (e.g., see sect. C.4.4.2). Values of Fµ given in Table 2-3 are upper limit values. For concrete structures, good design detailing practice and consistency with recent ACI 349 provisions should be followed. (For other materials, use relevant codes per Chapter 1). Existing facilities may not be consistent with the recent ACI 349 provisions, and, if not, must be assigned a reduced value of Fµ. • Implement peer review of engineering drawings and calculations (including proper application of Fµ values) and require increased inspection and testing of new construction or existing facilities. Minimum values of peak ground acceleration (PGA) shall be: 0.06g for Performance Category 3 0.10g for Performance Category 4 DOE-STD-1020-2002 2-14 2.3.3 Damping Values for Performance Category 3 and 4 Structures, Systems, and Components Damping values to be used in linear elastic analyses are presented in Table 2-2 at three different response levels as a function of DT/CC. DT is the elastically computed total demand, DT = DNS + DS (2-4) and CC is the code specified capacity.

When determining the input to subcomponents mounted on a supporting structure, the damping value to be used in elastic response analyses of the supporting structure shall be based on the response level reached in the majority of the seismic load resisting elements of the supporting structure. This may require a second analysis. In lieu of a second analysis to determine the actual response of the structure, Response Level 1 damping values may be used for generation of in-structure spectra. Response Level 1 damping values must be used if stability considerations control the design. When evaluating the structural adequacy of an existing SSC, Response Level 3 damping may be used in elastic response analyses independent of the state of response actually reached, because such damping is expected to be reached prior to structural failure. When evaluating a new SSC, damping is limited to Response Level 2. For evaluating the structural adequacy of a new SSC, Response Level 2 damping may be used in elastic response analyses independent of the state of response actually reached. The appropriate response level can be estimated from the following: Response Level DT/CC 3** 2* 1* ≥1.0 ≈0.5 to 1.0 ≤ 0.5 * Consideration of these damping levels is required only in the generation of floor or amplified response spectra to be used as input to subcomponents mounted on the supporting structure. For analysis of structures including soil-structure interaction effects (See C.4.3), DT/CC ratios for the best estimate case shall be used to determine response level. DOE-STD-1020-2002 2-15 ** Only to be used for justifying the adequacy of existing SSCs with adequate ductile detailing. However, functionality of SSCs in PC-3 and PC-4 must be given due consideration. DOE-STD-1020-2002 2-16 Table 2-2 Specified Damping Values Damping (% of critical) Type of Component Response Level 1 Response Level 2 Response Level 3 Welded and friction bolted metal structures 2 4 7 Bearing-bolted metal structures 4 7 10 Prestressed concrete structures (without complete loss of prestress) 2 5 7 Reinforced concrete structures 4 7 10 Masonry shear walls 4 7 12 Wood structures with nailed joints 5 10 15 Distribution systems*** 3 5 5 Massive, low-stressed components (pumps, motors, etc.) 2 3 –* Light welded instrument racks 2 3 –* Electrical cabinets and other equipment 3 4 5** Liquid containing metal tanks Impulsive mode 2 3 4 Sloshing mode 0.5 0.5 0.5 * Should not be stressed to Response Level 3. Use damping for Response Level 2. ** May be used for anchorage and structural failure modes which are accompanied by at least some inelastic response. Response Level 1 damping values should be used for functional failure modes such as relay chatter or relative displacement issues which may occur at a low cabinet stress level. *** Cable trays more than one half full of loose cables may use 10% of critical damping. DOE-STD-1020-2002 2-17 Table 2-3 Inelastic Energy Absorption Factors, Fµ Structural System Fµ MOMENT RESISTING FRAME SYSTEMS - Beams Steel Special Moment Resisting Frame (SMRF) 3.0 Concrete SMRF 2.75 Concrete Intermediate Moment Frame (IMRF) 1.5 Steel Ordinary Moment Resting Frame 1.5 Concrete Ordinary Moment Resisting Frame 1.25 SHEAR WALLS Concrete or Masonry Walls In-plane Flexure 1.75 In-plane Shear 1.5 Out-of-plane Flexure 1.75 Out-of plane Shear 1.0 Plywood Walls 1.75 Dual System, Concrete with SMRF 2.5 Dual System, Concrete with Concrete IMRF 2.0 Dual System, Masonry with SMRF 1.5 Dual System, Masonry with Concrete IMRF 1.4

STEEL ECCENTRIC BRACED FRAMES (EBF) Beams and Diagonal Braces 2.75 Beams and Diagonal Braces, Dual System with Steel SMRF 3.0 CONCENTRIC BRACED FRAMES Steel Beams 2.0 Steel Diagonal Braces 1.75 Concrete Beams 1.75 Concrete Diagonal Braces 1.5 Wood Trusses 1.75 Beams and Diagonal Braces, Dual Systems Steel with Steel SMRF 2.75 Concrete with Concrete SMRF 2.0 Concrete with Concrete IMRF 1.4 METAL LIQUID STORAGE TANKS Moment and Shear Capacity 1.25 Hoop Capacity 1.5 Note: 1. Values herein assume good seismic detailing practice per , ACI 349 and other relevant codes along with reasonably uniform inelastic behavior. Otherwise, lower values should be used. 2. Fµ for columns for all structural systems is 1.5 for flexure and 1.0 for axial compression and shear. For columns subjected to combined axial compression and bending, interaction formulas shall be used. 3. Connections for steel concentric braced frames should be designed for at least the lesser of: The tensile strength of the bracing. The force in the brace corresponding to Fµ of unity. The maximum force that can be transferred to the brace by the structural system. 4. Connections for steel moment frames and eccentric braced frames and connections for concrete, masonry, and wood structural systems should follow IBC 2000 provisions utilizing the prescribed seismic loads from these criteria and the strength of the connecting members. In general, connections should develop the strength of the connecting members or be designed for member forces corresponding to Fµ of unity, whichever is less. 5. Fµ for chevron, V, and K bracing is 1.5. K bracing requires special consideration for any building if acceleration is 0.25g or more. DOE-STD-1020-2002 2-18 2.4 Additional Requirements 2.4.1 Equipment and Distribution Systems For PC-1 and PC-2 systems and components, the design or evaluation of equipment or non-structural elements supported within a structure may be based on the total lateral seismic force, Fp, given by the IBC provisions (Ref. 2-7). For PC-2 equipment expected to remain functional during or after earthquake, testing or experience based data for such equipment shall be an additional qualification requirement. For PC-3 and PC-4 systems and components, seismic design or evaluation shall be based on dynamic analysis, testing, or past earthquake and testing experience data. In any case, equipment items and non-structural elements must be adequately anchored to their supports unless it can be shown by dynamic analysis or by other conservative analysis and/or test that the equipment will be able to perform all of its safety functions without interfering with the safety functions of adjacent equipment. Anchorage must be verified for adequate strength and sufficient stiffness. Evaluation by Analysis By the IBC provisions for PC-1 and PC- 2, parts of the structures, permanent non- structural components, and equipment supported by a structure and their anchorages and required bracing must be designed to resist seismic forces. All the provisions of the IBC () shall be followed for PC-1 & PC-2 SSCs. The lateral force determined using IBC 2000 shall be distributed in proportion to the mass distribution of the element or component. Forces determined shall be used for the design or evaluation of elements or components and their connections and anchorage to the structure, and for members and connections that transfer the forces to the seismic-resisting systems. Forces shall be applied in the horizontal direction that results in the most critical loadings for design/evaluation.

For PC-3 and PC-4 subsystems and components, support excitation shall be calculated by means of floor response spectra (also commonly called in-structure response spectra). Floor response spectra should be developed accounting for the expected response level of the supporting structure even though inelastic behavior is permitted in the design of the structure (see Section 2.3.3). It is important to account for uncertainty in the properties of the equipment, supporting structure, and supporting media when using in-structure spectra which typically have narrow peaks. For this purpose, the peak broadening or peak shifting techniques outlined in ASCE 4 shall be employed. Equipment or distribution systems that are supported at multiple locations throughout a structure could have different floor spectra for each support point. In such a case, it is acceptable to use a single envelope spectrum of all locations as the input to all supports to obtain the inertial loads. Alternatively, there are analytical techniques available for using different spectra at each support location or for using different input time histories at each different support. DOE-STD-1020-2002 2-19 Seismic Anchor Motion The seismic anchor motion (SAM) component for seismic response is usually obtained by conventional static analysis procedures. The resultant component of stress can be very significant if the relative motions of the support points are quite different. If all supports of a structural system supported at two or more points have identical excitation, then this component of seismic response does not exist. For multiple-supported components with different seismic inputs, support displacements can be obtained either from the structural response calculations of the supporting structure or from spectral displacements determined from the floor response spectra. The effect of relative seismic anchor displacements shall be obtained by using the worst combination of peak displacements or by proper representation of the relative phasing characteristics associated with different support inputs. In performing an analysis of systems with multiple supports, the response from the inertial loads shall be combined with the responses obtained from the seismic anchor displacement analysis of the system by the SRSS rule R = Rinertia( )2 + RSAM( )2      , where R = response parameter of interest. Evaluation by Testing Guidance for conducting testing is contained in IEEE 344 (Ref. 2-11). Input or demand excitation for the tested equipment shall be based on the seismic hazard curves at the specified annual probability for the Performance Category of the equipment (OBE provisions of Ref. 2-11 do not apply). When equipment is qualified by shake table testing, the DBE input to the equipment is defined by an elastic computed required-response-spectrum (RRS) obtained by enveloping and smoothing (filling in valleys) the in-structure spectra computed at the support of the equipment by linear elastic analyses. In order to meet the target performance goals established for the equipment, the Required Response Spectrum (RRS) must exceed the In- Structure Spectra by: RRS ≥ (1.1)(In-Structure Spectra) for PC-1 and PC-2 (2-5) RRS ≥ (1.4SF)(In-Structure Spectra) for PC-3 and PC-4 (2-6) where SF is the seismic scale factor from Equation 2- 1.

The Test Response Spectrum (TRS) of test table motions must envelop the RRS. If equipment has been tested and shown to meet NRC requirements, then it need not be subjected to further testing. Evaluation by Seismic Experience Data For new design of systems and components, seismic qualification will generally be performed by analysis or testing as discussed in the previous sections. However, for existing systems and components, it is anticipated that many items will be judged adequate for seismic loadings on the basis of seismic experience data without analysis or testing. Seismic experience data has been developed in a usable format by ongoing research programs sponsored by the DOE-STD-1020-2002 2-20 nuclear power industry. The references for this work are the Senior Seismic Review and Advisory Panel (SSRAP) report (Ref. 2-12) and the Generic Implementation Procedure (GIP) for Seismic Verification of Nuclear Plant Equipment (Ref. 2-13). Note that there are numerous restrictions ("caveats") on the use of this data as described in the SSRAP report and the GIP. It is necessary to conduct either seismic analyses or shake table testing to demonstrate sufficient seismic capacity for those items that cannot be verified by seismic experience data or for items that are not obviously inherently rugged for seismic effects. Currently, use of experience data is permitted for existing facilities and for the items specified in the three references, (Ref 2-5), (Ref. 2-12) and (Ref. 2-13). Anchorage and Supports Adequate strength of equipment anchorage requires consideration of tension, shear, and shear-tension interaction load conditions. The strength of cast-in-place anchor bolts and undercut type expansion anchors shall be based on IBC Chapter 19 provisions (Ref. 2-7) for PC- 1 and PC-2 SSCs and on ACl 349 provisions (Ref. 2-14) for Performance Category 3 and higher SSCs. For new design by AC1 349 provisions, it is required that the concrete pullout failure capacity be greater than the steel cast-in-place bolt tensile strength to assure ductile behavior. For evaluation of existing cast-in-place anchor bolt size and embedment depth, it is sufficient to demonstrate that the concrete pullout failure capacity is greater than 1.5 times the seismic induced tensile load. For existing facility evaluation, it may be possible to use relaxed tensile-shear interaction relations provided detailed inspection and evaluation of the anchor bolt in accordance with References 2-5 and 2-15 is performed. The strength of expansion anchor bolts should generally be based on design allowable strength values available from standard manufacturers' recommendations or sources such as site- specific tests or References 2-5 and 2-15. Design-allowable strength values typically include a factor of safety of about 4 on the mean ultimate capacity of the anchorage. It is permissible to utilize strength values based on a lower factor of safety for evaluation of anchorage in existing facilities, provided the detailed inspection and evaluation of anchors is performed in accordance with References 2-5 and 2-15. A factor of safety of 3 is appropriate for this situation. When anchorage is modified or new anchorage is designed, design-allowable strength values including the factor of safety of 4 shall be used. For strength considerations of welded anchorage, AISC allowable values (Ref. 2-10) multiplied by 1.7 shall be used. Where shear in the member governs the connection strength, capacity shall be determined by multiplying the AISC allowable shear stress by 1.4.

