DOE-STD-1153-2019, A Graded Approach for Evaluating Radiation Doses to Aquatic and Terrestrial Biota

DOE-STD-1153-2019 DOE STANDARD A GRADED APPROACH FOR EVALUATING RADIATION DOSES TO AQUATIC AND TERRESTRIAL BIOTA U.S. Department of Energy AREA ENVIR Washington, DC 20585 DISTRIBUTION STATEMENT A. Approved for public release; distribution is unlimited. NOT MEASUREMENT SENSITIVE DOE-STD-1153-2019 i Foreword Department of Energy (DOE) activities may expose plants and animals to radioactive materials in environmental media or to radioactive materials released in waste streams. This technical standard provides methods, models and guidance within a graded approach that DOE personnel and contractors may use to characterize radiation doses to aquatic and terrestrial biota that are exposed to radioactive materials. DOE Order 414.1D, Quality Assurance, defines the process for establishing a quality assurance program and employing a graded approach to be used to implement this standard. DOE elements may use a graded approach to implement the biota dose evaluations and associated guidance contained in this technical standard to address requirements for radiological protection of the environment contained in DOE Orders, specifically DOE Order 458.1, Radiation Protection of the Public and the Environment. The graded approach presented in this standard is also intended for use the RESRAD-BIOTA code. The RESRAD-BIOTA dose evaluation code was specifically designed to complement the graded approach and the Biota Concentration Guides (BCGs) contained herein. These methods (and the BCGs contained in them) are not intended to be used as design criteria, indicators of the severity of accidental releases of radioactive material, or guides for mitigating the consequences of accidental releases. Furthermore, this technical standard does not apply to the irradiation of biota for experimental purposes nor to research or experimental studies. This Standard uses the word “shall” to denote a requirement of this Standard; the word “should” denote a recommendation of this Standard; and, the word “may” denote permission, but not a requirement or a recommendation of this Standard. To satisfy this Standard, program participants need to meet all applicable “shall” statements. DOE technical standards, such as this Standard, do not establish requirements. However, all or part of the provisions in a DOE standard can become requirements under the following circumstances: a. They are explicitly stated as such in DOE requirements document; or b. The organization makes a commitment to meet the standard in a contract or in an implementation plan or program plan required by a DOE requirements document. Acknowledgements DOE-STD-1153-2002, A Graded Approach for Evaluating Radiation Doses to Aquatic and Terrestrial Biota, was developed by the Department’s Air, Water and Radiation Division and a Core Team of the Biota Dose Assessment Committee (BDAC). The BDAC was a technical standards topical committee organized under the DOE Technical Standards Program. The BDAC was convened to assist in developing and promoting technical standards and associated guidance for DOE-wide applications in assessing radiation dose to biota; to serve as a major forum within DOE for obtaining technical assistance, discussing technical issues and sharing lessons learned regarding biota dose standards and assessment methods; and to serve as a technical resource and advisory group for DOE program and field elements in the design and review of site-specific biota dose assessments.

The current technical standard is a revision to DOE-STD-1153 and was prepared by the Office of Public Radiation Protection (AU-22) and a team of DOE subject matter experts. In this revision, the document DOE-STD-1153-2019 ii has been made more user friendly, duplicate material has been deleted, and more realistic examples have been added to assist the user in preparation of compliance documents. The team consisted of Katharine McLellan, AU-22; Michael W. McNaughton, Los Alamos National Laboratory (LANL); G. Timothy Jannik, Savannah River National Laboratory; Jeffrey J. Whicker, LANL; Ronald W. Warren, Nevada National Security Site; Patricia Scofield, Oak Ridge National Laboratory; Jessica Gillis, LANL; Elizabeth Ruedig, LANL and Charley Yu, Argonne National Laboratory (ANL). We are grateful to them for their contributions. DOE-STD-1153-2019 iii INTENTIONALLY BLANK DOE-STD-1153-2019 iv Table of Contents Definitions ..................................................................................................................................................... 1 Acronyms and Abbreviations ........................................................................................................................ 8 References .................................................................................................................................................. 10 1. Introduction ........................................................................................................................................ 17 1.1 Purpose ....................................................................................................................................... 17 1.2 Background ................................................................................................................................. 18 1.2.1 Interest and Need for Biota Dose Evaluation Methods ...................................................... 18 1.2.2 Basis for Biota Dose Rate Criteria Applied in this Technical Standard ................................ 20 1.2.3 Protection of Populations ................................................................................................... 21 1.3 The Biota Dose Methodology ..................................................................................................... 22 2 Overview and Implementation of the DOE Graded Approach ........................................................... 23 2.1 Key Features of the Graded Approach ........................................................................................ 24 2.2 Principal and Alternative Uses of the Graded Approach ............................................................ 25 2.3 Relationship of the Graded Approach to Ecological Risk Assessment ........................................ 25 2.4 Step-By-Step Implementation of the Graded Approach ............................................................. 26 2.5 Parameter Values that Can Be Modified in the Graded Approach ............................................. 29 3 Application Considerations ................................................................................................................. 31 3.1 Evaluating Doses to Individual Organisms (see Appendix A) ...................................................... 33 3.1.1 Threatened and Endangered Species ................................................................................. 33

3.1.2 Commercially and Culturally Valued Species ...................................................................... 33 3.2 Evaluating Doses to Aquatic Plants ............................................................................................. 34 3.3 Background and Reference Areas ............................................................................................... 34 3.4 Frequency of Conducting Evaluations ........................................................................................ 35 4 Data Assembly Phase .......................................................................................................................... 36 4.1 Step 1: Consider the Sources, Receptors, and Routes of Exposure ............................................ 36 4.1.1 Radiation Sources................................................................................................................ 36 4.1.2 Receptors ............................................................................................................................ 37 4.1.3 Routes of Exposure ............................................................................................................. 38 4.2 Step 2: Define Your Area of Evaluation ....................................................................................... 38 4.3 Step 3: Assemble and Organize Data on Radionuclide Concentrations in Environmental Media .................................................................................................................................................... 39 4.3.1 Aquatic System Considerations........................................................................................... 39 4.3.2 Terrestrial System Considerations ...................................................................................... 40 4.3.3 Aquatic and Terrestrial Tissue Data .................................................................................... 40 DOE-STD-1153-2019 v 4.3.4 Field Instruments ................................................................................................................ 40 5 General Screening Phase .................................................................................................................... 41 5.1 Compare Data on Radionuclide Concentrations in Environmental Media with Generic BCGs .. 41 5.1.1 Aquatic System Considerations........................................................................................... 42 5.1.2 Terrestrial System Considerations ...................................................................................... 42 5.2 Dealing with High Background Levels of Naturally Occurring Radionuclides ............................. 43 6 Analysis Phase ..................................................................................................................................... 44 6.1 Site-Specific Screening (RESRAD-BIOTA Level 2 evaluation)....................................................... 44 6.1.1 Step 1: Assess Representativeness of Input Data on Radionuclide Concentrations in Environmental Media and Delineation of Evaluation Area ................................................ 44 6.1.2 Step 2: Re-Run the Screening Evaluation Using Revised Radionuclide Concentration Data and/or Evaluation Area ...................................................................................................... 46

6.1.3 Step 3: Assess Representativeness of Default Parameters/Assumptions for Generic BCGs; Select Site-Specific Parameters and Generate Site-Specific BCGs ..................................... 47 6.1.4 Step 4: Re-Run Screening Evaluation and Compare Data on Radionuclide Concentrations in Environmental Media with Newly-Generated Site-Specific BCGs .................................. 48 6.2 Site-Specific Analysis (RESRAD-BIOTA Level 3 evaluation) ......................................................... 49 6.2.1 Step 1: Assess Representativeness of Default Parameters/Assumptions for Kinetic/Allometric Models; Select Site-Specific Parameters and Generate Site-Specific BCGs .................................................................................................................................... 49 6.2.2 Step 2: Re-Run the RESRAD-BIOTA and Compare Data on Radionuclide Concentrations in Environmental Media with Newly-Generated Site-Specific BCGs ...................................... 52 6.3 Site-Specific Biota Dose Assessment (RESRAD-BIOTA Level 3 evaluation) ................................. 52 6.3.1 Determine if Additional Analysis is Warranted ................................................................... 52 6.3.2 Recommended Approaches to Designing and Conducting the Site-Specific Dose Assessment ......................................................................................................................... 53 7 Documenting Your Biota Dose Evaluation Results ............................................................................. 55 Appendix A. Evaluating Dose to Individual Organisms: Guidance on the Applicability of the Graded Approach 1 A.1. Considerations on the Meaning of "Individual" Organism ....................................................... A-1 A.2. Applicability of Methods and Models in the DOE Graded Approach to Evaluations of Individual Populations of Organisms ......................................................................................................... A-1 A.3. Applicability of Biota Dose Rate Criteria to Protection of Individual Organisms ...................... A-1 A.4. Use of the DOE Graded Approach for Evaluating Dose to Individual Organisms: Application Considerations .......................................................................................................................... A-2 A.5. Consideration of Deterministic vs. Stochastic Effects............................................................... A-2 Appendix B: Relative Biological Effectiveness (RBE) .............................................................................. B-1 B.1. Summary of Guidance ................................................................................................................ B-1 DOE-STD-1153-2019 vi B.2. Statement of Issue ..................................................................................................................... B-1 B.3. Background on Radiation Weighting Factor .............................................................................. B-2 B.4. Data on Deterministic RBEs for High-LET Radiations ................................................................. B-2 Appendix C: Guidance for Defining the Evaluation Area, Temporal and Spatial Averaging, and Estimating Mean Values .................................................................................................................... C-1

C.1. Area Factors: Defining the Evaluation Area ............................................................................... C-1 C.1.1. Determine whether this method is necessary ................................................................... C-2 C.1.2. Determine and map the boundaries of the contaminated areas ...................................... C-2 C.1.3. Determine the receptors ................................................................................................... C-2 C.1.4. Example receptors that could serve as good indicators of radiological impact ................ C-3 C.1.5. Determine and map the boundaries of discrete habitat types ......................................... C-3 C.1.6. Overlay the maps and identify the intersections ............................................................... C-4 C.2. Temporal Averaging Regarding Application of Biota Dose Rate Criteria and Mean Radionuclide Concentrations .......................................................................................................................... C-6 C.2.1. Use of Time Averaging in Applying Dose Rate Criteria for Aquatic and Terrestrial Biota . C-6 C.2.2. Guidance on Time Averaging in Applying Daily Dose Rate Criteria ................................... C-6 C.2.3. Rationale for Guidance on Time Averaging ....................................................................... C-7 C.3. Spatial Averaging Regarding Application of Biota Dose Rate Criteria and Mean Radionuclide Concentrations .......................................................................................................................... C-8 C.4. Guidance on Estimating Mean Values ....................................................................................... C-9 Appendix D: Kd Factors ......................................................................................................................... D-1 Appendix E: Dose Conversion Factors ................................................................................................... E-1 E.1. Introduction ............................................................................................................................... E-1 E.2. External DCFs ............................................................................................................................. E-1 E.2.1. Approach to Calculating External DCFs .............................................................................. E-1 E.3. Internal DCFs .............................................................................................................................. E-8 E.3.1. Approach to Calculating Internal DCFs .............................................................................. E-8 E.3.2. Screening-Level Internal DCFs ............................................................................................ E-9 E.4. Reference Comparison ............................................................................................................... E-9 Appendix F: Bioaccumulation Factors ................................................................................................... F-1 F.1. Estimating Internal Tissue Concentrations for Use in Dose Equations: The Bioaccumulation Factor ......................................................................................................................................... F-1

F.2. Default Bioaccumulation Factors,Bivs ........................................................................................ F-2 F.3. Site-specific Bioaccumulation Factors,Bivs ................................................................................ F-3 F.3.1. Potassium-40 ...................................................................................................................... F-8 F.3.2. Cesium-137 ........................................................................................................................ F-9 DOE-STD-1153-2019 vii F.3.3. Strontium-90 .................................................................................................................... F-10 F.3.4. Radium ............................................................................................................................. F-10 F.3.5. Uranium ........................................................................................................................... F-12 Appendix G: Biota Concentration Guides (BCGs) in Water, Sediment, and Soil ................................... G-1 G.1. Selection of Target Radionuclides ............................................................................................. G-1 G.2. Overview of the Technical Approach for Deriving the BCGs .................................................... G-3 G.3. Selection of the Most Limiting BCGs for Use in General Screening .......................................... G-4 G.4. Equations and Models for Aquatic Systems ............................................................................. G-5 G.4.1. Aquatic Animals ................................................................................................................ G-5 G.4.2. Riparian Animals ............................................................................................................... G-7 G.4.3. Important Considerations When Implementing Equations and Models in an Aquatic System Evaluation ............................................................................................................ G-8 G.5. Equations and Models for Terrestrial Systems ......................................................................... G-9 G.5.1. Terrestrial Plants ............................................................................................................... G-9 G.5.2. Terrestrial Animals .......................................................................................................... G-10 G.6. Alternatives to Bivs for Riparian and Terrestrial Animals: The Kinetic/Allometric Method ... G-12 G.6.1. A Scaling Approach to Predicting Tissue Concentrations ............................................... G-13 G.6.2. Application of the Kinetic/Allometric Method in the Derivation of BCGs for Riparian Animals ........................................................................................................................... G-17 G.6.3. Application of the Kinetic/Allometric Method in the Derivation of BCGs for Terrestrial Animals ........................................................................................................................... G-18 G.7. Selection of Bivs for Riparian and Terrestrial Animals ............................................................ G-19 G.8. Coefficients Used in the Kinetic/Allometric Method .............................................................. G-26

Appendix H: Exposure Parameters Considered in the Graded Approach ............................................. H-1 H.1. Introduction .............................................................................................................................. H-1 H.2. Default Parameters ................................................................................................................... H-1 H.3. Adjustments to Defaults using the Graded Approach .............................................................. H-4 H.4. Considerations for Aquatic Plants ............................................................................................. H-5 H.5. Air Pathway Dose ...................................................................................................................... H-5 H.5.1. Rationale for the Active Air Pathway as a Minor Source of Exposure .............................. H-5 H.5.2. Behavior of Radionuclides Discharged to the Atmosphere .............................................. H-6 H.5.3. Exposure Pathways Resulting from Atmospheric Releases .............................................. H-6 H.5.4. Compliance with Human Radiation Dose Limits at DOE Sites Relative to Biota Dose CriteriaCriteria: A Perspective .......................................................................................... H-6 H.5.5. Derivation of Biota Concentration Guides for Active Air Releases ................................... H-7 H.5.6. Summary ........................................................................................................................... H-8 DOE-STD-1153-2019 viii H.6. Direct Measurement of Radiation Fields .................................................................................. H-8 H.6.1. Considerations for Evaluating Doses to Biota around Accelerators or other Sources of Direct Radiation ................................................................................................................ H-8 Appendix I: Example Applications of Graded Approach ........................................................................ I-1 I.1. Aquatic System Cases (Levels 1-3) .............................................................................................. I-1 I.1.1. Data Assembly (Phase 1 of the Graded Approach) ............................................................. I-1 I.1.2. CASE 1: Use of Maximum Measured Radionuclide Concentrations for the Entire Poplar Springs Site ......................................................................................................................... I-3 I.1.3. CASE 2: Evaluation of Several Evaluation Areas Using Maximum Measured Radionuclide Concentration Data ............................................................................................................ I-6 I.2. Terrestrial System Cases (Levels 1-3) ........................................................................................ I-12 I.2.1. Data assembly ................................................................................................................... I-14 I.2.2. General Screening: Level 1 Screen .................................................................................... I-14 I.2.3. Site-Specific Screening: Level 2 Screen ............................................................................. I-15 DOE-STD-1153-2019 ix List of Figures

Figure 1-1 Comparison of DOE biota dose rate criteria with international recommendations for DCRL bands from ICRP (2014) ........................................................................................................................ 21 Figure 1-2 Approximate Acute Lethal Dose Ranges for Various Taxonomic Groups (Whicker and Schulz 1982; UNSCEAR 1996.) ......................................................................................................................... 22 Figure 2-1 Overview of the DOE Graded Approach for Evaluating Radiation Doses to Aquatic and Terrestrial Biota .................................................................................................................................... 23 Figure 2-2 Flowchart illustrating step-by-step guidance for progressing through the DOE graded approach ............................................................................................................................................... 29 Figure C-1 Hypothetical maps of contaminated areas and discrete habitat used to determine appropriately scaled assessment areas. Shading indicates contaminated areas. The cross-hatching indicates habitat types. Three cases are considered: (a) a single contaminated ............................... C-5 Figure C-2 A hypothetical map of multiple areas with the same contamination intersecting multiple patches of the same discrete habitat type used to determine appropriately scaled assessment areas. ............................................................................................................................................................. C-5 Figure F-1 Process for Selecting Default Biv Values for Use in the General Screening Phase of the Graded Approach ............................................................................................................................................. F-2 Figure G-1 Selection of Biota Concentration Guides (BCGs) for Use in Aquatic and Terrestrial System Evaluations ......................................................................................................................................... G-5 Figure H-1 Exposure Pathways for Aquatic Animals ................................................................................. H-2 Figure H-2 Exposure Pathways for Riparian Animals ................................................................................ H-3 Figure H-3 Exposure Pathways for Terrestrial Plants................................................................................ H-3 Figure H-4 Exposure Pathways for Terrestrial Animals............................................................................. H-4 DOE-STD-1153-2019 x List of Tables Table 1-1 Absorbed dose to Aquatic and Riparian Animals and Terrestrial Plants and Animals from exposure to radiation or radioactive materials to the aquatic or terrestrial environment……………………..17 Table 2-1 Summary of DOE's Three-Step Process for Evaluating Radiation Doses to Aquatic and Terrestrial Biota .................................................................................................................................... 24 Table 2-2 Summary of parameter values that can, with technical justification, be modified corresponding to each phase of the graded approach ................................................................................................ 30 Table 3-1 Applications matrix summarizing intended and potential uses of the DOE graded approach ... 31

