Age Dating of Uranium Sample by ICP-MS

Uranium age of sample is relevant to determine the date of production of the material and important to identifying the source of the material in nuclear forensics investigations. An analytical method for age dating of uranium-based nuclear materials by the measurement of ²³⁰Th/²³⁴U atomic ratio was developed. Uranium samples were diluted with ²²⁹Th and ²³³U spike respectively. Uranium and thorium in the samples were separated with TEVA resin. The atomic ratios of ²²⁹Th/²³⁰Th and ²³³U/²³⁴U were measured by multi-collected inductively coupled plasma mass spectrometry (MC-ICP-MS). The uranium age of the samples could be obtained by ²³⁰Th/²³⁴U atomic ratio according to the calculation formula of uranium age. The age of CRM U850 and U010 standard samples was determined. The results are consistent with those obtained by Lawrence Livermore National Laboratory in the United States. However, the results of both methods are older than the actual age. It was probably due to the incomplete purification process during production, which resulted in the residual ²³⁰Th in the samples. The established method can be used to determine the ²³⁴U-²³⁰Th model age of uranium samples and provide important information for verification investigation.