Session: 04-10: SMRs, Advanced Reactors and Fusion

Paper Number: 133881

133881 - Practice and Validation of Harmonic Method for Htr-Pm Power Distribution Monitoring 

Abstract: 

As the world's first Generation IV nuclear power plant in commercial operation, the Shandong Shidao Bay High Temperature Gas-cooled Reactor Demonstration Power Plant (HTR-PM) has inherent safety features. However, 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 as in the case of a pressurized water reactor. The power detectors of HTR-PM are located in a limited number within the concrete shielding wall, which is a certain distance from the active zone. All these features pose a challenge to real-time monitoring of the power distribution in HTR-PM.

Harmonic synthesis method is based on spatial response function and higher-order harmonic set, which can make full use of response readings given by the detectors to complete reconstruction of power distribution in the reactor. However, due to the fact that power distribution, harmonics and spatial response function of the core may differ greatly under different depletions and different insertion depths of the control rods, and that the number of detectors outside the reactor is limited, only a finite-order set of harmonics can be utilized to complete the power reconstruction. Thus, accuracy of the pre-calculated detector's spatial response function, as well as the selection of higher-order harmonic set are the key factors to achieve high-precision power distribution reconstruction.

Therefore, 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. In this process, reconstructive capability of the pre-calculated harmonic set and accuracy of spatial response function will be evaluated. In this work, the high-temperature gas-cooled reactor will be modeled using three-dimensional transport program. Different spatial response models will be established for different operating states, so as to describe the structure inside the reactor as accurately as possible, and to obtain spatial response functions and higher-order harmonics that meet the requirements.

Comparing the reconstructed power distribution with VSOP's tracking simulation results, 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.

Presenting Author: Jinpeng Li Tsinghua University

Presenting Author Biography: Jinpeng Li, male
-Major in nuclear science and engineering.
-Research on advanced reactor.

Authors:

Jinpeng Li Tsinghua University
Jiong Guo Tsinghua University
Fu Li Tsinghua University
Chunlin Wei Tsinghua University