Table 4-1 General considerations for defining radiation sources ............................................................... 37 Table 4-2 General considerations for defining routes of exposure ............................................................ 38 Table C-1 Examples of representative organisms that could serve as indicators of radiological impact .. C-3 Table D-1 Part 1 of Dose Factors and Common Parameters Spreadsheet ............................................... D-1 Table D-2 Most Probable Kd values for use in calculating BCGs for sediment or water for an aquatic system evaluation in the absence of co-located water and sediment data ...................................... D-3 Table E-1 Screening-Level External Dose Conversion Factors ................................................................... E-5 Table E-2 Screening Level Internal Dose Conversion Factors .................................................................... E-9 Table F-1 Aquatic Animal Biota Concentration Guide Spreadsheet .......................................................... F-4 Table F-2 Default bioaccumulation factors (Bivs for aquatic animals) ....................................................... F-5 Table F-3 Default bioaccumulation factors (Bivs) for Terrestrial Plants..................................................... F-6 Table F-4 Site-Specific Biv Values ............................................................................................................... F-8 Table G-1 General Dose Equation and Approach Used to Derive BCGs ................................................... G-1 Table G-2 Biota Concentration Guides (BCGs) for Water and Sediment for Use in Aquatic System Evaluations. For use with radionuclide concentrations from co-located water and sediment. ........ G-2 Table G-3 RESRAD-BIOTA Concentration Guides (BCGs) for Water and Soil for Use in Terrestrial System Evaluations. ........................................................................................................................................ G-3 Table G-4 Parameters Used in Kinetic/Allometric Method Uncertainty Analysis for Riparian and Terrestrial Animals ........................................................................................................................... G-21 Table G-5 A Comparison of Bivs Determined by Uncertainty Analysis on the Kinetic/Allometric Method, Product Approach, and Empirical Data (Literature Values): Riparian Animal to Sediment ............. G-22 Table G-6. A Comparison of Bivs Determined by Uncertainty Analysis on the Kinetic/Allometric Method, Product Approach, and Empirical Data (Literature Values): Riparian Animal to Water .................. G-23 Table G-7 A Comparison of Bivs Determined by Uncertainty Analysis on the Kinetic/Allometric Method, Product Approach, and Empirical Data (Literature Values): Terrestrial Animal to Soil ................... G-24 Table G-8 A Comparison of Bivs Determined by Uncertainty Analysis on the Kinetic/Allometric Method, Product Approach, and Empirical Data (Literature Values): Terrestrial Animal to Water ............... G-25 Table G-9 Source of Default f1 Values Used for Riparian and Terrestrial Animals ................................. G-26 DOE-STD-1153-2019 xi Table G-10 Source of Data Used in Estimating Biological Half-Times for Riparian and Terrestrial Animals (see Equation 37) .............................................................................................................................. G-28

Table G-11 Factors Used in Assessing the Relative Contribution to Internal Dose from Animal Inhalation versus Ingestion ................................................................................................................................ G-30 Table G-12 Allometric Equations and Parameter Values Used in Estimating Intake of Riparian Animal Organisms ......................................................................................................................................... G-32 Table G-13 Allometric Equations and Parameter Values used in Estimating Intake of Terrestrial Animal Organisms ......................................................................................................................................... G-33 Table H-1 Assumptions regarding sources, receptors, and routes of exposure applied in the general screening phase of the graded approach ........................................................................................... H-1 Table H-2 Reference organism geometries .............................................................................................. H-5 Table I-1 Surface water sampling locations for the Poplar Springs Site ..................................................... I-1 Table I-2 Measured radionuclide concentrations (pCi/L) in surface water collected from the Poplar Springs Site ........................................................................................................................................... I-2 Table I-3 Aquatic System Evaluation: General screening results for Poplar Springs Site using maximum measured radionuclide concentrations in surface water across the entire site .................................. I-3 Table I-4 Aquatic System Evaluation: Site-specific screening results using mean radionuclide concentrations in surface water for each evaluation area .................................................................. I-5 Table I-5 Aquatic System Evaluation: General screening results for Poplar Springs Site using maximum measured radionuclide concentrations in surface water .................................................................... I-6 Table I-6. Aquatic System Evaluation: Site-specific screening results for the Poplar Springs Site using mean radionuclide concentrations in surface water ........................................................................... I-7 Table I-7 Review of radionuclide concentration data and limiting organism type to determine path forward in the biota dose evaluation ................................................................................................... I-8 Table I-8 Default Biv Values used to derive generic water BCGs for riparian animals .............................. I-9 Table I-9 Review of default parameter values for possible modification using site-representative valueI-9 Table I-10 Site-specific bioaccumulation information for Cesium-137 .................................................... I-10 Table I-11 Site-specific bioaccumulation information for Strontium-90 .................................................. I-11 Table I-12 A Working Example of the Graded Approach for Evaluating Radiation Doses ........................ I-13 Table I-13 Results of the Level 1 Screen (using maximum concentrations) of dose evaluation areas (DEAs) on the NNSS ........................................................................................................................................ I-15

Table I-14 Results of the Level 2 Screen (using average concentrations) of dose evaluation areas (DEAs) on the NNSS ........................................................................................................................................ I-16 DOE-STD-1153-2019 1 Definitions As defined and used in this technical standard: Absorbed Dose (D) is the average energy imparted to matter by ionizing radiation per unit mass of irradiated material at the place of interest in that material. More specifically, for any radiation type and any medium, absorbed dose (D) is the total energy (e) absorbed per unit mass (m) of material: D = e/m. The absorbed dose is expressed in units of rad (gray), where 1 rad = 0.01 joule/kg material (1 gray = 100 rad). For the purposes of this technical standard, the absorbed dose in an organism is assumed to be the average value over the whole organism. Allometric refers to the relative growth of a part in relation to the entire organism. Alpha Particle is a helium-4 nucleus consisting of two protons and two neutrons, given off by the decay of many heavy elements, including uranium and plutonium. Because the particles are slow moving as well as heavy, a sheet of paper can block alpha radiation. However, once an alpha emitter is in living tissue, it can cause substantial damage because of the high ionization density along its path. Aquatic Biota is plant or animal life living in or on water. Area Factor is the correction factor for exposure and residence time for the selected organism for finite area of contamination. Arithmetic Mean is the most commonly used measure of central tendency, commonly called the “average.” Mathematically, it is the sum of all the values of a set divided by the number of values in the set: 𝑋̅ = ∑ 𝑋𝑖 𝑛 𝑖=1 𝑛 Assessment Endpoint is an explicit expression of the environmental value that is to be protected, operationally defined by an ecological entity and its attributes. For example, salmon are valued ecological entities; reproduction and age class structure are some of their important attributes. Together "salmon reproduction and age class structure" form an assessment endpoint. Average - See “Arithmetic Mean.” Beta Particle is an electron. It has a short range in air. Beta particles are moderately penetrating and can cause skin burns from external exposure, but can be blocked by a sheet of plywood. Bias is a consistent underestimation or overestimation of the true values representing a population. Bioaccumulation is the equilibrium ratio of the contaminant concentration in the fresh weight of biota relative to the contaminant concentration in an environmental medium resulting from the uptake of the contaminant from one or more routes of exposure. This ratio is typically described through a bioaccumulation factor (Biv). In technical literature, this ratio may also be called “concentration ratio (CR)” or “wet-weight concentration ratio (Bivs)”. This ratio is considered (and sometimes called) a DOE-STD-1153-2019 2 “lumped parameter” because it simplifies various complex ecological, physical, and chemical transfer pathways into a single, empirically derived parameter. Biomagnification is the tendency of some contaminants to accumulate to higher concentrations at higher levels in the food web through dietary accumulation. Biota is plant and animal life of a particular region. Biota Concentration Guide (BCG) is the limiting concentration of a radionuclide in soil, sediment, or

water that would not cause dose rate criteria for protection of populations of aquatic and terrestrial biota (as used in this technical standard) to be exceeded. Carnivore is a flesh-eating animal. Chronic refers to an extended continuous exposure to a stressor or the effects resulting from such an exposure. Community is an assemblage of populations of different species within a specified location in space and time. Concentration Ratio: See Bioaccumulation above. In International Commission on Radiological Protection (ICRP) 114 (ICRP 2012), the concentration ratio (CR) is defined as: 𝐶𝑅 = ⌈Activity concentration in biota whole body ( Bq kg whole weight)⌉ Activity concentration in soil ( Bq kg ) , sediment ( Bq kg ) , or filtered water ( Bq L ) Conceptual Model is a written description and visual representation of predicted relationships between ecological entities and the stressors to which they may be exposed. Data Quality Objectives (DQOs) are qualitative and quantitative statements that clarify technical and quality objectives for a study, define the appropriate type of data, and specify tolerable levels of uncertainty that a data user is willing to accept in the decision. DQOs specify the problem to be solved, the decision, decision inputs, boundaries of the study, the decision rule, and the limits of uncertainty. Deterministic Effects are those for which the severity is a function of dose, and for which a threshold usually exists. Discharge Point is a conduit through which any radioactively contaminated gas, water, or solid is discharged to the atmosphere, waters, or soils. Distribution Coefficient is the ratio of the mass of solute species absorbed or precipitated on the soil or sediment to the solute concentration in the water. This ratio is typically described through a 𝐾𝑑 factor. Ecological Relevance is one of three criteria for assessment endpoint selection. Ecologically relevant endpoints reflect important characteristics of the system and are functionally related to other endpoints. DOE-STD-1153-2019 3 Ecological Risk Assessment is the process that evaluates the likelihood that adverse ecological effects may occur or are occurring as a result of exposure to one or more stressors. Effluent is any treated or untreated air emission or liquid discharge, including storm water runoff. Effluent Monitoring is the collection and analysis of samples or measurements of liquid, gaseous, or airborne effluents for the purpose of characterizing and quantifying contaminant levels and process stream characteristics, assessing radiation exposures to members of the public and the environment, and demonstrating compliance with applicable standards. Environmental Medium is a discrete portion of the total environment, animate or inanimate, that may be sampled or measured directly. Environmental Surveillance is the collection and analysis of samples of air, water, soil, foodstuffs, biota, and other media and the measurement of external radiation and radioactive materials for purposes of demonstrating compliance with applicable standards, assessing radiation exposures to members of the public, and assessing effects, if any, on the local environment. Error is the difference between an observed or measured value and its true value. Evaluation Area is the area over which a specific dose evaluation is defined. This is the area of overlap between a contaminated area and the exposed biotic population(s).

Exposure is the co-occurrence or contact between the endpoint organism and the stressor (e.g., radiation or radionuclides). Facility means a building, structure, or installation subject to the regulations/standards pertinent to this technical standard. Forb is an herb other than grass. Fresh Weight is the weight or mass of a biota sample that includes the water in a fresh or living specimen. It may also be called "fresh mass" or "wet weight" and it may be reported with units such as "grams-wet" or "g-wet". Gamma Rays are high-energy, electromagnetic photons that are highly penetrating; several inches of lead or several feet of concrete are necessary to shield against them. Geometric Mean is mathematically expressed as the nth root of the product of all values in a set of n values: 𝑋̅𝑔 = [∏𝑋𝑖 𝑛 𝑖=1 ] 1 𝑛 or as the antilogarithm of the arithmetic mean of the logarithms of all the values of a set of n values: DOE-STD-1153-2019 4 𝑋̅𝑔 = antilog ⌈ ∑ log (𝑋𝑖) 𝑛 𝑖=1 𝑛 ⌉ The geometric mean is generally used when the logarithms of a set of values are normally distributed, as is the case for much of the monitoring and surveillance data. Geometric Standard Deviation is mathematically expressed as the antilog of the standard deviation of the logarithms of the measurements: 𝑆𝑔 = antilog [ ∑[ log(𝑋𝑖) − ∑ log(𝑋𝑖) 𝑛 𝑖=1 𝑛 𝑛 − 1 ] 𝑛 𝑖=1 2 ] 1 2 𝑋𝑖 ≠ 0 Grab Sample is a single sample acquired over a short interval of time. Herbivore is a plant-eating animal. Isotopes are nuclides with the same atomic numbers. Lentic refers to living in or relating to still waters (as lakes, ponds, or swamps). Lotic refers to living in or relating to actively moving water (as streams or rivers). Lumped parameter – See Bioaccumulation above. In the previous Biota Standard, the term “lumped parameter” was used to describe a single simplifying factor that is used in the model to represent various complex ecological, physical, and chemical pathways and mechanisms such as the bioaccumulation factor and distribution coefficient. Median is the middle value of a set of data when the data are ranked in increasing or decreasing order. If there is an even number of values in the set, the median is the arithmetic average of the two middle values; if the number of values is odd, it is the middle value. Mode refers to the value occurring most frequently in a data set. Monitoring is the use of instruments, systems, or special techniques to measure liquid, gaseous, solid, and/or airborne effluents and contaminants. Nuclide refers to an atomic species characterized by specific constitution of its nucleus, e.g., by its number of protons, its number of neutrons and its nuclear energy state. Phylogenetic refers to the evolution of a genetically related group of organisms as distinguished from the development of the individual organism. Poikilothermic refers to a cold-blooded organism. Population is an aggregate of individuals of a species within a specified location in space and time. Proportional Sample is a sample consisting of a known fraction of the original stream. DOE-STD-1153-2019 5 Quality Assurance (QA) refers to those planned and systematic actions necessary to provide adequate confidence that a measurement represents the sampled population. Quality assurance includes quality control (QC), which comprises all those actions necessary to control and verify the features and characteristics of a material, process, product, or service to specified requirements.

Quality Control (QC) refers to those actions necessary to control and verify the features and characteristics of a material, process, product, service, or activity to specified requirements. The aim of quality control is to provide quality that is satisfactory, adequate, dependable, and economical. Rad is a unit of absorbed dose of ionizing radiation defined as 100 rad is equal to 1 Gy. The Gray is the SI unit of measure of absorbed dose. Radiation (Ionizing) refers to alpha particles, beta particles, photons (gamma rays or x-rays), high- energy electrons, neutrons and any other particles capable of producing ions. Radiation weighting factor is a dimensionless multiplicative factor used to convert physical dose (Gy) to equivalent dose (Sv) to place biological effects from exposure to different types of radiation on a common scale. Radioactive Material refers to any material or combination of materials that contain radionuclides that spontaneously emit ionizing radiation. Radionuclide is an unstable nuclide that undergoes spontaneous transformation, emitting radiation. There are approximately 2,200 known radionuclides, both man-made and naturally occurring. A radionuclide is identified by the number of neutrons and protons in the atomic nucleus and its energy state. Random Error refers to variations of repeated measurements made within a sample set that are random in nature and individually not predictable. The causes of random error are assumed to be indeterminate or non-assignable. Random errors are generally assumed to be normally distributed. Random Samples are samples obtained in such a manner that all items or members of the lot, or population, have an equal chance of being selected in the sample. Range is the difference between the maximum and minimum values of a set of values. Reference Animals and Plants (RAP) is a hypothetical entity, with the assumed basic biological characteristics of a particular type of animal or plant as described to the generality of the taxonomic level of family, with defined anatomical, physiological and life history properties that can be used for the purpose of relating exposure to dose and dose effects for that type of living organism. Relative Biological Effectiveness (RBE) is defined as the ratio of the absorbed dose of a reference radiation (normally gamma rays or X rays) required to produce a level of biological response to the absorbed dose of the radiation of concern required to produce the same level of biological response, all other conditions being kept constant. DOE-STD-1153-2019 6 Representative Individual (biota) is an individual organism within a population that receives a radiation dose which is equivalent to the value of the appropriate measure of central tendency (e.g., mean, median, mode) of the distribution of doses received by that population. The individual is assumed to be representative of the population as a whole. Representative Person is an individual receiving a dose that is representative of the more highly exposed individuals in the population. Representative Sample is a sample taken to depict the characteristics of a lot or population as accurately and precisely as possible. A representative sample may be a “random sample” or a “stratified sample” depending upon the objective of the sampling and the characteristics of the conceptual population. Riparian Organisms are those organisms related to, living, or located on the bank of a natural

