Answer to Question #171 Submitted to "Ask the Experts"

One source is the National Council on Radiation Protection and Measurements (NCRP) Report No. 129, Recommended Screening Limits for Contaminated Surface Soil and Review of Factors Relevant to Site-Specific Studies. This report can be ordered from the NCRP's website. Included in the report are recommended screening limits for eight land-use scenarios to limit dose to the maximally exposed individual to 0.25 mSv/y (25 mrem/y). Included are screening limits for ²³⁹Pu and ²⁴⁰Pu as parent radionuclides and also screening limits for four other Pu isotopes which occur as decay products of another radionuclide when they are present in the absence of the parent. This report also cites some Environmental Protection Agency remedial action documents providing guidance for Pu.

Another source is recent work by Risk Assessments Corporation (RAC) for the Rocky Flats Radionuclide Soil Action Level Oversight Panel. This work addressed Pu and U Radionuclide Soil Action Levels (RSALs) for cleanup at Rocky Flats and included a review of previously adopted levels for Rocky Flats, review of soil radionuclide action level/dose relationships for various other sites around the world, and independent RSAL calculations. The project summary is Till, et al., Radionuclide Soil Action Level Oversight Panel, RAC Report No. 1-RSALOP-RSAL-2000-FINAL, February 2000. If more details are needed, they can be found in the individual technical reports for Tasks 1, 2, 3, 5, and 6, which are referenced in the Summary Report. The reports were submitted to the Rocky Flats Citizens' Advisory Board, 9035 Wadsworth Parkway, Suite 2250, Westminster, CO 80021.

The methodology for the Rocky Flats work was also described in a paper by J.E. Till, et al., Calculating Soil Action Levels and Uncertainties for Decision Making During Clean-Up of Contaminated Sites, which was presented at the 10^th International Congress of the International Radiation Protection Association (IRPA-10) held 14-19 May 2000 at Hiroshima, Japan. The paper is posted on the IRPA website.

Gen Roessler
Editor, HPS website