Research On Homogenization With Discrete Angel Based On Monte Carlo Method

This thesis discussed the advantages and disadvantages of deterministic and Monte Carlo methods of neutron transport.Considering accuracy,universality and computational efficiency,two-step transportation of Monte Carlo method is used.That is,firstly,continuous energy Monte Carlo method is used to generate multi-group constant with discrete scattering angles based on assembly or the pin cell of full core,and then the multi-group constant is used to carry out a transportation of full core based on Monte Carlo method.In the generation of group constants,this thesis discusses the method of making the multi-group constants,and analyzes the calculation methods of Legendre high-order scattering matrix,and points out its deficiencies.T he method of scattering matrix with discrete scattering angle is proposed.The 1^st,3rd,5th and 7th order Legendre scattering matrix are compared with scattering matrix with discrete scattering angles to prove that the scattering matrix with discrete scattering angles is more accurate in expressing anisotropic scattering.The MPI parallel mode is adopted in generation of multi-group constant and the multi-group constant of parallel mode coincides with the result of serial mode.In this paper,the group constants of the pressurized water reactor quadrilateral assembly and fast reactor hexagonal assembly based on RMC are compared with SERPENT to verify the group constant.In this thesis,the method of making multi-group constants of the ACE format is studied,which makes the scattering angle discrete group constants produced in this thesis compatible with the ACE format,and the anisotropic scattering function based on scattering matrix with discrete scattering angles is added,making it possible for RMC to read the multi-group constants of ACE format to perform multi-group transportation with Monte Carlo method.This thesis proposed an improved super-homogenization?SPH?method.SPH factor was replaced with new factor for cross section correction.The new factor converges to 1 in each energy group and each homogenized zone.Therefore,the fissile source distribution of the previous step is preserved during the iteration,which accelerates the convergence of fission sources.At last,this thesis proposes a homogenization method based on the real conditions with interfacial flux of assemblies or pin cell of the full core,and it was compared with the multi-group constants generated under reflect conditions.Then rationality and accuracy of homogenization with interfacial flux of assemblies or pin cell of the full core is analyzed and verified based on 2*2components,4*4 components,and C5G7 benchmark.