watercourse (as a river) or sometimes of a lake or a tidewater. Safety Factor is a factor applied to an observed or estimated toxic concentration or dose to arrive at a criterion or standard that is considered safe. Sample has two definitions: 1) A subset or group of objects selected from a larger set, called the “lot” or “population;” and 2) an extracted portion or subset of an effluent stream or environmental media. Sampling is the extraction of a prescribed portion of an effluent stream or of an environmental medium for purposes of inspection and/or analysis. Sequential Sampling refers to timed samples collected from an effluent stream. Site refers to the land or property upon which DOE facilities or activities are located and access to which is subject to Departmental or DOE contractor control. Source (Radioactive) is either (1) a known amount of radioactive material emanating a characteristic amount of energy in the form of alpha, beta, gamma, neutron, or x-ray emissions (or a combination of such emissions), or (2) a single process or release point that contributes to or causes a release to the environment and that can be separated from other processes by a break in the flow of material. Standard Deviation is an indication of the dispersion of a set of results around the average of samples collected or the mean of a population; it is the positive square root of the sample variance. For samples taken from a population, the standard deviation, s, is calculated as: 𝑠 = [ ∑ (𝑋𝑖 − 𝑋̅)2𝑛 𝑖=1 𝑛 − 1 ] 1 2 Where:  𝑋̅ = average value of the samples measured;  𝑛 = number of samples measured; and  𝑋𝑖 = individual measurement for sample 𝑖 For a finite population, the standard deviation (𝜎) is: DOE-STD-1153-2019 7 𝜎 = [ ∑ (𝑋𝑖 − µ)2𝑁 𝑖=1 𝑁 ] 1 2 Where:  𝜇 = mean value of the population; and  𝑁 = number of values within the population. Stochastic Effects are those for which the probability of occurrence is a function of dose, but the severity of the effects is independent of dose. Stratified Sample (Stratified Random Sample) refers to a sample consisting of various portions that have been obtained from identified subparts or subcategories (strata) of the total lot or population. Within each category or stratum, the samples are taken randomly. The objective of taking stratified samples is to obtain a more representative sample than might be obtained by a completely random sampling. Systematic Error is the condition in which there is a consistent deviation of the results from the actual or true values by a measurement process. The cause for the deviation, or bias, may be known or unknown; however, it is considered “assignable” (i.e., the cause can be reasonably determined). Terrestrial Biota is plant and animal life living on or in land. Variability is a general term for the dispersion of values in a data set. Variance is a measure of the variability of samples within a subset or the entire population. Mathematically, the sample variance (s2) is the sum of squares of the differences between the individual values of a set and the arithmetic average of the set, divided by one less than the number of values: 𝑠2 = ∑ (𝑋𝑖 − 𝑋̅)2𝑛 𝑖=1 𝑛 − 1 Where:  𝑋𝑖 = individual measurement for sample 𝑖  𝑋̅ = average value of the samples measured; and  𝑛 = number of samples measured. For a finite population, the variance (𝜎2) is the sum of squares of deviations from the arithmetic mean,

divided by the number of values in the population: 𝜎2 = ∑ (𝑋𝑖 − µ)2𝑁 𝑖=1 𝑁 Where:  𝜇 = mean value of the population; and  𝑁 = number of values within the population. DOE-STD-1153-2019 8 Acronyms and Abbreviations λbio biological decay constant λeff the combination of biological and radiological decay constants λrad radiological decay constant ACRP Advisory Committee on Radiation Protection AF Area Factor ASTM American Society for Testing and Materials Biv bioaccumulation factor BCG Biota Concentration Guide CERCLA Comprehensive Environmental Response, Compensation, and Liability Act CFR Code of Federal Regulations CR Concentration Ratio CV coefficient of variation D Absorbed dose DCRL Derived Consideration Reference Level H Equivalent dose DOE U.S. Department of Energy DQOs data quality objectives EE/CA engineering evaluation/cost analysis EH DOE’s Office of Environment, Safety, and Health EMS Environmental Management System EPA U.S. Environmental Protection Agency ERA Ecological Risk Assessment IAEA International Atomic Energy Agency ICRP International Commission on Radiological Protection Kd solid/solution distribution coefficient M&O management and operating (contractor) DOE-STD-1153-2019 9 NCRP National Council on Radiation Protection and Measurements NEA Nuclear Energy Agency NEPA National Environmental Policy Act NIST National Institute of Standards and Technology NOAEL No Observed Adverse Effects Levels NRC U.S. Nuclear Regulatory Commission NRDA Natural Resource Damage Assessment PRA Population-relevant attribute QA Quality assurance QC Quality control QF Quality factor RAPs Reference Animals and Plants RBE Relative biological effectiveness RESRAD RESidual RADioactivity RCRA Resource Conservation and Recovery Act RI/FS Remedial investigation/feasibility study UNSCEAR United Nations Scientific Committee on the Effects of Atomic Radiation USFWS U.S. Fish and Wildlife Service W Radiation weighting factor wt Tissue or organ weighting factor DOE-STD-1153-2019 10 References Department of Energy (DOE) Directives USDOE. 2011. Order 231.1B Environment, Safety and Health Reporting. Approved 2011 June 27. USDOE. 2013. Order 458.1 Radiation Protection of the Public and the Environment. Administrative Change 3. 2013 January 15. USDOE. 2013. Order 414.1D Quality Assurance. Administrative Change 1. 2013 May 8. DOE Technical Standards and Handbooks USDOE. 2015. Environmental Radiological Effluent Monitoring and Environmental Surveillance, DOE- HDBK-1216-2015. USDOE. 2011. Derived Concentration Technical Standard, DOE-STD-1196-2011 Other DOE Documents Bechtel Nevada, 2004. Nevada Test Site Environmental Report 2003, Report DOE/NV/11718—971, Bechtel Nevada, Las Vegas, NV. Bilyard, C. R., H. Beckert, J. J. Bascietto, C. W. Abrams, S. A. Dyer, and L. A. Haselow. 1997. Using the Data Quality Objectives Process During the Design and Conduct of Ecological Risk Assessments. DOE/EH- 0544, U.S. Department of Energy, Office of Environmental Policy and Assistance, Washington, D.C. Interagency Steering Committee on Radiation Standards (ISCORS), 2004. RESRAD-BIOTA: A tool for implementing a Graded Approach to Biota Dose Evaluation. ISCORS Technical Report 2004-02 (U.S. Department of Energy report DOE/EH-0676), Washington, D.C. USDOE. 1984. Atmospheric Science and Power Production. DOE/TIC-27601, D. Randerson, ed., U.S. Department of Energy, Washington, D.C.

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and Site Investigation Manual (MARSSIM). Revision 1, NRC Report NUREG-1575, Washington, D.C. Washington State Department of Ecology (WADOE). 1992. Statistical Guidance for Ecology Site Managers. Publ. No. 92-54, Washington State Dept. of Ecology, Toxics Cleanup Program, Olympia, Washington. WADOE. 1994. Natural Background Soil Metals Concentrations in Washington State. Publ. No. 94-115, Washington State Dept. of Ecology, Toxics Cleanup Program, Olympia, Washington. West, G.B., Brown, J.H., and B.J. Enquist. 1977. “A General Model for the Origin of Allometric Scaling Laws in Biology.” Science 276:122-126. Whicker, F.W. 1997. “Impacts on Plant and Animal Populators.” Health impacts for large releases of radionuclides, 74-93. Ciba Foundation, London, England. Whicker, F.W., Pinder, J.E., III, Bowling, J.W., Alberts, J.J., and I.L. Brisban. 1990. “Distribution of Long- Lived Radionuclides in an Abandoned Reactor Cooling Reservoir.” Ecological Monographs 60: 471- 496. Whicker, F.W. and V. Schultz. 1982. Radioecology: Nuclear Energy and the Environment. Vol. I and II. CRC Press, Inc., Boca Raton, Florida. Whicker, F.W., Shaw, G., Voigt, G, and E. Holm. 1999. “Radioactive Contamination: State of the Science and its Application to Predictive Models.” Environmental Pollution 100: 133-149. Wilson, D. E., F. R. Cole, J. D. Nichols, R. Rudran, and M. S. Foster. 1996. Measuring and Monitoring Biological Diversity: Standard Methods for Mammals. Smithsonian Inst. Press, Washington, D.C. Woodhead, D. S. 1998. “The Impact of Radioactive Discharges on Native British Wildlife and the Implications on Environmental Protection.” R & D Technical Report P135, Environmental Agency, Bristol, UK, 80 pp. Yu, C., et al. 1993. Data Collection Handbook to Support Modeling Impacts of Radioactive Material in Soil. Argonne National Laboratory, Argonne, Illinois. Yu, C., Kamboj, S., Wang, C., Cheng, J.J. 2015. Data Collection Handbook to Support Modelling Impacts of Radioactive Materials. Argonne National Laboratory, Argonne, Illinois Zach, R. 1985. “Contribution of Inhalation by Food Animals to Man’s Ingestion Dose.” Health Physics 49: 737-745. DOE-STD-1153-2019 17 1. Introduction Under the Atomic Energy Act, as amended, the U.S. Department of Energy (DOE) is responsible for the safe conduct of its activities, including facility operation, waste management and disposal activities, and remediation of environmental contamination. These activities may result in releases of radionuclides to the air and water, accumulation of radionuclides in soil and sediment, and the potential for plants, animals, and members of the public to be exposed to radiation. DOE Order 458.1, Radiation Protection of the Public and the Environment, requires radiological activities that have the potential to impact the environment to be conducted in a manner that protects populations of aquatic animals, terrestrial plants, and terrestrial animals in local ecosystems from adverse effects due to radiation and radioactive material released from DOE operations. Dose limits below which deleterious effects on populations of aquatic and terrestrial organisms have not been observed, as discussed by the United Nations Scientific Committee on the Effects of Atomic Radiation (UNSCEAR 2008 Annex E) (2011) and the International Commission on Radiation Protection (ICRP) Publication 124 (2014), are considered by DOE to be relevant to the protection of all aquatic and terrestrial biota on DOE sites.

1.1 Purpose This DOE technical standard provides a graded approach (including screening methods and methods for detailed analyses) and related guidance that DOE and DOE contractors may use to evaluate compliance with specified criteria on radiation dose to populations of aquatic animals, terrestrial plants, and terrestrial animals due to anthropogenic sources at DOE sites. This standard replaces the previous DOE-STD-1153-2002, A Graded Approach for Evaluating Radiation Doses to Aquatic and Terrestrial Biota. This technical standard provides dose evaluation methods that can be used to meet the requirements for protection of biota in DOE Order 458.1. This technical standard uses the biota dose rate criteria specified below within a graded approach to demonstrate that populations of plants and animals are adequately protected from the effects of ionizing radiation: DOE Category Average Dose Rate Criteria Aquatic Animals Absorbed dose < 1 rad/day (10 mGy/d) Riparian Animals Absorbed dose < 0.1 rad/d (1 mGy/d) Terrestrial Plants Absorbed dose < 1 rad/d (10 mGy/d) Terrestrial Animals Absorbed dose < 0.1 rad/d (1 mGy/d) Table 1-1 Absorbed dose to Aquatic and Riparian Animals and Terrestrial Plants and Animals from exposure to radiation or radioactive materials to the aquatic or terrestrial environment. The specific methods and guidance in this technical standard are acceptable for use by DOE and DOE- contractors when evaluating doses to biota in relation to the above dose rate criteria. The methods and guidance in this technical standard should be useful to ecological risk assessors who must evaluate risks to biota from radionuclides that occur on DOE sites. Using the graded approach provided in this technical standard, risk assessors can use soil, sediment, and water radionuclide concentration data to DOE-STD-1153-2019 18 determine whether radionuclide concentrations at a site are likely to result in doses in excess of those listed above and would, therefore, have the potential to impact resident populations of plants and animals. The methods can give risk assessors an immediate qualitative assessment of the importance of doses of ionizing radiation to the resident receptors. The dose equations in this technical standard also provide methods of estimating upper-bound (e.g., conservatively derived) doses to specific plants and animals. The remainder of this chapter discusses the basis and background to the dose rate guidelines. Readers that are just interested in applying the method may wish to skip to Chapter 2. 1.2 Background 1.2.1 Interest and Need for Biota Dose Evaluation Methods There is national interest in establishing a regulatory framework (e.g., to include standards or criteria) and supporting evaluation methodologies for demonstrating protection of the environment from the effects of ionizing radiation. Regarding environmental protection, the ICRP statement that "...if man is adequately protected then other living things are also likely to be sufficiently protected" (ICRP 1977; 1991) uses human protection to infer environmental protection from the effects of ionizing radiation. This assumption is most appropriate in cases where humans and other biota inhabit the same environment and have common routes of exposure. Exceptions include the following conditions:  Human access to a contaminated area is restricted but access by biota is not restricted;

 Unique exposure pathways exist for plants and animals that do not affect exposure of humans;  Rare or endangered species are present; or  Other stresses on the plant or animal population are significant. The inclusion of radiation as a stressor within ecological risk assessments is also a consideration. Ecological risk assessments at contaminated sites considered for remediation under the Comprehensive Environmental Response, Compensation, and Liability Act (CERCLA) generally require an assessment of all stressors, including radiation impacts on contaminated ecosystems (EPA 1998). In 1999, the International Atomic Energy Agency (IAEA) convened a technical committee examining protection of the environment from the effects of ionizing radiation and provided recommendations and discussion points for moving forward with the development of protection frameworks and dose assessment methods. The resulting IAEA Technical Document, "Protection of the Environment from the Effects of Ionizing Radiation" (1999) references multi-tiered screening as a potentially cost-effective and easy way of demonstrating compliance with radiation. DOE considers National Council on Radiation Protection and Measurements (NCRP), ICRP, other federal agencies’ recommendations in establishing appropriate limits for protection of biota. DOE-STD-1153-2019 19 In 2003, the International Conference on the Protection of the Environment from the Effects of Ionizing Radiation was held in Stockholm. The primary objective of the Stockholm conference was to promote the development of a coherent international policy on the protection of the environment from the effects of ionizing radiation by taking explicit account of the protection of species other than humans (IAEA 2003). In specifying this, the international community gathered in Stockholm set the following expectations: 1. The UNSCEAR should continue to provide findings on the sources and effects of ionizing radiation that can be used as the authoritative scientific basis for future international efforts in environmental radiation protection. 2. The ICRP should continue to issue recommendations on radiation protection, including specific recommendations for the protection of non-human species. 3. The IAEA should establish appropriate international undertakings, including international standards and mechanisms for their worldwide application, to restrict releases of radioactive materials into the environment over time, in order that not only humans but also the non-human component of the environment is protected adequately. IAEA should continue to foster information exchange by organizing international meetings on this subject. In response to these expectations, UNSCEAR published UNSCEAR 2008 Annex E on the effects of ionizing radiation on non-human biota (2011), IAEA revised the International Basic Safety Standards to include protecting people and the environment from harmful effects of radiation (2014b), and the ICRP published the following series of reports: 1. ICRP Publication 91, A Framework for Assessing the Impact of Ionising Radiation on Non-human Species (2003), recommended that a more comprehensive approach be developed to protect all living matter and proposed a framework for assessing the impacts on non-human species. 2. ICRP Publication 103, Recommendations of the ICRP (2007), extended the system of radiological protection to explicitly address the protection of the environment including non-human species.

The basis for using Reference Animals and Plants (RAPs) in flora and fauna assessments is provided. 3. ICRP Publication 108, Environmental Protection: the Concept and Use of Reference Animals and Plants (2008b), provided details on the use of RAPs and provided a range of Derived Consideration Reference Levels for each RAP. Benefits of a Screening Process “A multi-tiered screening approach is normally used in ecological risk assessments. Screening may also be a potentially cost-effective and easy way of demonstrating compliance with radiation criteria or standards for protection of the environment. Screening values should be used to identify radionuclides in situations of concern, and to determine whether these radionuclides warrant further assessment, or if they are at levels that require no further attention. In practice, this initial screening is expected to be sufficient in the majority of cases. When initial screening fails, additional analysis or assessment may be needed. A two- or three-tiered scheme would help ensure that the magnitude of the assessment effort would be scaled to the likelihood and severity of environmental impacts.” (IAEA 1999) DOE-STD-1153-2019 20 4. ICRP Publication 114, Environmental Protection: Transfer Parameters for Reference Animals and Plants (2009), provided transfer parameters for the RAPs. 5. ICRP Publication 124, Protection of the Environment under Different Exposure Situations (2014), consolidates the ICRP recommendations on environmental protection and provides guidance on their application. The methods and guidance provided in this DOE technical standard will continue to serve as a platform for national and international discussion of radiation protection frameworks, standards, and dose assessment methods for biota. Although DOE is not required to strictly follow international standards, DOE considers NCRP, ICRP, other Federal agency guidance in establishing appropriate standards. 1.2.2 Basis for Biota Dose Rate Criteria Applied in this Technical Standard DOE Order 458.1 specifies that when actions taken to protect humans from radiation and radioactive materials are not adequate to protect biota, evaluations must be done to demonstrate compliance and specific requirements in one or more of the following ways:  Use of the graded approach established in this standard;  Use of an alternative approach to demonstrate that the dose rates to representative biota populations do not exceed the dose rate criteria, Table 1-1, in this standard; or  Use of an ecological risk assessment to demonstrate that radiation and radioactive material released from DOE operations will not adversely affect populations within the ecosystem. The dose rate criteria for controlling radiological impacts from DOE activities to representative biota populations shall not exceed the dose rate criteria in Table 1-1 of this technical standard. The dose rate criteria used in this technical standard is consistent with the intent of DOE Order 458.1, and the intent of ICRP Publication 124 (2014). In ICRP 124 (2014), Derived Consideration Reference Levels (DCRLs) that are specific to each of the different types of RAPs have been defined. A DCRL can be considered as a band (over one order of magnitude) of dose rate within which there is some chance of deleterious effects to the RAP from ionizing radiation. DCRLs can be used as points of reference to inform on the appropriate level of effort

