Reactor power monitoring using neutron induced prompt gamma ray

Monitoring of only neutron flux in a nuclear reactor core has an advantage in reactor power monitoring accuracy. We started development of a new nuclear instrumentation based on measurement of prompt gamma rays originating from metals placed at the neutron flux monitoring positions. The thermal neutron flux at the position of each metal can be monitored by measuring the prompt gamma rays as the count rate of each energy. We conducted a neutron irradiation experiment for Ti, V, Ni, Cu and Sm. The energies of high intensity prompt gamma rays of more than 5 MeV showed good agreement between the experiment and nuclear data. And the energy spectra for the metals, excluding Sm, calculated with a Monte Carlo method showed rough agreement with experiments. We confirmed that gamma ray peaks were evaluable in the combined spectrum for Ti, V, Ni and Cu based on an estimation method using the peak ratio. The results indicated that the neutron flux monitoring method based on prompt gamma ray measurement had possible application to monitoring local reactor power at four positions. (author)