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A1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.
Abstract:
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 A1 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.
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