that should be expended on environmental protection. ICRP recommends that DCRLs should be used under all circumstances where there is, or may be, an incremental environmental exposure of significance above the natural background locally experienced by the relevant biota. For existing exposure situations (typical for most DOE sites), the upper bound of the relevant DCRL band should be used for protection of different types of biota within a given area, with consideration being given to possible cumulative effects. The dose rate criteria used in this technical standard for the aquatic animal, riparian animal, terrestrial plant, and terrestrial animal are generally consistent with the DCRL bands for the applicable Reference Animals and Plants (RAPs) documented in ICRP 124 (2014) and Figure 1-1. DOE-STD-1153-2019 21 DOE Category & Criteria Reference Organism DCRL mGy/d DCRL rad/d Aquatic Animals 10 mGy/d 1 rad/d Crab 10 to 100 1 to 10 Trout 1 to 10 0.1 to 1 Flatfish 1 to 10 0.1 to 1 Riparian Animals 1 mGy /d 0.1 rad/d Frog 1 to 10 0.1 to 1 Duck 0.1 to 1 0.01 to 0.1 Terrestrial Plants 10 mGy/d 1 rad/d Pine tree 0.1 to 1 0.01 to 0.1 Wild grass 1 to 10 0.1 to 1 Terrestrial Animals 1 mGy/d 0.1 rad/day Deer 0.1 to 1 0.01 to 0.1 Bee 10 to 100 1 to 10 Earthworm 10 to 100 1 to 10 Rat 0.1 to 1 0.01 to 0.1 None Brown seaweed 10 to 100 1 to 10 Figure 1-1 Comparison of DOE biota dose rate criteria with international recommendations for DCRL bands from ICRP (2014) The biota dose rate criteria specified in this technical standard are based on the current state of science and knowledge regarding effects of ionizing radiation on plants and animals. They should not be interpreted as a “bright line” that, if exceeded, would trigger a mandatory regulatory or remedial action. Rather, they should be interpreted and applied more as “Dose Rate Guidelines” that provide an indication that populations of plants and animals could be impacted from exposure to ionizing radiation and that further investigation and action is likely necessary. 1.2.3 Protection of Populations The intent of the graded approach (i.e., the screening and analysis methods) is to protect populations of aquatic animals, terrestrial animals, and terrestrial plants from the effects of exposure to anthropogenic ionizing radiation. As shown in Figure 1-2, certain taxa are more sensitive to ionizing radiation than others. Based on this observation, protecting the more sensitive taxa will adequately protect other, less sensitive taxa. Hence, in cases where site-specific evaluations may be required, receptors should be selected that:  Are important to the structure and function of the community;  Are expected to receive a comparatively high degree of exposure (e.g., expected to receive a radiation dose to reproductive tissues which is relatively high per unit of radionuclide present in the ecosystem, in comparison with other receptors in the same community); and DOE-STD-1153-2019 22  Have an established degree of radiosensitivity (i.e., radiation effects have a likelihood of occurring at the exposure levels being evaluated, in comparison with other receptors in the same community). Figure 1-2 Approximate Acute Lethal Dose Ranges for Various Taxonomic Groups (Whicker and Schulz 1982; UNSCEAR 1996.) 1.3 The Biota Dose Methodology The graded approach for evaluating radiation dose to biota is intended to be simple, defensible, and

more easily understood. It also has broad applicability from aquatic animals through terrestrial species and addresses radiation dose in small organisms (e.g., mice) and large carnivores (e.g., cougars). The method provides a logical and consistent departure point should additional in-depth evaluation of dose be required. Should additional analysis be required, the method allows for, and encourages, the use of existing data either from the technical literature or from site-specific monitoring whenever possible. Lastly, the method is useful in evaluating the potential impacts of combined media: water, sediment, and soil. DOE-STD-1153-2019 23 2 Overview and Implementation of the DOE Graded Approach DOE's graded approach for evaluating radiation doses to aquatic and terrestrial biota consists of a three- step process which is designed to guide a user from an initial, conservative general screening to, if needed, a more rigorous analysis using site-specific information (see Figure 2-1). The three-step process includes:  Data assembly;  General screening; and  Analysis as necessary. Any of the steps within the graded approach may be used at any time, but the general screening methodology will usually be the simplest, most cost-effective, and least time-consuming. Table 2-1 provides a summary of DOE’s graded approach. The RESRAD-BIOTA (RESidual RADioactivity) model (ISCORS 2004) is the recommended tool for implementing the screening and analysis methods contained in this technical standard. Figure 2-1 Overview of the DOE Graded Approach for Evaluating Radiation Doses to Aquatic and Terrestrial Biota Data Assembly •Assemble environmental media data and define evaluation area General Screening •Compare media concentrations with Biota Concentration Guides (BCGs) Analysis •Site-Specific Screening: employ site-representative parameters and conditions •Site-Specific Analysis: employ kinetic/allometric modeling tool •Site-Specific Biota Dose Assessment: employ ecological risk assessment DOE-STD-1153-2019 24 Table 2-1 Summary of DOE's Three-Step Process for Evaluating Radiation Doses to Aquatic and Terrestrial Biota 1. Data Assembly Knowledge of sources, receptors, and routes of exposure for the area to be evaluated is summarized. Measured radionuclide concentrations in water, sediment, and soil are assembled for subsequent screening. 2. General Screening Maximum measured radionuclide concentrations in an environmental medium (e.g., water, sediment, soil) are compared with a set of DOE BIOTA BCGs. Each radionuclide-specific BCG represents the limiting radionuclide concentration in an environmental medium which would not result in recommended dose standards for biota to be exceeded. 3. Analysis (a) Site-Specific Screening (b) Site-Specific Analysis (c) Site-Specific Biota Dose Assessment This phase consists of three increasingly more detailed steps of analysis. Site-specific screening, using more realistic site-representative bioaccumulation factors (Bivs) in place of conservative default parameters. Use of mean radionuclide concentrations in place of maximum values, taking into account time dependence and spatial extent of contamination, may be considered.

Site-specific analysis employing a kinetic modeling tool (applicable to riparian and terrestrial animal organism types) provided as part of the graded approach methodology. Multiple parameters which influence the organism’s internal dose (e.g., body mass, consumption rate of food/soil, inhalation rate, lifespan, biological elimination rates) can be modified to represent site and organism- specific characteristics. The kinetic model employs allometric equations relating body mass to these internal dose parameters. An actual site-specific biota dose assessment involving the collection and analysis of biota samples. The dose assessment would involve a problem formulation, analysis, and risk characterization protocol consistent with the widely-used ecological risk assessment paradigm. 2.1 Key Features of the Graded Approach The graded approach was designed for flexibility and acceptability:  It provides users with a tiered approach for demonstrating compliance with biota dose rate criteria that is generally cost-effective and easy-to-implement;  It allows for the use of measured radionuclide concentrations in environmental media typically collected as part of routine environmental surveillance programs;  It is designed for multiple applications. The technical standard is applicable to demonstrations of compliance with biota dose rate criteria and for use in ecological risk assessments of radiological impact;  It provides a framework that supports the use of site-specific information;  It incorporates ecological risk assessment (ERA) concepts and provides guidance for site- specific biota dose assessments, employing the widely-used ERA paradigm; and DOE-STD-1153-2019 25  It provides users with “a place to start” and “an analysis path forward.” The BCG’s are not stand-alone criteria. Exceedance of BCGs leads the user to the more-detailed tiers of analysis as needed in a stepwise manner. 2.2 Principal and Alternative Uses of the Graded Approach The principal driver and basis of need for developing the graded approach was to provide DOE field and program elements with methods for demonstrating compliance with DOE biota dose rate criteria and recommendations for radiological protection of the environment. Thus, many of the decisions that are traditionally made when conducting a case-specific ERA (e.g., choice of indicator receptors; defining receptor exposure profiles; selection of effects endpoints) were made at a programmatic level and incorporated into the screening phase of the graded approach a priori. For example, the thresholds for adverse effects were set at the recommended criteria for protection of natural populations of biota. Those are the appropriate effects levels for demonstrating compliance with DOE requirements and recommendations for the protection of the environment from ionizing radiation. The graded approach and BCGs can be used in support of other types of environmental assessments, provided that the user ensures that issues specific to the alternative application are appropriately addressed. Examples of other types of environmental assessments that the graded approach could potentially support include: ERAs at hazardous waste sites (i.e., Superfund sites), assessments for waste disposal and other facilities, and assessments at various stages of the Natural Resource Damage Assessment (NRDA) process. These typically include retrospective assessments of previously

contaminated areas. These could also include prospective assessments of migrating contaminants (e.g., groundwater plumes) and planned releases (e.g., National Environmental Policy Act (NEPA) alternatives analysis). If the graded approach is used for these or other purposes, then the programmatic objectives and the methods and model assumptions should be re-evaluated and discussed with the relevant decision makers and stakeholders, preferably via the Data Quality Objectives process (USEPA 2006) or comparable processes to ensure that the results obtained through application of the graded approach will support the management goals and objectives of the environmental assessment. 2.3 Relationship of the Graded Approach to Ecological Risk Assessment The graded approach for evaluating radiation doses to aquatic and terrestrial biota is consistent with the standard ERA paradigm (USEPA 1998). The ERA structure provides a process for organizing and evaluating information to determine the nature, likelihood, and magnitude of potential impacts on environmental receptors (Suter 1993). ERAs are typically done in successively rigorous tiers, each of which includes the three general ERA steps (Suter et al. 2000). The first and simplest tier is a scoping assessment, which establishes the need for an ERA. The second tier consists of a screening ERA, which is relatively simple and conservative in its application and assumptions. The third tier is a definitive ERA, which provides a relatively detailed and realistic assessment of the nature and magnitude of risks. The graded approach moves from a simple and relatively conservative screening evaluation to a more detailed and realistic assessment. Each step in the graded approach addresses, either explicitly or implicitly, all of the aforementioned ERA components. That is, the graded approach is a framework for organizing the successively rigorous ERA tiers, but with a particular emphasis on ionizing radiation. DOE-STD-1153-2019 26 The ERA process can be applied to the evaluation of radiation as a stressor, but not without some modifications and provision of additional guidance. There are some noteworthy technical issues concerning the evaluation of radiation that require further consideration and elaboration. Some issues are the same as for chemicals, but some are unique to radionuclides. 2.4 Step-By-Step Implementation of the Graded Approach Presented in this section is an overview of the complete process for implementing the graded approach. This section is provided to help orient you to the step-by-step guidance corresponding to each phase of the graded approach which follows in Sections 3-7. A flowchart showing how to progress through each phase of the graded approach, and the components of each phase, is provided in Figure 2-2. Refer to this figure as you proceed through the step-by-step guidance presented in subsequent sections. DOE-STD-1153-2019 27 Sum ≥ 1.0 Analysis Phase 1) Site-Specific Screening 2) Site-Specific Analysis 3) Site-Specific Dose Assessment General Screening Phase Compare maximum radionuclide concentrations with generic BCGs. Sum all fractions for each radionuclide and medium Is the Sum of the Fractions < 1.0? • Yes: Evaluation is complete. Document rationale and results • No: Proceed to Analysis Phase Data Assembly Phase Consider sources, receptors, and routes of exposure Define the area of evaluation

Assemble radionuclide concentration data for each medium DOE-STD-1153-2019 28 Analysis: Site-Specific Screening (I) • Consider using mean radionuclide concentration data for each medium • Consider refining size or dileneation of the evaluation area • Consider obtaining additional concentration data for each medium • Re-run the screening evaluation to compare revised radionuclide concentration data with the generic BCGs • Sum all fractions for each radionuclide and medium Analysis: Site-Specific Screening (II) • Identify media and nuclide-specific limiting organism types • Review and select 𝐵𝑖𝑣 values appropriate for site-specific conditions and receptors • Use site-specific 𝐵𝑖𝑣𝑠 to generate site-specific BCGs • Compare radionuclide concentration data with site- specific BCGs • Sum all fractions for each radionuclide and medium Sum of Fractions < 1.0? Yes: Evaluation is complete. Document rationale and results. No: Continue Yes: Evaluation is complete. Document rationale and results. No: Continue Sum of Fractions < 1.0? DOE-STD-1153-2019 29 Figure 2-2 Flowchart illustrating step-by-step guidance for progressing through the DOE graded approach 2.5 Parameter Values that Can Be Modified in the Graded Approach DOE's three-phased approach is designed to guide you from an initial conservative evaluation using general screening to, if needed, a more rigorous analysis using site-specific information. The amount of effort required for your biota dose evaluation and the information needed on site-specific conditions and receptors increases as you progress through the three phases of the graded approach, particularly during the analysis phase. The result will be a set of less conservative, more realistic site-representative BCGs. Table 2-2 provides a general summary of parameter values that can be modified or applied corresponding to each phase of the graded approach. Use this table as a reference when progressing through the step-by-step guidance provided in subsequent sections. Analysis: Site-Specific Analysis • Identify media and nuclide-specific limiting organism types • Consider correction factor for exposure area or receptor residence time • For riparian and terrestrial animals, review and select paramaters contributing to internal dose (e.g. body mass, ingestion and inhalation rates, biological decay and f1 values) appropriate for site-specific receptors • Use site-specific parameters to generate site-specific BCGs • Compare radionuclide concentration data with site-specific BCGs • Sum all fractions for each radionuclide and medium Analysis: Site-Specific Biota Dose Assessment • Consider use of available biota tissue data • Assemble a biota dose assessment team • Review requirements and assumptions • Design and conduct the biota dose assessment • Problem Formulation • Analysis • Risk Characterization Yes: Evaluation is complete. Document rationale and results. No: Continue Sum of Fractions< 1.0? Document rationale and results. Analysis complete DOE-STD-1153-2019 30 Table 2-2 Summary of parameter values that can, with technical justification, be modified corresponding to each phase of the graded approach Phase Parameters Data Assembly  Size of evaluation area  Radionuclide concentrations in environmental media  Presence of aquatic, riparian, or terrestrial biota populations General Screening  Initial general screening using maximum radionuclide concentrations:

No parameter modifications are allowed Analysis: Site-Specific Screening  Use of mean radionuclide concentrations, taking into account time dependence and spatial extent of contamination, may be considered  Site-specific Biv values in place of default values used in the general screening phase  Sediment Kd values may be modified, with technical justification, for aquatic system evaluations where only water or only sediment concentration data are available for the screening process Site-Specific Analysis  A correction factor for exposure area or receptor residence time for all organism types (Area Factor) may be considered  For riparian and terrestrial animals:  Food source Biv value for riparian and terrestrial animals  Body mass  Uptake fraction of radionuclide ingested/absorbed (f1)  Biological elimination rate constant of radionuclide exiting the organism (𝜆𝑏𝑖𝑜)  Food intake rate and supporting parameters  Soil intake rate and supporting parameters  Inhalation rate and supporting parameters  Soil inhalation rate and supporting parameters  Water consumption rate  Maximum life span  Allometric equations provided can be modified Site-Specific Biota Dose Assessment  Design, collection, and direct analysis of environmental media and biota DOE-STD-1153-2019 31 3 Application Considerations The principal application of the graded approach is to demonstrate that routine DOE operations and activities are in compliance with the biota dose rate criteria for protecting populations of plants and animals. In addition, the design of the graded approach (e.g., assumptions used; a multi-tiered screening and analysis approach; flexibility to allow use of site-specific information on sources, receptors, and routes of exposure) permits its application in ecological assessments of radiological impact and in other environmental assessment scenarios. Table 3-1 Applications matrix summarizing intended and potential uses of the DOE Graded Approach TYPES OF RECEPTORS Applications Intended / potential use Considerations Populations of plants and animals This is the primary intended use. No further considerations Individual plants and animals, including threatened and endangered species, and commercially or culturally valued species Equations used within the graded approach are technically sound for application to individual organisms. Applying dose rate criteria intended for the protection of populations to evaluations of individuals may require further consideration. Use of effects endpoints/dose rate criteria appropriate for protection of the individuals being evaluated; and/or application of safety factors, conservative exposure assumptions, and parameter values. Dose evaluations should be performed under the provisions of the applicable Federal and/or state statutes or regulations for rare and endangered species. TYPES OF EXPOSURE Applications Intended / potential use Considerations Chronic The methodology assumes chronic exposure and equilibrium conditions. The models and assumptions used in the graded approach assume equilibrium conditions. Acute The methodology is not intended to be used for assessing acute exposures. The models and assumptions used in the graded approach assume equilibrium conditions that will occur over longer exposure horizons. Accidents Could be used to provide an indication of long-term "recovery" or health of the population over time following an accident. Equations and models used within the graded approach are technically sound for this application.

