A STUDY OF ISOTOPIC HOMOGENEITY IN 'BLENDED URANIUM' USING ICP-MS

摘要

A 20 kg uranium metal ingot was prepared from two isotopically distinct feedstocks, and drillings from various ingot sections were dissolved in a mixture of HC1, HNO_3, and HF. Uranium isotope ratios in each solution were determined by inductively coupled plasma-mass spectrometry (ICP-MS); total dissolved solid content was 20 ug/L for determination of ~(238)U/~(235)U, and 2 mg/L for determination of ~(236)U/~(235)U and ~(234)U/~(235)U. Between-sample coefficients of variation (n=35) for ~(238)U/~(235)U, ~(236)U/~(235)U, and ~(234)U/~(235)U were 0.70%, 0.90%, and 1.4%, respectively. Linear regression indicated that ~(236)U/~(235)U versus ~(238)U/~(235)U and ~(234)U/~(235)U versus ~(238)U/~(235)U were significantly correlated at the 90% confidence interval; ~(234)U/~(235)U versus ~(236)U/~(235)U was significantly correlated at the 98% confidence interval. These data show that the samples were not isotopically homogeneous, and demonstrate that ICP-MS can be used to assess isotopic homogeneity, even in cases where aggregate variations in isotopic composition are on the order of 1%.