Multi-channel modeling based on a multi-point reactor model for the regional instability in a BWR

An advanced model is presented to study the regional instability in a BWR core. This model, called 'Multi-point reactor model', takes into consideration the regional dependence of the nuclear effect by directly modeling the neutron dynamics for a multi-region or multi-point reactor core. In the multi-point reactor model, the subcore model presented in a previous paper of the authors is refined to take the effect of neutron migration between subcores into consideration directly in the stage of constructing a neutron dynamics equation for a subcore. Liner stability analysis is carried out with the frequency-domain method. The dominant factors affecting unstable oscillation modes are investigated with the stability map of the system. Although the multi-point reactor model is based on simple assumptions and needs refinement for the quantitative estimation of the three-dimensional space-dependence of nuclear effect, it reveals well the characteristics of the instabilities. (author)