Accidents typically result in short- term, acute exposures for which the methodology is not intended. However, it can be applied for assessing long-term exposures due to accidents. TYPES OF ENVIRONMENTS Applications Intended / potential use Considerations Fresh water, coastal, and marine environments The methodology is intended to be applied to fresh water environments, and can be applied to coastal and marine environments. Care must be taken when selecting parameter values (e.g., receptor Bivs; Kd values), as fresh water, coastal, and marine equilibrium chemistry differ considerably. Table 3-1 (Cont’d) Applications Matrix Summarizing Intended and Potential Uses of the DOE Graded Approach DOE-STD-1153-2019 32 Terrestrial environments The methodology is intended to be applied to terrestrial environments No further considerations. COMPLIANCE / IMPACT ASSESSMENT Applications Intended / potential use Considerations Demonstration that DOE activities are in compliance with biota dose rate criteria This is a principal DOE application of the graded approach. Population is defined as an aggregate of individuals of a species within a specified location and time. The fraction of the population of interest, and the fraction of time, exposed to anthropogenic ionizing radiation are important considerations in determining the dose to biota. National Environmental Policy Act (NEPA) The graded approach could be coupled with predictive dispersion codes that model a facility’s effluents prior to construction, to estimate doses to biota in the Environmental Impact Statement.  Comparison of alternatives  Screen for issues needing analysis  Defining significance criteria  Mitigation action plan Effects and assessment endpoints selected for use in the biota dose evaluation should be relevant to the management goals of the study. Comprehensive Environmental Response, Compensation, and Liability Act (CERCLA) Screening for potential radiological impacts within an ecological risk assessment.  Remedial Investigation/ Feasibility Study (RI/FS)  Engineering Evaluation/ Cost Analysis (EE/CA) Effects and assessment endpoints selected for use in the biota dose evaluation should be relevant to the management goals of the study. Natural Resource Damage Assessments (NRDA) Screening assessments. Effects and assessment endpoints selected for use in the biota dose evaluation should be relevant to the management goals of the study. Decommissioning Could be used to evaluate doses to biota, and to predict future doses to biota, associated with pre- and post- site or facility decommissioning activities. Effects and assessment endpoints selected for use in the biota dose evaluation should be relevant to the management goals of the study. Resource Conservation and Recovery Act (RCRA)  Mixing zone definition  Alternative concentration limits Effects and assessment endpoints selected for use in the biota dose evaluation should be relevant to the management goals of the study. Clean Water Act Mixing zone assessments. Effects and assessment endpoints selected for use in the biota dose evaluation should be relevant to the management goals of the study. DOE-STD-1153-2019 33 Many of the decisions that are traditionally made when conducting a case-specific assessment (e.g., choice of indicator receptors; defining receptor exposure profiles; selection of effects endpoints) were made at a programmatic level and incorporated into the screening phase of the graded approach a

priori in order to demonstrate compliance with DOE biota dose rate criteria and recommendations. If the graded approach is used for other purposes (see Table 3-1), then the programmatic objectives and the methods should be reviewed and discussed with the relevant decision makers and stakeholders, preferably via the Data Quality Objectives process (USEPA 2006) to ensure that the results obtained through application of the graded approach will support the management goals and objectives of the environmental assessment. 3.1 Evaluating Doses to Individual Organisms (see Appendix A) The equations and models used within the graded approach for estimating the dose per unit concentration of radionuclides in environmental media and for deriving the BCGs are also applicable to individual organisms. However, there are questions concerning the applicability of the biota dose rate criteria to individual organisms. While the biota dose rate criteria presented in Section 1.1 were derived based on dose-response information for the most radiosensitive of all species studied, and taking into account the most radiosensitive life stages, the question of whether these dose rate criteria can be applied to protection of individual members of a species, in contrast to protection of populations of species, requires further consideration. That is, for individual plants and animals, especially threatened and endangered species, the health effects of concern could be different from the effects of concern in protection of populations. The application of safety factors to these dose rate criteria is one approach that has been used in evaluating doses to individual organisms (e.g., for culturally valued species). Use of safety factors, appropriate default parameter values, maximum radionuclide concentrations in environmental media, and 100 percent organism residence time and exposure are factors to consider in the application of the graded approach for evaluating doses to individuals. Specific cases where evaluation of individual organisms may be needed are discussed below. 3.1.1 Threatened and Endangered Species Care must be taken by the user if the graded approach is applied in an evaluation of potential radiological impacts to endangered, threatened, rare, or otherwise sensitive species of plants and animals managed under the Federal Endangered Species Act or similar state laws or regulations pertaining to rare or endangered species (Endangered Species Act, 16 USC 1531 et seq.). It is the user’s responsibility to select effects and assessment endpoints, and the required input parameter values that reflect actual or expected exposure profiles, for the individuals being evaluated. Protection of endangered species should be performed under the provisions of the applicable Federal and/or state statutes or regulations for rare and endangered species. 3.1.2 Commercially and Culturally Valued Species Care must be taken by the user if the graded approach is applied in an evaluation of potential radiological impacts to these categories of species. These would include species that are routinely harvested for their economic value (e.g., salmon) or their cultural value (e.g., medicinal plants used by Native Americans). One issue is whether or not these species should be evaluated at the individual or DOE-STD-1153-2019 34 the population level. It is the user’s responsibility to select effects and assessment endpoints, and the

required input parameter values that reflect actual or expected exposure profiles, for the individuals being evaluated. 3.2 Evaluating Doses to Aquatic Plants Available information about the effects of ionizing radiation on aquatic plants does not appear to be adequate to characterize their sensitivity to ionizing radiation, or to establish defensible recommendations (e.g., in the form of dose standards or criteria) for allowable exposures of populations or individuals. However, regarding this technical standard, indirect means can provide a general qualitative indication of the effects to aquatic plants relative to effects on other organisms. In general, one would expect substantially lower radiosensitivity in higher plants in comparison to the most sensitive birds, fishes and mammals (Whicker and Schultz 1982; Whicker 1997). Therefore, an evaluation using this technical standard that demonstrates protection of aquatic and riparian animals should provide an indication that aquatic plants are also likely protected. Alternatively, appropriate bioaccumulation factors Bivs for aquatic plants could be used to calculate BCGs for aquatic plants. Refer to Appendix F: BIVs and Appendix G: BCGs for guidance in this area. 3.3 Background and Reference Areas In addition to originating from anthropogenic sources, radionuclides are naturally occurring and ubiquitous in the environment. Quantities of naturally occurring radionuclides in the environment can vary dramatically, depending on the geology of an area (Eisler 1994). The BCGs and the biota dose rate criteria for the protection of biota applied in this technical standard do not differentiate between radionuclides originating from anthropogenic and natural sources. It is important to recognize that it is the total weighted dose rate (i.e., taking into account all sources and types of radiation) to biota at the site that is to be evaluated. Therefore, background dose rates should be included in the total weighted dose rate and should not be subtracted from the dose rates at the site (Jones 2000). However, radiation dose rates at local background areas can be used to ensure that the site-related dose rates represent an actual increase in exposure. This is particularly important if remedial activities are being considered, so that limited resources are not applied to an effort to remediate background levels of radionuclides. The solution is to compare the data from the contaminated site to that collected from one to several uncontaminated background or reference sites. These sites should be selected such that they are as comparable as possible to the contaminated site. Background sites should possess similar geological, physical, chemical, and biological attributes, while being uninfluenced by the activities or releases from the contaminated site. The level above which contaminated media are determined to be greater than background should be determined through the Data Quality Objectives process (USEPA 2006). Maximum site concentrations that are twice the mean background concentration have been commonly employed at hazardous waste sites to establish differences from background (Suter et al. 2000). Other comparison approaches are outlined in WADOE (1994), California EPA (1997), and Suter (1995). If the total weighted dose rate at the site is comparable to or less than that at the local background area, then

it is unlikely that endemic biota populations are adversely affected from ionizing radiation at the site. DOE-STD-1153-2019 35 3.4 Frequency of Evaluations Dose evaluations for aquatic and terrestrial biota shall be reviewed and reported in the annual site environmental reports that are required under DOE Order 231.1B, Environment, Safety and Health Reporting. More frequent evaluations may be required if new information or data suggests previous assessments may not be adequate to ensure compliance. DOE-STD-1153-2019 36 4 Data Assembly Phase The DOE graded approach for evaluating radiation doses to aquatic and terrestrial biota was designed to minimize the need for additional data collection above and beyond environmental radionuclide concentration data typically available through routine environmental monitoring and surveillance programs. The data assembly phase encompasses three steps:  Considering the sources of radioactivity, the key receptors, and the routes of exposure to these receptors;  Defining the geographic area to be evaluated; and  Assembling and organizing data on radionuclide concentrations in water, sediments, and soil for use in the general screening phase, and for use in the analysis phase, if needed. Additionally, tissue data may be collected or estimated using field measurements to supplement the general screening phase. The three steps are interdependent and should be considered collectively when implementing the data assembly phase. 4.1 Step 1: Consider the Sources, Receptors, and Routes of Exposure It is expected that general knowledge concerning sources, receptors, and routes of exposure will be sufficient for defining the geographic area of evaluation when implementing the general screening phase of the graded approach. However, more detailed information regarding these elements may need to be considered as you progress through the graded approach. For example, if the BCGs for the general screening evaluation are exceeded, you may wish to refine your input data for site-specific screening (e.g., using mean radionuclide concentration data in place of maximum values; re-defining the geographic area of evaluation). Alternatively, you may wish to move to the site-specific analysis component of the graded approach, which may require consideration of internal dose parameters relating to site-specific receptors and routes of exposure. Detailed guidance on consideration of sources, receptors, and routes of exposure, for application in defining the area of evaluation and for use in the analysis phase is provided in Appendix C: Area Factors and Appendix H: Exposure Parameters. 4.1.1 Radiation Sources Sources of radioactive material may be present in the environment at concentrations that are measurable using routine survey methods. Nuclide-specific information is preferred. Measurements of gross alpha radiation and/or gross beta radiation may be useful in defining the areas of contamination and the identification of localized areas of high concentration. If long-lived radionuclides are present in measurable concentrations and receptors are exposed to them, an evaluation will be needed. Short-lived radionuclides (e.g., with a half-life less than 3 months), if continuously or regularly released into the environment, could be present on a regular basis. As a guide, radionuclides with half-lives less than 6 months that are discharged into the environment in measurable

quantities at least twice in a given 12-month period may warrant an evaluation. DOE-STD-1153-2019 37 Table 4-1 General considerations for defining radiation sources Biogeochemical Properties of Radionuclides  The biogeochemical properties of the released radionuclides are important because they determine the forms of the material in environmental media (e.g., solid, liquid, gaseous, dissolved), hence, its mobility and bioavailability. For example, radionuclides that are easily dissolved in water are more likely to migrate and disperse throughout the environment. These properties are also important because they determine whether a material bioaccumulates and the degree to which bioaccumulation occurs. Nature of the Sources of Contamination  The sources of contamination may exist in place (e.g., in soil or sediment) with or without further inputs of released radionuclides. These sources may be on the surface, buried, or moving through the medium by one or more processes. Alternatively, the sources of contamination may be point or non-point discharges of radioactive materials into the air, water, or soil.  Where the sources of contamination are located in the environment, if and how they are discharged into the environment and their subsequent mobility through environmental media are important determinants of their distribution throughout the environment in space and time. 4.1.2 Receptors The rationale used in identifying example representative organisms includes, but is not limited to, the following:  The home range of the organism should be considered, with preference given to organisms with small home ranges;  The organism should be susceptible (i.e., exposed and sensitive) to ionizing radiation. Organisms that are good accumulators of radionuclides but are not very radiosensitive are generally not the most appropriate organisms. For example, mammals and other vertebrates are generally more radiosensitive than are invertebrates. Higher plants are more radiosensitive than mosses and lichens;  The organism should represent the major exposure pathways for aquatic and terrestrial biota;  The organism should be indigenous to the evaluation area and utilize the principal habitat present in the evaluation area;  The organism is one that the general public is familiar with pertaining to the potential exposures (i.e., internal and external exposures);  The organism has a reasonable amount of data available about it in the published literature or from site-specific studies (e.g., in terms of characterizing its radiosensitivity; environmental transfer factor parameters needed for application in the biota dose evaluation);  The organism should be appropriate to the ecosystem type being evaluated (e.g., regional differences in ecosystems); and DOE-STD-1153-2019 38  The organism is one of the keystone or focal species for the ecosystem type being evaluated. It should be important to the function and structure of the ecosystem. 4.1.3 Routes of Exposure Table 4-2 General considerations for defining routes of exposure Environmental Media  The environmental media in which the released radionuclides are found (e.g.,, water, soil, or sediment) set the boundaries for the mobility of the released radionuclides through and among media. For example, released radionuclides in water may be dissolved or suspended as particulates, and their concentrations may be diluted through natural processes (e.g., currents, waves).

 Suspended particulates may be deposited in the sediments, re-suspended, or even eroded by the wind if the water evaporates.  Materials in the air may be dispersed over large distances, subsequently deposited in the water or on the soil.  Released radionuclides in the soil may exist as immobile particulates or mobile dissolved forms, and may move from one form to another in space and through time, depending on the pH and redox potential of the soil. Other factors such as carbonates, organic matter, and clay content and type can also be important. Ecology of the Receptors  The interactions of each receptor within its environment define the routes of its exposure. A species that burrows in the soil and preys on soil organisms will have a different exposure profile than herbivores that live on the surface.  The ecology determines how the receptor is exposed in time and space. Rates of exposure and total doses will vary among similar types of organisms, based on whether an organism is immobile, mobile and local, or mobile and migratory.  Depending upon the phase of the graded approach you are working in (i.e.,, if you are moving from general screening to a site-specific analysis) it may be useful to develop a site conceptual model of the type used in ecological risk assessments. Helpful references include ASTM (1995), EPA (1998), and Suter (1996). An ecological scoping checklist for assembling a conceptual model is provided in Ryti et al. (1999). An automated conceptual model builder is also available (DOE 1997). 4.2 Step 2: Define Your Area of Evaluation In high level analyses, it is necessary to determine the spatial extent over which the graded approach will be applied. The assumptions regarding sources, receptors, and routes of exposure used in the development of the graded approach provide for conservative BCGs. In the derivation of the screening approach, the source medium to which the organisms are exposed is assumed to be infinite in extent and to contain uniform concentrations of radionuclides. The organisms are also assumed to be resident in the contaminated area (e.g., exposed to contaminated media) 100 percent of the time. Given these assumptions, the first approach shall be to use maximum radionuclide concentration data applicable to DOE-STD-1153-2019 39 your geographic area of interest (e.g., the entire site).1 It is not necessary for levels where only concentration matters. If use of the maximum concentrations over the entire site does not pass the general screening phase, then the boundaries of specific habitat / populations of interest should be defined. It is then within these boundaries that the evaluation will continue. Guidance on delineating evaluation areas can be found in Appendix C: Area Factors. 4.3 Step 3: Assemble and Organize Data on Radionuclide Concentrations in Environmental Media The next step is to collect and organize relevant data on radionuclide concentrations in environmental media. Radionuclide concentrations in surface water and/or sediment and in soil are needed for implementing the graded approach. Acceptable sources of data include but are not limited to:  Annual Site Environmental Reports;  Effluent monitoring and environmental surveillance data;  Remediation data; and  Data from special site-specific studies (i.e., ecological studies conducted for other purposes). The data should be organized by location and medium, and be applicable to the geographic area of

evaluation identified in Step 2 above. Locations may be defined by management and administrative characteristics (e.g., remediation sites; operations areas; operable units), physical characteristics (e.g., watershed; pond; stream), or ecological characteristics (i.e., corresponding to habitat types). Maximum radionuclide concentrations in environmental media shall be used in the initial application of the general screening phase to provide the most conservative evaluation.2 4.3.1 Aquatic System Considerations If you are conducting an aquatic system evaluation, note that use of radionuclide concentration data from co-located surface water and sediment samples is preferred and will result in a less conservative, more realistic evaluation. A mix of data from water and/or sediment samples collected from different locations within the vicinity of one another may be used, with justification. Note that where co-located samples are not available, only water or only sediment data may be used, but will result in a significantly more conservative evaluation. This is because the BCGs derived using individual water or sediment values involve the use of a conservative sediment distribution coefficient Kd to calculate the environmental media radionuclide concentration and dose contribution of either the missing water or sediment component. 1 If the data set is large, it is statistically likely there will be outliers with concentrations that may be much higher than the majority of data suggests. In this case, a concept of using the mean concentration plus one standard deviation would be acceptably conservative. 2 Data from very small areas with significantly higher concentrations (i.e., hot spots) should not be used, as it may not be representative of the entire area of evaluation. DOE-STD-1153-2019 40 4.3.2 Terrestrial System Considerations If you are conducting a terrestrial system evaluation, you should consider the types of receptors resident in your area of evaluation and the appropriateness of your soil samples with regard to these receptors. For example, surface soil samples may not be representative of potential radionuclide exposure to deep- rooted plant receptors. Note that if you have a water body in your evaluation area, you must also conduct an aquatic system evaluation. 4.3.3 Aquatic and Terrestrial Tissue Data Tissue concentration data are valuable for several reasons:  They may be entered into RESRAD-BIOTA, bypassing the need for Bivs;  They may be combined with soil, sediment, or water data to calculate site-specific Bivs; or  They may be used to calculate internal doses (see Appendix E: Dose Conversion Factors and Table E-2). For each radionuclide, Table E-2 lists the internal dose that results from a specific tissue concentration. For example, for Cs-137 the table lists 4.3E-6 Gy/y per Bq/kg (4.3E-5 rad/d per pCi/g). The reciprocal, 2.3E5 Bq/kg per Gy/y (2.3E4 pCi/g per rad/d) is the tissue concentration that will cause 1 Gy/y or 1 rad/day, respectively. Similarly, for Sr-90, 1.8E5 Bq/kg will cause 1 Gy/y and 1.7E4 pCi/g will cause 1 rad/day. Note that tissue concentrations are often reported on the basis of dry-weight or ash-weight. These must be converted to wet-weight concentrations for comparison with Table E-2. 4.3.4 Field Instruments Screening data may be obtained using field instruments such as those used by radiological control

