Evaluation of functional loss to radiation detector in tomographic device for spent-fuel inspection by high-energy photons and neutrons: A preliminary study

•High-dose irradiation by spent fuels can affect functions of the inspection device.•Function-loss of radiation detector was investigated for photon/neutron irradiation.•No significant function loss to the detector was observed with photon irradiation.•Signal noise was highly produced even only signal processing board was irradiated.•Considerable function loss was produced to the detector with neutron irradiation. The aim of this study was to investigate functional loss of radiation detectors used for spent fuel inspections due to radiations from spent fuel. Dose to a radiation detector was evaluated by Geant4 simulation. Subsequently, the radiation detector measured counts, according to the irradiation time, for the test source with presence of external 60Co and 252Cf sources in almost identical condition to those of the simulation, where gamma and neutron emission rates of the sources were similar to the actual spent fuels. The counts during the 60Co irradiation were changed with discrepancy of 1.17% while neutron beam decreased more than 25% of total counts after its irradiation. Additionally, abnormalities in the detector’s measured background counts were observed following the neutron irradiation. The results can be applied to efforts to define the tolerance dose for radiation detectors used in neutron-abundant environments such as nuclear power plants or spent-fuel storage facilities.