Radiation damage evaluation of YSECT v.2 for spent nuclear fuel inspection in wet storage facility

Abstract

The Yonsei Single-photon Emission Computed Tomography version 2 (YSECT v.2) for inspection of spent nuclear fuel in the wet storage facility is currently under development. However, the high radiation fields of the facility can potentially damage the system. In this study, we evaluated radiation damage to the scintillator and silicon photomultiplier (SiPM) and its impact on performance. The facility was modeled using Monte Carlo simulation, and the gamma dose and neutron flux delivered to the detector were calculated. Based on the calculated values, experiments were conducted to evaluate damage by irradiating photons and neutrons to the detector. Radiation damage was assessed by comparing 137Cs spectra obtained before and after irradiation. Additionally, the damage was assessed by comparing the spectra obtained for gamma rays emitted from 252Cf during neutron irradiation. As a result, no detector damage due to photon irradiation was observed. For neutron irradiation, when the neutron fluence reaches approximately 3.0 × 109 neutrons/cm2, the signal gain decreases by 16.66 % due to SiPM damage. Nevertheless, there was no change in the measured counts, which are important for image reconstruction of the system. It is expected that the wet storage environment will not affect the results of YSECT v.2 spent fuel inspection.