Stiffness of equipment anchorage shall also be considered. Flexibility of base anchorage can be caused by the bending of anchorage components or equipment sheet metal. Excessive eccentricities in the load path between the equipment item and the anchor is a major cause of base anchorage flexibility. Equipment base flexibility can allow excessive equipment movement and reduce its natural frequency, possibly increasing dynamic response. In addition, flexibility can lead to high stresses in anchorage components and failure of the anchorage or equipment sheet metal. DOE-STD-1020-2002 2-21 2.4.2 Evaluation of Existing Facilities It is anticipated that these criteria would also be applied to evaluations of existing facilities. General guidelines for the seismic evaluation of existing facilities are presented in National Institute of Standards and Technology documents (Refs. 2-16 and 2-17). In addition, guidelines for upgrading and strengthening equipment are presented in Ref. 2-20. Also, guidance for evaluation of existing equipment by experience data is provided in References 2-5 and 2-13. These documents should be referred to for the overall procedure of evaluating seismic adequacy of existing facilities, as well as for specific guidelines on upgrading and retrofitting. Once the as-is condition of a facility has been verified and deficiencies or weak links have been identified, detailed seismic evaluation and/or upgrading of the facility as necessary can be undertaken. Obvious deficiencies that can be readily improved should be remedied as soon as possible. Seismic evaluation for existing facilities would be similar to evaluations performed for new designs except that a single as-is configuration is evaluated instead of several configurations in an iterative manner (as is often required in the design process). Evaluations should be conducted in order of priority. Highest priority should be given to those areas identified as weak links by the preliminary investigation and to areas that are most important to personnel safety and operations with hazardous materials. Input from safety personnel and/or accident analyses should be used as an aid in determining safety priorities. The evaluation of existing facilities for natural phenomena hazards can result in a number of options based on the evaluation results. If the existing facility can be shown to meet the design and evaluation criteria presented in Sections 2.3.1 or 2.3.2 and good seismic design practice had been employed, then the facility would be judged to be adequate for potential seismic hazards to which it might be subjected. If the facility does not meet the seismic evaluation criteria of this chapter, a back-fit analysis should be conducted. Several alternatives can be considered: 1. If an existing SSC is close to meeting the criteria, a slight increase in the annual risk to natural phenomena hazards can be allowed within the tolerance of meeting the target performance goals (See Section 1.3). Note that reduced criteria for seismic evaluation of existing SSCs is supported in Reference 2-16. As a result, some relief in the criteria can be allowed by performing the evaluation using hazard exceedance probability of twice the value recommended in Table 2-1 for the Performance Category of the SSC being considered. 2. The SSC may be strengthened such that its seismic resistance capacity is sufficiently increased to meet these seismic criteria. When upgrading is required it should be designed for the current design criteria.

3. The usage of the facility may be changed such that it falls within a less hazardous Performance Category and consequently less stringent seismic requirements. DOE-STD-1020-2002 2-22 4. It may be possible to conduct the aspects of the seismic evaluation in a more rigorous manner that removes conservatism such that the SSC may be shown to be adequate. Alternatively, a probabilistic assessment might be undertaken in order to demonstrate that the performance goals can be met. Requirements of Executive order 12941 (Ref. 1-8), as discussed in the DOE Guide 420.1- 2 are to be implemented. The requirements of ICSSC RP6 are minimum requirements to be met for existing buildings, especially the mitigation requirements triggered by section 2 of this standard. The line organization may define “Exceptionally High Risk buildings” to meet their safety and mission needs. Provisions in FEMA 310 and FEMA 356 should be taken into account while evaluating and upgrading existing buildings. Specific provisions may have to be modified to meet criteria for PC-3 and PC-4 in this standard. DOE O 420.1 requires that the sites should prepare upgrade plans for buildings that are deemed deficient to meet NPH equirements. Some of these deficiencies may have been discovered during the facility safety reviews and or during implementation of Executive Order 12941 (Reference 1-8). One of the prioritization schemes to upgrade such deficient building is given in Table 2-4, although sites may choose their own schemes. DOE-STD-1020-2002 2-23 Table 2-4 Suggested Priortization Scheme* Definitions: Seismicity Very High: Area where earthquakes could happen in the near future, say the next 30 years. High: Area where damaging earthquakes could happen within the life of a typical building say 100 years. Moderate: Area where earthquakes could happen. Low: Area where earthquakes are not expected to happen at all. Occupancy Groups High: Greater than 200 People Moderate/Low: Up to 200 people Definitions above are based on 24 hours average occupancies. Priority Model Building Occupancy Description Group Function Groups Seismicity Groups Buildings which pose the greatest risk to life or loss of essential function Buildings which pose the least risk to life or loss of essential function 1 All Extremely Poor Buildings Very High Hazard High Occupancy 2 All Extremely Poor Buildings Very High Hazard M/L Occupancy 3 All Extremely Poor Buildings High Hazard High Occupancy 4 All Very Poor Buildings High Hazard High Occupancy 5 All Very Poor Buildings High Hazard High Occupancy 6 All Poor Buildings Very High Hazard High Occupancy 7 All Poor Buildings High Hazard High Occupancy 8 Essential Very Poor Buildings Very High Hazard M/L Occupancy 9 Essential Poor Buildings Very High Hazard M/L Occupancy 10 Essential All Building Moderate Hazard High Occupancy 11 Non-essential Extremely Poor Buildings Moderate Hazard High Occupancy 12 Essential All Buildings High Hazard M/L Occupancy 13 Non-essential Extremely Poor Buildings High Hazard M/L Occupancy 14 Non-essential Very Poor Buildings Moderate Hazard High Occupancy 15 Non-essential Poor Buildings Moderate Hazard High Occupancy 16 Essential All Buildings Moderate Hazard M/L Occupancy 17 Non-essential Extremely Poor Buildings Moderate Hazard M/L Occupancy 18 Non-essential Very Poor Buildings Very High Hazard M/L Occupancy 19 Non-essential Very Poor Buildings High Hazard M/L Occupancy 20 Non-essential Poor Buildings Very High Hazard M/L Occupancy 21 Non-essential Poor Buildings High Hazard M/L Occupancy 22 Non-essential Very Poor Buildings Moderate Hazard M/L Occupancy 23 Non-essential Poor Buildings Moderate Hazard M/L Occupancy

* SOURCE: DRAFT FEMA REPORT TO CONGRESS ON E.O.12941 D ec re as in g R is k DOE-STD-1020-2002 2-24 Model Building Groups The model building types listed in Table 2-4 are defined in FEMA 178, (Ref. 2-22) NEHRP Handbook for the Seismic Evaluation of Existing Buildings. Extremely Poor: Concrete Moment Frame, Precast/Tilt-up Concrete Walls with Lightweight Flexible Diaphragms, Precast Concrete Frames with Concrete Shear Walls, Unreinforced Masonry Buildings. Very Poor: Steel Braced Frame, Steel Frame with Infill Shear Walls, Concrete Shear Walls, Concrete Frame with infill Shear Walls, Reinforced Masonry Bearing Walls with Precast Concrete Diaphragms. Other type Unknown type. Poor: Wood, Light Frame, Wood, Commercial and Industrial, Steel Moment Frame, Steel Light Frame, Steel Frame with Concrete Shear Walls, Reinforced Masonry Bearing Walls with Wood or Metal Deck Diaphragms. Essential Buildings: Buildings that, in the judgement of the owning agency require a level of seismic resistance higher than life safety in order to support earthquake response, critical functions, hazardous materials or extremely valuable contents. 2.4.3 Basic Intention of Dynamic Analysis Based Deterministic Seismic Evaluation and Acceptance Criteria The basic intention of the deterministic seismic evaluation and acceptance criteria defined in Section 2.3 is to achieve less than a 10% probability of unacceptable performance for a structure, system, or component (SSC) subjected to a Scaled Design/Evaluation Basis Earthquake (SDBE) defined by: SDBE= 1.5SF( ) DBE( ) (2-7) where SF is the appropriate seismic scale factor from Equation 2-1. The seismic evaluation and acceptance criteria presented in this section has intentional and controlled conservatism such that the target performance goals are achieved. The amount of intentional conservatism has been evaluated in Reference 2-1 such that there should be less than 10% probability of unacceptable performance at input ground motion defined by 1.5SF times the DBE. Equation 2-7 is useful for developing alternative evaluation and acceptance criteria which are also based on the target performance goals such as inelastic seismic response analyses. To evaluate items for which specific acceptance criteria are not yet developed, such as overturning or sliding of foundations, or some systems and components; this basic intention must be met. If a nonlinear inelastic response analysis which explicitly incorporates the hysteretic energy dissipation is performed, damping values that are no higher than Response Level 2 should be used to avoid the double counting of this hysteretic energy dissipation which would result from the use of Response Level 3 damping values. DOE-STD-1020-2002 2-25 2.5 Summary of Seismic Provisions Table 2-5 summarizes recommended earthquake design and evaluation provisions for Performance Categories 1 through 4. Specific provisions are described in detail in Section 2.3. The basis for these provisions is described in Reference 1. DOE-STD-1020-2002 2-26 Table 2-5 Summary of Earthquake Evaluation Provisions Performance Category (PC) 1 2 3 4 Hazard Exceedance Probability, PH (MCE) G.M.2 (MCE) G. M.2 4x10-4 (1x10-3)1 1x10-4 (2x10-4)1 Response Spectra Median amplification (no conservative bias) Damping for Structural Evaluation 5% Table 2-3 Acceptable Analysis Approaches for Structures Static or dynamic force method normalized to code level base

shear Dynamic analysis Analysis approaches for systems and components IBC Force equation for equipment and non-structural elements (or more rigorous approach) Dynamic analysis using in- structure response spectra (Damping from Table 2-2) Seismic Use group Seismic Use Group I Seismic Use Group III Not used Load Factors Code specified load factors appropriate for structural material Load factors of unity Scale Factors Not Used SF = 0.9 SF = 1.25 Inelastic Energy Absorption Ratios For Structures Accounted for by R in IBC 2000 Fµ from Table 2-3 by which elastic response is reduced to account for permissible inelastic behavior Material Strength Minimum specified or 95% non-exceedance in-situ values Structural Capacity Code ultimate strength or allowable behavior level Code ultimate strength or limit-state level Quality Assurance Program Required within a graded approach (i.e., with increasing rigor ranging from the IBC requirements from PC-1 to nuclear power plant requirements for PC-4) Peer Review Not Required Required within a graded approach (i.e., with increasing rigor ranging from IBC requirements from PC-2 to nuclear power plant requirements for PC-4) 1 For sites such as LLNL, SNL-Livermore, SLAC, LBNL, & ETEC which are near tectonic plate boundaries. 2MCE GM = Maximum considered earthquake ground motion (generally, PH = 4x10-4 ) - for Seismic Use Group I (PC-1) use 2/3 MCE, for Seismic Group III (PC-2) use 2/3 MCE with importance Factor of 1.5. DOE-STD-1020-2002 2-27 2.6 References 2-1. Kennedy, R.P., and S.A. Short, Basis for Seismic Provisions of DOE-STD-1020, UCRL- CR-111478 Revision 1, prepared for Lawrence Livermore National Laboratory, April,1994. 2-2. Newmark, N. M. and W. J. Hall, Development of Criteria for Seismic Review of Selected Nuclear Power Plants, NUREG/CR-0098, U.S. Nuclear Regulatory Commission, May 1978. 2-3. American Society of Civil Engineers (ASCE), Seismic Analysis of Safety-Related Nuclear Structures and Commentary on Standard for Seismic Analysis of Safety-Related Nuclear Structures, ASCE Standard 4, September 1998. 2-4. Guidelines and Procedures for Implementation of the Executive Order on Seismic Safety of New Building Construction, ICSSC RP 2.1-A, NISTR 4-852, National Institute of Standards and Technology, June 1992. 2-5. U.S. Department of Energy, Seismic Evaluation Procedure for Equipment in U.S. Department of Energy Facilities, DOE-EH-0545, March 1997. 2-6. NEHRP Recommended Provisions for the Development of Seismic Regulations for New Buildings and other structures, 1997 Edition, FEMA 302, Federal Emergency Management Agency and Building Seismic Safety Council, Washington, D.C., 1997. 2-7. International Code Council Inc., International Building Code 2000, Falls Church, VA 2000. 2-8 ACI 318-99, Building Code Requirements for Reinforced Concrete, American Concrete Institute, Farmington Hills, Michigan, 1999. 2-9 American Institute of Steel Construction, Manual of Steel Construction, Load & Resistance Factor Design (LRFD), Chicago, Illinois, 1998. 2-10 American Institute of Steel Construction, Manual of Steel Construction, Allowable Stress Design (ASD), Ninth Ed., Chicago, Illinois, 1989 2-11. Institute of Electrical and Electronic Engineers, ANSI/IEEE 344, IEEE Recommended Practice for Seismic Qualification of Class 1E Equipment for Nuclear Power Generating Stations, New York, NY, 1987.

2-12. Kennedy, R.P., W.A. Von Riesemann, P. Ibanez, A.J. Schiff, and L.A. Wyllie, Use of Seismic Experience and Test Data to Show Ruggedness of Equipment in Nuclear Power DOE-STD-1020-2002 2-28 Plants, Senior Seismic Review and Advisory Panel, SAND92-0140.UC-523, Sandia National Laboratory, June 1992. 2-13. SQUG, Generic Implementation Procedure (GIP) for Seismic Verification of Nuclear Plant Equipment, Revision 2 Seismic Qualification Utility Group, 1991. 2-14. American Concrete Institute, Code Requirements for Nuclear Safety-Related Concrete Structures (ACI 349-97) and Commentary - ACI 349R-97, Farmington Hills, Michigan. 2-15. URS Corporation/John A. Blume & Associates, Engineers, Seismic Verification of Nuclear Plant Equipment Anchorage Volumes 1, 2, 3 and 4, Revision 1. EPRI Report NP-5228. Prepared for Electric Power Research Institute, Palo Alto, CA., June 1991. 2-16. Guidelines for Identification and Mitigation of Seismically Hazardous Existing Federal Buildings, NISTIR 890-4062, ICSSC RP-3, National Institute of Standards and Technology, U.S. Department of Commerce, Gaithersburg, Maryland, March 1989. 2-17. Standards of Seismic Safety for Existing Federally Owned or Leased Buildings and Commentary, ICSSC RP 6 National Institute of Standards and Technology, U. S. Department of Commerce, Gaithersburg, Maryland, 2001. 2-18. Hom, S., R. Kincaid, and P.I. Yanev, Practical Equipment Seismic Upgrade and Strengthening Guidelines, UCRL-15815, EQE Incorporated, San Francisco, California, September 1986. 2-19 U. S. Department of Energy, Natural Phenomena Hazards Assessment Criteria, DOE- STD-1023-95, Washington, D. C., September 1995. 2-20 Federal Emergency Management Agency, Pre-standard and Commentary for the Seismic Rehabilitation of Buildings, FEMA 356, November 2000 2-21 Federal Emergency Management Agency, NEHRP Handbook for the Seismic Evaluation of Existing Building, FEMA 310, January 1998. 2-22 Federal Emergency Management Agency, NEHRP Handbook for the Seismic Evaluation of Existing Building, FEMA 178, June 1992. DOE-STD-1020-2002 3-1 Chapter 3 Wind Design and Evaluation Criteria 3.1 Introduction This chapter presents a uniform approach to wind load determination that is applicable to the design of new and evaluation of existing structures, systems and components (SSCs). For existing SSCs, Figure B-2 (in Appendix B) may be utilized appropriately and judiciously. As discussed in Appendix D.1, a uniform treatment of wind loads is recommended to accommodate straight, hurricane, and tornado winds. SSCs are first assigned to appropriate Performance Categories by application of DOE-STD-1021. Criteria are recommended such that the target performance goal for each category can be achieved. Procedures according to the wind load provisions of current version of ASCE 7 (Ref. 3-1) are recommended for determining wind loads produced by straight, hurricane and tornado winds. The straight wind design basis is derived from the national wind map in Figure 6-1 of Reference 3-1 except in few cases where hazard models for DOE sites published in Reference 3-2 are used to establish site-specific criteria for these few DOE sites. For other sites, the wind/tornado hazard data shall be determined in accordance with DOE-STD-1023. Tornado hazard is based on recent studies conducted for various NNSA sites (Reference 3-14). Use of the same methodology is recommended for use by sites other than NNSA sites, and the tornado hazard curves should be developed for sites with tornado hazard (Reference Table 3-2).

