RADIONUCLIDES IN SOILS COLLECTED FROM WITHIN AND AROUND LOS-ALAMOS NATIONAL LABORATORY - 1974-1996

A soil sampling program is the most direct means of determining the ty pes, concentration/activity, and distribution of radionuclides within and around nuclear facilities. Los Alamos National Laboratory (LANL), for example, has had a soil surveillance program since the early 1970s and the purpose of this paper was to 1) evaluate this 20+ year data s et to determine if there are any statistical differences in radionucli des (H-3, Cs-137, Pu-238, Pu-239,Pu-240, Am-241, Sr-90, U-tot) and rad ioactivity (gross alpha, beta, and gamma), as a function of air emissi ons and fugitive dust, in surface soils (0-5 cm depth) collected from LANL, perimeter (PM) and background (BG) sites, and 2) determine if ra dionuclide concentrations are increasing or decreasing over time. Also , the total effective dose equivalent (TEDE) and the corresponding ris k of excess cancer fatalities (RECF) to a PM community were estimated. Based on the long-term average, nine out of the ten radionuclide para meters measured in LANL soils (n=12) were significantly (p<0.05) highe r in concentration than BG (n=6). Perimeter soils (n=10), on the other hand, showed less differences with only four out of the ten parameter s being statistically higher in concentration than BG. Most radionucli des in LANL and PM areas, with the exception of Pu-238 in soils from P M, significantly decrease in concentration over time, so that by 1996 most radionuclides were approaching values similar to BG. The maximum net positive TEDE (i.e., the TEDE + two sigma for each radioisotope mi nus background and then only the positive doses summed) for a resident living around the PM of LANL, as modeled by the residual radioactive (RESRAD) code using a residential scenario for soils collected from 19 74-1996, 1993-1996, and in 1996 was 2.9 mrem y(-1) (29 mu Sv y(-1)), 2 .3 mrem y(-1) (23 mu Sv y(-1)), and 0.8 mrem y(-1) (8 mu Sv y(-1)), re spectively. All upper bound TEDEs were far below the International Com mission of Radiological Protection permissible dose limit of 100 mrem y(-1) (1000 mu Sv y(-1)) for all pathways, and the highest TEDE corres ponds to a RECF of 1.5 x 10(-6)-an estimate far below the Environmenta l Protection Agency guideline of 10(-4).