Determination of the in vitro dissolution rates of 238U, 230Th, and 231Pa in contaminated soils from the St. Louis FUSRAP sites

The dissolution rates for ²³⁸U, ²³⁰Th, and ²³¹Pa from 8 contaminated soils in simulated lung fluid were determined. The soil samples were provided by the US Army Corps of Engineers and were collected from various areas at their St. Louis, Missouri FUSRAP sites. Each soil was subjected to a 100 day in vitro dissolution experiment, during which the amount of each radionuclide that had dissolved was periodically measured. At the conclusion of the experiment, a plot of the relative amount of radionuclide dissolved vs. time was constructed for each radionuclide in each soil. The dissolution rates for each radionuclide were then determined by fitting multiple first-order exponential functions to each plot. The results of these experiments were then used assign in vitro dissolution rate classifications to each radionuclide in each soil according to ICRP 30 guidelines.