Parameter Optimization Of Discrete Ordinates Shielding Calculation Method

High-fidelity radiation transport calculation is essential to enhance and improve the design in the field of nuclear engineering.Discrete ordinates method is one of the main stream methods for radiation shielding calculation of nuclear system.Many factors,including spatial discretization and angular discretization,have a significant effect to the calculated results when adopting discrete ordinates methods to solve the radiation transport equation.Comprehensive analyses for the sensitivity of these discretization parameters can improve the reliability of shielding calculations.The large variety of cross section,resulted from the complexity material distribution in engineering,poses great chanllenge of selecting optimal discretization parameters.In this study,the multi-dimensional discrete ordinates shielding transport program ARES was used to study the sensitivity of key calculation parameters to the flux,by taking the commonly used materials in the typical PWR shielding problem as the research goal.Due to the geometrical model and the complicated material types of the actual three-dimensional engineering problems,it is difficult to accurately measure the influence of each calculation parameter.And it is also difficult to locate the main source of calculation error.Therefore,this paper selects a single shielding material for research and analysis,such as water,low carbon alloy steel,air and concrete.The energy spectrum of each material region calculated by PWR is taken as the input source intensity,and the discrete ordinates method is used to simulate the single shielding material.The mesh size,the difference scheme and the discrete quadrature set are used to analyze the shielding area’s neutron and photon energy spectrum,flux and dose equivalent rate and other results.Numerical results show that under the same conditions of other parameters,different mesh sizes have a great influence on the calculation results of the shielding materials.The order of influence is concrete,low carbon alloy steel,water and air.The research on different difference schemes show that the results of each difference scheme is close to each other under the fine mesh size,and the EDW difference scheme is less sensitive to the mesh size,obtains better accuracy with coarse mesh size.Due to the low scattering effect of air material,the anisotropy of angular flux density is strong,and the angular discretization error of SN calculation is large,diffirent discrete quadrature sets have a significant influence on the calculation results.This research on single material problem is applied to complex three-dimensional geometric and multi-material shielding problems.The test results of ASPIS which is an international benchmark for OECD.shows that the calculated results of’ neutron energy spectrum and reaction rate are in good agreement with the results of MCNP and are within acceptable error compared with the experimental values,which further illustrates the research value of the parameter optimization in discrete ordinates numerical method.In addition,this paper also simulates the modular miniature nuclear power reactor and analyzes the decay rules of neutron and photon flux at different thickness and different azimuth of pressure vessel.The research of this project will help to improve the accuracy and reliability of the shielding calculation.It is of great significance to solve the key technical problems of the shielding calculation.The application prospect of the project is promising.