SPENT NUCLEAR FUEL DEGREE-OF-SUBCRITICALITY MEASUREMENT DEVICE AND SPENT NUCLEAR FUEL CRITICALITY MANAGEMENT METHOD

• Main Authors: ODA TADAYOSHI, SUGITA TSUKASA, YOSHIOKA KENICHI, ODANAKA SHIGERU
• Format: Patent
• Language: English; Japanese
• Published: 08.03.2023
• Subjects: NUCLEAR ENGINEERING; NUCLEAR PHYSICS; NUCLEAR REACTORS; PHYSICS

To provide a spent nuclear fuel degree-of-subcriticality measurement device and the like that achieve cost reduction, and enable an estimation of a neutron multiplication factor to be implemented as a function of a second step.SOLUTION: A spent nuclear fuel degree-of-subcriticality measurement device, which performs measurement of a first step of measuring the number of neutrons of a spent nuclear fuel to measure the degree of burn-up, and measurement of a second step with respect to the spent nuclear fuel not meeting the degree of burn-up limit value in the first step, comprises: accumulation means of accumulating the number of neutrons as time-series data; time-series data analysis means of calculating a prompt neutron attenuation constant α from the time-series data; pre-analysis means of calculating a delayed neutron ratio β and a prompt neutron lifetime L by preliminarily neutron transport analysis; and neutron multiplication factor means of calculating a neutron multiplication factor k from the prompt neutron attenuation constant α, delayed neutron ratio β and prompt neutron lifetime L. The degree of subcriticality of the second step is determined by the neutron multiplication factor k.SELECTED DRAWING: Figure 1 【課題】コストの低減を図ることができるとともに、第２ステップの機能である中性子増倍率の推定を可能とすることのできる使用済み核燃料の未臨界度測定装置等を提供する。【解決手段】使用済み核燃料の中性子計数を測定して燃焼度を測定する第１ステップと、第１ステップにおいて燃焼度制限値を満たさない使用済み核燃料に対して第２ステップの測定を行う使用済み核燃料の未臨界度測定装置であって、中性子計数を時系列データとして蓄積する蓄積手段と、時系列データから、即発中性子減衰定数αを算出する時系列データ分析手段と、予め中性子輸送解析により、遅発中性子割合βと即発中性子寿命Ｌとを算出する事前解析手段と、即発中性子減衰定数αと、遅発中性子割合βと、即発中性子寿命Ｌとから中性子増倍率ｋを算出する中性子増倍率手段と、を具備し、中性子増倍率ｋによって第２ステップの未臨界度を判定する。【選択図】図１