Simulation of dynamic response of Self-Powered-Inconel-Neutron-Detector lead cables using a semi-empirical model

Abstract

The work presented here was devoted to the modelling and simulation of the dynamic response of lead cables of Inconel self-powered neutron detectors in a CANDUpower reactor. The main goal was to develop a semi-empirical dynamic model of theInconel lead-cables in Ontario Power Generation’s Darlington Nuclear GenerationStation (NGS) able to simulate the lead cables’ response to arbitrary neutron-fluxtransients. A secondary goal was to compare lead-cable dynamic characteristicsevaluated in the Darlington reactor to lead-cable characteristics previously evaluated inAECL’s NRU reactor.A Simulink model of the lead cable was developed. The model’s parameterswere obtained by fitting simulation results to measured lead-cable signals acquiredduring reactor shutdown. The functionality of the Simulink model was demonstrated forarbitrary neutron flux transients and simulation results were found to agree within 1.2%with measurements for reactor trip transients. At the same time, differences between thedynamic characteristics (e.g. prompt fraction) of lead cables in a power reactor(Darlington) and research reactor (NRU) were identified. A tentative explanation ofthose differences was formulated. A comprehensive elucidation of the reasons for the observed differences will have to be addressed by future studies.