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裂变径迹测年方法中,母体的测量是通过热中子诱发235U裂变产生的诱发裂变径迹间接测得的.当热化不充分时,还会诱发238U和232Th裂变,造成母体测量的误差.因此,中子热化充分与否对年龄测试结果存在重要影响.2007年,由于安全生产的原因,原101反应堆关闭,本研究尝试492反应堆做热中子辐照的可行性及从理论上探讨相关因素对裂变径迹结果可能的影响.本文采用SRM612和CN5标准玻璃成对辐照方法,通过多次的监测结果,研究了反应堆中子热化(thermalization)的情况.研究表明,热中子在空间上(无论在横向上,还是在纵向上)表现出不均匀性,特别是横向上的不均匀性较大.但是在原子能反应堆中适当的位置,可以满足裂变径迹测试的辐照条件.本文计算、评估了当前热化不充分条件对裂变径迹年龄测定的影响,发现影响年龄的主要因素是标准样与样品中的232Th/238U比值.当样品中的232Th/238U比值与标准样品一致时,对测试结果无影响;当样品的232Th/238U比值大于标准样品232Th/238U比值时,测试结果偏小;相反,则偏大.研究认为,为了减小辐照带来的误差,应严格地限定辐照的通道及位置,另外减小每包的样品量,降低横向上热化不均匀性的影响,也是减小误差的一种方式.
In fission track dating, the maternal measurements are indirectly measured by induced fission tracks generated by thermal neutron-induced 235U fission, which can also induce 238U and 232Th fissions when the heating is inadequate, resulting in errors in maternal measurements Therefore, the adequacy of neutron heating has an important influence on the age test results.In 2007, due to safety reasons, the original 101 reactor was closed, the feasibility of using 492 reactor to do thermal neutron irradiation and theoretically And discuss the possible influence of the relevant factors on the fission track results.In this paper, the pairs of SRM612 and CN5 standard glass irradiation method were used to study the neutron thermalization of the reactor through several monitoring results.Research shows that heat In spatially (both horizontally and longitudinally), the subzones exhibit inhomogeneities, especially in the lateral direction, but at suitable locations in the nuclear reactor, the fission track test radiation Conditions.This paper calculates and evaluates the influence of the current inadequate heating conditions on the determination of fission track age and finds that the main factor influencing age is the ratio of 232Th / 238U in the standard sample and the sample Of the 232Th / 238U ratio is consistent with the standard sample, the test results have no effect; when the sample 232Th / 238U ratio is greater than the standard sample 232Th / 238U ratio, the test results are small, on the contrary, it is too large.Research that, in order to reduce The error caused by irradiation should be strictly limited irradiation channel and location, while reducing the amount of each sample package to reduce the impact of non-uniformity of the horizontal heat, but also to reduce the error of a way.