Core Barrel Vibration Monitoring of KSNP Using Statistical Reactor Noise Descriptors

摘要

The vibration of core barrel (CB) in a typical pressurized water reactor can be monitored by noise analysis of the reactor instrumentation signals. This paper aims to prepare the CB motion quantification of the Korean Advanced Power Reactor (APR 1400) by comparing the results obtained from laboratory test and prototype vibration measurements of the Korean Standardized Nuclear Power (KSNP). The CB vibration of test and measurements is evaluated by using a scale factor and statistical reactor noise descriptors. Normalized power spectral density (NPSD), normalized cross-power spectral density (NCPSD), amplitude probability density (APD), coherence (COH) functions and phase are calculated to obtain the beam and shell modes of core barrel motion by processing the signal from two ex-core power range neutron detectors positioned diametrically of the reactor. The rms value of the CB motion is obtained from the integral of the NCPSD function over the appropriately restricted frequency range. The peak value of the motion is also obtained from an APD function which is constructed from a time signal over the properly limited to this same frequency range. Wide-band APD and CPSD functions are both demonstrated to yield erroneous estimates for the magnitude of CB motion. After processing the signal from two ex-core power range neutron detectors, the response of CB is lastly compared with the output from scale model test to verify the Scale Factor and confirm the structural integrity of CB. The reasonably good agreement shows in the restricted frequency range and resonance peaks.