Rapid and Accurate Characterization of Enriched Uranium Materials by Inductively Coupled Plasma Mass Spectrometry

The characteristics of enriched uranium materials are very important for nuclear fuel cycle and nuclear forensic analysis. Among all those fingerprints, the uranium isotope ratios and the uranium age are considered to be of major parameters for tracing the sources and process conditions. To the best of our knowledge, there are only a few relevant articles focusing on the analysis of ²³³U isotope abundance. In most of the published literatures subjected to uranium age dating, either ²³⁰Th-²³⁴U chronometer or ²³¹Pa-²³⁵U chronometer was employed to determine the age of enriched uranium materials with the isotope dilution mass spectrometry and anion exchange separation procedure, where the most time-consuming step was the sample preparation. Hence, this project aimed to develop a fast and flexible method for the determination of the uranium isotope ratios, ²³⁰Th/²³⁴U and ²³¹Pa/²³⁵U atom ratios of the enriched uranium samples by the combination of multiple collector inductively coupled plasma mass spectrometry (MC-ICP-MS) and triple quadrupole inductively coupled plasma mass spectrometry（ICP-QQQ-MS）. The results showed that the limits of detection (LODs) of ²³³U by Neptune XT MC-ICP-MS and Agilent 8800 ICP-QQQ-MS were 3×10^-9 and 6×10^-10, respectively, and the relative standard deviations (RSDs) of ²³³U/²³⁵U isotope ratios at the level of 10-7 by MC-ICP-MS and ICP-QQQ-MS were 1.0% (2σ) and 4.8% (2σ), respectively. The standard sample bracketing (SSB) method of ICP-QQQ-MS based on the calibration of GBW04240 reference material was established to correct the mass fractionation of ²³⁰Th/²³⁴U and ²³¹Pa/²³⁵U atom ratios simultaneously. The ages of the uranium materials were diagnosed by the two parent-daughter relations of ²³⁴U-²³⁰Th and ²³⁵U-²³¹Pa, indicating that the LODs of age dating were 0.2 a and 0.5 a, respectively. Meanwhile, the isotope ratios of ²³⁴U/²³⁵U, ²³⁵U/²³⁸U and ²³⁶U/²³⁵U were determined by MC-ICP-MS. The fingerprints showed that the last purification time of the enriched uranium samples were around 2009 and the samples had been irradiated by the nuclear reactor. Overall, this method can reveal precise and accurate genetic signatures within one week, providing rapid technical supports for nuclear forensics, certification of nuclear reference materials and nuclear safeguards.