Sample preparation methods for the determination of plutonium and strontium in environmental samples by low level liquid scintillation counting and a-spectrometry

Two different methods - leaching and microwave assisted total dissolution - have been exploited for the treatment of environmental samples for the determination of plutonium and strontium. Leaching applied to reference materials demonstrated the procedure to be applicable for the recovery of technogenic Pu and Sr from environmental samples. For the measurement of the alpha emitters of plutonium, co-precipitation with calcium oxalate and ferric hydroxide and separation with anion exchange has been used. For preparation of a-spectrometry sources, co-precipitation with NdF3 on a membrane filter or electro-deposition using the (NH4)2C2O4/HCl method have been tested. The beta emitter 241Pu was measured by liquid scintillation counting. Pu isotope concentrations determined in the reference materials agreed well with the certified concentrations. 90Sr was measured in the leachate solutions from environmental samples collected close to a nuclear facility and from reference materials, after separation from the other leached elements, by liquid scintillation counting and Cherenkov counting. The 90Sr-concentrations determined in the reference materials agreed well with the certified concentrations. In the samples collected close a nuclear facility (soil, grass and sheep faeces), 90Sr was found at higher levels, which could also be correlated with the location of the sampling.