Modeling Radionuclide Transport in the Environment and Assessing

Modeling Radionuclide Transport in the Environment and Assessing Doses to Humans, Flora, and Fauna: The RESRAD Family of Codes Charley Yu, Ph. D, CHP RESRAD Program Manager Environmental Science Division University of Cincinnati / Ohio State University Joint Nuclear & Radiological Engineering Graduate Seminar Series May 9, 2006 Argonne National Laboratory Office of Science U. S. Department of Energy A U. S. Department of Energy Office of Science Laboratory Operated by The University of Chicago

Presentation Outline ● ● ● ● ● Pioneering Science and Technology What is RESRAD Family of Codes Pathway Analysis Cleanup Criteria Dose Calculation for Human Parameter Databases Indoor Contamination and Exposure Dose Limits for Human and Biota Reference Animals and Plants Dose Calculation for Biota 2

What Is RESRAD? RESRAD is a computer code developed at ANL to calculate: • Site specific RESidual RADioactive material guidelines (cleanup criteria or DCGLs), and • Radiation dose and excess lifetime cancer risk to an on-site resident (a maximally exposed individual or a member of a critical population group) Pioneering Science and Technology 3

RESRAD Family of Codes Pioneering Science and Technology 4

Major Pathways Considered in RESRAD Radiological Dose/Cancer Risk Calculation: • External radiation exposure • Internal radiation dose from inhalation (dust and radon) • Internal radiation dose from ingestion - drinking water (surface and/or groundwater) - produce, meat and milk - fish - soil Pioneering Science and Technology 5

Scenarios Are Generated by Selecting Various Pathways in RESRAD Plant Foods Milk Meat Dust, Radon Soil Ingestion Infiltration External Radioactively Contaminated Material in Soil Leaching Groundwater Pioneering Science and Technology Drinking Water Fish Surface Water 6

Radiological Release Criteria HE (t) < HEL HE (t) = dose from all pathways (mrem/year) HEL= basic dose limit = 25 mrem/year (NRC) = 0. 25 m. Sv/year Pioneering Science and Technology 7

Single Radionuclide Guideline • RESRAD calculates homogeneous soil guidelines (cleanup criteria or DCGLs) for each radionuclide specified by the user for the applicable exposure pathways • Guidelines are concentrations of radionuclides in soil for which the basic dose limit will not be exceeded over the selected time horizon (usually 1000 years following remedial action) • Use Sum of Fraction rule for multiple radionuclides Pioneering Science and Technology 8

Source Term and Mass Balance • Mass balance is maintained between the contaminated source and each transport pathway • RESRAD keeps track of source losses from radioactive decay, leaching, erosion, resuspension and volatilization • RESRAD accounts for ingrowth of daughters from initially present parent radionuclides • ICRP-38 radionuclide database is recently incorporated (~ 830 nuclides) Pioneering Science and Technology 9

Schematic Representation of the Water Pathway Segments Pioneering Science and Technology 10

Water Pathway Models • Leaching model: sorption-desorption exchange - Input of distribution coefficient (Kd) Input of groundwater concentration Input of solubility limit Input of leach rate Correlation of Kd with soil-plant transfer factors • Independent transport of daughter radionuclides • Radionuclide transport models: Nondispersive flow, mass balance, and 3 -D dispersion Pioneering Science and Technology 11

Ingestion Pathways Residual Radioactive Soil Contamination Water Air Plants Meat/Milk Fish Ingestion Dose Pioneering Science and Technology 12

Source Environmental Pathway Exposure Pathway On Site Direct Exposure On Site Air Concentration Dose or Cancer Risk External Radiation Dust/ H 3 Radon On Site Biotic Contamination Residual Radioactive Material In Soil Inhalation Effective Dose Equivalent/ Excess Cancer Risk to an Exposed Individual Plant Foods Livestock Meat Milk Aquatic Foods Ingestion On Site Water Contamination Pioneering Science and Technology On Site Soil Contamination 13

Dose Conversion Factors • External exposure pathway: - various depths volume factors (mrem/yr per p. Ci/g) • Inhalation pathway: - inhalation factors (mrem/p. Ci) • Ingestion pathways - ingestion factors (mrem/p. Ci) References: External DCFs - Federal Guidance Report No. 12 (1993) Inhalation/Ingestion DCFs -FGR No. 11 (1988) Pioneering Science and Technology 14

Risk Coefficients or Slope Factors • Units of Slope Factors: For external radiation -- risk/yr per p. Ci/g For inhalation and ingestion pathways-- risk/p. Ci • Source of Slope Factors: EPA publications -- HEAST (2001) Federal Guidance Report No. 13 Ø Morbidity Ø Mortality Pioneering Science and Technology 15

