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우명현,홍서기 한국원자력학회 2022 Nuclear Engineering and Technology Vol.54 No.11
In this paper, a new multi-group neutron-gamma transport calculation code system STRAUM-MATXST for complicated geometrical problems is introduced and its development status including numerical tests is presented. In this code system, the MATXST (MATXS-based Cross Section Processor for SN Transport) code generates multi-group neutron and gamma cross sections by processing MATXS format libraries generated using NJOY and the STRAUM (SN Transport for Radiation Analysis with Unstructured Meshes) code performs multi-group neutron-gamma coupled transport calculation using tetrahedral meshes. In particular, this work presents the recent implementation and its test results of the Krylov subspace methods (i.e., Bi-CGSTAB and GMRES(m)) with preconditioners using DSA (Diffusion Synthetic Acceleration) and TSA (Transport Synthetic Acceleration). In addition, the Krylov subspace methods for accelerating the energy-group coupling iteration through thermal up-scatterings are implemented with new multi-group block DSA and TSA preconditioners in STRAUM.
Unstructured Discrete Ordinates Method Based on Radial Basis Function Approximation
Quang Huy Khuat,Sy Minh Tuan Hoang,우명현,김재현,김종경 한국물리학회 2019 THE JOURNAL OF THE KOREAN PHYSICAL SOCIETY Vol.75 No.1
Numerical treatment of the boundary value problem with meshfree methods has been a popular research area in recent years. In the nuclear transport field, several applications of meshfree methods are employed to develop a solution for the neutron diffusion and transport equations. Among the meshfree methods, which based on radial basis function (RBF) approximation exhibits more advantages than others. By applying the RBF approximation, a flexible technique for discretizing the spatial variable of the neutron transport equation is provided without any requirements related to the shape of the unstructured mesh or the number of spatial dimensions. However, use of the RBF approximation without specified constraints on the number of data points used for constructing the approximation function may cause instability in the discrete equation system. In addition, it decreases the accuracy of the numerical solution near the geometric boundary. In this study, a numerical method is developed to solve the discrete ordinates equation (S$_{\rm N}$) on unstructured mesh for neutron transport. Several benchmarks are implemented to evaluate the efficiency of the proposed method. Results are compared with analytical and reference results from the standard S$_{\rm N}$ method. The proposed method provides a stable and accurate solution for the transport problem with curved boundaries.