~(235)U/~(231)Pa质谱法测铀年龄

建立了同位素稀释-多接收电感耦合等离子体质谱法测~(235)U/~(231)Pa原子比得到高浓铀年龄的方法。经过两次TTA萃取-反萃后从母体237 Np中分离得到233Pa稀释剂,Pa中去Np的去污因子均在200以上。在用标准物质CRM U900对233Pa稀释剂的浓度进行标定后,分别以233 U、233 Pa作为~(235)U、231 Pa的稀释剂,质谱测得~(235)U/~(231)Pa原子比计算高浓铀年龄,采用该法对标准物质CRM U850进行年龄测量,其结果与参考值的相对偏差为1.97%。该法可用于核法证与核保障监督中的高浓铀年龄测定。

Determination of Uranium Age by Measuring 235U/231Pa With Mass Spectrometry

Isotope dilution combining with multi-collector inductively coupled plasma mass spectrometry through measuring 235U/231Pa to determine the age of high enriched uranium (HEU) was studied.The spike of 233Pa was separated from 237Np after twice TTA extraction and back-extraction.The decontamination factor(DF)(Np) in 233Pa exceeds 200.The concentration of 235U and 231Pa was measured by isotope dilution mass spectrometry using spike of 233U and 233Pa which calibrated in-house by the reference material CRM U900,respectively.So the ratio of 235U and 231pa can be calculated,and HEU age can be obtained.The method was used to determine the age of the reference material CRM U850,and the relative error of results are 1.97％.The method can be used to measure HEU age in nuclear forensics and nuclear safeguard.