technicians. The general principles are described in McNaughton (2009), and an example for the use of field instruments to measure Cs-137 in deer is described in Padgett (2006). Generally, the advantages include:  Many measurements;  Short times;  Immediate results;  Minimal disturbance; and  Low cost. The methods are generally sensitive enough for comparison with the default BCGs for soil. They may also be used to measure tissue concentrations, as described in Section 4.3.3 above. The method described by Padgett (2006) can be used with concentrations as low as 1 pCi/g, so it is not difficult to detect the concentration of 23,300 pCi/g that corresponds to 1 rad/d (see Appendix E.). DOE-STD-1153-2019 41 5 General Screening Phase A major goal of the general screening phase is to provide a method to easily apply data on radionuclide concentrations in an environmental medium to evaluate compliance with the dose rate criteria for biota. In the general screening phase, data on radionuclide concentrations in environmental media are compared with a set of generic BCGs. Each radionuclide-specific DOE BCG represents the limiting radionuclide concentration in environmental media which would not result in DOE’s established or recommended dose rate criteria for biota to be exceeded. These limiting radionuclide concentrations, or BCGs, are presented in Appendix G. These "look-up" tables allow for comparisons of radionuclide concentrations in environmental media with the BCGs. 5.1 Compare Data on Radionuclide Concentrations in Environmental Media with Generic BCGs A sum of fractions approach is used in comparing data on measured radionuclide concentrations in environmental media with the BCGs contained in the look-up tables. That is, when multiple radionuclides are present in multiple environmental media, the sum of fractions rule shall be applied to account for all sources of exposure. Hence, the sum of the ratios of the measured concentration of each radionuclide to its corresponding BCG for each medium shall then be summed across media, and the total sum of fractions shall not exceed 1.0. For each environmental medium, for radionuclides A, B, ... N, with concentrations CA CB…CN and corresponding screening BCG values 𝐵𝐶𝐺𝐴, 𝐵𝐶𝐺𝐵, …𝐵𝐶𝐺𝑁, this relationship for aquatic and terrestrial system evaluations is as follows: Aquatic System Evaluation [ 𝐶𝐴 𝐵𝐶𝐺𝐴 + 𝐶𝐵 𝐵𝐶𝐺𝐵 + ⋯+ 𝐶𝑁 𝐵𝐶𝐺𝑁 ] water + [ 𝐶𝐴 𝐵𝐶𝐺𝐴 + 𝐶𝐵 𝐵𝐶𝐺𝐵 + ⋯ + 𝐶𝑁 𝐵𝐶𝐺𝑁 ] sediment < 1.0 (Eq.1) Terrestrial System Evaluation [ 𝐶𝐴 𝐵𝐶𝐺𝐴 + 𝐶𝐵 𝐵𝐶𝐺𝐵 + ⋯+ 𝐶𝑁 𝐵𝐶𝐺𝑁 ] water + [ 𝐶𝐴 𝐵𝐶𝐺𝐴 + 𝐶𝐵 𝐵𝐶𝐺𝐵 + ⋯+ 𝐶𝑁 𝐵𝐶𝐺𝑁 ] soil < 1.0 (Eq.2) If the sum of fractions (the summed ratios between the radionuclide concentrations in environmental media and the radionuclide-specific BCGs) is less than 1.0, the dose to an aquatic or terrestrial receptor Sum of Fractions Rule When multiple radionuclides are present in multiple environmental media, the sum of fractions rule shall be applied to account for all sources of exposure. RESRAD-BIOTA Model Perhaps the easiest way to conduct and document a general screening phase is to enter the maximum concentrations of each radionuclide into the RESRAD-BIOTA software for a Level 1 evaluation for either a terrestrial or an aquatic ecosystem. DOE-STD-1153-2019 42 is below the biota dose limit, and you have passed the general screening evaluation. Proceed to Section

7, Documenting Your Biota Dose Evaluation Results. If the sum is greater than 1.0, further investigation is required (e.g., initiating site-specific screening or analysis). 5.1.1 Aquatic System Considerations In situations where co-located water and sediment data are not available, in the general screening phase you must estimate the missing radionuclide concentration data through the use of “most probable” radionuclide-specific Kd values. Radionuclide-specific most probable Kd values are provided in Appendix D and shown on the RESRAD-BIOTA main menu if the sediment check box is not checked. The radionuclide concentration data estimated for the missing water or sediment medium is then used along with the radionuclide concentration data for the available medium in the sum of fractions calculation as described previously. Judgment should be applied in determining if measured radionuclide concentration data for water and sediment media can be considered as originating from co-located water and sediment samples. If measured radionuclide concentration data for water and sediment media are only available from separate locations, calculate the missing radionuclide concentration data for each missing medium, and apply the approach that results in the highest (e.g., most conservative) sum of fractions in your biota dose evaluation. If the sum of fractions is less than 1.0, the dose to an aquatic receptor is below the biota dose limit, and you have passed the general screening evaluation. Proceed to Section 7, Documenting Your Biota Dose Evaluation Results. If the sum is greater than 1.0, further investigation is required (e.g., initiating site- specific screening or analysis). 5.1.2 Terrestrial System Considerations Typically, soil and water samples will not be co-located. Judgment should be applied to determine the likely source of drinking water for a terrestrial animal. Things to consider when making this judgment Example: Using the Sum of Fractions Rule Maximum radionuclide concentrations for water and soil collected within the evaluation area and available through the existing site environmental surveillance program were summarized. Maximum radionuclide concentrations for Cs-137 and Sr-90 in soil were 1.21 and 1.30 pCi/g, respectively. Maximum radionuclide concentrations for Cs-137 and Sr-90 in water were 49.6 and 84.5 pCi/L, respectively. Applying the sum of fractions rule, and using the RESRAD BCG values listed in Table G-3, one obtains the following: 𝑆𝑜𝑖𝑙: 1.21 pCi g 800 pCi g + 1.3 pCi g 800 pCi g = 3.1 × 10−3 𝑊𝑎𝑡𝑒𝑟: 49.6 pCi g 6 × 105 pCi g + 84.5 pCi g 5 × 104 pCi g = 1.63 × 10−3 3.1 × 10−3 + 1.63 × 10−3 = 4.8 × 10−3(𝑡𝑜𝑡𝑎𝑙 𝑠𝑢𝑚 𝑜𝑓 𝑓𝑟𝑎𝑐𝑡𝑖𝑜𝑛𝑠) Conclusion: Because 0.005 is less than 1.0, the dose to a terrestrial receptor does not exceed the recommended dose rate criteria for protection of populations of terrestrial plants and animals. Note that the soil medium provides most of the contribution to dose. DOE-STD-1153-2019 43 are the home range of your site’s terrestrial animals and the temporal availability of potential drinking water. 5.2 Dealing with High Background Levels of Naturally Occurring Radionuclides Radiation dose rates at local background reference sites can be used to ensure that the site-related dose rates represent an actual increase in exposure. If the evaluation area is suspected or has been documented to have high background levels of naturally occurring radionuclides, these background

levels may be taken into account when determining compliance of DOE activities with the biota dose rate criteria. For example, this may be a consideration for the two isotopes of radium (see BCGs for Ra- 226 and Ra-228, Appendix G). Background levels for environmental media should be estimated based on data for the same or similar media types in uncontaminated areas. If the sum of fractions for measured radionuclide concentrations in media from the contaminated area exceeds 1.0, this sum should be compared with the sum of fractions calculated using measured radionuclide concentrations in media from the background area. If the sum of fractions from the contaminated area does not exceed that from the background area, the contaminated area has passed the screening evaluation. Proceed to Section 7, Documenting Your Biota Dose Evaluation Results and document the results of the comparison. If the contaminated area sum of fractions does exceed the background sum of fractions, proceed to the next phases of the graded approach. DOE-STD-1153-2019 44 6 Analysis Phase The analysis phase of the graded approach contains three increasingly more detailed components of analysis for evaluating doses to biota: site-specific screening, site-specific analysis, and site-specific biota dose assessment. In the analysis phase, you are also increasingly moving away from the default parameters and assumptions used in the general screening phase of the graded approach. The amount of effort required for your biota dose evaluation and the information needed about site-specific conditions and receptors increase as you progress through the three components of the analysis phase. The amount of specialized assistance (e.g., in health physics, radioecology, and eco-risk assessment) that might be needed also increases as you progress through the components of the analysis phase. In return, the result will be a set of less conservative, more realistic and site-representative BCGs. The rationale for selection of site-specific parameters applied in this phase shall be sufficiently documented when reporting your biota dose evaluation results. Each of the three analysis components is described below. 6.1 Site-Specific Screening (RESRAD-BIOTA Level 2 evaluation) Site-specific screening allows you to apply knowledge of site-specific conditions and receptors in your biota dose evaluation in place of the default parameter values and assumptions used in the general screening phase of the graded approach. For example, use of mean radionuclide concentrations in place of values that were used in the level 1 screening, taking into account time dependence and spatial extent of contamination, may be considered. Parameters representative of site-specific receptors also may be considered. These considerations and their application in site-specific screening are discussed below. 6.1.1 Step 1: Assess Representativeness of Input Data on Radionuclide Concentrations in Environmental Media and Delineation of Evaluation Area Spatial and temporal variability relative to the distribution of contamination in the evaluation area can be taken into account when evaluating doses to biota. Each of the elements presented below should be considered collectively as you proceed through this step. 6.1.1.1 Consider Using Mean Radionuclide Concentrations Determine if mean radionuclide concentrations can be used in place of maximum concentrations. For

example, use of mean values is appropriate and permitted in situations where time-series data are Questions to Consider in Determining Your Path Forward in Site-Specific Screening:  Can I use mean radionuclide concentrations rather than maximum values?  Does it make sense to adjust or re-define my evaluation area, using knowledge of the spatial-temporal extent of my contamination with respect to receptor habitats?  Are the "limiting organism types" corresponding to my media and radionuclides expected to be present in my evaluation area?  Do I have site-representative parameters (e.g., Biv, Kd values) that can be used in place of default values? DOE-STD-1153-2019 45 available and of sufficient quality. Spatial variability in the distribution of contamination can also be taken into account. Location-specific data for individual radionuclides in specific environmental media are used in the screening process. When conducting a screening evaluation, it is important to use radionuclide concentrations that are estimated to be mean values or greater than mean values for the contaminated area. Only data at or above the mean are adequate for screening purposes because mean concentrations are assumed in this technical standard to approximate those concentrations to which a representative individual within a population would be exposed. Available data may not be adequate to ascertain that radionuclide concentrations are likely at or above mean values for the contaminated area. Non-representative measurements may occur and result in values that are considerably higher (or lower) than the actual mean concentration. That is, concentrations are so far above the mean value that they falsely indicate that biota are receiving doses above the recommended, criteria, or so far below the mean value that they falsely indicate that biota are receiving doses below the recommended limits. In these cases, it is acceptable to account for both spatial and temporal distributions of radionuclides in the environment when estimating mean values of radionuclides for use in site-specific screening. Radionuclide concentrations can be adjusted to account for site-specific spatial and temporal factors that will bring them closer to mean values. Consider the following examples:  If the source of radionuclides is an intermittent discharge to the environment, concentrations of radionuclides discharged to the receiving environment may be adjusted over time based on discharge records.  A correction factor for exposure area or organism residence time may be applied in the site- specific analysis component to account for intermittent sources of exposure that would affect all receptors in the evaluation area, or to account for the movements of organisms in and out of the contaminated area over time, for example, because of seasonal migration or diurnal migration in and out of the contaminated area.  If the contamination exhibits a decreasing gradient of concentration away from the source, then mean concentrations of contaminants within the contaminated area may be used, taking into account the intersections with distinct habitats. Where available contaminant data are comprehensive, it would be possible to accurately estimate the size of the contaminated area and the distribution of contamination within that area. Statistical methods may be used to calculate mean values. The statistical methods selected should be widely-used methods

referenced in standard statistical texts and/or recommended by a qualified statistician. However, where contaminant data are not sufficiently comprehensive to conduct rigorous statistical analyses but provide a semi-quantitative basis for estimating mean values, subjective judgment may be used with justification.  If the area being considered has been documented to have high background levels of naturally occurring radionuclides, these background levels may be taken into account when determining compliance of DOE activities with the recommended biota dose limits. For example, this may be an important consideration for the two isotopes of radium (see BCGs for Ra-226 and Ra-228 DOE-STD-1153-2019 46 in Appendix G). Background levels for water, soil and sediment media should be estimated based on data for the same or similar water, soil or sediment types in areas unaffected by facility effluents.  If available data does not produce a representative value of contaminant concentrations, additional data may need to be collected to obtain more realistic estimates of mean values. Either or both of the following types of data may be needed: (a) data on the spatial distribution of concentrations of radionuclides within the contaminated area; and (b) data on the size of the contaminated area. Both of these types of data are needed for estimating the mean concentrations of contaminants that are assumed to approximate the concentrations that a representative individual would encounter. In cases where very little data are available on the distributions of radionuclide concentrations, a preliminary survey may be needed. 6.1.1.2 Consider Using Less-Than-Detectable Values Environmental media often include extremely low concentrations of radionuclides. Measurements of these radionuclides are typically referred to as “non-detects.” It is possible to calculate net results that are less than zero (negative results). A common misconception is that negative or non-detect results should not be reported as is, but should be assigned a value of zero, the detection limit, or a fraction of the detection limit. These practices are not recommended because they bias the data. The best practice is to report and use all results in the summary statistics, whether positive, negative, or zero, as obtained. Refer to Chapter 8 of DOE Handbook 1216, Environmental Radiological Effluent Monitoring and Environmental Surveillance for more complete guidance on data analysis and statistical treatment of environmental datasets. 6.1.1.3 Consider Refining the Evaluation Area It may be useful to re-assess your rationale for delineating the evaluation area i.e., breaking one large area into several smaller areas) through consideration of the quality and spatial-temporal distribution of radionuclide concentration data, the ecological susceptibility and habitats of the receptors, and the spatial distribution of contaminants with respect to these habitats. Refer to Appendix C, Section C.1: Area Factors for detailed guidance in this area. 6.1.1.4 Consider Obtaining Additional Radionuclide Concentration Data Consider collecting additional radionuclide concentration data. For an aquatic system evaluation, consider using co-located water and sediment data if you have not already done so. 6.1.2 Step 2: Re-Run the Screening Evaluation Using Revised Radionuclide Concentration Data and/or Evaluation Area

Here you are comparing your refined data on measured radionuclide concentrations corresponding to your original or re-defined evaluation area, with the generic BCGs. This is done by re-entering these revised radionuclide concentration data for RESRAD-BIOTA Level 2. It is important to note that in this step you have not modified the initial, generic RESRAD-BIOTA Level 1 BCG values. They are the same generic BCGs that are used in the general screening phase of the graded approach. This step is DOE-STD-1153-2019 47 considered a site-specific screen in that you are now making site-specific judgements relative to your measured radionuclide concentration data and your evaluation area. If the sum of fractions is less than 1.0, then you have passed the site-specific screening evaluation. Proceed to Section 7, Documenting Your Biota Dose Evaluation Results. If the sum of fractions is greater than 1.0, then continue to progress through the graded approach. 6.1.3 Step 3: Assess Representativeness of Default Parameters/Assumptions for Generic BCGs; Select Site-Specific Parameters and Generate Site-Specific BCGs This step allows you to replace default parameters used in the general screening phase with site- representative parameters for use in site-specific screening. Each of the elements presented below should be considered collectively as you proceed through this step. 6.1.3.1 Identify Radionuclide-Specific Limiting Medium and Organism Type Review the radionuclide-specific BCGs used in the general screening phase of the graded approach. First, identify the environmental medium and individual radionuclides from your evaluation that provide the greatest contribution to potential dose (i.e., medium concentration: BCG ratios that represent the largest contributors to the sum of fractions). Then, for each of these radionuclides, identify the limiting organism type from which the generic BCGs were derived. Limiting organism types corresponding to generic BCGs are listed for each radionuclide in Appendix G. If you did not conduct a general screen prior to site-specific screening, go to the organism type table or spreadsheet that corresponds to the site-specific receptor you have chosen to use in your analysis. The site-specific receptor you select should be important to the structure and function of the community, in that protection of this organism within your evaluation area assures that all other organisms in your evaluation area are also protected. Some examples of receptors that could serve as good indicators of radiological impact are provided in Appendix C (Section C.1.4). 6.1.3.2 Review and Select Site-Specific Bioaccumulation Factors The general screening phase (Level 1) uses a conservative default bioaccumulation factor (Biv) in the estimation of internal radionuclide concentrations of an organism. This Biv, along with dose conversion factors, determines the internal dose to an organism. The Biv is based largely on empirical measurements of radionuclides in biological tissues of organisms collected in contaminated habitats. In cases where empirical measurements are unavailable or limited, the Biv is based on a conservative value derived using uncertainty analysis on the kinetic/allometric method (see Appendix F). The Biv serves as Selecting a Site-Specific Receptor The receptor should be important to the structure and function of the community. It should: (1) be expected to receive a comparatively high degree of exposure (e.g., expected to receive a radiation dose