The performance goals established for Performance Categories 1 and 2 are met by model codes or national standards (see discussion in Appendix B). These criteria do not account for the possibility of tornado winds because wind speeds associated with straight winds typically are greater than tornado winds at annual exceedance probabilities greater than approximately 1x10-4. Since model codes specify winds at probabilities greater than or equal to 1x10-2, tornado design criteria are specified only for SSCs in Performance Categories 3 and higher, where hazard exceedance probabilities are less than 1x10-2. In determining wind design criteria for Performance Categories 3 and higher, the first step is to determine if tornadoes should be included in the criteria. The decision logically can be made on the basis of geographical location, using historical tornado occurrence records. However, since site specific hazard assessments are available for the DOE sites, a more quantitative approach can be taken. Details of the approach are presented in Appendix D. The annual exceedance probability at the intersection of the straight wind and tornado hazard curves is used to determine if tornadoes should be a part of the design criteria. If the exceedance probability at the intersection of the curves is greater than or equal to 2x10-5, then tornado design criteria are specified. By these criteria, tornado wind speeds are determined at 2x10-5 for PC-3 and 2x10-6 for PC-4. If the exceedance probability is greater than 2x10-5 only the effects of straight winds or hurricanes need be considered. For straight winds and hurricanes, wind speeds are determined at 1x10-3 for PC-3 and 1x10-4 for PC-4. DOE-STD-1020-2002 3-2 3.2 Wind Design Criteria The criteria presented herein meet or exceed the target performance goals described in DOE O 420.1 for each Performance Category. SSCs in each category have a different role and represent different levels of hazard to people and the environment. In addition, the degree of wind hazard varies geographically. Facilities in the same Performance Category, but at different geographical locations, will have different wind speeds specified to achieve the same performance goal. The minimum wind design criteria for each Performance Category are summarized in Table 3-1. The recommended basic wind speeds for straight wind, hurricanes and tornadoes are contained in Table 3-2 for non-reactor nuclear and other hazardous facilities, reservations, and production facilities. All wind speeds are 3 second gust, which is consistent with the ASCE 7 approach. Importance factors as given in ASCE 7 should be used where applicable. Degrees of conservatism are introduced in the design process by means of load combinations. The combinations are given in the appropriate material national consensus design standard. Designers will need to exercise judgment in choosing the most appropriate combinations in some situations. Designs or evaluations shall be based on the load combination causing the most unfavorable effect. For PC-3 and 4 the load combination to be used should invoke either wind or tornado depending on which speed is specified in Table 3-2.

Most loads, other than dead loads, vary significantly with time. When these variable loads are combined with dead loads, their combined effect could be sufficient to reduce the risk of unsatisfactory performance to an acceptably low level. When more than one variable load is considered, it is unlikely that they will all attain their maximum value at the same time. Accordingly, some reduction in the total of the combined load effects is appropriate. This reduction is accomplished through load combination multiplication factors as given in the appropriate material national consensus standard. DOE-STD-1020-2002 3-3 Table 3-1 Summary Of Minimum Wind Design Criteria Performance Category 1 2 3 4 Hazard Annual Probability Of Exceedance 2x10-2 1x10-2 1x10-3 1x10-4 W i n d Importance Factor 1.0 1.00 1.0 1.0 Missile Criteria NA NA 2x4 timber plank 15 lb @50 mph (horiz.); max. height 30 ft. 2x4 timber plank 15 lb @50 mph (horiz.); max. height 50 ft. Hazard Annual Probability of Exceedance NA NA (1) 2x10-5 (1) 2x10-6 Importance Factor NA NA I = 1.0 I = 1.0 APC NA NA 40 psf @ 20 psf/sec 125 psf @ 50 psf/sec T o r n a d o Missile Criteria NA NA 2x4 timber plank 15 lb @100 mph (horiz.); max. height 150 ft.; 70 mph (vert.) 3 in. dia. std. steel pipe, 75 lb @ 50 mph (horiz.); max. height 75 ft, 35 mph (vert.) 2x4 timber plank 15 lb @150 mph (horiz.), max. height 200 ft.; 100 mph (vert.) 3 in. dia. std. steel pipe, 75 lb @ 75 mph (horiz.); max. height 100 ft, 50 mph (vert.) 3,000 lb automobile @ 25 mph, rolls and tumbles (1) These values for APC and tornado missile criteria are minimum and need to be revisited after new tornado hazard curves are developed using Livermore methodology (Reference 3-14). These values may need to be upgraded to higher values depending on outcome of tornado hazard analysis at each site. In the interim, it is recommended that for sites with PC-3 facilities where Tornado wind speeds have substantially increased (above 175 mph), the APC and missile criteria for PC-4 should be used in lieu of Pc-3. Forces due to missiles and Tornado wind effects should be combined appropriately unless it can be justified that this is not deemed necessary. Such justification may consider situations where the mode of failure does not require these forces to be combined. DOE-STD-1020-2002 3-4 Table 3-2 Recommended Peak Gust Wind Speeds for Straight Winds (for Category C Exposure) And Tornadoes in miles per hour at 33 Ft. (10 m) above ground Current Performance Category PC1 PC2 PC3 Wind PC3 Tornado(2) PC4 Wind PC4 Tornado(2) Return period (yrs) 50 100 1000 50000 10000 500000 Annual Probability 2.00E-02 1.00E-02 1.00E-03 2.00E-05 1.00E-4 2.00E-06 Site Kansas City Plant, MO 90 96 - (3) - (3) Los Alamos National Laboratory, NM 90 96 117 - 135 - Mound Laboratory, OH 90 96 - (3) - (3) Pantex Plant, TX 90 96 - 195 - 248 Rocky Flats Plant, CO 125 134 163 (1) 188 (1) Sandia National Laboratories, NM 90 96 117 - 135 - Sandia National Laboratories, CA 85 91 111 - 128 - Argonne National Laboratories-East, IL 90 96 - (3) - (3) Argonne National Laboratories-West, ID 90 96 117 - 135 - Brookhaven National Laboratory, NY 125 138 178 (1) 219 (1) Princeton Plasma Physics Laboratory, NJ 110 122 156 (1) 193 (1) Idaho National Engineering Laboratory , ID 90 96 117 - 135 - Oak Ridge, X-10, K-25, and Y-12, TN 90 96 - 200 - 255 Paducah Gaseous Diffusion Plant, KY 90 96 - (3) - (3) Portsmouth Gaseous Diffusion Plant, OH 90 96 - (3) - (3) Nevada Test Site, NV 90 96 117 - 135 - Hanford Project Site, WA 85 91 111 - 128 - Lawrence Berkeley Laboratory, CA 85 91 111 - 128 - Lawrence Livermore National Laboratory, CA 85 91 111 - 128 - LLNL, Site 300, CA 95 102 124 - 143 - Energy Technology & Engineering Center, CA 85 91 - (3) - (3)

Stanford Linear Accelerator Center, CA 85 91 111 128 - Savannah River Site, SC 100 107 - 169 - 213 1. Although straight wind speeds govern, because the potential for a tornado strike is high, it is recommended that facilities be designed for tornado missiles using the missile speeds for the relevant performance category. APC may not be considered. 2. Tornado speed includes rotational and translational effects 3. For non-NNSA sites tornado wind speeds need to be generated by sites from tornado hazard curves utilizing LLNL methodology (Reference 3-14). DOE-STD-1020-2002 3-5 3.2.1 Performance Category 1 The performance goals for Performance Category 1 SSCs are consistent with objectives of ASCE 7 Building Category II, Ordinary Structures. Similar criteria in model building codes such as the current International Building Code, IBC 2000 (Ref. 3-3) are also consistent with the performance goal and may be used as an alternative criteria. The wind- force resisting system of structures should not collapse under design load. Survival without collapse implies that occupants should be able to find an area of relative safety inside the structure during an extreme wind event. Breach of structure envelope is acceptable, since confinement is not essential. Flow of wind through the structure and water damage are acceptable. Severe loss, including total loss, is acceptable, so long as the structure does not collapse and occupants can find safe areas within the building. In ASCE 7, wind design criteria is based on an exceedance probability of 2x10 -2 per year. The importance factor is 1.0. Distinctions are made in ASCE 7 between buildings and other structures and between main wind-force resisting systems and components and cladding. In the case of components and cladding, a further distinction is made between buildings less than or equal to 60 ft and those greater than 60 ft in height. Terrain surrounding SSCs should be classified as Exposure B, C, or D as defined in ASCE 7. Gust effect factors (G) and velocity pressure exposure coefficients (K) should be used according to the rules of the ASCE 7 procedures. Wind pressures are calculated on walls and roofs of enclosed structures by using appropriate pressure coefficients specified in ASCE 7. Internal pressures on components and cladding develop as a result of unprotected openings, or openings created by wind forces or missiles. The worst cases of combined internal and external pressures should be considered in wind design as required by ASCE 7. SSCs in Performance Category 1 may be designed by either allowable stress design (ASD) or strength design (SD). Load combinations shall be considered to determine the most unfavorable effect on the SSC being considered. When using ASD methods, customary allowable stresses appropriate for the material shall be used as given in the applicable material design standard (e.g. see Reference 3-4 for steel). The SD method requires that the nominal strength provided be greater than or equal to the strength required to carry the factored loads. Appropriate material strength reduction factors should be applied to the nominal strength of the material being used. See Reference 3-5 for concrete or Reference 3-6 for steel for appropriate load combinations and strength reduction factors. DOE-STD-1020-2002 3-6 3.2.2 Performance Category 2

Performance Category 2 SSCs are equivalent to essential facilities (Category IV), as defined in ASCE 7 or model building codes. The structure shall not collapse at design wind speeds. Complete integrity of the structure envelope is not required because no significant quantities of toxic or radioactive materials are present. However, breach of the SSC containment is not acceptable if the presence of wind or water interferes with the SSCs function. An annual wind speed exceedance probability of 1x10 -2 is specified for this Performance Category. The importance factor is 1.0. Once the design wind speeds are established and the importance factors applied, the determination of wind loads on Performance Category 2 SSCs is identical to that described for Performance Category 1 SSCs. ASD or SD methods may be used as appropriate for the material being used. The load combinations described for Performance Category 1 are the same for Performance Category 2. 3.2.3 Performance Category 3 The performance goal for Performance Category 3 SSCs requires more rigorous criteria than is provided by national standards or model building codes. In some geographic regions, tornadoes must be considered. Straight Winds and Hurricanes For those sites where tornadoes are not a viable threat, the recommended basic wind speed based on an annual exceedance probability of 1x10 ?3 . The importance factor is 1.0. Once the design wind speeds are established and the importance factors applied, determination of Performance Category 3 wind loads is identical to Performance Category 1, except as noted below. SSCs in Performance Category 3 may be designed or evaluated by ASD or SD methods, as appropriate for the material used in construction. Because the hazard exceedance probability in Performance Category 3 contributes a larger percentage to the total probabilistic performance goal than in Performance Categories 1 or 2, less conservatism is needed in the Performance Category 3 design and evaluation criteria. This trend is different for seismic design as discussed in Chapter 2 and Appendix C. (See Appendix D for further explanation.) Thus, the load combinations given in the applicable material national consensus design standard may be reduced by 10 percent. In combinations where gravity load reduces wind uplift, the reduction in conservatism is achieved by modifying only the gravity load factor. When using ASD, allowable stresses shall be determined in accordance with applicable codes and standards (e.g. see Reference 3-4 for steel). Load combinations shall be evaluated DOE-STD-1020-2002 3-7 to determine the most unfavorable effect of wind on the SSCs being considered. The SD load combinations shall be used along with nominal strength and strength reduction factors. A minimum missile criteria is specified to account for objects or debris that could be picked up by straight winds, hurricanes or weak tornadoes. A 2x4 timber plank weighing 15 lbs is the specified missile. This missile represents a class of missiles transported by straight winds, hurricanes and weak tornadoes. Recommended impact speed is 50 mph at a maximum height of 30 ft above ground. The missile will break annealed glass; it will perforate sheet metal siding, wood siding up to 3/4-in. thick, or form board. The missile could pass through a window or weak exterior wall and cause personal injury or damage to interior contents of a building. The specified missile will not perforate unreinforced concrete masonry or brick veneer walls or other more substantial wall construction. See Table 3-3 for recommended wall barriers (Ref. 3-7).

