Impact and cause analysis of IRC γ compensation effect deviated from the expected level

The conclusion that the IRC γ overcompensation during the re-critical process after the emergency reactor shutdown has the risk of triggering the shutdown signal due to the excessive SRC neutron count rate was got by analyzing the change trend of the γ absorbed dose rate after the shutdown. The IRC γ under-compensation has the risk of causing nuclear power measurements outside of the reactor to fail after the reactor shutdown and during the critical process according to the function of IRC and SRC. Based on the theoretical influence of the composition and pressure of the working gas on the saturation starting voltage and saturation current of the gas ionization chamber and the experimental results, the analysis indicates that the gas pressure of IRC detectors used in Y4 nuclear power plant was less than the design value, and the IRC γ under-compensation was caused by compensation negative high voltage set improperly according to the corresponding relationship between the compensation negative high voltage and current of the detector. According to the trend of γ ionization current with argon pressure, it was judged that the IRC γ overcompensation of F2 nuclear power plant was caused by the gas pressure in the compensation chamber was higher than the gas pressure in the measurement chamber. (authors)