Investigation of radiological contamination of soil samples from Idaho National Laboratory

Anthropogenic radionuclides have been introduced into the environment through a variety of mechanisms ranging from nuclear weapons testing to satellite failures to leakage from waste disposal sites. In this study, 137Cs, 241Am and Pu isotopes were utilized to gain a better understanding of the contamination history of soils collected in 1972 near the Subsurface Disposal Area (SDA) at the Idaho National Laboratory. The atom and activity ratios of these isotopes have been well characterized for many environmental contamination events and can therefore be used as markers for identifying the processes from which the isotopes originated.; A suite of traditional and new radiochemical methodologies were modified to analyze small soil samples for the above mentioned isotopes. Activity detection and determination limits were calculated to evaluate the methods employed. Further investigation was done to couple fission track analysis (FTA) to laser ablation mass spectrometry (LAMS). The purpose of this study was to interrogate the soil aggregates that were associated with fissile material.; Two sampling locations were investigated and two depths at each of these locations. The total activity of the samples were higher in the surface soils and contained more 241Am than could be accounted for by ingrowth from 241Pu alone. This indicates that there must be an additional contamination source of 241Am. The 137Cs activity was slightly elevated over background levels in the surface soil and at background below that, indicating that the primary contamination pathway was on-site activities. Plutonium atom and activity ratios are radically different from expected fallout values and correlate well with the ratios expected for weapons grade Pu in a soil matrix. The Pu contamination most likely originated from waste generated by activities at Rocky Flats Site, CO which was buried at the SDA. The work on using FTA to located contaminated soil, prior to LAMS showed values for correlation coefficients between masses of greater that 0.6. This indicates that the soil was influenced by a flooding event which occurred in 1969.