Table 3-3 Recommended Straight Wind Missile Barriers for Performance Categories 3 and 4 Missile Criteria Recommended Missile Barrier 2x4 timber plank 15 lb @ 50 mph (horiz.) 8-in. CMU wall with trussed horizontal joint reinforced @ 16 in. on center Max. height 30 ft. above ground Performance Category 3 Single width brick veneer with stud wall Max. height 50 ft. above ground Performance Category 4 4-in. concrete slab with #3 rebar @ 6 in. on center each way in middle of slab Tornadoes For those sites requiring design for tornadoes, the criteria are based on site-specific studies, as presented in Reference 3-14. Other non-NNSA sites may utilize the same methodology to develop their tornado hazard curves.. An annual exceedance probability of 1x10-3, which is the same for straight wind, could be justified. As explained in Appendix D, a lower value is preferred because (1) the straight wind hazard curve gives wind speeds larger than the tornado hazard curve and (2) a lower hazard probability can be specified without placing undue hardship on the design. The basic tornado wind speed associated with an annual exceedance probability of 2x10-5 is recommended for Performance Category 3. The wind speed obtained from the tornado hazard curve are already converted from peak gust to fastest quarter-mile; use importance factor of 1.0 for Performance Category 3. For DOE-STD-1020-2002 3-8 the use in this standard fastest quarter-mile and 3 second gusts are deemed to be equivalent for all practical purposes. With the wind speed given in fastest quarter-mile wind and an importance factor of 1.0, the equations in ASCE 7 should be used to obtain design wind pressures on SSCs. Exposure Category C should always be used with tornado winds regardless of the actual terrain roughness. Non-conservative results will be obtained with exposure B. Tornadoes traveling over large bodies of water are waterspouts, which are less intense than land-based tornadoes. Thus, use of exposure category D also is not necessary. The velocity pressure exposure coefficient and gust effect factor are obtained from ASCE 7. External pressure coefficients are used to obtain tornado wind pressures on various surfaces of structures. Net pressure coefficients are applicable to systems and components. On structures, a distinction is made between main wind-force resisting systems and components and cladding. If a structure is not intentionally sealed to maintain an internal negative pressure for confinement of hazardous materials, or, if openings greater than one square foot per 1000 cubic feet of volume are present, or, if openings of this size can be caused by missile perforation, then the effects of internal pressure should be considered according to the rules of ASCE 7. If a structure is sealed, then atmospheric pressure change (APC) associated with the tornado vortex should be considered instead of internal pressures. (see Table 3-1 and note below for APC values). The maximum APC pressure occurs at the center of the tornado vortex where the wind speed is theoretically zero. A more severe loading condition occurs at the radius of maximum tornado wind speed, which is some distance from the vortex center. At the radius of maximum wind speed, the APC may be one-half its maximum value. Thus, a critical tornado load combination on a sealed building is one-half maximum APC pressure combined with maximum tornado wind pressure. A loading condition of APC alone can occur on the roof of a buried tank or sand filter, if the roof is exposed at the ground surface. APC pressure always acts outward. A rapid rate of pressure change, which can accompany a rapidly translating tornado, should be analyzed to assure that it does not damage safety-related ventilation systems. Procedures and computer codes are available for such analyses

(Ref. 3-8). When using ASD methods, allowable stresses appropriate for the materials shall be used. Since in this case, the hazard probability satisfies the performance goal, little or no additional conservatism is needed in the design. Thus, for ASD the tornado wind load combinations are modified to negate the effect of safety factors. For example, the combinations from ASCE 7 become: (a) 0.63 (D + Wt) (b) 0.62 (D + L + Lr + Wt) DOE-STD-1020-2002 3-9 (c) 0.62 (D + L + Lr + Wt + T) (3-1) Along with nominal material strength and strength reduction factors, the following SD load combinations for Performance Category 3 shall be considered: (a) D + Wt (b) D + L + Lr + Wt (c) D + L + Lr + Wt + T (3-2) where: Wt = tornado loading, including APC and missile, as appropriate. The notation and rationale for these load combinations are explained in Appendix D. Careful attention should be paid to the details of construction. Continuous load paths shall be maintained; redundancy shall be built into load-carrying structural systems; ductility shall be provided in elements and connections to prevent sudden and catastrophic failures. Two tornado missiles are specified as minimum criteria for this Performance Category. The 2x4-in. timber plank weighing 15 lbs is assumed to travel in a horizontal direction at speeds up to 100 mph. The horizontal speed is effective up to a height of 150 ft above ground level. If carried to great heights by the tornado winds, the timber plank can achieve a terminal vertical speed of 70 mph in falling to the ground. The horizontal and vertical speeds are assumed to be uncoupled and should not be combined. Table 3-4 describes wall and roof structures that will resist the postulated timber missile. A second missile to be considered is a 3-in. diameter standard steel pipe, which weighs 75 lbs. Design horizontal impact speed is 50 mph; terminal vertical speed is 35 mph. The horizontal speed of the steel pipe is effective up to a height of 75 ft above ground level. Table 3-4 summarizes certain barrier configurations that have been successfully tested to resist the pipe missile. Although wind pressure, APC and missile impact loads can occur simultaneously, the missile impact loads can be treated independently for design and evaluation purposes. These are the minimum missile design criteria and should be reviewed for upgrading with the concurrent use of new tornado hazard assessment methodology (Reference 3-14). DOE-STD-1020-2002 3-10 Table 3-4 Recommended Tornado Missile Barriers * for Performance Category 3 Missile Criteria Recommended Missile Barrier Horizontal Component: 2x4 timber plank 15 lb @ 100 mph 8-in. CMU wall with one #4 rebar grouted in each vertical cell and trussed horizontal joint reinforced @ 16 in. on center max. height 150 ft. above ground Single width brick veneer attached to stud wall with metal ties 4 in. concrete slab with #3 rebar @ 6 in. on center each way in middle of slab Vertical Component: 2x4 timber plank 15 lb @ 70 mph 4 in. concrete slab with #3 rebar @ 6 in. on center each way in middle of slab Horizontal Component: 3-in. diameter steel pipe 75 lb @ 50 mph 12-in. CMU wall with #4 rebar in each vertical cell and grouted; #4 rebar horizontal @ 8 in. on center max. height 75 ft. above ground Nominal 12-in. wall consisting of 8-in. CMU with #4 rebar in each vertical cell and grouted; #4 rebar horizontal @ 8 in. on center; single width brick masonry on outside face; horizontal ties @ 16 in. on center

9.5- in. reinforced brick cavity wall with #4 rebar @ 8 in. on center each way in the cavity; cavity filled with 2500 psi concrete; horizontal ties @ 16 in. on center 8-in. concrete slab with #4 rebar @ 8 in. on center each way placed 1.5 in. from each face Vertical Component: 3-in. diameter steel pipe 75 lb @ 35 mph 6-in. concrete slab with #4 rebar @ 12 in. on center each way 1.5 in. from inside face * See Footnote of Table 3-1 for interim conservative approach. DOE-STD-1020-2002 3-11 3.2.4 Performance Category 4 The performance goal for Performance Category 4 requires more conservative criteria than Performance Category 3. In some geographic regions, tornadoes must be considered. Straight Winds and Hurricanes For those sites where tornadoes are not a viable threat, the recommended basic wind speed is based on an annual exceedance probability of 1x10-4. The importance factor is 1.0. Once the design wind speeds are established and the importance factors applied, determination of Performance Category 4 wind loads is identical to Performance Category 3, except as noted below. SSCs in category Performance Category 4 may be designed or evaluated by ASD or SD methods, as appropriate for the material being used in construction. As with Performance Category 3, the wind hazard exceedance probability contributes a larger percentage of the total probabilistic performance goal than Performance Categories 1 or 2. Less conservatism is needed in the design and evaluation procedure. The degree of conservatism for Performance Category 4 is the same as Performance Category 3. Thus, the load combinations for both the ASD and SD are the same for Performance Categories 3 and 4. Although the design wind speeds in Performance Category 4 are larger than Performance Category 3, the same missiles are specified (Table 3-3), except the maximum height above ground is 50 ft instead of 30 ft for Performance Category 4. Tornadoes For those sites requiring design for tornadoes, the criteria are based on LLNL tornado hazard assessment methodology presented in Reference 3-14. Again, as with Performance Category 3, an annual exceedance probability of 1x10-4 could be justified. However, for the same reasons given for Performance Category 3, a lower value is recommended. The basic tornado wind speed associated with an annual exceedance probability of 2x10-6 and an importance factor of 1.0 is recommended. Once the basic tornado wind speed is determined for the specified annual exceedance probability and given in fastest-quarter mile, the procedure is as described for Performance Category 3, except as noted below. Three tornado missiles are specified for Performance Category 4: a timber plank, a steel pipe and an automobile. The 2x4 timber plank weighs 15 lbs and is assumed to travel in a horizontal direction at speeds up to 150 mph. The horizontal component of the timber missile is effective to a maximum height of 200 ft above ground level. If carried to a great height by the tornado winds, it could achieve a terminal vertical speed of 100 mph as it falls to the ground. The second missile is a 3-in. diameter standard steel pipe, which weighs 75 lbs. It can achieve a horizontal impact speed of 75 mph and a vertical speed of 50 mph. The horizontal speed could be effective up to a height of 100 ft above ground level. The horizontal and vertical speeds of DOE-STD-1020-2002 3-12

the plank and pipe are uncoupled and should not be combined. The third missile is a 3000-lb automobile that is assumed to roll and tumble along the ground at speeds up to 25 mph. Table 3-5 lists wall barrier configurations that have been tested and successfully resisted the timber and pipe missile. Impact of the automobile can cause excessive structural response to SSCs. Impact analyses should be performed to determine specific effects. In structures, collapse of columns, walls or frames may lead to further progressive collapse. Procedures for structural response calculations for automobile impacts is given in References 3-9, 3-10 and 3-11. Although wind pressure, APC, and missile impact loads can occur simultaneously, the missile impact loads can be treated independently for design and evaluation purposes. These are minimum missile design criteria and should be reviewed for upgrading with the concurrent use of new tornado hazard assessment methodology (Reference 3-14). Table 3-5 Recommended Tornado Missile Barriers for Performance Category 4 Missile Criteria Recommended Missile Barrier Horizontal Component: 2x4 timber plank 15 lb @ 150 mph 6 in. concrete slab with #4 rebar @ 6 in. on center each way in middle of slab max. height 200 ft. above ground 8-in. CMU wall with one #4 rebar grouted in each vertical cell and horizontal trussed joint reinforced @ 16 in. on center Vertical Component: 2x4 timber plank 15 lb @ 100 mph 4 in. concrete slab with #3 rebar @ 6 in. on center each way in middle of slab Horizontal Component: 3-in. diameter steel pipe 75 lb @ 75 mph 10-in. concrete slab with #4 rebar @ 12 in. on center each way placed 1.5 in. from each face max. height 100 ft. above ground Vertical Component: 3-in. diameter steel pipe 75 lb @ 50 mph 8-in. concrete slab with #4 rebar @ 8 in. on center each way placed 1.5 in. from inside face DOE-STD-1020-2002 3-13 3.2.5 Design Guidelines Reference 3-12 provides guidelines and details for achieving acceptable wind resistance of SSCs. Seven principles should be followed in developing a design that meets the performance goals: (a) Provide a continuous and traceable load path from surface to foundation (b) Account for all viable loads and load combinations (c) Provide a redundant structure that can redistribute loads when one structural element is overloaded (d) Provide ductile elements and connections that can undergo deformations without sudden and catastrophic collapse (e) Provide missile resistant wall and roof elements (f) Anchor mechanical equipment on roofs to resist specified wind and missile loads (g) Minimize or eliminate the potential for windborne missiles 3.3 Evaluation of Existing SSCs The objective of the evaluation process is to determine if an existing SSC meets the performance goals of a particular Performance Category. The key to the evaluation of existing SSCs is to identify potential failure modes and to calculate the wind speed to cause the postulated failure. A critical failure mechanism could be the failure of the main wind-force resisting system of a structure or a breach of the structure envelope that allows release of toxic materials to the environment or results in wind and water damage to the building contents. The structural system of many old facilities (25 to 40 years old) have considerable reserve strength because of conservatism used in the design, which may have included a design to resist abnormal effects. However, the facility could still fail to meet performance goals if breach of the building envelope is not acceptable.

