Layout Optimization of Self-Powered Neutron Detector for HPR1000

Self-Powered Neutron Detector (SPND) has been widely applied for the on-line monitoring of the key core parameters, including the power distribution, power-peak factor and so on. For the SPND layout design, the vital parameters include the SPND amount and loading position in the radial direction and segment amount in the axial direction. Different SPND layout reflects different ability of power distribution reconstruction, which is directly related to the safety and economy of nuclear power plant. For HPR1000, the neutronics sensitivity of SPND layout design is analyzed based on a 3D on-line power distribution monitoring system NECP-ONION. Through the comparison and analysis of the reconstruction errors of power distribution, the design rationality of SPND is evaluated and the optimization design is recommended. For the recommended SPND layout design, the loading positions in the radial direction are arranged at intervals and segment amount in the axial direction is 15. The recommended SPND layout design shows stable performance in the whole life for HPR1000 reactor, and the RMS errors of the power distribution reconstruction has been in the range of [0.32%, 0.48%], meeting the safety limit and accuracy requirements of power distribution reconstruction. This work verifies the on-line monitoring ability of NECP-ONION system. Additionally, it provides a technical reference for the SPND experiment in HPR1000.