Research on numerical method and experimental verification of the vanadium SPND gamma effect based on current component separation model

BackgroundThe vanadium self-powered neutron detector (SPND) generates significant gamma noise current in the mixed radiation field of a nuclear reactor, which adversely affects the accuracy of neutron flux measurements and online monitoring of reactor core.PurposeThis study aims to explore the gamma effect of vanadium SPND through a combination of theoretical calculation method and experimental verification.MethodsFirst of all, a current component separation model was established according to the vanadium detector response mechanism, and the current calculation method of SPND in the pulsed research reactor was constructed. Then, multi-step Monte Carlo method was used to realize the coupling calculation of the core scale and the detector signal. Based on the temporal characteristics of different current components, the prompt γ current component was quantified by using the shutdown attenuation measurement experiment at the 200 kW radiation chamber of a research reactor. Finally, the measured signals were used to verify the sensitivity component separation model, and the dynamic response tracking and prompt γ current simulation capabilities of the detector numerical model were further verified by the vanadium SPND simulation of the commercial pressurized water reactor load rejection test process.ResultsThe established vanadium SPND calculation model can be used to effectively distinguish the detector response current component with a relative deviation of 2.27% for steady-state current calculation, and the calculated results agree well with the experimental data in terms of calculating the steady-state current and the prompt component of the steady-state current for the vanadium detector.ConclusionsThis study has shown that the gamma effect of vanadium SPND needs to be considered in both theoretical calculations and measurement analysis, and there is a mutual compensation effect among different current components in the gamma response of the actual reactor core.