Investigation of a radioactive particle and a soil sample obtained from the Windscale area in 1956

Abstract

Specimens of an irradiated uranium oxide particle and soil contaminated with fission products and actinides, which originated from the deposition of irradiated uranium oxide particles in the Windscale area during the 1950s, have been investigated with the primary aim of assessing whether the analytical procedures used in the 1950s for the determination of ⁹⁰Sr in soil would correctly have reflected the ⁹⁰Sr content of soils contaminated with such particles. The key issue is whether the use of 6 mol l^–1 HCl as an extractant would be effective in taking ⁹⁰Sr contained in irradiated uranium oxide particles into solution. In this investigation, extraction efficiencies for ⁹⁰Sr of 95 and 96% were measured for the soil and particle specimen, respectively, thus indicating that the early analytical procedures would be effective for soil samples containing irradiated uranium oxide particles. The relative amounts of the Pu isotopes assayed (²³⁸Pu, ^239/240Pu and ²⁴¹Pu) were consistent with those expected for material emitted from the Windscale Piles in the 1950s, based on operating conditions and conventional radionuclide inventory codes for irradiated fuel. However, the amounts of ⁹⁰Sr and ¹³⁷Cs relative to the Pu isotopes suggest that some removal of the former radionuclides may have occurred by leaching in the environment between the time of deposition and collection. The results of this investigation differ from other recently published work, which shows lower extraction efficiencies for ⁹⁰Sr by HCl leaching; one explanation is the likely importance of sample preparation procedures.