Gamma-spectroscopic determination of the isotopic ratios 235U to 238U

It is well known that the 235U content in uranium can be determined by comparing γ-activities from 235U and those from 234Th and 234m, 234Pa formed by the disintegration of 238U and in the radiochemical equilibria. Although this method looks convenient, it is not utilized widely, because about 8 months are necessary for attaining the equilibria after any chemical separation of uranium and thorium. In the present work, the above γ-spectrometric method was extended to uranium samples in which the equilibria are not yet attained. The proposed method determines 0.41% 235U at about 20 days after the purification of uranium from thorium. Values obtained agree well with those by the mass-spectrometry.