Diffusion coefficients for uranium, cesium and strontium in unsaturated prairie soil

Abstract

Soil samples were collected at the site of a 1951 leak from an underground storage tank of 6.7 liter of an aqueous solution of irradiated uranium. Laboratory simulations were conducted using irradiated and non-irradiated natural uranium metal, dissolved in acidic aqueous solutions and added to soil columns. Contaminant transport experiments were conducted for a period of 12 to 14 months, followed by sample analysis employing gamma-spectroscopy, neutron activation analysis and liquid scintillation counting. The concentration distributions of U, Cs and Sr found from the experiments were used to derive diffusion coefficients. The measured diffusion coefficients from the field samples were: for ¹³⁷Cs, 3.0E-04 cm²·s⁻¹; for ²³⁸U, 1.8E-09 cm²·s⁻¹; and for ⁹⁰Sr, 2.6E-09 cm²·s⁻¹. Corresponding values for the laboratory simulations were 5E-06, 3E-05 and 1.9E-05 cm²·s⁻¹, respectively.