to reproductive tissues which is relatively high per unit of radionuclide present in the ecosystem, in comparison to other receptors in the same community); (2) have a comparably high degree of radiosensitivity (e.g., radiation effects of concern occur at relatively low doses, in comparison with other receptors in the same community); and (3) exhibit a high degree of bioaccumulation. DOE-STD-1153-2019 48 a “natural integrator” of internal contamination, in that, it inherently reflects all pathways of intake by an organism. Here, in site-specific screening, Biv values representative of site-specific conditions and receptors can be used to generate site-specific BCGs in place of the default Biv values that were used in generating the generic BCGs. This site-specific screening result is a less conservative, but more realistic, evaluation of potential doses to biota for your area of evaluation. The initial values of the Biv were specifically chosen to produce conservative (i.e., overly protective) BCGs. It is recognized that actual Biv for a single radionuclide may range over several orders of magnitude, depending upon biotic and abiotic features of the environment. The default Biv values (and other input parameters) are contained in a set of organism type tables (Tables F-1 – F-4) and similar values are available in RESRAD-BIOTA. Review and select Biv values representative of site-specific conditions and receptors you have selected for your evaluation area. These site-specific Biv are entered into the appropriate organism type spreadsheet in RESRAD-BIOTA and used to generate site-specific BCGs. Sources for Biv values representative of your site-specific conditions and receptors include:  Your own derived values for site-specific receptors; and  Values published in the scientific literature or in site-specific technical reports (i.e., from specialized ecological studies) for receptors that are comparable to site-specific receptors in your evaluation area. 6.1.3.3 Review and Select Site-Representative Kd Values For aquatic system evaluations where co-located water and sediment samples are not available, recall that in the general Level 1 screening phase a default most probable Kd is used to calculate the environmental media radionuclide concentration and dose contribution of either the missing water or sediment component. Site-specific screening allows you to consider the use of a site-representative Kd value in place of the default most probable value that was used in the general screening phase. Minimum, maximum, and most probable Kd values for each radionuclide are provided in Appendix D, Tables D-1 andD-2. Sources of Kd values representative of your site-specific conditions include:  Your own site-derived Kd values; and  Values published in the scientific literature or in site-specific technical reports. Site-representative Kd values can be entered into RESRAD-BIOTA Level 2 evaluations and used in generating site-specific BCGs. 6.1.4 Step 4: Re-Run Screening Evaluation and Compare Data on Radionuclide Concentrations in Environmental Media with Newly-Generated Site-Specific BCGs The use of Biv values appropriate for site-specific conditions or receptors should result in more realistic, site-representative BCGs. When using RESRAD-BIOTA, the generic Level 1 BCGs are automatically updated with the newly generated BCGs, allowing for easy evaluation. If the sum of fractions (the

summed ratios between the radionuclide concentrations in environmental media and the radionuclide- specific BCGs) is less than 1.0, the dose to the aquatic or terrestrial receptor is below the biota dose limit. If the sum is greater than 1.0, further analysis is required. DOE-STD-1153-2019 49 6.2 Site-Specific Analysis (RESRAD-BIOTA Level 3 evaluation) In site-specific analysis, a kinetic/allometric model is employed to conduct a more rigorous analysis of riparian animal and terrestrial animal organism types. Here you are conducting a very site-specific evaluation (essentially estimating an upper-bound dose) to a site-specific riparian or terrestrial animal of known characteristics (e.g., body mass, behavior, internal exposure pathways, and parameters). Recall that the general and site-specific screening approaches use a Biv value in the estimation of internal dose to an organism. As mentioned earlier, the Biv serves as a "natural integrator" of internal contamination, in that, it inherently reflects all pathways of intake by an organism. In site-specific analysis, simplistic, first-order kinetic modeling is used to examine the internal pathways of exposure for riparian animal and terrestrial animal receptors in greater detail. Appropriate parameters representing individual mechanisms (e.g., ingestion; inhalation) that contribute to internal dose are applied in place of the Biv (one value which reflects all mechanisms contributing to internal dose). Appropriate values (e.g., organism body mass; ingestion rate; inhalation rate; biological uptake and elimination rates) that are representative of site-specific conditions and receptors are used in the estimation of internal dose and generation of site-specific BCGs. Allometric equations relating body size to many of these parameters (e.g., ingestion rate; inhalation rate; life span) are used in the estimation of internal dose. Alternatively, you can enter your own values in place of allometrically derived parameters. A correction factor for exposure area or organism residence time may also be applied for all organism types in site-specific analysis. 6.2.1 Step 1: Assess Representativeness of Default Parameters/Assumptions for Kinetic/Allometric Models; Select Site-Specific Parameters and Generate Site-Specific BCGs This step allows you to examine and replace default parameters, assumptions, and allometric relationships used in kinetic/allometric models to derive BCGs for riparian animals and terrestrial animals. A correction factor for exposure area or organism residence time may also be applied for all organism types. Each of the elements presented below should be considered collectively when implementing this step. 6.2.1.1 Identify Radionuclide-Specific Limiting Medium and Organism Type Review the radionuclide-specific BCGs used in the general or site-specific screening portions of the graded approach. First, identify the environmental medium and individual radionuclides from your evaluation that provide the greatest contribution to potential dose (i.e, medium concentration: BCG ratios that represent the largest contributors to the sum of fractions). Then, for each of these radionuclides, identify the limiting organism type from which the general or site-specific BCGs were derived. Limiting organism types corresponding to general BCGs are listed for each radionuclide in Appendix G, and in the corresponding RESRAD-BIOTA tables. If the riparian animal or terrestrial animal

organism types are listed, then you may consider the guidance in Sections 6.2.1.2 – 6.2.1.4 below. If riparian or terrestrial animals are not listed as the limiting organism types, then you need only consider Section 6.2.1.2. If you did not conduct a general or site-specific screen prior to site-specific analysis, the proceeding statement applies to the site-specific receptor you have chosen to use in your analysis. DOE-STD-1153-2019 50 6.2.1.2 Consider Correction Factor for Exposure Area or Receptor Residence Time A correction factor for exposure area or receptor residence time should be among the first parameters that you consider in site-specific analysis. Temporal and spatial variability can be taken into account when evaluating doses to biota. For example:  radionuclides will typically be distributed non-uniformly in the environment; and  organisms are typically distributed non-uniformly within the environment such that exposure may vary among individuals in an affected population (i.e., organisms may migrate into and out of areas of greater and lesser contamination). The general and site-specific screening portions of the graded approach assume for conservative purposes that an organism's residence time in the evaluation area is 100 percent and that the contaminated media are available 100 percent of the time to provide a source of exposure. These assumptions can be modified in site-specific analysis. Correction Factor for Receptor Residence Time The term "residence time" as used in the graded approach refers to the fraction of time that biota resides in a radioactively contaminated area. In site-specific analysis, a correction factor for residence time (i.e., as a fraction of time) may be applied to take into account a specific receptor's home range, movements, and behavior relative to the evaluation area. This correction factor is entered into the “Area Factor” box on the dose conversion factors (DCF)/Exposure tab on the Organism edit screen of RESRAD-BIOTA. This is then factored into RESRAD-BIOTA generating site-specific BCGs. Correction Factor for Exposure Area Radionuclides will typically be distributed non-uniformly in the environment. In site-specific analysis, a correction factor for contaminated area (i.e., as a fraction of time) can be applied to take into account an intermittent source of exposure to all receptors in the evaluation area. This correction factor is entered into the “Area Factor” box on the DCF/Exposure tab on the Organism edit screen of RESRAD- BIOTA. This is then factored into RESRAD-BIOTA generating site-specific BCGs. 6.2.1.3 Riparian and Terrestrial Animals: Review and Select Parameters Representative of Site-specific Conditions and Receptors In site-specific analysis you can also modify the individual parameters that relate to internal exposure pathways for site-specific conditions and receptors. RESRAD-BIOTA is designed for easy modification of these parameters and subsequent generation of site-specific BCGs that are derived using these new parameter values. Refer back to Table 2-2 for a complete list of parameters that can be modified when conducting a site-specific analysis. 6.2.1.4 An Important Note Concerning the Use of Available Biota Tissue Data It is important to note that the use of measured concentrations of radionuclides in tissues of plants and animals in estimating internal dose is a reasonable and acceptable approach if adequate data are

available. That is, if it can be justified that the available tissue data: DOE-STD-1153-2019 51  Are representative of species within the evaluation area that are capable of receiving the highest dose; and  Reflect a representative sampling of the population within the evaluation area. These considerations are especially important in cases where biota tissue data becomes available as a result of opportunistic sampling (e.g., road kills; hunting). If available biota tissue data is determined to be inadequate, then collection and analysis of biota from the evaluation area will be required. The internal dose conversion factors for biota and external dose conversion factors for water, sediment and soil used to derive the generic BCGs in the graded approach are provided in Appendix E. These values, together with your measured radionuclide concentrations in water, sediment and soil, and biota tissue data, can be used to estimate an upper-bound dose to a receptor. 6.2.1.5 Riparian and Terrestrial Animals: Review and Select Food Source Parameter Values Representative of Site-Specific Receptors The kinetic/allometric method for deriving riparian and terrestrial animal BCGs uses a radionuclide- specific food source parameter in calculating the internal dose contribution for these organism types. The method uses radionuclide-specific default Bivs for aquatic animals and terrestrial plants (Appendix F) as the default food source parameter values for riparian and terrestrial animals respectively. You may review the appropriateness of these default food source parameter values (i.e., Biv s and their source organisms) and replace these with food source parameter values Bivs corresponding to organisms which are more representative of the expected food sources for the riparian or terrestrial animal you have selected to use in your site-specific analysis. When using RESRAD-BIOTA, changing the radionuclide- specific Biv values in the aquatic animal and terrestrial plant spreadsheets will automatically change the riparian animal and terrestrial animal BCG values, respectively. These new site-specific BCGs will also show up on the Results screen and BCG Report, allowing for easy comparisons with previously entered radionuclide concentration data. Entering Site-Representative Parameters for Riparian Animals and Terrestrial Animals in RESRAD Biota First, click on the edit button below the appropriate Organism Type in RESRAD-BIOTA, then select the “Input Source” tab. 1) If you have data for representative or maximum radionuclide concentrations in the tissue of the organism of interest, change the values in the “UseTissue” column from “No” to “Yes.” Then click on the “Input” tab and the “Tissue Concentrations” tab to allow this data to be entered. 2) If you do not have representative tissue concentrations for organism of interest, the Kinetic/Allometric Method can be used to obtain more realistic dose estimates by the following: a. In the “UseAllom” column on the “Input Source” tab, change the values from “No” to “Yes” to allow these parameters to be modified. b. Click on the “Input” tab then on the “Allometric” tab to access the individual parameters (e.g., body mass; ingestion rate; inhalation rate; radionuclide uptake and retention factors) related to mechanisms providing an internal dose may be modified. Changing the radionuclide-specific food source Biv values for the aquatic animal and terrestrial plant will automatically change the BCG values in the riparian animal and terrestrial animal spreadsheets, respectively.

DOE-STD-1153-2019 52 6.2.2 Step 2: Re-Run the RESRAD-BIOTA and Compare Data on Radionuclide Concentrations in Environmental Media with Newly-Generated Site-Specific BCGs The use of parameter values and a correction factor appropriate for site-specific conditions or receptors should result in more realistic, site-representative BCGs. If the sum of fractions (the summed ratios between the radionuclide concentrations in environmental media and the radionuclide-specific BCGs) is less than 1.0, the dose to the aquatic or terrestrial receptor organism is below the biota dose limit. Proceed to Section 7, Documenting Your Biota Dose Evaluation Results. If the sum is greater than 1.0, further analysis is required. 6.3 Site-Specific Biota Dose Assessment (RESRAD-BIOTA Level 3 evaluation) 6.3.1 Determine if Additional Analysis is Warranted While the majority of the graded approach centers on the use of measured radionuclide concentrations in environmental media for comparison with the BCGs, the site-specific biota dose assessment component of the analysis phase centers on the actual collection and analysis of biota from the evaluation area. This is so that measured concentrations of radionuclides in the tissues of biota can then be used to more realistically estimate the internal dose contribution to a site-specific receptor. Additional analysis may be warranted if biota dose evaluations using the screening and analysis methods described to this point continue to indicate that there is a potential adverse impact from radiation as a stressor to populations of biota (i.e., the BCGs are exceeded). An important point is that exceeding the BCGs should not force a mandatory decision regarding remediation of the evaluation area, but rather is an indication that further investigation is likely necessary. There are many factors that should be considered when deciding how to respond following a determination that the BCGs are exceeded (e.g., ecological relevance and susceptibility of the affected population; size of the contaminated area and persistence of contaminants; impacts of remediation alternatives). If radionuclide concentrations in environmental media exceed the BCGs, two courses of action may be taken. It may be desirable to perform detailed dose assessments for relevant receptors but given the potentially large expense that such a site-specific assessment could incur, removing the sources of ionizing radiation by reducing or eliminating discharges, or remediating existing environmental contamination, should also be considered. Site-specific conditions, especially the cost of eliminating discharges and/or remediating contaminated areas, will determine which approach is the most desirable. DOE-STD-1153-2019 53 6.3.2 Recommended Approaches to Designing and Conducting the Site-Specific Dose Assessment It is strongly recommended that all dose assessments be designed and conducted following the Guidelines for Ecological Risk Assessment (EPA 1998). Use of these guidelines will help ensure that the resulting dose assessments are technically sound. In addition, some of the steps in the ecological risk process (i.e., development of a site conceptual model) will be useful for assessing toxicological risks associated with some radionuclides (e.g., uranium isotopes) as well as the ecological risks from other co- occurring substances or stressors within the contaminated area (e.g., hazardous chemicals). The site

conceptual model will also be useful for understanding the large-scale distribution of contaminants and the sources of ecological risk to the populations within and beyond the study area. If multiple stressors are present and need to be evaluated, then appropriate guidance concerning cumulative risk assessment should be considered (i.e., see EPA 1997b). In addition to the references found in EPA’s Guidelines for Ecological Risk Assessment, the following references and materials may be useful.  Bilyard, C. R., H. Beckert, J. J. Bascietto, C. W. Abrams, S. A. Dyer, and L. A. Haselow. 1997. Using the Data Quality Objectives Process During the Design and Conduct of Ecological Risk Assessments. DOE/EH-0544, U.S. Department of Energy, Office of Environmental Policy and Assistance, Washington, D.C prepared by Pacific Northwest National Laboratory, Richland, Washington.  Sample, B. E., M. S. Aplin, R. A. Efroymson, G. W. Suter II, and C. J. E. Welsh. 1997. Methods and Tools for Estimation of the Exposure of Terrestrial Wildlife to Contaminants. ORNL/TM-13391, prepared for U.S. Department of Energy, Office of Environmental Policy and Assistance by Oak Ridge National Laboratory, Oak Ridge, Tennessee. Should Additional Analysis or Remedial Action be Considered? Factors to consider if initial general screening, site-specific screening, and site-specific analysis elements of the graded approach indicate a potential radiological impact to populations of biota within the evaluation area:  The geographical extent of the contamination  The magnitude of potential or observed effects of the contamination relative to the level of biological organization affected  The likelihood that these effects could occur or will continue to occur  The presence of genetically-isolated populations  The ecological relationship of the affected area to the surrounding habitat  The preservation of threatened or endangered species, or commercially or culturally valued species  The recovery potential of the affected ecological resources and expected persistence of the radionuclides of concern under present site conditions  The short- and long-term effects of the remedial alternatives on the habitat and the surrounding ecosystem  Information obtained through a “lines of evidence” approach DOE-STD-1153-2019 54  U.S. Department of Energy. 2015. Environmental Radiological Effluent Monitoring and Environmental Surveillance. DOE-HDBK-1216-2015, U. S. Department of Energy, Washington, D.C.  U.S. Department of Energy. 1998. Compendium of EPA-Approved Analytical Methods for Measuring Radionuclides in Drinking Water. Office of Environmental Policy and Assistance, Assistant Secretary for Environment, Safety and Health, U.S. Department of Energy, Washington, D.C.  U.S. Environmental Protection Agency (EPA). 1997. Ecological Risk Assessment Guidance for Superfund: Process for Designing and Conducting Ecological Risk Assessments. EPA 540-R-97- 006 (Interim Final June 5, 1997), U.S. EPA, Washington, D.C.  U.S. Environmental Protection Agency (EPA). 2006. Guidance on Systematic Planning Using the Data Quality Objectives Process. EPA/240/B-06/001, U.S. EPA, Washington, D.C. DOE-STD-1153-2019 55 7 Documenting Your Biota Dose Evaluation Results At a minimum, your results shall be documented in your Annual Site Environmental Report (DOE O 231.1B, 2011). The following information shall be summarized in the Annual Site Environmental Report,

