Development of a new method for simultaneous monitoring of criticality and nuclear material security/accountancy in a multiplicative system

From the perspective of integrating the 3S (safety, security, and safeguards), especially in developing innovative advanced nuclear power systems using HALEU (High Assay Low Enrichment Uranium), it is crucial to ensure that all 3S requirements are thoroughly met during the operational phase. However, monitoring systems currently in use are generally designed to monitor individual components of the 3S, and no comprehensive system that addresses all three components together has been developed yet. Therefore, this study proposes a new method for nuclear material monitoring systems that can simultaneously evaluate the target’s criticality (safety) and the amount of nuclear material (security and safeguards). To demonstrate the effectiveness of the newly developed method, experiments were conducted at Kyoto University Critical Assembly (KUCA) with HALEU samples and a DD neutron source. As a result, the simultaneous use of criticality monitoring and nuclear material accountancy achieved through the newly developed method was confirmed, and its capability to detect the absence of nuclear materials was also demonstrated. Therefore, the effectiveness of the new method was confirmed.