SEDL / STP / STP1344-EB / STP15722S

A Study of Isotopic Homogeneity in “Blended Uranium” Using ICP-MS

Crain, JS
Chemist, Argonne National LaboratoryUnion Carbide Corporation, ArgonneSouth Charleston, ILWV

Pages: 6    Published: Jan 1998

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Abstract

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 HCl, HNO³, and HF. Uranium isotope ratios in each solution were determined by inductively coupled plasma-mass spectrometry (ICP-MS); total dissolved solid content was 20 μg/L for determination of ²³⁸U/²³⁵U, and 2 mg/L for determination of ²³⁶U/²³⁵U and ²³⁴U/²³⁵U. Between-sample coefficients of variation (n=35) for ²³⁸U/²³⁵U, ²³⁶U/²³⁵U, and ²³⁴U/²³⁵U were 0.70%, 0.90%, and 1.4%, respectively. Linear regression indicated that ²³⁶U/²³⁵U versus ²³⁸U/²³⁵U and ^{234 234 234}U/²³⁵U versus ²³⁸U/²³⁵U were significantly correlated at the 90% confidence interval; ²³⁴U/²³⁵U versus ²³⁶U/²³⁵U 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%.