and described in more detail within a report retained on file for future reference:  Specify the biota dose rate criteria being complied with, such as those presented in this technical standard. Note DOE Order 458.1 does not specify dose limits for biota but does specify use of a process;  Identify the methods used to demonstrate compliance with these criteria. Cite the method used (i.e., this technical standard). Describe the process used (e.g., general screening phase, site- specific analysis, actual biota dose assessment involving the collection and analysis of biota);  Describe the area(s) of evaluation, sources of exposure, organism types, media types, and radionuclide data used in the evaluation;  Summarize the results (e.g., sum of fractions for media and radionuclides are less than 1; doses calculated are less than biota dose rate criteria) for the site area(s) of evaluation; and conclusions;  Summarize why the evaluation was conducted and how the results will be used (e.g., to demonstrate compliance with DOE dose rate criteria, for use in outreach activities, in response to stakeholder or regulator requests, or for use in an eco-risk assessment.); and  All detailed information used in calculations (e.g., site-specific parameters selected and the rationale for their use) shall be described and retained on file for future reference and for sharing as lessons learned. DOE-STD-1153-2019 A-1 Appendix A. Evaluating Dose to Individual Organisms: Guidance on the Applicability of the Graded Approach A.1. Considerations on the Meaning of "Individual" Organism At the outset, the concept of an “individual” organism needs to be understood. A system for protection of an “individual” organism, such as the system for radiation protection of humans, is never intended to apply to each and every specific, identifiable individual (i.e., a named member of the public). Rather, the concept of an “individual” organism refers to a reference organism that is intended to represent typical characteristics within a particular population group. The main reason for use of the concept of a reference individual organism is that the characteristics of specific, identifiable organisms (e.g., individual radiosensitivities, the behavior of radionuclides in the body of an individual) can never be known. In radiation protection of humans, for example, compliance with the dose limits for individual workers or members of the public is demonstrated by calculating doses to a hypothetical construct called Reference Person. Calculating a limiting dose (and risk) to a reference individual organism, provides reasonable confidence that no real population of individuals will experience unacceptable doses (and risks), but it cannot be ensured that unacceptable outcomes will never happen to a specific individual organism. A.2. Applicability of Methods and Models in the DOE Graded Approach to Evaluations of Individual Organisms The graded approach for evaluating radiation doses to aquatic and terrestrial biota developed by DOE, taken as a whole, can be viewed as consisting of two components:  Methods or models for calculating dose to biota per unit concentration of radionuclides in environmental media (water, sediment, and soil); and  A set of dose rate criteria for aquatic animals, terrestrial plants, and terrestrial animals, which represent dose levels of concern based on current information on dose-response relationships

in a variety of organisms. An ecological risk assessment may also be done instead. By combining calculated doses per unit concentration of radionuclides in environmental media with the dose rate criteria, BCGs are obtained. The BCGs then are compared with measured concentrations to assess compliance with the dose rate criteria. The models for calculating dose per unit concentration of radionuclides in environmental media clearly apply to individual organisms. Thus, these models are directly applicable to individual organisms (i.e., for application to individual members of threatened and endangered species). DOE does not apply the dose rate criteria to protection of individual members of a species, instead the criteria applies to protection of populations of species. A.3. Applicability of Biota Dose Rate Criteria to Protection of Individual Organisms The dose rate criteria used by DOE are based on studies of dose-response relationships in populations of aquatic animals, terrestrial plants, and terrestrial animals. The particular biological endpoints for which dose-response relationships have been obtained include early mortality and impairment of reproductive DOE-STD-1153-2019 A-2 capability, the latter including effects on reproductive tissues and the embryo/fetus or seeds. Since reproductive effects in a population generally occur at lower doses than early mortality, the dose- response relationships for reproductive effects were used to derive the dose rate criteria. Thus, at first sight, it would appear that the dose rate criteria should be applied only when protection of populations of organisms is of concern, but they may also be appropriate when protection of individual members of a species is of concern. However, the following points about the dose rate criteria should be noted. First, even if protection of populations is the primary concern, effects on populations of organisms can be inferred only by considering effects in individual organisms comprising a given population. In determining effects on populations, one would essentially need to count the number of impaired organisms in an irradiated population compared with the number of similarly impaired organisms in an unexposed population. Second, the dose rate criteria are based on the lowest dose at which any reproductive effects are observed in any species of aquatic animals, terrestrial plants, or terrestrial animals. Thus, if it is assumed that the species studied include those which are among the more radiosensitive, the dose rate criteria intended to reasonably ensure that there would be no significant effects at a population level should ensure that there would be no observable effects on individual members of a species, bearing in mind that there is always a background of similar effects from all causes, which limits the ability to observe or differentiate radiation-induced effects. A.4. Use of the DOE Graded Approach for Evaluating Dose to Individual Organisms: Application Considerations In examining the models and methods contained in the graded approach, and the basis for the biota dose rate criteria one key difference between applying them to protection of individuals or protection of populations is in regard to the extent to which calculated doses could be averaged over the spatial extent of contamination and over time. In protecting populations, considerable averaging over space

and time could be allowed and still ensure adequate protection. In protecting individuals, however, it could be more appropriate to allow little or no averaging over space and time. Thus, in protecting individuals organisms, use of the maximum concentrations of radionuclides in the environment at any location and at any time could be more appropriate. Use of safety factors, appropriate default parameter values, maximum radionuclide concentrations in environmental media, and 100 percent organism residence time and exposure may support the application of the graded approach for evaluating doses to individuals. A.5. Consideration of Deterministic vs. Stochastic Effects There is one additional caution that should be considered when applying the dose rate criteria to individual organisms, such as those for a threatened and endangered species. The dose rate criteria were derived from observed dose-response relationships for effects that generally are assumed to be deterministic in character, meaning that there should be no observable effects at doses below some threshold. However, there also is a possibility that stochastic radiation effects could be important in exposures of biota. DOE-STD-1153-2019 A-3 Information on stochastic effects in biota was considered in the 1996 UNSCEAR report on Effects of Radiation on the Environment (UNSCEAR 1996). The effects studied were at the cellular level, and include scorable cytogenetic effects (effects on DNA). The UNSCEAR report concluded that as long as the dose was kept below the dose rate criteria derived from dose-response relationships for reproductive effects, stochastic effects should not be significant at a population level. However, the discussion in the UNSCEAR report leaves open the question of whether stochastic effects could cause harm in an individual organism (e.g., induction of a tumor that would result in premature death of an individual compared with the normal life span). There are two difficulties with interpreting the available data. First, the data on scorable cytogenetic effects appear to be considerably limited compared with the data on early mortality and reproductive effects. Second, although the available data in mammals and arthropods appear to indicate that scorable cytogenetic effects can be observed at dose rates roughly 100 times lower than the lowest dose rates causing early mortality and roughly 10 times lower than the lowest dose rates causing reproductive effects, it is difficult to interpret the significance of these effects in regard to harm to an individual organism (i.e., induction of tumors). For example, effects on DNA in humans who live in areas of unusually high natural background are easily observed, but increased incidence of cancers has not been observed in these populations. Therefore, it is difficult to know how to apply the available information on scorable cytogenetic effects in a system for protection of individuals or populations. The best that can be said is that observations of these effects provide one more piece of information that could be used in evaluating the consequences of radiation exposures of biota and in deciding how to respond to those consequences. DOE-STD-1153-2019 B-1 Appendix B: Relative Biological Effectiveness (RBE) B.1. Summary of Guidance Radiation weighting factor (Wr) is a parameter used in dose calculation and is meant to account for the

varying impacts that differing radiation types have on tissue (at identical radiation doses Wr values are estimated from cellular data measuring relative biological effectiveness (RBE) factors (i.e., the inverse ratio of doses causing the same level of effect) and are used to harmonize the different types of ionizing radiation (e.g., alpha, electrons, and photons). The use of Wr allows a dosimetrist to weight absorbed dose rates according to the biological harm inflicted by a certain type of radiation exposure. The use of radiation weighting factors in biota dose assessment is complex; the ICRP (2008b) has acknowledged this and promises forthcoming guidance on the issue. To accommodate this complexity, the default effects thresholds and radiation weighting factors used in the graded approach (and RESRAD-BIOTA) can be adjusted. In RESRAD-BIOTA for example, the expected safe level of radiation exposure in populations of terrestrial animals might be divided by a modifying factor (i.e, 20) when evaluating the potential for adverse effects on individuals of a threatened or endangered species. Conversely, UNSCEAR has adopted the default radiation weighting factor of 10 for alpha particles and might be reduced to 5, to be consistent with new data concerning deterministic effects in biota as a consequence of radiation exposure. At that time, the RESRAD Biota code will need to be updated along with the affected Tables in Appendix E referenced in this standard. To be conservative, all DOE sites should use a radiation weighting factor of 10 (which may be reduced to 5 in the future) for alpha particles when calculating internal absorbed dose to aquatic and terrestrial biota for the purpose of demonstrating protection with the applicable dose rate criteria applied in this technical standard. The result of this calculation should be reported in rem. The reader should be aware that RESRAD-BIOTA does not have an input field for Wr and instead requires the user to enter RBE. While RBE and Wr are not the same quantity, for the purposes of using RESRAD- BIOTA, they should be treated as such. B.2. Statement of Issue The dose rate criteria to aquatic and terrestrial biota adopted in this technical standard are expressed in terms of absorbed dose. These dose rate criteria are based on studies of radiation effects in biota resulting from exposure to photons having a low linear energy transfer (LET); e.g., NCRP (1991) and IAEA (1992). For biota exposed to alpha particles, which are high-LET radiations, consideration must be given to increasing absorbed dose by a factor representing the RBE of this type of radiation.3 The increased RBE of alphas, relative to gamma or beta radiations, arises due to increased tissue damage from higher LET radiations. Using Wr in this situation accounts for this increased tissue damage. 3 The RBE of any radiation is defined as the ratio of the absorbed dose of a reference radiation (normally gamma rays or X rays) required to produce a level of biological response to the absorbed dose of the radiation of concern required to produce the same level of biological response, all other conditions being kept constant. DOE-STD-1153-2019 B-2 The use of a radiation weighting factor is of concern only in estimating dose to biota resulting from internal exposure to alpha-emitting radionuclides. Alpha particles are assumed not to contribute to the absorbed dose from external exposure, due to their very short range in matter.

B.3. Background on Radiation Weighting Factor In human dosimetry, Wr is used to correct for differing RBEs of radiation (e.g., alpha vs neutron vs beta vs gamma). RBEs generally depend on LET and the particular biological effect of concern.4 For alpha particles of any energy, the assumption for humans is that Wr =20 (ICRP 1991, ICRP 2007). This value represents the increased RBE for the stochastic effects of alpha particles in humans (NCRP 1990). Controversy exists around the practice of applying a radiation weighting factor for alpha particles to the calculated absorbed dose to biota. Some investigators argue that a radiation weighting factor of 20, based on the value Wr =20 used in radiation protection of humans, may be inappropriate for biota (Baker and Soldat 1992; Amiro 1997, ICRP 2008b). They argue a value of Wr = 20 is inappropriate because the radiation effects of concern are not the same for humans versus biota (i.e., stochastic risk vs deterministic risk). The NCRP recommends omitting a Wr value altogether for biota, arguing that the conservative models used to estimate tissue concentrations of alpha-emitting radionuclides offer sufficient conservativism to be protective (NCRP 1991). Others (e.g., Blaylock et al., 1993, Jones 2000) have applied the human Wr =20 value in biota dose assessment. The ICRP (2008b) has acknowledged the problem of Wr in biota dosimetry and has promised forthcoming guidance on the issue. However, as discussed previously, all DOE sites should use a Wr of 10 for alpha particles when calculating internal absorbed dose to aquatic and terrestrial biota for the purpose of demonstrating protection with the applicable dose rate criteria applied in this technical standard. B.4. Data on Deterministic RBEs for High-LET Radiations RBE data for deterministic radiation effects have been reviewed and evaluated by the ICRP (1990). The RBEs at low doses and dose rates for different types of high-LET radiation estimated by the ICRP may be summarized as follows.  The RBE for deterministic effects induced by 1-5 MeV neutrons varies from 4 to 12, and the average value based on the results of 19 determinations is about 7.  The RBE for deterministic effects induced by 5-50 MeV neutrons varies from 1 to 10, and the average value based on the results of 31 determinations is about 5.  The RBE for deterministic effects induced by heavy ions (C, Ne, and Ar) varies from 1 to 8, and the average value based on the results of 19 determinations is about 4.  The data on deterministic effects induced by alpha particles are much less extensive than the data for the other high-LET radiations, but two separate determinations yielded estimated RBEs of about 7 and 10. 4 The radiation weighting factor (Wr) replaced the average quality factor (𝑄̅) in ICRP report 60 (1991). DOE-STD-1153-2019 B-3  The average RBE for deterministic effects, based on all determinations, is about 5. The information summarized above leads to the conclusion that, for high-LET radiations, the radiation weighting factor for deterministic effects is substantially less than the corresponding radiation weighting factor used in radiation protection of humans. Based on this information, the radiation weighting factor for deterministic effects induced by alpha particles appears to lie in the range of about 5-10. DOE-STD-1153-2019 C-1 Appendix C: Guidance for Defining the Evaluation Area, Temporal and Spatial Averaging, and Estimating Mean Values

C.1. Area Factors: Defining the Evaluation Area As stated in Section 5, the approach in the general screening phase should be to use maximum radionuclide concentration data applicable to the largest area of interest (i.e., the entire site). If the screening analyses using the default BCGs identify a need for additional analyses, then mean radionuclide concentrations may be applied in the site-specific screening phase of the graded approach. The definition of the evaluation area is an important aspect of any spatial averaging of radionuclide concentrations that may be applied in the graded approach. This section provides an approach for defining the evaluation area which uses the intersections of contaminated areas and populations of interest to define the areas over which concentrations can be averaged. The selection of an appropriate biota dose evaluation area is governed by the principles of susceptibility and ecological relevance (EPA 1999). For large DOE sites, the entire site would, in most cases, be too large an evaluation area, because most of the biota on the reservation would not be exposed to the contamination. Focus should be on most exposed and most radiosensitive biota populations or on areas where it has been deemed important to protect individual organisms (i.e., endangered species). Biota which do not come into contact with contaminants, do not receive dose, and the inclusion of non- contaminated areas in the calculation of mean concentrations could result in low doses not representative of the actual impacts to the affected biota. On the other hand, the individual operable unit, waste trench, or contamination source would, in most cases, be too small to be ecologically meaningful and bias doses high. Although biota living in a 100 m2 waste trench may be affected by trench contaminants, the loss of, or effects to, these individuals will likely have little impact on the population of small mammals in the region or on a broader scale ecosystem function. There are operations that utilize short high-energy beams that would cause a large dose to any small creatures that got in the way of the beam. Such unlikely and infrequent exposures would not have significant effect on the populations and should not be used as a scenario in the graded approach. Beyond these criteria, the scale of application depends greatly on site-specific conditions. It is possible, however, to provide general guidance for selecting an appropriately scaled application area. This guidance is not meant to be prescriptive. Each step of the process involves a significant element of professional judgment and policy; and requires appropriate justification and documentation. In particular, the environmental monitoring organization at the site will be required to determine, justify, and document appropriate boundaries for areas with similar environmental concentrations of the same radionuclides (referred to hereafter as contaminated areas). Similarly, the site ecologists will need policy guidance and will be required to determine, justify, and document appropriate boundaries defining populations of interest or similar habitat types for which populations could be inferred. The intersection of contaminated areas and the population or habitat boundaries define the areas over which concentrations can be averaged if use of the maximum concentrations at any locations does not

show compliance with the dose rate criteria. This kind of analysis is most easily done using area maps, and Geographic Information Systems (GIS) will prove an invaluable tool. The following steps can be applied to determine this intersection. DOE-STD-1153-2019 C-2 C.1.1. Determine whether this method is necessary First, use the default BCGs in the general screening phase with the input contaminant concentrations set at the highest concentrations, or a representative maximum value as discussed previously, found in your area of interest (e.g., the entire site or the evaluation area), based on local sampling guidance and procedures. If you pass the general screening phase, no further consideration is necessary. If use of the maximum concentrations at any location does not pass the general screening phase, then proceed below. The following steps of the process center on determining the boundaries of the contaminated areas and their relationship to biota populations. This will likely involve consideration of:  Boundaries presented by the quality, quantity, and distribution of available environmental radionuclide data, and resulting from the design of the site environmental monitoring and surveillance program;  Boundaries presented by the susceptibility, ecological relevance, and habitat of receptors relative to the radionuclide contamination; and  Boundaries resulting from the management and administration of facilities and operations areas on the site (e.g., location and extent of waste management facilities, production facilities, operable units, and operations areas). C.1.2. Determine and map the boundaries of the contaminated areas One possible set of boundaries might be the initial isopleths of a contamination plume, but there are other possibilities, particularly if the radionuclides present, their historical deposition, or their present environmental concentrations differ from location to location. The environmental monitoring organization should determine the most meaningful and justifiable boundaries across their site, ensuring consistency for subsequent analyses as much as possible C.1.3. Determine the receptors In order to have an understanding of the appropriate boundaries for exposed biota, it is necessary to understand which organisms are used in the graded approach. The choice of organisms used in this methodology, as illustrated in Table C-1, evolved from consideration of the existing and radiation dose rate criteria for biota. Biota dose rate criteria had been set for aquatic animals, and were being considered for terrestrial plants and animals. Accordingly, the screening methodology had to accommodate these three general categories. A fourth, riparian animal, was added after recognizing that the riparian pathways of exposure combined aspects of both the terrestrial and aquatic systems. Four organism types and their corresponding dose rate criteria were used in deriving the screening and analysis methods contained in this technical standard. The principal exposure pathways considered for aquatic animal (1 rad/d), riparian animal (0.1 rad/d), terrestrial plant (1 rad/d), and terrestrial animal (0.1 rad/d) organism types are shown in Appendix H. Dose evaluations for site-specific receptors (as DOE-STD-1153-2019 C-3 defined by the user in the analysis phase of the graded approach) should reflect consideration of all relevant exposure pathways depicted in these figures. C.1.4. Example receptors that could serve as good indicators of radiological impact Selected examples of representative organisms from several DOE sites that could be used in the analysis phase of the graded approach as indicators of radiological impact are provided in Table C-1. These examples are provided for illustrative purposes and are not all-inclus