The weakest link in the load path of an SSC generally determines the adequacy or inadequacy of the performance of the SSC under wind load. Thus, evaluation of existing SSCs normally should focus on the strengths of connections and anchorages and the ability of the wind loads to find a continuous path to the foundation or support system. Experience from windstorm damage investigations provides the best guidelines for anticipating the potential performance of existing SSCs under wind loads. Reference 3-13 provides a methodology for estimating the performance of existing SSCs. The approach is directed primarily to structures, but can be adapted to systems and components as well. The methodology described in Reference 3-13 involves two levels of evaluation. Level I is essentially a screening process and should normally be performed before proceeding to Level DOE-STD-1020-2002 3-14 II, which is a detailed evaluation. The Level II process is described below. The steps include: (a) Data collection (b) Analysis of element failures (c) Postulation of failure sequence (d) Comparison of postulated performance with performance goals 3.3.1 Data Collection Construction or fabrication drawings and specifications are needed to make an evaluation of potential performance in high winds. A site visit and walkdown is usually required to verify that the SSCs are built according to plans and specifications. Modifications not shown on the drawings or deteriorations should be noted. Material properties are required for the analyses. Accurate determination of material properties may be the most challenging part of the evaluation process. Median values of material properties should be obtained. This will allow an estimate of the degree of conservatism in the design, if other than median values were used in the original design. 3.3.2 Analysis of Element Failures After determining the as-is condition and the material properties, various element failures of the SSCs are postulated. Nominal strength to just resist the assumed element failure is calculated. Since the nominal strength is at least equal to the controlling load combination, the wind load to cause the postulated failure can be calculated. Knowing the wind load, the wind speed to produce the wind load is determined using the procedures of ASCE 7 and working backwards. Wind speeds to cause all plausible failure modes are calculated and tabulated. The weakest link is determined from the tabulation of element failures. These are then used in the next step to determine the failure sequence. 3.3.3 Postulation of Failure Sequence Failure caused by wind is a progressive process, initiating with an element failure. Examples are failure of a roof to wall connection, inward or outward collapse of an overhead door, window glass broken by flying roof gravel. Once the initial element failure occurs at the lowest calculated wind speed, the next event in the failure sequence can be anticipated. For example, if a door fails, internal pressure inside the building will increase causing larger outward acting pressures on the roof. The higher pressures could then lead to roof uplift creating a hole in the roof itself. With the door opening and roof hole, wind could rapidly circulate through the structure causing collapse of partition walls, damage to ceilings or ventilation systems or transportation of small objects or debris in the form of windborne

DOE-STD-1020-2002 3-15 missiles. Each event in the sequence can be associated with a wind speed. All obvious damage sequences should be examined for progressive failure. 3.3.4 Comparison of Postulated Failures with Performance Goals Once the postulated failure sequences are identified, the SSC performance is compared with the stated performance goals for the specified Performance Category. The general SSC evaluation procedures described in Appendix B(Figure B-2) are followed. If an SSC is able to survive wind speeds associated with the performance goal, the SSC meets the goal. If the performance criteria are not met, then the assumptions and methods of analyses can be modified to eliminate conservatism introduced in the evaluation methods. The acceptable hazard probability levels can be raised slightly, if the SSC comes close to meeting the performance goals. Otherwise, various means of retrofit should be examined. Several options are listed below, but the list is not exhaustive: (a) Add x-bracing or shear walls to obtain additional lateral load resisting capacity (b) Modify connections in steel, timber or pre-stressed concrete construction to permit them to transfer moment, thus increasing lateral load resistance in structural frames (c) Brace a relatively weak structure against a more substantial one (d) Install tension ties that run from roof to foundation to improve roof anchorage (e) Provide x-bracing in the plane of a roof to improve diaphragm stiffness and thus achieve a better distribution of lateral load to rigid frames, braced frames or shear walls. To prevent breach of structure envelope or to reduce the consequences of missile perforation, the following general suggestions are presented: (a) Install additional fasteners to improve cladding anchorage (b) Provide interior barriers around sensitive equipment or rooms containing hazardous materials (c) Eliminate windows or cover them with missile-resistant grills (d) Erect missile resistant barriers in front of doors and windows (e) Replace ordinary overhead doors with heavy-duty ones that will resist the design wind loads and missile impacts. The door tracks must also be able to resist the wind loads. DOE-STD-1020-2002 3-16 Each SSC will likely have special situations that need attention. Personnel who are selected to evaluate existing facilities should be knowledgeable of the behavior of SSCs subjected to extreme winds. 3.4 References 3-1. American Society of Civil Engineers (ASCE), Minimum Design Loads for Buildings and Other Structures, ASCE 7-98, New York, NY, 1998. 3-2. Coats, D.W. and R.C. Murray, Natural Phenomena Hazards Modeling Project: Extreme Wind/Tornado Hazard Models for Department of Energy Sites, UCRL-53526 Rev. 1, Lawrence Livermore National Laboratory, Livermore, California, 1985. 3-3. International Code Council Inc., International Building Code 2000, Falls Church,VA. 3-4. American Institute of Steel Construction, Manual of Steel Construction, Allowable Stress Design (ASD), Ninth Ed., Chicago, Illinois, 1989. 3-5. American Concrete Institute, Building Code Requirements for Reinforced Concrete, ACI 318 99, Farmington Hills, Michigan,1999. 3-6. American Institute of Steel Construction, Manual of Steel Construction, Load & Resistance Factor Design (LRFD), Chicago, Illinois,1998. 3-7. McDonald, J.R., Rationale for Wind-Borne Missile Criteria for DOE Facilities, LLNL,

Livermore, CA, September, 1999 (UCRL-CR-135687) 3-8. Los Alamos National Laboratory, TVENT, Los Alamos, NM, 1979. 3-9. Kuilanoff, G. and Drake, R.M., Design of DOE Facilities for Wind-Generated Missiles, Proceedings of the Third DOE Natural Phenomena Hazards Mitigation Conference, St. Louis, MO, CONF-9110122, Lawrence Livermore National Laboratory, Livermore, CA, 1991. 3-10. Report of the ASCE Committee on Impactive and Impulsive Loads (Volume 5), Appendix C - Aircraft and Automobile Impact, 2nd ASCE Conference on Civil Engineering in Nuclear Power, Knoxville, Tennessee, September 15-17, 1980. 3-11. American Society of Civil Engineers, Structural Analysis and Design of Nuclear Plant Facilities, Manuals and Reports on Engineering Practice - No. 58, 1980. 3-12. McDonald, J.R., Structural Details for Wind Design, Lawrence Livermore National Laboratory, Report UCRL-21131, November 1988. DOE-STD-1020-2002 3-17 3-13. Mehta, K.C., McDonald, J.R., and Smith, D.A., Procedures for Predicting Wind Damage to Buildings, Journal of the Structural Division, ASCE, Vol. 107, No. ST11, 2089-2096,1981. 3-14. Auguste Boissonade, et. al., Development of a Probabilistic Tornado Wind Hazard Model for the Continental United States, July 2000UCRL-ID-140922 Volume I. 3-15. U.S. Department of Energy, Guide for the Mitigation of Natural Phenomena Hazards for DOE Nuclear Facilities and Non-nuclear Facilities, DOE G 420.1-2, March 28, 2000. DOE-STD-1020-2002 3-18 Intentionally Blank DOE-STD-1020-2002 4-1 Chapter 4 Flood Design and Evaluation Criteria 4.1 Flood Design Overview The flood design and evaluation criteria seek to ensure that safety structures, systems and components (SSCs) at DOE sites satisfy the performance goals described in the appendices B and C of this STD. These criteria consider the design of SSCs for regional flood hazards (i.e., river flooding) and local precipitation that effects roof design and site drainage. This chapter describes the flood criteria, presents the design basis flood (DBFL) that must be considered in flood design, presents the criteria for the design of civil engineering systems (e.g., structures, site drainage, roof systems and roof drainage, etc.) and presents alternative design strategies for flood hazards. Guidance is also provided to evaluate existing SSCs that may not be located above the DBFL, to assess whether the performance goals are satisfied. Determination of the DBFL shall be accomplished in accordance with DOE-STD-1023 (Ref. 4-1). Table 4-1 provides the flood criteria for Performance Categories 1 through 4. The criteria are specified in terms of the flood hazard input, hazard annual probability, design requirements, and emergency operation plan requirements. The hazard annual probability levels in Table 4-1 correspond to the mean hazard. Evaluation of the flood design basis for SSCs consists of: 1. determination of the DBFL for each flood hazard as defined by the hazard annual probability of exceedance and applicable combinations of flood hazards, 2. evaluation of the site stormwater management system (e.g., site runoff and drainage, roof drainage), 3. development of a flood design strategy for the DBFL that satisfies the criteria performance goals (e.g., build above the DBFL, harden the facility), and 4. design of civil engineering systems (e.g., buildings, buried structures, site drainage, retaining walls, dike slopes, etc.) to the applicable DBFL and design requirements.

Each of these areas is briefly described in the following subsections. DOE-STD-1020-2002 4-2 Table 4-1 Flood Criteria Summary Performance Category Item 1 2 3 4 Flood Hazard Input Flood insurance stu- dies or equivalent input, including the combinations in Table 4-2 Site probabilistic haz- ard analysis, including the combinations in Table 4-2 Site probabilistic haz- ard analysis, including the combinations in Table 4-2 Site probabilistic haz- ard analysis, including the combinations in Table 4-2 Mean Hazard Annual Probability 2x10-3 5x10-4 1x10-4 1x10-5 Design Requirements Applicable criteria (e.g., governing local regulations, IBC 2000) shall be used for building design for flood loads (i.e., load factors, design allowables), roof design and site drainage. The design of flood mitigation systems (i.e., levees, dams, etc.) shall comply with applicable standards as referred to in these criteria. Emergency Operation Plans Required to evacuate on-site personnel if facility is impacted by the DBFL Required to evacuate on-site personnel and to secure vulnerable areas if site is impacted by the DBFL Required to evacuate on-site personnel not involved in essential operations. Provide for an extended stay for personnel who remain. Procedures must be established to secure the facility during the flood such that operations may continue following the event. 4.1.1 Design Basis Flood (DBFL) As part of the flood hazard assessment1 that is performed for a site, the sources of flooding (e.g., rivers, lakes, local precipitation) and the individual flood hazards (e.g., hydrostatic forces, ice pressure, hydrodynamic loads) are identified. A site or individual SSC may be impacted by multiple sources of flooding and flood hazards. For example, many DOE sites must consider the hazards associated with river flooding. In addition, all sites must design a stormwater management system to handle the runoff due to local (on-site or near site) precipitation. Events that contribute to potential river flooding such as spring snowmelt, upstream-dam failure, etc. must be considered as part of a probabilistic flood hazard analysis. Therefore, at a site there may be multiple DBFLs that are considered. For sites with potential for river flooding a DBFL is determined for river flooding and for local precipitation which determines the design of the site stormwater management systems. (Note, for sites located on rivers or streams, the meteorologic and hydrologic events that produce intense local precipitation are often distinct from those which produce high river flows). In this instance, various aspects of the design for a SSC may be determined by different flood hazards. As a result, the term DBFL is used in a general sense that applies to the multiple flood hazards that may be included in the design basis. 1 Guidelines for conducting a probabilistic flood hazard assessment are contained in (DOE-STD-1023). The analysis includes an evaluation of the hydrologic and hydraulic characteristics of a site and site region. As part of the probabilistic assessment, an evaluation of uncertainty is also performed. DOE-STD-1020-2002 4-3 Table 4-2 Design Basis Flood Events Primary Hazard Case No. Event Combinations* River Flooding 1 Peak flood elevation. Note: The hazard analysis for river flooding should include all contributors to flooding, including releases from upstream dams, ice jams, etc. Flooding associated with upstream-dam failure is included in the dam failure category.

2 Wind-waves corresponding, as a minimum to the 2-year wind acting in the most favorable direction (Ref. 4-2), coincident with the peak flood or as determined in a probabilistic analysis that considers the joint occurrence of river flooding and wind generated waves. 3 Ice forces (Refs. 4-2 and 4-3) and Case 1. 4 Evaluate the potential for erosion, debris, etc. due to the primary hazard. Dam Failure 1 All modes of dam failure must be considered (i.e., overtopping, seismically induced failure, random structural failures, upstream dam failure, etc.) 2 Wind-waves corresponding, as a minimum to the 2-year wind acting in the most favorable direction (Ref. 4-2), coincident with the peak flood or as determined in a probabilistic analysis that considers the joint occurrence of river flooding and wind generated waves. 3 Evaluate the potential for erosion, debris, etc. due to the primary hazard. Local Precipitation 1 Flooding based on the site runoff analysis shall be used to evaluate the site drainage system and flood loads on individual facilities. 2 Ponding on roof to a maximum depth corresponding to the level of the secondary drainage system. 3 Rain and snow, as specified in applicable regulations. Storm Surge, Seiche (due to hurricane, seiche, squall lines, etc.) 1 Tide effects corresponding to the mean high tide above the MLW** level (if not included in the hazard analysis). 2 Wave action and Case 1. Wave action should include static and dynamic effects and potential for erosion (Ref. 4-2). Levee or Dike Failure 1 Should be evaluated as part of the hazard analysis if overtopping and/or failure occurs. Snow 1 Snow and drift roof loads as specified in applicable regulations. Tsunami 1 Tide effects corresponding to the mean high tide above the MLW** level (if not included in the hazard analysis). * Events are added to the flood level produced by the primary hazard. ** MLW-Mean Low Water. The DBFL for a SSC for a flood hazard (e.g., river flooding, local precipitation) is defined in terms of: 1. Peak-hazard level (e.g., flow rate, depth of water) corresponding to the mean, hazard annual exceedance probability (see Table 4-1), including the DOE-STD-1020-2002 4-4 combination of flood hazards (e.g., river flooding and wind-wave action) given in Table 4-2, and 2. Corresponding loads associated with the DBFL peak-hazard level and applicable load combinations (e.g., hydrostatic and/or hydrodynamic forces, debris loads). The first item is determined as part of the probabilistic flood hazard assessment. Limited flood hazard assessments for some DOE sites have been conducted (see Refs. 4-4, 4-5, and 4-6). Flood loads are assessed for the DBFL on a SSC-by-SSC basis. Table 4-2 defines the flood design basis events that must be considered. The events listed in Table 4-2 should be considered as part of the site flood hazard assessment. For example, if a river is a source of flooding, wind waves must be considered. The DBFL is determined by entering the flood hazard curve which includes the combination of events in Table 4-2. For example, at a site located on an ocean shore, the flood hazard curve should include the effects of storm surge, tides and wind-waves. If the hazard annual probability for a primary flood hazard is less than the design basis hazard annual probability for a given Performance Category (see Table 4-1), it need not be considered as a design basis event. For instance, if the hazard annual probability for Performance Category 1 is 2x10-3 per year, failure of an upstream dam need not be considered if it is demonstrated that the mean probability of flooding due to dam failure is less than 2x10-3.

