~(95)Zr-~(95)Nb活度比确定核事件零时
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摘要
裂变产物活度比可确定核事件的零时。本文系统研究了通过测量~(95)Zr-~(95)Nb活度比计算核事件零时的方法。研究表明,~(95)Nb~m分支对零时计算影响较小,~(95)Zr-~(95)Nb活度比可准确计算核事件零时。在零时后100 d内测量样品,零时计算结果与参考值在1 d内符合;零时后1 a内测量样品,计算的零时与参考值相差小于10 d。零时不确定度随样品开测时刻至零时的时间间隔的增加迅速增加,不确定度区间是不对称的,不确定度正值大于不确定度负值,当~(95)Zr-~(95)Nb接近平衡时,零时的不确定度正值趋向于无穷大。
Zero-time of nuclear events can be determined by activity ratio of fission products. The calculation method of zero-time of nuclear events was investigated by measuring ~(95)Zr-~(95)Nb activity ratio. The study results show that the zero-time can be determined accurately by ~(95)Zr-~(95)Nb activity ratio. In addition, the influence of the ~(95)Nb~m decay branch can be ignored. The deviations of zero-time between the result determined by ~(95)Zr-~(95)Nb activity ratio and reference value are less than 1 d and 10 d for decay of 100 d and 1 a from zero-time respectively. The uncertainty of zero-time increases rapidly as the increasing of interval time between measurement start time and zero-time. The uncertainty interval is asymmetric and the positive uncertainty is larger than negative uncertainty. The positive uncertainty approaches infinity when the ~(95)Zr-~(95)Nb equilibrium is reached.
Zero-time of nuclear events can be determined by activity ratio of fission products. The calculation method of zero-time of nuclear events was investigated by measuring ~(95)Zr-~(95)Nb activity ratio. The study results show that the zero-time can be determined accurately by ~(95)Zr-~(95)Nb activity ratio. In addition, the influence of the ~(95)Nb~m decay branch can be ignored. The deviations of zero-time between the result determined by ~(95)Zr-~(95)Nb activity ratio and reference value are less than 1 d and 10 d for decay of 100 d and 1 a from zero-time respectively. The uncertainty of zero-time increases rapidly as the increasing of interval time between measurement start time and zero-time. The uncertainty interval is asymmetric and the positive uncertainty is larger than negative uncertainty. The positive uncertainty approaches infinity when the ~(95)Zr-~(95)Nb equilibrium is reached.
引文
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[3] de GEER L E.Comprehensive Nuclear-Test-Ban Treaty:Relevant radionuclides[J].Kerntechnik,2001,66(3):113-120.
[4] NIR-EI Y.Dating the age of a nuclear event by gamma spectrometry[J].Appllied Radiation and Isotopes,2004,60:197-201.
[5] 王世联,王军,张利兴,等.γ能谱法确定CTBT国际比对样品的零时[J].原子能科学术,2006,40(增刊):117-121.WANG Shilian,WANG Jun,ZHANG Lixing,et al.Dating zero time of CTBT intercomparison sample by gamma spectrometry[J].Atomic Energy Science and Technology,2006,40(Suppl.):117-121(in Chinese).
[6] DOUYSSET G,PETIT G L,GROSS P,et al.Long-term performances of the 95Zr/95Nb chronometer for nuclear events dating[J].Applied Radiation and Isotopes,2014,87:152-156.
[7] Evaluated Nuclear Data File.[2018-02-02].http://www.nndc.bnl.gov/exfor/endf00.jsp.
[8] Decay Data Evaluation Project.[2016-09-22].http://www.nucleide.org/DDEP.htm.