Study on multi-objective optimization method for shielding structure of nuclear reactors with complex constraints

Abstract：[Background] The nuclear reactor shielding structure is an important barrier that encloses the radioactive substances of the reactor to protect personnel or devices. The design of the nuclear reactor shielding structure is a typical multi-objective global optimization problem, and there are complex constraint relationships among various sub-objectives and shielding structure parameters.[Purpose] This study aims to solve the multi-objective optimization problem with complex constraints of the nuclear reactor shielding structure.[Methods] This paper respectively studied the Adaptive Weight Genetic Algorithm, the Multi-Objective Optimization Algorithm Based on Objective Decomposition (MOEA/D algorithm), as well as the Non-dominated Sorting Genetic Algorithm II (NSGA-II algorithm) and the Non-dominated Sorting Genetic Algorithm III (NSGA-III algorithm). By combining the multi-objective optimization algorithms with the three-dimensional SN program HYDRA and the Monte Carlo program MCNP, this paper innovatively developed a constraint processing method for optimization parameters and optimization sub-objectives, and applied it to the optimized design of the shielding structures of marine nuclear reactors and space nuclear reactors.[Results] The optimization study shows that the method treating weight and volume as optimization objectives while treating other radiation related sub-objectives as constraints is more suitable for the shielding structure design problem of marine nuclear reactors, and a structure different from the traditional design is obtained for space nuclear reactors with the proposed method.[Conclusion] Regarding the shielding problem of marine reactors, taking the shielding weight and volume as the optimization objectives, and using other radiation-related sub-objectives as constraint conditions is more suitable for the optimization design of marine reactor shielding problems, and can achieve good optimization results. The global optimization results of the shielding structure of space nuclear reactors show that the optimal structure is LiH, W-B4C, LiH, which is quite different from the traditional design idea of using heavy material-light material-heavy material.