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RESRAD-OFFSITE Code and Derivation of Cleanup Criteria Presented at EMRAS II NORM & Legacy Sites WG Meeting

RESRAD-OFFSITE Code and Derivation of Cleanup Criteria Presented at EMRAS II NORM & Legacy Sites WG Meeting. Charley Yu, PhD, CHP RESRAD Program Manager Environmental Science Division January 27, 2010. RESRAD Development Timeline. RESRAD Family of Codes. Plant Foods. Drinking Water.

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RESRAD-OFFSITE Code and Derivation of Cleanup Criteria Presented at EMRAS II NORM & Legacy Sites WG Meeting

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  1. RESRAD-OFFSITE Code and Derivation of Cleanup CriteriaPresented at EMRAS II NORM & Legacy Sites WG Meeting Charley Yu, PhD, CHP RESRAD Program Manager Environmental Science Division January 27, 2010

  2. RESRAD Development Timeline

  3. RESRAD Family of Codes

  4. Plant Foods Drinking Water Milk Meat Dust, Radon Soil Ingestion Infiltration External Fish Radioactively Contaminated Material in Soil Leaching Surface Water Groundwater EXPOSURE PATHWAYS CONSIDERED IN RESRAD (Subsistence Farming Scenario)

  5. Radioactively Contaminated Material in Soil EXPOSURE PATHWAYS CONSIDERED IN RESRAD (Industrial Use Scenario) Drinking Water Dust, Radon Soil Ingestion Infiltration External Leaching Surface Water Groundwater

  6. RESRAD PATHWAYS Pathway Analysis - nine environmental pathways • Ingestion of aquatic foods • Ingestion of water • Ingestion of soil • Radon • Direct Exposure • Inhalation • Ingestion of plant foods • Ingestion of meat • Ingestion of milk

  7. SINGLE RADIONUCLIDE GUIDELINE • RESRAD calculates homogeneous soil guidelines (DCGL’s) 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)

  8. RADIOLOGICAL RELEASE CRITERIA • HE (t) < HEL • HE (t) = dose from all pathways (mSv/year) • HEL= basic dose limit • = 0.25 mSv/year

  9. Gi = minimum Gi (t) for t < 1000 years • Gi (t) = • DSRi (t) = • = dose/source concentration ratio for radionuclide i at time t (mSv/year per Bq/g) SINGLE RADIONUCLIDE GUIDELINE

  10. DOSE CONVERSION FACTORS • External exposure pathway: • - infinite depth volume factors (mrem/yr per pCi/g) • Inhalation pathway: • - inhalation factors • Ingestion pathways • - ingestion factors • References: External DCFs - Federal Guidance Report No.12 (1993) Inhalation/Ingestion DCFs - FGR No.11 (1988)

  11. SLOPE FACTORS USED IN RESRAD • Units of Sfj,p: • For external radiation -- risk/yr per pCi/g • For inhalation and ingestion pathways-- risk/pCi • Source of Sfj,p: • EPA publications -- HEAST (2001) • Federal Guidance Report # 13 (1999) • Morbidity • Mortality • Note: Values of Sfj,p include contributions from associate decay products with half-lives < cutoff, which are assumed to be in equilibrium with their parent principal radionuclide.

  12. ANALYSIS OF MULTIPLE SCENARIOS • Current use and plausible future use scenarios can be easily simulated • One or more exposure pathways may be added or suppressed • Occupancy factors and consumption parameters may be tailored according to the scenario being simulated • Typical exposure scenarios include industrial, recreational, residential, and subsistence farming

  13. WATER PATHWAY MODELS • Leaching model: sorption-desorption ion 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 or mass balance

  14. SPECIAL MODEL FOR RADON • Radionuclides: • - radon-222 and progeny • - radon-220 (thoron) and progeny • Multimedia radon transport: • - soil • - water • - building materials • Ingrowth from parents: • - Uranium and thorium series

  15. RESRAD PARAMETER DATABASE • Decay and ingrowth data • Dose conversion factors • Cancer slope factors • Food transfer factors (plant/soil, meat/feed, milk/feed, fish/water) • All 838 radionuclides contained in ICRP-38 are in RESRAD database (New DECDATA >1200 radionuclides are being included)

