Reagent grade uranium salts

A rapid non-destructive neutron activation technique for the determination of the 238U/235U ratio is described. The photopeaks of 239Np and 131I were used for the determination of 238U and 235U. The interference from sup(129m)Te on the 277.8 keV photopeak used for 239Np is quite small and of the order of 0.07% in natural uranium at the end of the irradiation. The integrated photopeak activities of 239Np and 131I, after correction for decay during counting, were extrapolated to a constant clock time representing the counting time of the first sample. The individual activities of 239Np and 131I and the activity ratios of 239Np/131I for the six depleted uranium standards are tabulated. The mean activity ratio of 239Np/131I from the six standards was 1.839+-0.017 corresponding to a 238U/235U atomic ratio of 203.28+-0.21. The maximum deviation observed between the low and high values is about 2.7%. Reagent grade uranium salts from commercial sources have a widely variable 238U/235U ratio. The isotopic composition of uranium found in such salts is quite different from the natural value. This difference is largely due to the use of by-product uranium depleted in 235U. The technique can be used to determine the 238U/235U ratio in natural silicate materials. The choice of the activation product selected for 235U depends on the matrix composition. Any fission products other than 140Ba and 144Ce are some of the candidates. (T.G.)