RESRAD Parameter Databases • Decay and ingrowth data (ICRP-38) • Dose conversion factors • Cancer slope factors (risk coefficients) • Food transfer factors (plant/soil, meat/feed, milk/feed, fish/water) Pioneering Science and Technology 16

Site-Specific Input Parameters • Physical parameters (size, depth, density, porosity, diffusion coefficient) • Hydrological parameters (conductivity, gradient, soil b parameter, water table depth) • Geochemical parameters (distribution coefficient, leach rate, solubility) • Meteorological parameters (precipitation, evapotranspiration, erosion, runoff, mass loading • Usage and consumption parameters (inhalation, irrigation, ingestion, occupancy) Pioneering Science and Technology 17

Selection of Input Parameters • For most parameters, RESRAD defaults are representative of national average values or reasonable maximum values • Guidance on selecting input values is given in the Data Collection Handbook and the Compilation of Parameter Distributions • Sensitivity analysis and probabilistic analysis may be used to focus on parameters for which the use of site-specific data is highly recommended Pioneering Science and Technology 18

Summary of RESRAD Major Features • PC-based, easy to install, user-friendly code • Performs multimedia pathways analysis • Simulates multiple exposure scenarios • Sensitivity/uncertainty analysis identifies important parameters • Many supporting documents to assist users to properly run the model and interpret the results • Downloadable free of charge from the RESRAD web site (http: //www. ead. anl. gov/resrad) Pioneering Science and Technology 19

Comparison of RESRAD and RESRAD-BUILD RESRAD (soil) and RESRAD-BUILD (building) codes address different contamination sources and uses: • RESRAD: Soil contamination which might lead to foodstuffs and water contamination through movement by natural processes • RESRAD-BUILD: Building contamination in man-made products and air-flows which might lead to exposure during normal building occupancy or D&D activities in indoor environment Pioneering Science and Technology 20

RESRAD-BUILD Basic Problem z y x Pioneering Science and Technology 21

RESRAD-BUILD Code ● A computer model for analyzing the radiological doses from remediation and occupancy of buildings contaminated with radioactive material ● Includes an air quality model that considers air exchange, deposition and resuspension, and radioactive decay and ingrowth Pioneering Science and Technology 22

Typical Building Geometry Pioneering Science and Technology 23

Pathways, Sources, and Receptors • External exposure: direct from source, air submersion, deposited material • Inhalation: dust, radon • Ingestion: direct from removable material, deposited dust • Up to 10 sources: volume, area, line, and point sources • Up to 10 receptors in 3 rooms/compartments Pioneering Science and Technology 24

RESRAD-BUILD Pathways Pathway Inhalation Rn External Gamma Ingestion Pioneering Science and Technology 25

Dose (Limits) for Human (mrem or mrem/yr) • • • Pioneering Science and Technology 5000 100 25 10 4 300 10 3 1 1 Worker dose Public dose NRC cleanup level NESHAPS air dose limit EPA drinking water limit Background radiation Chest X-ray Air travel for 3000 miles IAEA clearance level Watch color TV for one year 26

ICRP Statements “…if man is adequately protected then other living things are also likely to be sufficiently protected. ” (ICRP 1977) “The Commission believes that the standards of environmental control needed to protect man to the degree currently thought desirable will ensure that other species are not put at risk. ” (ICRP 1991) “Occasionally, individual members of non human species might be harmed, but not to the extent of endangering whole species or creating imbalance between species. ” (ICRP 1991) “…ICRP therefore needs to revise its current system of protection, and particularly, develop a comprehensive approach to the study of the effects on, and protection of, all living matter with respect to the effects of ionising radiation…” (ICRP 2003) Pioneering Science and Technology 27

Evolution of Dose Limits for Biota • Historical setting: – Human limits are dose based – Protection established by examining all exposure pathways • 1990’s DOE considered parallel protection for biota – DOE Standard (DOE Order 5400. 5): Ø 1 rad/d (10 m. Gy/d) for aquatic organisms Pioneering Science and Technology 28

Dose Limits for Biota ● Based on NCRP and IAEA findings ● Other standards proposed 10 CFR 834, Subpart F: Ø 1 rad/d for aquatic animals Ø 1 rad/d for terrestrial plants Ø 0. 1 rad/d for terrestrial animals Pioneering Science and Technology 29

DOE Developed BCGs for Screening BCGs* aquatic riparian terrestrial animal plant *Biota Pioneering Science and Technology Concentration Guides 30

Basic Screening Methodology ● BCG = Dose Limit (rad/yr) Internal + External Dose (rad/yr per p. Ci/kg) ● Evaluate for unit concentration (e. g. , 1 p. Ci kg-1) for single media (e. g. , soil) ● Use sum of fractions approach for multiple media (e. g. , sediment, water) and radionuclides Pioneering Science and Technology 31

