A preliminary investigation into the use of molecular oxide and hydride secondary ion relationships for improvement of the (236)U/(238)U determination on a NanoSIMS 50L

A NanoSIMS 50L is used to investigate uranium molecular ((235)U(16)O, (236)U(16)O, (238)U(16)O, (235)U(1)H, (238)U(1)H, (236)U(16)O(1)H, and (238)U(16)O(1)H) and elemental ((235)U, (236)U, and (238)U) secondary ion production during sputtering of synthetic UO(2) and the NIST-610 standard to determine if: (1) the (236)U(16)O/(238)U(16)O molecular oxide ratio performs better than the (236)U/(238)U elemental ratio, and (2) there is co-variance between the molecular hydrides and oxides. Despite an order of magnitude greater abundance of (236)U(16)O secondary ions (compared to (236)U), the (236)U(16)O/(238)U(16)O ratios are less accurate than the (236)U/(238)U ratios. Further work is needed before the higher count rate of the (236)U(16)O secondary ion can be used to obtain a better (236)U/(238)U ratio. The second objective was undertaken because correction for the interference of (235)U(1)H on the (236)U secondary ion species typically utilizes the (238)U(1)H/(238)U ratio. This becomes problematic in samples containing (239)Pu, so our aim was to understand if the hydride formation rate can be constrained independently of having to measure the (238)U(1)H. We document correlations between the hydride ((238)U(1)H and (238)U(16)O(1)H) and oxide ((236)U(16)O) secondary ions, suggesting that pursuing an alternative correction regime is worthwhile.