Investigation of separation/purification methodologies for the determination of 232U and 236Pu in solution of spent nuclear fuels by α-spectrometry

A methodology based on the use of several separation/purification steps exploiting TOPO, Dowex anion exchanger and UTEVA for attaining U and Pu fractions for α-spectrometry measurements is presented. The methodology is applied to the determination of the concentration of 236Pu and 232U in a normal burn-up fuel (30 GWd/t) and in a high burn-up fuel (50 GWd/t). The results are compared with those from the calculations performed with the ORIGEN code. After 2 years cooling time, the amount of 232U was measured to be 4.9 x 10-10 g/g UO2 in the 30 GWd/t burn-up fuel sample and 1.5 x 10-9 g/g UO2 in the high burn-up fuel sample. The amount of 236Pu after the same cooling time was found to be 4.2 x 10-10 and 1.2 x 10-9 g/g UO2 in the two samples, respectively. Comparison of the experimental concentrations of 232U and 236Pu with the computed ones shows that the code overestimates the amounts of 232U and 236Pu formed in the reactor. The inventory of the major U and Pu are also determined by radiometric methods. The results are in agreement with those from isotopic dilution mass spectrometry. (orig.)