BWR Core Simulator Using Three-Dimensional Direct Response Matrix and Analysis of Cold Critical Experiments

A new core analysis method has been developed in which neutronic calculations using a three-dimensional direct response matrix (3D-DRM) method are coupled with thermal-hydraulic calculations. As it requires neither a diffusion approximation nor a homogenization process of lattice constants, a precise representation of the neutronic heterogeneity effect in an advanced core design is possible. Moreover, the pin-by-pin power distribution can be directly evaluated, which enables precise evaluations of core thermal margins. Verification of the neutronic calculation using the 3D-DRM method was examined by analyses of cold criticality experiments of commercial power plants. The standard deviations and maximum differences in predicted neutron multiplication factors were 0.07%Δk and 0.19%Δk for a BWR5 plant, and 0.11%Δk and 0.25%Δk for an ABWR plant, respectively. A coupled analysis of the 3D-DRM method and thermal-hydraulic calculations for a quarter ABWR core was done, and it was found that the thermal power and coolant-flow distributions were smoothly converged.