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RESRAD-OFFSITE Code and Derivation of Cleanup Criteria Presented at EMRAS II NORM & Legacy Sites WG Meeting Charley Yu, PhD, CHP RESRAD Program Manager.

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Presentation on theme: "RESRAD-OFFSITE Code and Derivation of Cleanup Criteria Presented at EMRAS II NORM & Legacy Sites WG Meeting Charley Yu, PhD, CHP RESRAD Program Manager."— Presentation transcript:

1 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

2 2 RESRAD Development Timeline

3 3 RESRAD Family of Codes

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

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

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

7 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 H E (t) < H EL H E (t) = dose from all pathways (mSv/year) H EL = basic dose limit = 0.25 mSv/year

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

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

12 12 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 ANALYSIS OF MULTIPLE SCENARIOS

13 13 WATER PATHWAY MODELS Leaching model: sorption-desorption ion exchange -Input of distribution coefficient (K d ) -Input of groundwater concentration -Input of solubility limit -Input of leach rate -Correlation of K d with soil-plant transfer factors Independent transport of daughter radionuclides Radionuclide transport models: Nondispersive flow or mass balance

14 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 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 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 17 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 PROBABILISTIC RESRAD Codes

18 18 PROBABILISTC vs. DETERMINISTIC ANALYSIS

19 19 COMPILATION OF PARAMETER DISTRIBUTIONS WAS A MAJOR EFFORT

20 20 Derivation of Site-specific Cleanup Criteria

21 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 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 (w U-23* ) are: w U-234 = 1/2.046 = w U-235 = 0.046/2.046 = w U-238 = 1/2.046 = 0.489

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

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

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

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 29 Thank You! RESRAD Web Site:


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