Structural Optimization And Characteristic Analysis Of Radiation Shield For Megawatt Space Reactor

With the development of the space industry,its requirements for long endurance energy and environmental adaptability are increased.At present,the mature energy supply means can’t meet the energy needs of space missions with high power,long endurance and low environmental dependence.Therefore,fission energy is the most feasible way to provide high power level energy for spacecraft at present and in the short term of future.The space application of nuclear energy will inevitably bring radiation safety problems.However,the large mass of the shielding often accounts for 50% of the total mass of the reactor system,which is not conducive to the lightweight of the nuclear power system.Therefore,this paper carried out the research on the optimization algorithm of efficient shielding of nuclear powered spacecraft,and carried out the radiation characteristics and radiation safety analysis of nuclear powered spacecraft from the aspects of full-field radiation characteristics and radiation thermal effect.Based on the existing historical experience and the analysis of the space nuclear power system,this paper obtains the size,layout and system parameters of the nuclear power spacecraft under the power of 1.18 MW,and provides boundary conditions for the optimization of the shield.In this paper,the radiation characteristics of the main structural materials and shielding materials of nuclear powered spacecraft are studied,and the shielding characteristics of single materials and combined materials for neutrons and photons under the space stack layout are mastered,providing a theoretical basis for shielding optimization.On this basis,a design idea of composite material is proposed,the accuracy of theoretical analysis results is verified,and the basic idea of shielding body design is determined.In this paper,based on the radiation protection goal of nuclear powered spacecraft and the layout of the reactor system,the shield optimization algorithm is studied.In this paper,the evolutionary algorithm coupling Monte Carlo calculation method is taken as the basic idea,and the evaluation of the evolutionary algorithm is carried out.Finally,the optimization and calculation of the shadow shield structure was realized,and a lightweight shield scheme that met the radiation protection index of nuclear powered spacecraft was obtained.Carry out calculation acceleration research on optimization algorithms for the problem of long Monte Carlo solution time,establish a prediction model for radiation calculations by training neural networks,and achieve fast solutions through calculations that are independent of material ordering.Establish the calculation model of the full radiation field of the nuclear powered spacecraft,carry out the analysis of the influence mechanism of the coverage of the shadow area of the shielding body,and obtain the main influencing factors of the angle,width and radiation field distribution of the shadow area,and analyze the results according to the shielding characteristics of the shadow area The optimization index and decision variables of the chamfering of the shielding body are proposed,so that the mass of the shielding body scheme is reduced from 1483 kg to 1214 kg.Finally,this paper analyzes the radiation heat effect and radiation characteristics of the shielding body.The main reason for the energy deposition of the shielding body and the distribution of thermal power brought by the deposition energy are mastered,and the temperature changes of the shielding body and partial shielding body due to the radiation deposition energy under different working conditions are obtained.