Three-dimensional method of characteristics/diamond-difference transport analysis method in STREAM for whole-core neutron transport calculation

Abstract

A new three-dimensional (3D) transport analysis method is developed and implemented in the light water reactor (LWR) whole-core analysis code STREAM. The method is named as 3D method of characteristics/Diamond-difference (MOC/DD). In this method, 3D variables such as flux and source are expressed as a combination of the two-dimensional (2D) radial component and the one-dimensional (1D) axial component. The 2D method of characteristics (MOC), which is widely used in 2D neutron transport analysis in reactor physics, is used to solve complicated radial geometries composed of fuel pin, burnable absorber, structural material, etc. The axial neutron source, which is discretized by the diamond-difference (DD) method, is merged into the 3D MOC source term. This paper presents a detailed derivation of the 3D MOC/DD method and a parallelization technique to apply the 3D MOC/DD method to a whole-core problem. The accuracy and performance are examined by solving the C5G7 benchmark and the BEAVRS whole-core benchmark problems