Plutonium and Americium Contamination near a Transuranic Storage Area in Southeastern Idaho

Abstract

AbstractFrom 1954 through 1970, transuranic waste from the Rocky Flats facility near Golden, Colorado, was shipped to the Idaho National Engineering Laboratory and buried in the Subsurface Disposal Area (SDA) at the Radioactive Waste Management Complex. Soil samples collected near the SDA indicate that this storage has resulted in transuranic contamination outside the SDA perimeter. Maximum concentrations in surface soils (0–4 cm) occurred in the drainage depression near the perimeter of the SDA and were 2,048 nCI 241Am/m2, 1,377 nCi 239Pu/m2, and 32 nCi 238Pu/m2. Contamination outside this drainage channel was lower and has primarily spread in the northeast‐southwest directions. The maximum distances from the SDA perimeter that above background concentrations of 241Am, 239Pu, and 238Pu could be detected were approximately 2,500, 2,400, and 1,000 m, respectively. Surface water runoff in 1962 and 1969 and wind transport appear to be the primary mechanisms which transported these nuclides out of the SDA. The vertical soil migration of 238Pu from 0–4 cm to the 4–8 cm depth was significantly greater than that for 239Pu (P = 0.001).Hides and gastrointestinal tracts of deer mice (Peromyscus maniculatus) had higher concentrations of transuranics than lungs or carcass. Ingestion appeared to be a more important mechanism than inhalation in the intake of transuranics into the deer mice. The 241AM/239Pu ratio in the carcass was significantly (P = 0.02) higher than the ratio in soil indicating a greater uptake of 241Am into deer mice.The data indicate that 238Pu, 239Pu, and 241Am may behave differently in the terrestrial environment.