铀颗粒物中^(230)Th与^(234)U物质的量比值分析及生产年龄诊断

Ratio of Amount of Substance Between^(230)Th and^(234)U Used for Age Diagnosis of Uranium Particles

铀颗粒物中^(230)Th与^(234)U物质的量比值n(^(230)Th)/n(^(234)U)可用于诊断铀材料的生产年龄。转移并消解多个不同铀丰度的CRM124-4,GBW04234和GBW04238铀颗粒物制备最初溶液,分样后在各溶样瓶中分别加入定量的^(233)U稀释剂和^(229)Th稀释剂。其中,加入^(229)Th稀释剂的^(230)Th定量样品进一步分离纯化去铀,采用多接收电感耦合等离子体质谱仪(multiple colletor inductively coupled plasma mass spectrometry,MC-ICP-MS)分别测定n(^(238)U)/n(^(233)U)和n(^(230)Th)/n(^(229)Th),由同位素稀释质谱法得到最初溶液中^(238)U的质量分数w(^(238)U)和^(230)Th的质量分数w(^(230)Th)。待测铀颗粒物中n(^(238)U)/n(^(234)U)已知,计算出最初溶液中w(^(234)U)及n(^(230)Th)/n(^(234)U),最后诊断出颗粒物的生产年龄。研究结果表明:6.1×10^(-5)~3.8×10^(-4) g量级CRM124-4,GBW04234和GBW04238铀颗粒物中n(^(230)Th)/n(^(234)U)测量值的相对偏差分别为2.7%、6.1%和1.8%;CRM124-4,GBW04234和GBW04238所对应铀材料的生产年龄诊断结果分别为57.81±1.55 a,23.32±1.42 a和22.99±0.40 a(2σ),诊断精度达到国际同等先进水平。

The amount of substance ratio of^(230)Th to^(234)U in uranium particles can be used to diagnose the age of uranium particles.The n(^(238)U)/n(^(233)U)and n(^(230)Th)/n(^(229)Th)in CRM124-4,GBW04234,and GBW04^(238)Uranium particles with different uranium abundances are determined by multiple colletor inductively coupled plasma mass spectrometry(MC-ICP-MS).The age of uranium particles is diagnosed by isotope dilution mass spectrometry after uranium thorium separation and purification.The results show that the relative experimental standard uncertainty of the n(^(230)Th)/n(^(234)U)is 2.7%,6.1%,and 1.8%,respectively in CRM124-4,GBW04234,and GBW04238.Correspondingly,the diagnostic age of CRM124-4,GBW04234 and GBW04^(238)Uranium particles are(57.81±1.55)a,(23.32±1.42)a,and(22.99±0.40)a,respectively.This method can provide technical support for nuclear safeguards and nuclear forensics by determining the n(^(230)Th)/n(^(234)U)in a single uranium particle simulation sample at the level of 100 microns or sub milligram uranium materials,and diagnosing the age of uranium materials.