A nodal method based on CMFD for pin-by-pin SP3 calculation

A nodal method based on Coarse Mesh Finite Difference (CMFD) is proposed for pin-by-pin core simulation with SP3 approximation. The Laplace operators of the 0th moment flux of SP3 equations are treated using CMFD, while the Laplace operators of the 2nd moment flux are treated using fine mesh finite difference (FMFD). Correction factor is determined by solving local two-node problems. Transverse 0th moment flux is expanded to second-order Legendre polynomials. SP3 equations are then transformed to a generalized eigenvalue problem which is solved using Krylov subspace methods, including Jacobi-Davidson method, Generalized Davidson method, and Krylov-Schur method. Standard nonlinear iterative strategy is carried out to obtain converged correction factor. A prototype code CORCA-PIN is developed. Numerical results show that solver option of CMFD using 1 × 1 radial mesh per cell and Jacobi Davidson iteration method is suitable for pin-by-pin whole core calculations with SP3 approximation.