4.1.2 Flood Evaluation Process The following describes the steps involved in the evaluation of SSCs. The procedure is general and applies to new and existing construction. It is oriented toward the evaluation of individual SSCs. However, due to the nature of flood events (i.e., river flooding may inundate a large part of a site and thus many SSCs simultaneously), it may be possible to perform an evaluation for the entire site or a group of SSCs. The flood evaluation process is illustrated in Figure 4-1. It is divided into the consideration of regional flood hazards and local precipitation. For new construction, design practice (see Section 4.1.3) is to construct the SSC above the DBFL, thus avoiding the flood hazard and eliminating the consideration of flood loads as part of the design. The design of the site stormwater management system and structural systems (i.e., roofs) for local precipitation must be adequate to prevent flooding that may damage a SSC or interrupt operations to the extent that the performance goals are not satisfied. DOE-STD-1020-2002 4-5 Figure 4-1 Flood Evaluation Process To perform the flood evaluation for a SSC, the results of a flood screening analysis (as a minimum) or a probabilistic flood hazard analysis should be available (Refs 4-4 to 4-6). The steps in the flood evaluation process include: 1. Determine the SSC Performance Category (see Chapter 2 and DOE-STD- 1021). Evaluation for Regional Flood Hazards 2. Determine the DBFL for each type or source of flooding (see Tables 4-1 and 4-2). The assessment of flood loads (e.g., hydrostatic and DOE-STD-1020-2002 4-6 hydrodynamic loads) or other effects (e.g., scour, erosion) is made on a SSC-by-SSC basis. 3. For new construction locate the SSC above the DBFL, if possible. If this cannot be done, proceed to Step 4. 4. Develop a design strategy to mitigate flood hazards that impact the SSC. Options include hardening the SSC, modifying the flood path, and developing emergency operation plans to provide for occupant safety and to secure vulnerable areas. The flood hazard must be mitigated such that the performance goals are met. 5. If the SSC is located below the DBFL level (even if the SSC has been hardened), emergency procedures must be provided to evacuate personnel and to secure the SSC prior to the arrival of the flood (see Step 10). Evaluation for Local Precipitation 6. Develop an initial site-drainage system and roof-system drainage plan and structural design per applicable regulations. Typical stormwater management systems are designed for not less than the 25-year, 6-hour storm. The minimum storm sewer size is typically 12 inches and the minimum culvert size 15 inches. For roof drain systems, the minimum pipe size for laterals and collectors are typically 4 inches. Stormwater management systems usually have sufficient capacity to ensure that runoff from the 100 year, 6 hour design storm will not exceed a depth of 0.87 feet at any point within the street right-of-way or extend more than 0.2 feet above the top of the curb in urban streets. 7. Perform a hydrological analysis for the site to evaluate the performance of the site stormwater management system (considering roof drainage and man-made and natural watercourses) for the DBFL local precipitation for each SSC. The site analysis must determine the level of flooding (if any) at each SSC. Guidelines for performing a hydrological analysis are contained in DOE-STD-1023 and DOE-STD-1022.

For SSCs where flooding occurs, the engineer must assess whether the performance goals are satisfied. If the SSC performance is unsatisfactory, a modification of the site stormwater management system is required (see Step 9). Due to the different Performance Category DBFLs, this step may be performed for a number of flood events. 8. Evaluate the drainage and structural design of roof systems for the DBFL local precipitation. The structural design of the roof system must satisfy design criteria for loads due to ponding that result from clogged/blocked DOE-STD-1020-2002 4-7 drains and snow and ice loads. These were either developed during the design of existing facilities or will be those from applicable regulations. If the design criteria for the roof is exceeded (i.e., deflection, stress allowables), the design must be revised (see Step 9). 9. If the DBFL for a SSC due to local precipitation produces levels of flooding such that the performance goals (i.e., damage level due to inundation or exceedance of design criteria allowables), are not satisfied, design modifications must be developed. The design modifications must provide additional capacity (i.e., runoff capacity, additional strength) to satisfy the performance goals. Alternative design strategies are discussed in Section 4.1.3. 10. For SSCs that are impacted by the DBFL, emergency operation plans must be developed to provide for the safety of personnel and to secure critical areas to satisfy performance goals. In principle, each SSC is designed in accordance with the requirements for the applicable Performance Category. However, because floods have a common-cause impact on SSCs that are in proximity to one another, the design basis for the most critical SSC may govern the design for other SSCs or for the entire site. Stated differently, it may be more realistic economically and functionally to develop a design strategy that satisfies the performance goals of the most critical SSC and simultaneously that of other SSCs. For example, it may be feasible to harden a site (e.g., construct a levee system), thus protecting all SSCs. Conversely, it may be impractical to develop a design strategy that protects the entire site when SSC locations vary substantially (i.e., they are at significantly different elevations or there are large spatial separations). The possible structural or functional interaction between SSCs should be considered as part of the evaluation process. For example, if an SSC in Performance Category 4 requires emergency electric power in order to satisfy the performance goals, structures that house emergency generators and fuel should be designed to the DBFL for the Performance Category 4 SSC. In general, a systematic review of a site for possible structural or functional dependencies is required. As an aid to the review, the analyst can develop a logic model that displays the functional/structural dependencies between SSCs. 4.1.3 Flood Design Strategies The basic design strategy for SSCs in Performance Categories 2 to 4 (excluding local precipitation), is to construct the SSC above the DBFL. When this can be done, flood hazards are not considered in the design basis except that possible raised ground water level must be considered. The flood criteria have been established with this basic strategy in mind. Note that local precipitation is an exception since all sites must consider this hazard in the design of the site stormwater management system, roof systems, etc.

DOE-STD-1020-2002 4-8 Since it may not always be possible to construct a new SSC above the DBFL level, alternate design strategies must be considered. The following lists the hierarchy of flood design strategies: 1. Situate the SSC above the DBFL level, 2. Modify the flood, or 3. Harden the site or SSC to mitigate the effects of the DBFL such that the performance goals are satisfied, and 4. Establish emergency operation plans to safely evacuate employees and secure areas with hazardous, mission-dependent, or valuable materials. If an SSC is situated above the DBFL, the performance goals are readily satisfied. If an SSC is located below the DBFL, alternatives can be considered to modify the magnitude of the flood or mitigate its effects such that the likelihood of damage and interruption of operations is acceptably low (i.e., performance goals are satisfied). In addition, emergency operation plans must be developed that establish the procedures to be followed to recognize/identify the flood hazard in a timely manner and provide for occupant safety and secure areas that may be vulnerable to the effects of flooding. The implementation of emergency operation plans is not, in general, an alternative to satisfy the performance goals. While they are necessary to provide for occupant safety, generally they do not adequately limit the level of damage and interruption to facility operations. Under certain circumstances the flood can be modified to limit the magnitude of the hazard. Alternatives include the construction of detention ponds that provide for the collection and controlled release of runoff on-site, modification of stream channels, etc. The strategy of hardening a SSC or site and providing emergency operation plans is secondary to siting facilities above the DBFL level because some probability of damage does exist and SSC operations may be interrupted. If it is determined that a SSC may be impacted by the DBFL and thus must be hardened, the designer must determine the flood loads associated with the DBFL. The design of flood mitigation systems (i.e., exterior walls, flood-proof doors, etc.) must be conducted in accordance with the requirements specified in applicable regulations. The evaluation of the site stormwater management system and roof design (i.e., drainage and structural capacity) differs somewhat from that for other flood hazards. First, all sites must be designed for the effects of local precipitation. Secondly, from the perspective of the performance goals, the adequacy of the site stormwater management system is measured in terms of the impact of local flooding on SSCs at the site. For example, the initial design of the site stormwater management system may correspond to the 25-year rainfall 6-hour storm. If the DBFL for a SSC corresponds to a 5x10-4 rainfall, the site stormwater management system design clearly does not meet this criterion. However, at this point the only conclusion that can be reached is that the system (i.e., storm sewers, etc.) will be filled to capacity. The actual impact of the DBFL precipitation on the SSC is assessed by conducting a hydrologic evaluation for the site that accounts for natural and man-made watercourses on site, roof drainage, etc. The analysis may conclude that flooding is limited to streets and parking lots. If temporary flooding DOE-STD-1020-2002 4-9

in these areas does not significantly affect the operation and safety of the SSC, then it may be concluded that the design of the site-drainage system (i.e., for the 25-year rainfall) is adequate. Conversely, if flooding does result in significant damage which impairs the operation or safety of SSCs, appropriate measures must be taken to satisfy the performance goals. This may include increasing the capacity of the drainage system, constructing detention ponds on site, or hardening an SSC against the effects of flooding caused by local precipitation. 4.2 Flood Design Criteria Unlike design strategies for seismic and wind hazards, it is not always possible to provide margin in the flood design of a SSC. For example, the simple fact that a site is inundated (even if structural damage does not occur), will cause significant disruption (e.g., down time during the flood, clean-up). This is often unacceptable in terms of the economic impact and disruption of the mission-dependent function of the site. Under these circumstances, there is no margin, as used in the structural sense that can be provided when a site or SSC is inundated. Therefore, the SSC must be kept dry and operations must not be interrupted in order to satisfy the performance goals. Since a risk reduction cannot, in general, be specified, the hazard annual probability is set to the performance goal probability of damage with the exception of Performance Category 1. For Performance Category 1, a risk reduction corresponding to a factor of 2 is defined. This risk reduction is based on the limited warning time that is required to evacuate personnel from an area that may be flooded (Ref. 4-7). The DBFL for Performance Category 1 can generally be estimated from available flood hazard assessment studies. These include: the results of flood-screening studies, flood-insurance analyses, or other comparable evaluations. For this Performance Category it is not necessary that a detailed site-probabilistic hazard evaluation be performed, if the results of other recent studies are available and, if uncertainty in the hazard estimate is accounted for. For Performance Categories 2 through 4, a comprehensive site-specific flood hazard assessment should be performed, unless the results of a screening analysis (see References 4-4 and 4-5) demonstrates that the performance goals are satisfied. 4.2.1 Performance Category 1 The performance goal for Performance Category 1 specifies that occupant safety be maintained and that the probability of severe structural damage be less than or about 10-3 per year. The mean hazard annual probability of exceedance is 2x10-3. In addition, event combinations that must be considered are listed in Table 4-2. To meet the performance goal for this category, two requirements must be met: (1) the building structural system must be capable of withstanding the forces associated with the DBFL, and (2) adequate time for warning must be available to ensure that building occupants can be evacuated (i.e., 1 to 2 hours, Ref. 4-7). If the building is located above the DBFL, then structural and occupant safety requirements are met. DOE-STD-1020-2002 4-10 Where a structure cannot be constructed above the DBFL level, an acceptable design can be achieved by: 1. Modifying the flood or providing flood protection for the site or for the specific structure, such that severe structural damage does not occur, and 2. Developing emergency procedures in order to provide adequate warning

and evacuation capability to provide for the safety of building occupants. For structural loads applied to roofs, exterior walls, etc., the applicable regulations should be used. 4.2.2 Performance Category 2 The performance goal for Performance Category 2 is to limit damage and interruption of operations while also maintaining occupant safety. The DBFL is equal to the flood whose annual probability of exceedance is 5x10-4 per year including the event combinations listed in Table 4-2. For purposes of establishing the DBFL for Performance Category 2, a site-specific hazard assessment should be performed. This analysis must include the uncertainty in the hazard assessment in order to obtain an accurate estimate of the mean-annual probability level. SSCs in this category should be located above the DBFL. For SSCs that cannot be located above the DBFL, an acceptable design can be achieved by the same measures described for Performance Category 1. Emergency operation plans must be developed to provide for occupant safety and to mitigate the damage to mission-dependent SSCs. These procedures may include installation of temporary flood barriers, removal of equipment to protected areas, anchoring vulnerable items, or installing sumps or emergency pumps. As in the case of SSCs in Performance Category 1, applicable regulations should be used to incorporate flood loads in the building design. 4.2.3 Performance Category 3 The performance goal for Performance Category 3 is continued function of the facility, including confinement of hazardous materials and occupant safety. SSCs in this category should be located above flood levels whose mean-annual probability of exceedance is 10-4, including the event combinations shown in Table 4-2. If SSCs in this category cannot be constructed above the DBFL level, a design must be developed that provides continued facility operation. The strategy must mitigate the flood (i.e., modifying the flood, hardening the facility, building a levee to prevent flood encroachment) to an extent that facility operations can continue. A higher level of protection is required for SSCs in Performance Category 3 as compared to Categories 1 and 2. Limited damage and interruption DOE-STD-1020-2002 4-11 of operations may be acceptable for Performance Categories 1 and 2, however, for Performance Category 3 the DBFL must be mitigated such that the flood does not impact operations. The design of Performance Category 3 SSCs that may be impacted by the DBFL should be based on the loads (i.e., hydrostatic forces) and other hazards (i.e., ice forces, debris) that occur. The design requirements in applicable regulations should be used to incorporate flood loads in the design. If mitigation systems such as watertight doors, sealants, etc. are used, manufacturer specifications should be applied. Section 4.3 describes design requirements for flood-mitigation systems such as levees, dikes, etc. For SSCs that may be impacted by the DBFL, emergency operation plans must be developed to evacuate personnel not involved in the emergency operation of the facility, secure hazardous materials, prepare the facility for possible extreme flooding and loss of power, and provide supplies for personnel who may have an extended stay on-site. Emergency procedures should be coordinated with the results of the flood hazard analysis, which provides input on the time variation of flooding, type of hazards to be expected and their duration. The use of emergency operation plans is not an alternative to hardening a facility to provide adequate confinement unless all hazardous materials can be completely removed from the site.

