Nuclear analysis method based on current coupling neutron response reconstruction method

The current coupling neutron response reconstruction method has been developed, based on the already developed direct response matrix method. In the current coupling neutron response reconstruction method, by setting fuel rod neutron production rates as new unknown values, the need to calculate the response matrix is eliminated, and the calculation time can be reduced compared to the direct response matrix method. Furthermore, by evaluating the neutron fluxes and the cross sections using the reconstruction method of homogenized cross sections which has already been developed, the neutron effective multiplication factor is directly evaluated from the reaction rate ratio, and convergence can be improved. For the purpose of verification, calculations for heterogeneous systems were performed. The results obtained using the current coupling neutron response reconstruction method agreed well with those obtained using direct calculations by the Monte Carlo method, and they were almost the same as those obtained using the direct response matrix method. These good agreements with the direct calculations using the Monte Carlo method meant that the current coupling neutron response reconstruction method accurately reflected the effects of intra- and inter-assembly heterogeneities. In terms of calculation time, the current coupling neutron response reconstruction method was 33 to 60 times faster than the direct response matrix method by eliminating the need for a response matrix and improving convergence. (author)