An efficient 3D multigroup diffusion nodal algorithm for reactor core analysis

An advanced high-order self-consistent nodal method is developed for 3D multigroup diffusion calculations. The formalism is based on the transverse integration procedure and a response matrix formulation of the local problem. Neutron fluxes in a cell are approximated by polynomial expansions using Legendre moment functionals. The transverse leakage spatial profiles consistent with this approximation are nodewise linear. The algorithm provides a highly accurate 'pin-by-pin' flux distribution. Intrinsic properties of the nodal scheme and transverse integration ensure a decoupling of the resulting algebraic system, thereby reducing the computational work. Numerical results on PWR benchmarks show that besides its accuracy, the method is stable. (author)