A Coupled Deterministic and Monte-Carlo Method for Modeling and Simulation of Self-Powered Neutron Detector

To improve the efficiency of numerical calculation of self-powered neutron detector (SPND) current in pressurized water reactors (PWRs), a coupling method based on high-fidelity neutronics code and an SPND direct response model is proposed. On the detector scale, a Monte-Carlo analysis toolkit, GEANT4-SPND, is developed and verified. The toolkit, which calculates the effective contribution of insulator materials to current, has been proven to be conducive to the calculation of gamma sensitivity. On the reactor scale, detectors modeled using the deterministic method provide information of the nuclear density for the depletion calculation. The particle flux information based on the energy and spatial angular distribution is regarded as the medium of coupling strategy, thus enabling an efficient simulation of SPND current for PWR problems. This work has confirmed the necessity of particle anisotropy for current calculation in real reactor environments. The numerical code and its coupling method are verified based on the experimental values of rhodium, vanadium, platinum, and hafnium SPNDs and the K1 assembly benchmark as well. Moreover, the method is used to calculate a real VVER-1000 reactor operating in China. The numerical results are in good agreement with the values measured in realistic circumstances. What is more, the spatial distribution of the neutron sensitivity of PWR is characterized.