Research On Fabrication Of Neutron-photon Coupling Multi-group Cross Section Library And Shielding Optimization Design Method For Nuclear Reactor

Nuclear energy possesses key attributes of cleanliness,low carbon emissions,efficiency,and stability,making it a crucial option for energy development in the modern era.As nuclear energy advances,the demand for precise nuclear reactor physics and shielding calculations has grown substantially,along with an increased emphasis on efficient and high-quality nuclear reactor design.Radiation shielding calculation plays a critical role in ensuring the safety of nuclear reactors,as it directly impacts equipment irradiation damage and personnel dose rate calculations.In the field of nuclear reactor shielding calculations,deterministic computing codes are commonly used due to their computational efficiency and capability to solve deep penetration problems.However,the accuracy of deterministic codes heavily relies on the precision of the multi-group cross section library.In reality,the energy spectra differ significantly among various reactor types and even within different regions of the same reactor.Currently available universal multi-group crosssection libraries,such as Bugle96,struggle to meet the accuracy requirements of the rapidly evolving nuclear industry for radiation shielding calculations.To enhance the computational accuracy of deterministic codes,the Monte Carlo method has been employed to create a multi-group cross section library.Leveraging the open-source Monte Carlo code Open MC,improvements have been made to the fabrication method of the multi-group cross section library,allowing for the creation of a neutron-photon coupling multi-group cross section library.The Open MC code,with its capabilities to calculate flux,reaction rates,and Legendre scattering components,has been enhanced to include the counting of photon production cross sections resulting from neutron reactions.Additionally,the functionality to account for the scattering and merging of photon sources generated by atomic relaxation,bremsstrahlung,positron-electron annihilation has been added.In order to verify the applicability of this method,the suitable energy group structure was selected first,and then the OECD/NEA fast reactor benchmark,Savannah thermal reactor benchmark,and HBR-2 benchmark were used to make the neutron-photon coupling multigroup cross sections.These multi-group cross section libraries were provided to the deterministic code DORT for calculations.The calculated results are compared with the Open MC results,and the results show that the keff,neutron flux,photon flux,flux distribution with energy,and dose rate are in good agreement,indicating that the neutron-photon coupling multi group cross section library produced by this method has high accuracy.The optimization of radiation shielding plays a crucial role in nuclear reactor design.Determining the appropriate thickness and material for the shielding layer is key to achieving effective radiation protection.Obtaining an optimal design scheme is vital to meet the requirements of radiation protection,weight reduction,and other specific needs of nuclear devices.However,radiation shielding design is a complex multi-objective optimization problem.Traditional optimization methods rely on manual adjustment and experience,resulting in inefficiency and difficulty in obtaining the optimal shielding scheme.Therefore,the development of an automated shielding optimization design method is necessary.In this study,we propose a multi-objective optimization design method for shielding by integrating particle swarm optimization(PSO)algorithm with shielding calculation code ANISN.Additionally,a mutation operation is incorporated into the standard PSO algorithm to prevent convergence to local optima.Two fitness evaluation strategies,namely linear weighted combination and Pareto frontier,are provided.Based on this multi-objective shielding optimization design method,we have developed a code capable of automatically adjusting the thickness and material of the shielding layer for optimization design.To validate the proposed method,we conducted a case study on the shielding optimization of the Savannah marine reactor.Using the Monte Carlo method,a multi-group cross-section library was generated.The radiation dose outside the secondary shielding layer and the total weight of the shielding layer were considered as the optimization objectives for the radiation shielding optimization design.This case study confirms the effectiveness of the proposed multi-objective shielding optimization design method and the developed code.Subsequently,the optimized shielding scheme was evaluated using the Monte Carlo code Open MC to ensure compliance with dose requirements.The results show that using this method and code for radiation shielding design of nuclear reactors is reliable and effective,and can improve the efficiency of shielding optimization design and the quality of shielding schemes.