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

BackgroundThe 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.PurposeThis study aims to solve the multi-objective optimization problem with complex constraints of the nuclear reactor shielding structure.MethodsThe Adaptive Weight Genetic Algorithm, the Multi-Objective Optimization Algorithm Based on Objective Decomposition (MOEA/D) algorithm, the Non-dominated Sorting Genetic Algorithm II (NSGA-II) algorithm and the Non-dominated Sorting Genetic Algorithm III (NSGA-III) algorithm and their application for reactor shielding structure optimization were explored in this study. By combining the multi-objective optimization algorithms with the 3D SN program HYDRA and the Monte Carlo program MCNP, a constraint processing method for optimization parameters and optimization sub-objectives was innovatively developed, and applied to the optimized design of the shielding structures of Savannah ship marine nuclear reactor and space nuclear reactor with protecting target of the electronic components at the dose surface from irradiation by neutrons and gamma rays in the reactor core.ResultsThe optimization study shows that the method treating weight and volume as optimization objectives while keeping 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.ConclusionsRegarding 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.