摘要: 准确定量铀氧化物样品中²³⁸U的含量对于裂变产额测量等工作具有重要意义，其定量方法的研究对于涉及²³⁸U的绝对测量的诸多实验都具有参考价值。利用四川大学2.5 MeV质子静电加速器产生的准单能中子对八氧化三铀样品进行中子活化，用高纯锗探测器测量活化产物的β衰变子体²³⁹Np的277.6 keV特征γ射线，利用已知的活化截面，算出样品中²³⁸U的质量占比为79.1%，不确定度为6.2%。利用电感耦合等离子体质谱法对样品中²³⁸U的含量进行了测量，其质量占比为59.2%。此外，基于EA3000元素分析仪、卡尔费休电位滴定仪和TGA-DSC2同步热分析质谱联用仪，测知样品中不含N元素，含水量在2.2%以下。并利用PIXE方法排除了样品中含有Al元素以上杂质，利用EPBS方法测知样品中U/O原子数比为1：3.6，误差约2%，推知样品中²³⁸U质量占比为80%，验证了活化法测得的²³⁸U含量。最终测得样品中²³⁸U的质量占比为79.1%，不确定度6.2%。对照按U3O8分子式折算的84.5%，考虑到水分含量等，此结果合理。


The accurate quantification of ²³⁸U in uranium oxides is of great importance for measurements of fission yield. The study for the method of ²³⁸U quantification has significance to lots of experiments involving absolute measurement of ²³⁸U. The reaction (n, γ) in the triuranium octoxide samples was induced by T(p,n)³He quasi-monoenergetic neutrons provided by the 2.5 MeV proton electrostatic accelerator in Sichuan University. The 277.6 keV characteristic γ ray of ²³⁹Np that comes from β-decay of the activation product ²³⁹U was detected by a HPGe detector. With the known (n, γ) cross section, the mass percentage of ²³⁸U in samples was determined to be 79.1%, with the uncertainty of 6.2%. ICP-MS was also used in the quantification of ²³⁸U in samples, its result was 59.2%. Meanwhile, the samples were analyzed by other several methods and the results showed that less than 2.2% H₂O, no nitrogen, and no other impurity elements above Al were contained in the samples. EPBS was used to measure the atomic ratio of U and O and it was found that the mass percentage of ²³⁸U in samples was about 80%, verifying the result 79.1% of INAA.