Time-Dependent Experiment on Reactor Power Distribution Estimation by Ex-Core Detectors at UTR-KINKI

An experiment was conducted that demonstrates a novel core power distribution reconstruction method based on ex-core detectors using time-dependent measurement at the University Teaching and Research Reactor of Kindai University (UTR-KINKI). Although the proposed method PHOEBE was able to identify the power distribution change caused by control rods under static conditions in a previous experiment, time-dependent experiments were not conducted. Hence, the present study measured time-dependent neutron counts using ex-core detectors to reconstruct the power distribution based on PHOEBE. Extraction of the control rods was expected to cause a shift in the reactor power distribution from the north side to the south, and the results of the power distribution reconstruction also demonstrated this power shift. This result experimentally and qualitatively demonstrated the detection of time-dependent power shifts based on PHOEBE. However, quantitative verification was difficult in this study because there are no verified time-dependent three-dimensional neutronics codes available. This issue will be addressed in a future study when a code becomes available.