Abstract :
A correction factor for the improved coarse mesh (ICM) method was analytically derived based on an explicit solution of a diffusion equation in one-dimensional geometry. In the conventional approach, the correction factors of the ICM method were derived by a neutron balance equation on virtual mesh points in an actual mesh. However, in the analytical approach, the correction factors were derived using a rigorous form of a finite-difference formulation of diffusion equation in one-dimensional geometry. Test calculations in one-dimensional slab and two-dimensional PWR colorset geometries showed that the spatial discretization error can be further reduced by utilizing the analytically derived correction factors in stead of the original ones. The newly derived correction factors for the ICM method can be easily implemented in the existing code since only expression of the correction factor is modified. Furthermore, since the ICM can be applied to existing finite-difference diffusion code with minor modifications and slight additional computation time, it is useful for scoping purpose which requires fairly accurate results within a short computation time, e.g. in-core fuel management calculations.