Calculation of Dose to Flora and Fauna ● Calculate tissue concentrations Using a simple lumped parameter to relate radionuclide concentration in the media external to the organism to its internal tissues Using empirical allometric equations ● Calculate external and internal dose conversion coefficients using the MCNP radiation transport code for various reference animals and plants Pioneering Science and Technology 32

Methodology for Determining DCC • Used Monte Carlo transport code MCNP • Pioneering Science and Technology For internal DCC – Organism uniformly contaminated – Calculate energy absorbed in the organism for the electrons and photons emitted from a contaminant (radionuclide) – Assume 100% energy absorbed for alpha emission – Convert energy absorbed to dose • For external DCC – Media is uniformly contaminated – Calculate energy absorbed in the organism for the electrons and photons emitted from the contaminated media for each given radionuclide – Assume zero energy absorbed from alpha emission – Convert energy absorbed to dose Internal contamination Soil is contaminated 33

Organism Geometries in RESRAD-BIOTA Model Geometry No. Mass Category (Kg) 1 1 E-5 2 Specific Mass (Kg) Fish egg*, Fish (larvae), Plant root (meristem), Plant seed, Plant shoot (meristem) 0. 2 x 0. 2 4. 2 E-6 1 E-3 Fish (young-of-year) Molluscs*, Plant seedling, Tadpoles 2. 5 x 1. 2 x 0. 62 1 E-3 3 1 E-2 Fathead minnow, Frogs, Hispid cotton rat, Sculpins, Shrews, Voles, White-footed Mouse* 10 x 2 2. 1 E-2 4 1 Black bass, Large fish* Suckers 45 x 8. 7 x 4. 9 1 5 1 E 1 Beaver, Carp, Catfish (Channel and Blue), Coyote, Fox (red or grey), Raccoon*, Striped bass 50 x 26 x 13 8. 8 6 1 E 2 Mule deer, White-tailed deer* 100 x 42 x 33 72. 6 7 5 E 2 Elk* 270 x 66 x 48 447. 9 8 Pioneering Science and Technology Specific Geometry Dimensions (cm) 1 E 3 Grizzly bear* 220 x 100 1150 Example Receptors 34

Dose Coefficients for Duck Internal α DCC (µGy/h Radionuclide per Bq/kg) External (γ + β) DCC (µGy/h per Bq/kg) Soil surface (µGy/h per Bq/kg) Air (µGy/h per Bq/m 3) Water surface (µGy/h per Bq/L) H-3 0 3. 27 E-06 7. 2 E-14 1. 7 E-11 9. 5 E-14 C-14 0 2. 85 E-05 3. 1 E-09 8. 5 E-09 1. 4 E-09 Co-60 0 2. 28 E-04 4. 0 E-04 3. 7 E-05 2. 9 E-04 Sr-90 0 1. 13 E-04 1. 8 E-07 3. 4 E-07 1. 5 E-07 Sr-90+D 0 6. 34 E-04 8. 5 E-06 6. 4 E-06 7. 6 E-06 Cs-137+D 0 1. 87 E-04 8. 4 E-05 9. 9 E-06 6. 6 E-05 U-238 2. 45 E-03 4. 87 E-06 9. 6 E-09 5. 6 E-08 4. 2 E-08 Am-241 3. 21 E-03 2. 37 E-05 1. 4 E-06 8. 8 E-07 3. 1 E-06 Soil density = 1. 6 g/cm 3; air density = 0. 00129 g/cm 3; and water density = 1 g/cm 3 Pioneering Science and Technology 35

Features of RESRAD-BIOTA ● Has a user-friendly input interface with Help files ● Users can view dose conversion coefficients (DCCs), dose results, BCG results, etc. , and select radiological units ● User can modify lumped parameters (Biv values and Kds), dose limits, area factors, radiation weighting factors, DCFs, and allometric parameters, etc. ● Shows screening results (pass or fail) instantly and have text reports and bar charts. Pioneering Science and Technology 36

RESRAD Family of Codes Downloads by month 1192 661 425 Pioneering Science and Technology 447 479 422 412 385 37

RESRAD Downloads by Foreign Countries (56 Total) Argentina Finland Israel Malaysia Philippines Serbia Thailand Australia Chile France Italy Mexico Poland Slovakia Turkey Austria China Germany Japan Monaco Portugal South Africa United Kingdom Banglades h Croatia Greece Kazakhsta n Montenegr o Republic of Moldova Spain Ukraine Belgium Pioneering Science and Technology Canada Czech Republic Hungary Korea Morocco Romania Sweden Venezuela Brazil Egypt India Latvia Netherland s Russia Switzerlan d Yugoslavia Bulgaria Estonia Iran Macedonia Pakistan Saudi Arabia Taiwan 38

Thank You! RESRAD Web Site: http: //www. evs. anl. gov/resrad Email: resrad@anl. gov Pioneering Science and Technology 39