Method to Minimize Power Peaking in Refueling Schedule of Boiling Water Reactor

Abstract

A method of optimizing fuel assembly allocation is proposed for a certain type of refueling schedule problem of Boiling Water Reactor (BWR) in which cycle length and number of fresh fuel assemblies to be loaded are predetermined The optimization is aimed at minimizing power peaking factor. The problem is decomposed into two subproblems: one to optimize the global region-wise shuffling scheme and the other to optimize assembly allocation. Linear programming is iteratively solved in the former subproblem such that the maximum excess reactivity is minimized and a direct search method is used in the latter subproblem The method is successfully applied to the 2nd and the 3rd cycle refueling schedule problems of a 460 MWe BWR. The optimized reloading patterns are compared with other non-optimal patterns which have much simpler or more symmetrical shuffling schemes. The optimization shows merit in reducing power peaking without sacrificing the cycle length.