Core Power Distribution Reconstruction Based on the Neutron Detectors outside a Biological Shield of the UTR-KINKI

In the past decade, various institutions have developed small modular reactors and microreactors with the aims of reducing capital costs and improving safety through simplified reactor systems.Monitoring the core power distribution is crucial for detecting abnormal core conditions.Although in-core neutron detectors are currently used for this purpose, they face harsh environments, increasing the risk of failure.In contrast, ex-core detectors, placed outside the reactor, offer a milder environment.We have developed a monitoring method using ex-core detectors, called PHOEBE.In this study, we experimentally reconstruct the power distribution of the Kindai University Research Reactor (UTR-KINKI) using neutron detectors placed outside a thick shield.We develop a new method for adjusting the neutron detector response coefficients to reproduce a known power distribution based on measurement results.With the new method, the results show good agreement with a 4.06% average difference from the reference power distribution.