  16. SITE SPECIFIC INPUT PARAMETERS • Physical parameters (size, depth, density, porosity, diffusion coefficient) • Hydrological parameters (hydraulic 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)

  17. PROBABILISTIC RESRAD Codes • Developed probabilistic modules for RESRAD (onsite) (6.0), RESRAD-BUILD (3.0), and RESRAD-OFFSITE (2.0) • Identified key parameters and compiled parameter distribution data for probabilistic analysis • Developed integrated RESRAD codes to perform probabilistic dose assessment for site-specific analysis • Developed postprocessor to analyze and display probabilistic results

  18. PROBABILISTC vs. DETERMINISTIC ANALYSIS

  19. COMPILATION OF PARAMETER DISTRIBUTIONS WAS A MAJOR EFFORT

  20. Derivation of Site-specific Cleanup Criteria

  21. Procedures to Determine & Apply Site-Specific Guidelines • Determine exposure scenario(s) • Determine exposure pathway(s) • Gather data • Understand calculations • Calculate guidelines • Set cleanup criteria for the site • Cleanup • Postremediation dose assessment Use RESRAD Family of Codes

  22. EXPOSURE SCENARIOS • Exposure scenarios may be classified as: • Expected • Plausible • Unlikely • Typical exposure scenarios: • Industrial use • On-site resident (variations: suburban or subsistence farmer) • Recreational use

  23. NATURAL URANIUM CLEANUP CRITERIA CONSIDERATION The activity-based weighting factors for natural uranium (wU-23*) are: wU-234 = 1/2.046 = 0.489 wU-235 = 0.046/2.046 = 0.0225 wU-238 = 1/2.046 = 0.489

  24. Guideline (pCi/g)* Radionuclide Uranium-234 Uranium-235 Uranium-238 Uranium-Tot Scen. A 2400 450 1600 1800 Scen. B 5400 1100 3600 4000 Scen. C 590 150 430 470 Scen. D 120 47 120 120 A = Industrial-use scenario (current use) B = Recreationist C = Residential-use scenario (pond water) D = Residential-use scenario (well water) Guideline set by DOE: 70 pCi/g (2590 Bq/kg) Total Uranium * Based on dose limit of 1 mSv/yr RESIDUAL RADIOACTIVE MATERIAL GUIDELINES FOR THE ELZA GATE SITE

  25. Application of DOE’s ALARA Policy Note: volume estimate based on DOE’s residual contamination guidelines for Ra-226, Th-230, Th-232, and a variable U-238 guideline.

  26. Derivation of Soil Guidelines (DCGLs) Dose Limit/ Constraint (100 / 25 mrem/yr) Operational DCGLs Single Radionuclide DCGLs Sum of Ratios Field Implementation Pathway Analysis Regulations

  27. Average Radionuclide Concentrations: 4.9 pCi/g U-238 (measured) 4.9 pCi/g U-234, 0.22 pCi/g U-235 (derived) Scen. A 1.5 Scen. B 0.66 Scen. C 12 Scen. D 42 Dose Rate (mrem/yr) A = Industrial-use scenario (current use) B = Recreationist C = Residential-use scenario (pond water) D = Residential-use scenario (well water) POSTREMEDIATION DOSE ASSESSMENT FOR THE ELZA GATE SITE

  28. Summary • RESRAD has been in existence for more than 20 years • RESRAD is the most extensively tested, benchmarked, verified, and validated code in the environmental risk assessment and site cleanup field • RESRAD has been widely used by federal and state agencies and their contractors • Over 100 training workshops have been sponsored by DOE, NRC, EPA, DOD, and state agencies • Many universities have used RESRAD as a teaching and research tool • Many papers and theses have been published based on RESRAD (some in foreign languages) • RESRAD has been widely used nationally and internationally. • Comprehensive supporting documents are available for the application of RESRAD • RESRAD is continuously maintained and improved • RESRAD can be downloaded free of charge

  29. Thank You! RESRAD Web Site: http://www.evs.anl.gov/resrad Email: resrad@anl.gov

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