Abstract
The reload design of a boiling water reactor (BWR) consists of fuel loading pattern design and control rod pattern design. The fuel loading pattern design is to permute the fuel assemblies so that shutdown margin requirement is fulfilled and the thermal limit margin is good enough to guarantee the satisfactory control rod pattern design. The control rod pattern design is to determine the inserted depth of control rods at each exposure point so that the thermal limits such as minimum critical power ratio (MCPR), maximum linear heat generation rate (MLHGR), and maximum average planar linear heat generation rate (MAPLHGR) meet the margin requirement and shutdown margin and cycle length are fulfilled. Automatic design of boiling water reactor loading pattern and control rod pattern were developed using the rank-based ant system (RAS) which is a variety of ant colony optimization (ACO) algorithm. The ACO algorithm is an effective optimization algorithm for combinatorial optimization problem and the heuristic rules of ACO algorithm were adopted to reduce search space and computation time. In loading pattern design, to reduce design complexity, fuel assemblies (FAs) were chosen to load the positions of one-eighth core geometry using probabilistic solution construction of ACO algorithm and then the corresponding fuel assemblies were loaded into the other part of the core. When the pattern was determined, Haling cycle length, the thermal limits at the end of cycle, and beginning of cycle (BOC) shutdown margin (SDM) were calculated using SIMULATE-3 code, which were used to evaluate the loading pattern for updating pheromone concentration of ACO algorithm. In control rod pattern design which followed either the A2-B1-A1-B2 or A1-B2-A2-B1 sequence in this study. After the control rod pattern was determined, the axial power distribution, effective multiplication factor (keff), shutdown margin, and three thermal limits were calculated using SIMULATE-3 code, which were then used to evaluate the control rod pattern and update the pheromone concentration. The developed design methodology was demonstrated using two fuel reload cycle of Kuosheng nuclear power plant. The results show that the designed satisfactory reload design with an acceptable cycle length can be achieved within a reasonable computation time.