ABSTRACT

For an university training and research reactor of Kindai University, the Feynman-α analyses based on several formulae are carried out to examine the applicability of these formulae to the subcritical thermal reactor system. The original formula, in which the effect of delayed neutrons is neglected, results in a prompt-neutron decay constant sensitive to an upper limit of the gate time range of the analysis and consequently has difficulty in determining the decay constant. This difficulty originates from the neglect of delayed neutrons. An improved formula, where a term proportional to the gate time is added to the original formula, gives a desirable decay constant insensitive to the upper limit and the insensitive decay constant well agrees with that obtained from the Rossi-α analysis. The application of a difference filtering technique also leads to a successful result similar to the above improved formula. An alternative index Z to the traditional index Y of the original formula has been sometimes employed as an indication of the non-Poisson nature of the counting statistics. The Z is defined as dividing the Y by the mean number of neutron counts accumulated in the gate time. The formula for the Z never results in a reasonable decay constant even though the effect of delayed neutrons is considered. This study suggests that the improved formula considering delayed neutrons for the Y and the formula for the difference filtering technique should be employed to determine the prompt-neutron decay constant of thermal reactors.

摘要

针对近代大学某高校培训研究堆，基于多个公式进行了Feynman-α分析，检验了这些公式在亚临界热堆系统中的适用性。原始公式中忽略了延迟中子的影响，导致瞬发中子衰变常数对分析门限时间范围的上限敏感，因此难以确定衰变常数。这种困难源于对延迟中子的忽视。一个改进的公式，其中一个与门时间成正比的项被添加到原始公式中，给出了一个对上限不敏感的理想衰减常数，并且这个不敏感衰减常数与从 Rossi-α 分析中得到的非常吻合。差分滤波技术的应用也导致了类似于上述改进公式的成功结果。原始公式的传统索引 Y 的替代索引 Z 有时被用作计数统计的非泊松性质的指示。Z 定义为 Y 除以门控时间内累积的中子计数的平均数。即使考虑了延迟中子的影响，Z 的公式也永远不会产生合理的衰减常数。该研究表明，应采用改进的Y考虑延迟中子公式和差分滤波技术公式来确定热反应堆的瞬发中子衰变常数。原始公式的传统索引 Y 的替代索引 Z 有时被用作计数统计的非泊松性质的指示。Z 定义为 Y 除以门控时间内累积的中子计数的平均数。即使考虑了延迟中子的影响，Z 的公式也永远不会产生合理的衰减常数。该研究表明，应采用改进的Y考虑延迟中子公式和差分滤波技术公式来确定热反应堆的瞬发中子衰变常数。原始公式的传统索引 Y 的替代索引 Z 有时被用作计数统计的非泊松性质的指示。Z 定义为 Y 除以门控时间内累积的中子计数的平均数。即使考虑了延迟中子的影响，Z 的公式也永远不会产生合理的衰减常数。该研究表明，应采用改进的Y考虑延迟中子公式和差分滤波技术公式来确定热反应堆的瞬发中子衰变常数。即使考虑了延迟中子的影响，Z 的公式也永远不会产生合理的衰减常数。该研究表明，应采用改进的Y考虑延迟中子公式和差分滤波技术公式来确定热反应堆的瞬发中子衰变常数。即使考虑了延迟中子的影响，Z 的公式也永远不会产生合理的衰减常数。该研究表明，应采用改进的Y考虑延迟中子公式和差分滤波技术公式来确定热反应堆的瞬发中子衰变常数。