Determination of the 243Cm/244Cm Ratio Alpha Spectrometry and Spectral Deconvolution in Environmental Samples Exposed to Discharges from the Nuclear Fuel Cycle

The presence of curium nuclides in irradiated nuclear fuel is well known, as is their occurrence in environmental materials exposed to liquid waste discharges from reprocessing plants and to fallout following the Chernobyl accident. Knowledge of the 242Cm/244Cm and 243Cm/244Cm atom ratios can be a useful tool for characterizing a source-term and assessing the burn-up history of nuclear fuel. Here, a practical technique, based on high-resolution α spectrometry and spectral deconvolution, is described by which the 243,244Cm multiplet can be resolved at the low activities typical of most environmental samples. The resulting 243Cm/244Cm ratio is then used to correct for any interference by 243Cm in the 242Cm window. The technique has been applied to the determination of the 243Cm/244Cm ratio in samples of seabed sediment collected near the Sellafield outfall, riverine sediment sampled downstream of the Mayak reprocessing plant and soil and lichen from within the Chernobyl exclusion zone. Near Sellafield, the 243Cm/244Cm ratio was found to be <2%, while near Mayak and Chernobyl it was considerably higher, being not, vert, similar6–8%.