Core Design Optimization of a 200 MWt Pressurized Water SMR Using Evolutionary Simulated Annealing

The paper presents the design optimization of a pressurized small modular reactor (SMR) core using evolutionary simulated annealing (ESA). The core was designed for the power output of 200 MWt based on the typical 17 × 17 fuel assemblies of a traditional PWR. The core consists of 37 fuel assemblies of F235, F340 and F445 types corresponding to the 235U enrichment levels of 2.35, 3.40 and 4.45 wt%, respectively. The design target is to attain the fuel cycle length of about 900 effective full power days (EFPDs) with a minimum core average 235U enrichment, while flattening the radial power distribution. Lattice and core physics calculations were performed using the SRAC code system. The COREBN module of the SRAC code system was coupled with the ESA method for performing the core burnup calculations during the optimization process. A fitness function was chosen to combine the objectives of the cycle length, the core average enrichment and the radial power peaking factor (PPF). A survey was conducted for determining the optimal control parameters of the ESA method and the weighting factors in the fitness function associated to the design objectives. The optimal core was selected from the ESA search consisting of 21 assemblies of F235, 8 of F340 and 8 of F445 type, respectively. The core average 235U enrichment is 3.031 wt% with the cycle length of about 840 EFPDs. The PPF of the selected core is 1.428 which appears at the centered assembly.