4.2.4 Performance Category 4 The performance goals for Performance Category 4 are basically the same as for Performance Category 3. However, a higher confidence is required that the performance goals are met. SSCs in this category should be located above flood levels whose mean-annual probability of exceedance is 10-5, including the combinations of events listed in Table 4-2. 4.3 Flood Design Practice for SSCs Below the DBFL Elevation For SSCs located below the DBFL level, mitigation measures can be designed that provide an acceptable margin of safety. In practice, a combination of structural and non- structural measures (i.e., flood warning and emergency operation plans) are used. The design criteria for facilities that must consider flood loads are described for SSCs located below the DBFL level, in this section. 4.3.1 Flood Loads To evaluate the effects of flood hazards, corresponding forces on structures must be evaluated. Force evaluations must consider hydrostatic and hydrodynamic effects, including the impact associated with wave action. In addition, the potential for erosion and scour and debris loads must be considered. The flood hazards that must be considered are determined in the flood hazard analysis. Good engineering practice should be used to evaluate flood loads (Refs. 4-8 to 4-12) including the forces due to ice formation on bodies of water. DOE-STD-1020-2002 4-12 4.3.2 Design Requirements Design criteria (i.e., for allowable stress or strength design, load factors, and load combinations) for loads on exterior walls or roofs due to rain, snow, and ice accumulation should follow applicable regulations. The design criteria are to be used in conjunction with flood loads and effects derived from the SSCs DBFL (see Tables 4-1 and 4-2). 4.3.2.1 Performance Categories 1 and 2 Facilities that are subject to flood loads should be designed according to provisions in applicable regulations. Design loads and load combinations are determined from the DBFL. Load factors specified in applicable regulations shall be used. 4.3.2.2 Performance Categories 3 and 4 The exterior wall of buildings and related structures that are directly impacted by flood hazards should be constructed of reinforced concrete and designed according to current versions of ACI 349 (Ref. 4-13). Design loads and load combinations are determined from the DBFL. Load factors specified in applicable regulations shall be used. 4.3.3 Site Drainage and Roof Design For new construction the stormwater-management system (i.e., street drainage, storm sewers, open channels, roof drainage) can be designed according to applicable procedures and design criteria specified applicable regulations. Applicable local regulations must be considered in the design of the site stormwater management system. The minimum design level for the stormwater management system is the 25-year, 6-hour storm. Once the site and facility drainage design has been developed, it should be evaluated for the DBFL precipitation for each SSC. The evaluation should consider the site-drainage area, natural and man-made watercourses, roof drainage, etc. The analysis shall determine the level of flooding that could occur at each SSC. The analyst may choose to evaluate the site stormwater management system for the highest category DBFL (as a limiting case). If the results of this analysis demonstrate that flooding does not compromise the site SSCs, then it may be concluded that the site stormwater management system is adequate. Note, that local flooding in streets, parking lots, etc. may occur due to the DBFL precipitation. This is acceptable if the effect of local flooding does not exceed the requirements of the performance goals. If however, flooding does have an unacceptable impact, increased drainage capacity and/or flood protection will be required.

Building roof design should provide adequate drainage in accordance with applicable regulations. Secondary drainage (overflow) should be provided at a higher level and have a capacity at least that of the primary drain. Limitations of water depth on a roof are specified by Ref. 4-15 or other applicable local regulations. The roof should be designed to consider the DOE-STD-1020-2002 4-13 maximum depth of water that could accumulate if the primary-drainage system is blocked (Refs. 4-1, 4-14, and 4-15). Roof-drainage systems should be designed according to applicable regulations. The drainage system should be verified as part of the site analysis for the DBFL (discussed above). In the case of rainfall, a limiting check of the roof system structural design should be made. Ponding on the roof is assumed to occur to a maximum depth corresponding to the level of the secondary drainage outlet system (i.e., assuming the primary system has clogged). As part of this evaluation, the deflection of the roof due to ponding must be considered. The design of the roof should be adequate to meet the applicable codes. Design criteria for snow and rain-snow loads are defined in the model building codes and standards. The DOE criteria specify the importance factors that should be used to scale snow loads in the design. In the design of roof systems for snow loads, the importance factor for Performance Categories 1 and 2 is 1.0. For Performance Categories 3 and 4 an importance factor of 1.2 should be used. 4.3.4 Flood Protection and Emergency Operations Plans For SSCs that may be exposed to flood hazards (i.e., are located below the DBFL), a number of design alternatives are available. Depending on the flood hazards that an SSC must withstand, various hardening systems may be considered. These include, 1. structural barriers (e.g., exterior building walls, floodwalls, watertight doors), 2. wet or dry flood proofing (e.g., waterproofing exterior walls, watertight doors), 3. levees, dikes, seawalls, revetments, and 4. diversion dams and retention basins. The design of structural systems (i.e., exterior building walls) shall be developed in accordance with applicable regulations. Waterproofing requirements are also given in applicable design standards. Guidelines for the design of earth structures such as levees, seawalls, etc. are provided in References 4-8, 4-16, and 4-17. Guidance for the design of diversion dams and retention basins can be found in U.S. Army Corps of Engineers, U.S. Bureau of Reclamation, Soil Conservation Service reference documents (Refs. 4-12 and 4-16). Emergency operation plans are required in cases where the health and safety of on-site personnel must be provided for and where the facility must be secured to prevent damage or interruption of operations. The elements of an emergency operation plan are: • flood recognition system - capability to identify impending floods and predicting their timing and magnitude. • warning system - procedures and means to provide warning to those in the affected areas. DOE-STD-1020-2002 4-14 • preparedness plan - establish the procedures, responsibility and capability (i.e., materials, transportation, etc.) to evacuate on-site personnel, secure vulnerable areas, etc. • maintenance plan - program to insure that the emergency operation plan is up-to-date and operational.

Guidance for the development of the emergency operation plans can be found in emergency procedures developed for nuclear power plants, dams and local flood warning systems. The development of the emergency operation plan should be coordinated with the results of the flood hazard assessment and local agencies responsible for flood forecasting. The availability of warning time will vary depending on the type of flood hazard and local forecasting capabilities. Specific information on flood emergency procedures can be found in Reference 4-18. 4.4 Considerations for Existing Construction Existing SSCs may not be situated above the DBFL as defined by these criteria. In this case, an SSC should be reviewed to determine the level of flooding, if any, that can be sustained, without exceeding the performance goal requirements. This is referred to as the Critical Flood Elevation (CFE). If the CFE is higher than the DBFL, then the performance goals are satisfied. This situation may not be unique for existing construction. For new construction, it may not be possible to situate all facilities above the DBFL, in which case other design strategies must be considered. For example, it may be possible to wet proof an SSC, thus allowing some level of flooding to occur. For each SSC, there is a critical elevation, which if exceeded, causes damage or disruption such that the performance goal is not satisfied. The CFE may be located: • below grade due to the structural vulnerability of exterior walls or instability due to uplift pressures, • at the elevation of utilities that support SSCs, or • at the actual base elevation of an SSC. Typically, the first floor-elevation or a below-grade elevation (i.e., foundation level) is assumed to be the critical elevation. However, based on a review of an SSC, it may be determined that greater flood depths must occur to cause damage (e.g., critical equipment or materials may be located above the first floor). If the CFE for an SSC exceeds the DBFL, then the performance goal is satisfied. If the CFE does not exceed the DBFL, options must be considered to harden the SSC, change the Performance Category, etc. For Performance Categories 3 and 4, the performance goals require that little or no interruption of the facility operations should occur. This is an important consideration, since the assessment of the CFE must consider the impact of the flood on operations (i.e, uninterrupted access) as well as the damage to the physical systems. DOE-STD-1020-2002 4-15 4.5 Probabilistic Flood Risk Assessment In some cases the need may arise for DOE or the site manager to perform a quantitative probabilistic flood risk assessment for a site. There may be a variety of reasons to require a risk assessment. These include: 1. Demonstration that the performance goals are satisfied. 2. Evaluation of alternative design strategies to meet the performance goals. 3. Detailed consideration of conditions at a site that may be complex, such as varying hydraulic loads (e.g., scour, high velocity flows), system interactions, secondary failures, or a potential for extraordinary health consequences. 4. A building is not reasonably incorporated in one of the four Performance Categories. The objective of a risk assessment is to evaluate the risk of damage to SSCs important for maintaining safety and site operations. Risk calculations can be performed to evaluate the likelihood of damage to on-site facilities and public-health consequence. Procedures to perform probabilistic flood risk assessments are discussed in References 4-19 to 4-22.

4.6 References 4-1. U.S. Department of Energy, Natural Phenomena Hazards Assessment Criteria, DOE- STD-1023-95, Washington, D.C. 4-2. 4-2. American Nuclear Society, Determining Design Basis Flooding at Power Reactor Sites, ANSI/ANS - 2.8-1981, La Grange Park, Illinois, 1992. 4-3. American Society of Civil Engineers, Design for Ice Forces, Technical Council on Cold Regions Engineering, New York, 1983. 4-4. McCann, M.W. Jr., Boissonnade, A.C., Preliminary Flood Hazard Estimates for Screening Department of Energy Sites: Albuquerque Operations Office, UCRL-21045, Lawrence Livermore National Laboratory, Livermore, California, 1988. 4-5. Savy, J.B. and R.C. Murray, Natural Phenomena Hazards Modeling Project: Flood Hazard Models for Department of Energy Sites, UCRL-53851, Lawrence Livermore National Laboratory, Livermore, California, 1988. DOE-STD-1020-2002 4-16 4-6. McCann, M.W. Jr., Boissonnade, A.C., Probabilistic Flood Hazard Assessment for the N-Reactor, Hanford, Washington, UCRL-21069, Lawrence Livermore National Laboratory, Livermore, California, 1988. 4-7. U.S. Department of the Interior, Guidelines to Decision Analysis, ACER Technical Memorandum No. 7, Bureau of Reclamation, Denver, Colorado, 1986. 4-8. U.S. Army Corps of Engineers, Shore Protection Manual, U.S. Army Coastal Engineering Research Center, Waterways Experiment Station, Vicksburg, Mississippi, 1983. 4-9. Merritt, F. S. (ed.), Standard Handbook for Civil Engineering, McGraw-Hill Company, 1968. 4-10. Streeter, V. L., Fluid Mechanics, McGraw-Hill Book Company, 1971. 4-11. Linsley, R. K. and J. B. Franzini, Water-Resources Engineering, McGraw-Hill Book Company, New York, 1964. 4-12. U.S. Department of Agriculture, National Engineering Manual, Soil Conservation Service, 1980. 4-13. American Concrete Institute, Code Requirements for Nuclear Safety-Related Concrete Structures (ACI 349-97) and Commentary - ACI 349R-97, Detroit, Michigan. 4-14. Uniform Building code, International Conference of Building Officials, Whittier, California, 1997. 4-15. Minimum Design Loads for Buildings and Other Structures, ASCE 7-98, American Society of Civil Engineers (ASCE), New York, NY, 1998. 4-16. Design of Small Dams, U.S. Bureau of Reclamation, Department of the Interior, Washington, D.C., 1977. 4-17. U. S. Army Corps of Engineers, Design and Construction of Levees, EM 110-2-1913, Department of the Army, Office of the Chief of Engineers, Washington, D.C., 1978. 4-18. Federal Energy Regulatory Commission, Engineering Guidelines for the Evaluation of Hydropower Projects, Office of Hydropower Licensing, Washington, D.C., 1986. 4-19. Brookhaven National Laboratory, Probabilistic Safety Analysis Procedures Guide, prepared for U.S. Nuclear Regulatory Commission, NUREG/CR-2815, BNL/NUREG- 51559 Rev., Vols. 1 and 2, 1985. 4-20. American Nuclear Society and Institute of Electrical and Electronic Engineers, PRA Procedures Guide, prepared for U.S. Nuclear Regulatory Commission, NUREG/CR- 2300, January 1983. DOE-STD-1020-2002 4-17 4-21. McCann, Jr., M. W., An Introduction to Flood Probabilistic Risk Assessment Methodology, Proceedings, Department of Energy Natural Phenomena Hazards Mitigation Conference, Las Vegas, Nevada, October 1985. 4-22. Wagner, D. D., J. J. Rooney and J. B. Fussell, A Flood Analysis of the Surry Power Station Unit 1, Auxiliary Feedwater System, JBF Associates, JBFA-109-80, 1980.

4-23. International Code Council, Inc, International Building Code 2000, Falls Church, VA. 2000. 4-24. U.S. Department of Energy, Guide for the Mitigation of Natural Phenomena Hazard for DOE Nuclear Facilities and Non-nuclear Facilities, DOE G 420.1-2, March 28, 2000. DOE-STD-1020-2002 4-18 Intentionally Blank DOE-STD-1020-2002 A-1 ( ) ( )EP p T e n n n T= − − = − − ≈ − −1 1 1 1 1 1/ / Appendix A Terminology and Definitions Note: - Definitions common to DOE O 420.1, the accompanying Guide, this Standard, and other NPH Standards are contained in the NPH Guide. Annual Probability of Exceedance - The likelihood of natural phenomena hazards must be evaluated on a probabilistic basis for this performance goal based NPH criteria. The frequency of occurrence of parameters describing the external hazard severity (such as earthquake ground acceleration, wind speed, or depth of inundation) is estimated by probabilistic methods. Common frequency statistics employed for rare events such as natural phenomena hazards include return period and annual probability of exceedance. Return period is the average time between consecutive events of the same or greater severity (for example, earthquakes with maximum ground acceleration of 0.2g or greater). It must be emphasized that the return period is only an average duration between events and should not be construed as the actual time between occurrences, which would be highly variable. A given event of return period, T, is equally likely to occur any year, thus the probability of that event being exceeded in any one year is 1/T. The annual probability of exceedance, p, of an event is the reciprocal of the return period of that event (i.e., p = 1/T). As an example, consider a site at which the return period for an earthquake of 0.2g or greater is 1000 years. In this case, the annual probability of exceedance of 0.2g is 10-3 or 0.1 percent. It is of interest in the design of facilities to define the probability that an event will be exceeded during the design life of the facilities. For an event with return period, T, and annual probability of exceedance, p, the exceedance probability, EP, over design life, n, is given by: (A-1) Where EP and p vary from 0 to 1, and n and T are expressed in years. As an example, the exceedance probabilities over a design life of 50 years of a given event with various annual probabilities of exceedance are as follows: p EP over 50 years 10-3 0.05 10-4 0.005 10-5 0.0005 DOE-STD-1020-2002 A-2 Hence, an event with a 10-3 annual probability of exceedance (1000 year return period) has a 5 percent chance of being exceeded in a 50-year period, while an event with a 10-4 annual probability of accedence has only a 0.5 percent chance of being exceeded during a 50-year period. Performance Goal is the annual probability of exceedance of acceptable behavior limits used as a target to develop NPH design and evaluation criteria. Goals for structure, system, component (SSC) performance during natural phenomena hazards have been selected and expressed in terms of annual probability of exceedance. Numerical values of annual probabilities of exceedance for performance goals depend on SSC characteristics. For example, probability values specified for normal use SSCs are consistent with performance obtained through the use for model building code provisions for natural phenomena hazards. Probability values specified for hazardous use SSCs approach performance obtained through the use of nuclear power plant NPH criteria. Acceptable behavior limits considered in the performance goals also depend on the SSC characteristics. For example, the acceptable behavior limits for normal use SSCs is major damage but limited in extent to below that at which occupants are endangered. However, the acceptable behavior limits for hazardous use SSCs is lesser damage such that the facility can perform its function.

