Application of particle swarm optimization to the reconstruction of the energy group structure for shielding library

To improve the accuracy and efficiency of shielding calculation, particle swarm optimization algorithm was applied to optimize the neutron broad-group structure based on ENDF-B-VII.0. The position of the particle represented the solution of collapsing the fine-group library. The fitness function was constructed based on the errors between results by the fine-group library and broad-group library. Four energy broad-group structures were optimized, including a 47-group, a 38-group, a 29-group and a 25-group. Benchmarks from SINBAD, including Iron-88, PCA-Replica and HBR-2, were employed to test the optimized energy group structures. Results of the test show that the accuracy of the optimized 47-group structure is better than that of typical BUGLE structure, and the optimized 29-group structure is computationally more efficient because of its less energy group number.