Modeling Radionuclide Transport in the Environment and Assessing ...

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Modeling Radionuclide Transport in the Environment and Assessing ...

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1. Modeling Radionuclide Transport in the Environment and Assessing Doses to Humans, Flora, and Fauna: The RESRAD Family of Codes Charley Yu, PhD, CHP RESRAD Program Manager Environmental Science Division

2. 2

3. 3 What Is RESRAD? This slide is linked to the previous slide, providing the purpose of the RESRAD code (i.e., for use in deriving site-specific guidelines).This slide is linked to the previous slide, providing the purpose of the RESRAD code (i.e., for use in deriving site-specific guidelines).

4. 4 RESRAD Family of Codes

5. 5 Major Pathways Considered in RESRAD

6. 6 Scenarios Are Generated by Selecting Various Pathways in RESRAD

7. 7 Radiological Release Criteria

8. 8 Single Radionuclide Guideline

9. 9 Source Term and Mass Balance This slide highlights the purpose of the “source factor” in RESRAD, which is to modify the source at various points in time to account for source losses and ingrowth.This slide highlights the purpose of the “source factor” in RESRAD, which is to modify the source at various points in time to account for source losses and ingrowth.

10. 10 Schematic Representation of the Water Pathway Segments This slide follows from the last bullet on the previous slide and gives a graphical presentation of the non-dispersion model.This slide follows from the last bullet on the previous slide and gives a graphical presentation of the non-dispersion model.

11. 11 Water Pathway Models The next two slides expand the fourth bullet from the “Major Features” slide. This slide summarizes the leaching/transport mechanisms for radionuclides in the water pathway.The next two slides expand the fourth bullet from the “Major Features” slide. This slide summarizes the leaching/transport mechanisms for radionuclides in the water pathway.

12. 12 Ingestion Pathways This slide is included to highlight the some of the complex multimedia interactions that are implemented in the RESRAD code for a single exposure pathway.This slide is included to highlight the some of the complex multimedia interactions that are implemented in the RESRAD code for a single exposure pathway.

13. 13 This slide gives a detailed graphical representation of the multimedia exposure and transport pathways incorporated in the RESRAD code, as well as the endpoints. In the presentation I will indicate that, when deriving soil guidelines, the code performs a back-calculation starting from the dose limit.This slide gives a detailed graphical representation of the multimedia exposure and transport pathways incorporated in the RESRAD code, as well as the endpoints. In the presentation I will indicate that, when deriving soil guidelines, the code performs a back-calculation starting from the dose limit.

14. 14 Dose Conversion Factors

15. 15 Risk Coefficients or Slope Factors

16. 16 RESRAD Parameter Databases The next four slides expand the sixth bullet from the “Major Features” slide. This slide highlights the “not-so-site-specific” parameters in the RESRAD data base. I will mention that the demonstration will show how to access some of these parameters. The next four slides expand the sixth bullet from the “Major Features” slide. This slide highlights the “not-so-site-specific” parameters in the RESRAD data base. I will mention that the demonstration will show how to access some of these parameters.

17. 17 Site-Specific Input Parameters This slide will give the audience and idea of the major categories of site-specific input parameters (along with examples in each category). I will indicate that not all parameters are accessible to the user, only the ones that are relevant to active pathways used in the scenario being modeled. I will mention that the demonstration will show how to access these parameters.This slide will give the audience and idea of the major categories of site-specific input parameters (along with examples in each category). I will indicate that not all parameters are accessible to the user, only the ones that are relevant to active pathways used in the scenario being modeled. I will mention that the demonstration will show how to access these parameters.

18. 18 Selection of Input Parameters This slide informs the audience that defaults are included for RESRAD parameters and provides documentation for the selection of these parameters (to reinforce the last bullet in the “Major Features” slide. the last bullet is a link to the sensitivity analysis feature of the code.This slide informs the audience that defaults are included for RESRAD parameters and provides documentation for the selection of these parameters (to reinforce the last bullet in the “Major Features” slide. the last bullet is a link to the sensitivity analysis feature of the code.

19. 19 Summary of RESRAD Major Features This slide lists the salient features of RESRAD that would be of interest to project managers. Each bullet forms the stepping off point for the next series of slides, which are grouped in the order of each item in the list (except groundwater transport and special models in hidden slides, shown only if there is interest). This slide lists the salient features of RESRAD that would be of interest to project managers. Each bullet forms the stepping off point for the next series of slides, which are grouped in the order of each item in the list (except groundwater transport and special models in hidden slides, shown only if there is interest).

20. 20

21. 21

22. 22 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

23. 23 Typical Building Geometry

24. 24 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

25. 25

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

27. 27 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)

28. 28 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): 1 rad/d (10 mGy/d) for aquatic organisms

29. 29 Dose Limits for Biota Based on NCRP and IAEA findings Other standards proposed 10 CFR 834, Subpart F: 1 rad/d for aquatic animals 1 rad/d for terrestrial plants 0.1 rad/d for terrestrial animals

30. 30 DOE Developed BCGs for Screening BCGs* aquatic riparian terrestrial terrestrial animal animal animal plant *Biota Concentration Guides

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

32. 32 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

33. 33 Methodology for Determining DCC Used Monte Carlo transport code MCNP 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

34. 34 Organism Geometries in RESRAD-BIOTA

35. 35

36. 36 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.

37. 37 RESRAD Family of Codes Downloads by month

38. 38 RESRAD Downloads by Foreign Countries

39. 39 Thank You! RESRAD Web Site: http://www.evs.anl.gov/resrad Email: [email protected]

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