Performance goal probability values apply to each natural phenomena hazard (NPH) individually. Hence, the annual probability of exceedance of acceptable behavior limits for all NPH would be somewhat larger than the performance goal value if structures, systems, and components are designed exactly to the criteria in this document for all NPH. Natural Phenomena Hazard Curves - The likelihood of earthquake, wind, and flood hazards at DOE sites can be defined by graphical relationships between ground acceleration, wind speed, or water elevation and annual probability of exceedance. These relationships are termed seismic, wind or flood hazard curves. The earthquake or wind loads or the flood levels used for the design or evaluation of DOE facilities are based on hazard parameters from these curves at selected annual probabilities of exceedance as illustrated in Figure A-1. There is considerable uncertainty in natural phenomena hazard curves which is not indicated by the single curve shown in Figure A-1. The means of accounting for this uncertainty is discussed in the different chapters on individual natural phenomena hazards. NNSA - National Nuclear Security Administration. DOE-STD-1020-2002 A-3 Figure A-1 Example Probabilistic Natural Phenomena Hazard Curve DOE-STD-1020-2002 A-4 Intentionally Blank DOE-STD-1020-2002 B-1 Appendix B Commentary on General NPH Design and Evaluation Criteria B.1 NPH Design and Evaluation Philosophy The natural phenomena hazard (NPH) design and evaluation criteria presented in this document (DOE-STD-1020) implement the requirements of DOE Order 420.1, "Facility Safety" (Ref. B-1) and the associated Guides: "Guide for the Mitigation of Natural Phenomena Hazards for DOE Nuclear Facilities and Non-nuclear Facilities" (Ref. B-2), "Guide for Nonreactor Nuclear Safety Design Criteria and Explosives Safety Criteria" (Ref. B-3), and "Implementation Guide for Use with DOE Orders 420.1 and 440.1 Fire Safety Program" (Ref. B-4) which are intended to assure acceptable performace of DOE facilities in the event of earthquake, wind/tornado, and flood hazards. As discussed in Chapter 1, performance is measured by target performance goals expressed as an annual probability of exceedance of acceptable behavior limits (i.e., behavior limits beyond which damage/failure is unacceptable). DOE O 420.1 and the associated Guides establishes a graded approach for NPH requirements by defining performance categories (numbered 0 through 4) each with a qualitative performance goal for behavior (i.e., maintain structural integrity, maintain ability to function, maintain confinement of hazardous materials) and a qualitative target probabilistic performance goal. DOE-STD-1020 provides four sets of NPH design and evaluation criteria (explicit criteria are not needed for Performance Category 0). These criteria range from those provided by model building codes for Performance Category 1 to those approaching nuclear power plant criteria for Performance Category 4.

DOE-STD-1020 employs the graded approach by following the philosophy of probabilistic performance goal-based design and evaluation criteria for natural phenomena hazards. Target performance goals range from low probability of NPH-induced damage/failure to very high confidence of extremely low probability of NPH-induced damage/failure. In this manner, structures, systems, and components (SSCs) are governed by NPH criteria which are appropriate for the potential impact on safety, mission, and cost of those SSCs. For example, a much higher likelihood of damage would be acceptable for an unoccupied storage building of low value than for a high-occupancy facility or a facility containing hazardous materials. SSCs containing hazardous materials which, in the event of damage, threaten public safety or the environment, and/or which have been determined to require special consideration, should have a very low probability of damage due to natural phenomena hazards (i.e., much lower probability of damage than would exist from the use of model building code design and evaluation procedures). For ordinary SSCs of relatively low cost, there is typically no need or requirement to add conservatism to the design beyond that of model building codes. For these SSCs, it is also typically not cost-effective to strengthen structures more than required by model building codes that consider extreme loads due to natural phenomena hazards. Performance goals correspond to probabilities of structure or equipment damage due to natural phenomena hazards; they do not extend to consequences beyond structure or equipment damage. The annual probability of exceedance of SSC damage as a result of natural phenomena DOE-STD-1020-2002 B-2 hazards (i.e., performance goal) is a combined function of the annual probability of exceedance of the event, factors of safety introduced by the design/evaluation procedures, and other sources of conservatism. These criteria specify hazard annual probabilities of exceedance, response evaluation methods, and permissible behavior criteria for each natural phenomena hazard and for each performance category such that desired performance goals are achieved for either design or evaluation. The ratio of the hazard annual probability of exceedance and the performance goal annual probability of exceedance is called the risk reduction ratio, RR. This ratio establishes the level of conservatism to be employed in the design or evaluation process. For example, if the performance goal and hazard annual probabilities are the same (RR = 1), the design or evaluation approach should introduce no conservatism. However, if conservative design or evaluation approaches are employed, the hazard annual probability of exceedance can be larger (i.e., more frequent) than the performance goal annual probability (RR > 1). In the criteria presented herein, the hazard probability and the conservatism in the design/evaluation method are not the same for earthquake, wind, and flood hazards. However, the accumulated effect of each step in the design/evaluation process is to aim at the performance goal probability values which are applicable to each natural phenomena hazard separately.

Design and evaluation criteria are presented in Chapters 2, 3, and 4 for earthquake, wind, and flood hazards, respectively. These criteria are deterministic procedures that establish SSC loadings from probabilistic natural phenomena hazard curves; specify acceptable methods for evaluating SSC response to these loadings; provide acceptance criteria to judge whether computed SSC response is acceptable; and to provide detailing requirements such that behavior is as expected as illustrated in Figure B-1. These criteria are intended to apply for design of new facilities and for evaluation of existing facilities. In addition, the criteria are intended to cover buildings, equipment, distribution systems (piping, HVAC, electrical raceways, etc.), and other structures. DOE-STD-1020 primarily covers (1) methods of establishing load levels on SSCs from natural phenomena hazards and (2) methods of evaluating the behavior of structures and equipment to these load levels. These items are very important, and they are, typically, emphasized in design and evaluation criteria. However, there are other aspects of facility design that are equally important and that should be considered. These aspects include quality assurance considerations and attention to design details. Quality assurance requires peer review of design drawings and calculations; inspection of construction; and testing of material strengths, weld quality, etc. The peer reviewers should be qualified personnel who were not involved in the original design. Important design details include measures to assure ductile behavior and to provide redundant load paths, as well as proper anchorage of equipment and nonstructural building features. Although quality assurance and design details are not discussed in this report to the same extent as NPH load levels and NPH response evaluation and acceptance criteria, the importance of these parts of the design/evaluation process should not be underestimated. Quality assurance and peer review are briefly addressed in Section 1.4, in addition to discussions in the individual chapters on each natural phenomena hazard. Design detailing for earthquake and wind hazards is covered by separate manuals. Reference B-5 describes earthquake design DOE-STD-1020-2002 B-3 considerations including detailing for ductility. Reference B-6 gives structural details for wind design. Figure B-1 DOE-STD-1020 Combines Probabilistic and DeterminsticMethods to Achieve Performance Goals B.2 Graded Approach, Performance Goals, and Performance Categories As stated above, DOE O 420.1 and the associated Guide establishes a graded approach in which NPH requirements are provided for various performance categories each with a specified performance goal. The motivation for the graded approach is that it enables design or evaluation of DOE structures, systems, and components to be performed in a manner consistent with their importance to safety, importance to mission, and cost. There are only a few "reactor" facilities in the DOE complex and many facilities with a wide variety of risk potential, mission, and cost. Also, the graded approach enables cost-benefit studies and establishment of priorities for existing facilities. There are few new designs planned for the DOE complex and the evaluation of existing facilities requires cost benefit considerations and prioritizing upgrading and retrofit efforts. Finally, the graded approach is common practice by model building codes such as the Uniform Building Code (Ref. B-7), IBC-2000 (Ref. B-19) Department of Defense

DOE-STD-1020-2002 B-4 earthquake provisions (Ref. B-8), and even by the Nuclear Regulatory Commission which provides graded criteria from power plants to other licensed nuclear facilities. The motivation for the use of probabilistic performance goals by the NPH Guide for DOE O 420.1 and DOE-STD-1020 is to accomplish the graded approach using a quantified approach consistent with the variety of DOE facilities as well as meeting the risk-based DOE safety policy. Furthermore, the use of probabilistic performance goals enables the development of consistent criteria both for all natural phenomena hazards (i.e., earthquakes, winds, and floods) and for all DOE facilities which are located throughout the United States. The use of performance goal based criteria is becoming common practice as: it is embedded in recent versions of the Uniform Building Code, International Building Code and in the DOD seismic provisions for essential buildings; it has been used for DOE new production reactor NPH criteria; and it has been utilized in recent Nuclear Regulatory Commission applications such as for the advanced light water reactor program and for revisions to commercial reactor geological siting criteria in 10CFR100, Appendix A. Five performance categories are specified in the Guide for DOE O 420.1for design/evaluation of DOE structures, systems, and components for natural phenomena hazards ranging from 0 through 4. Table B-1 presents both the qualitative and quantitative descriptions of the performance goals for each performance category. Both the qualitative description of acceptable NPH performance and the quantitative probability value for each performance category are equally significant in establishing these NPH design and evaluation criteria within a graded approach. SSCs are to be placed in categories in accordance with DOE G 420.1-2 and DOE-STD-1021-93 (Ref. B-9). Additional guidance on performance categorization is available in Reference B-10. For Quantitative values of performance goals for PC-1 and PC-2, further elaboration is provided in Appendix C. As mentioned previously, the quantitative performance goal probability values are applicable to each natural phenomena hazard (earthquake, wind, and flood) individually. The earthquake and flood design and evaluation criteria presented in this document are aimed at meeting the target performance goals given in Table B-1. The extreme wind and tornado design and evaluation criteria presented in this document are conservative compared to earthquake and flood criteria in that they are aimed at lower probability levels than the target performance goals in Table B-1. It is estimated that for extreme winds, the probabilities of exceeding acceptable behavior limits are less than one order of magnitude smaller than the performance goals in Table B-1. For tornado criteria, the probabilities of exceeding acceptable behavior limits are greater than one but less than two orders of magnitude smaller than the performance goals for Performance Categories 3 and 4. This additional conservatism in wind and tornado criteria for design and evaluation of DOE facilities is consistent with common practice in government and private industry. Furthermore, this additional conservatism can be accommodated in the design of SSCs without significantly increasing costs. SSCs in Performance Categories 3 and 4 should be designed for tornadoes at certain sites around the country where tornado occurrences are high. The tornado hazard probability must be set lower than necessary to meet the performance goals in order for tornadoes rather than straight winds or hurricanes to control the design criteria.

DOE-STD-1020-2002 B-5 Table B-1 Structure, System, or Component (SSC) NPH Performance Goals for Various Performance Categories Performance Category Performance Goal Description NPH Performance Goal Annual Probability of Exceeding Acceptable Behavior Limits, PF 0 No Safety, Mission, or Cost Considerations No requirements 1 Maintain Occupant Safety 10-3 of the onset of SSC(1) damage to the extent that occupants are endangered 2 Occupant Safety, Continued Operation with Minimum Interruption 5x10-4 of SSC damage to the extent that the component cannot perform its function 3 Occupant Safety, Continued Operation, Hazard Confinement 10-4 of SSC damage to the extent that the component cannot perform its function 4 Occupant Safety, Continued Operation, Confidence of Hazard Confinement 10-5 of SSC damage to the extent that the component cannot perform its function (1) These performance goals are for each natural phenomena hazard (earthquake, wind, and flood). For seismic performance goals for PC-1 and PC-2, refer to Appendix C. (2) SSC refers to structure, system, or component (equipment). The design and evaluation criteria for SSCs in Performance Categories 0, 1, and 2 are similar to those given in model building codes. Performance Category 0 recognizes that for certain lightweight equipment items, furniture, etc., and for other special circumstances where there is little or no potential impact on safety, mission, or cost, design or evaluation for natural phenomena hazards may not be needed. Assignment of an SSC to Performance Category 0 is intended to be consistent with, and not take exception to, model building code NPH provisions. Performance Category 1 criteria include no extra conservatism against natural phenomena hazards beyond that in model building codes that include earthquake, wind, and flood considerations. Performance Category 2 criteria are intended to maintain the capacity to function and to keep the SSC operational in the event of natural phenomena hazard