Practice and Validation of Harmonic Method for HTR-PM Power Distribution Monitoring

Abstract Due to the pebble-bed reactor design, core of the HTR-PM consists of a stack of pebble fuel elements, which, together with the high temperature environment inside the reactor, prevents the installation of power detectors in the active zone of the core. Power detectors of HTR-PM are in a limited number within the concrete shielding wall, which is a certain distance from the active zone. As a result, detectors are not capable to give sufficient information and it is challenging to monitor power distribution in HTR-PM. In this paper we reconstruct power distribution of various operating states of the reactor using harmonic synthesis method based on actual operating data of HTR-PM and readings of detectors at different positions. Afterwards, the VSOP program is used to track the reactor operation process and calculate the power distribution of various states. Comparisons are made between reconstructed results and VSOP’s results for verification. We notice that harmonic synthesis method is capable to realize power distribution reconstruction of high-temperature gas-cooled reactors, but reconstructive ability of the harmonic set is still a little bit insufficient for some special operating states, and it’s necessary to improve the ability and accuracy of the harmonic set and spatial response function for certain special operating states.