Dif3d-nodal Neutronics Option For 2 & 3d Diffusion Theory Calculation In Hex Geometry By R.d.lawrence

Transcript

A nodal method is developed for the solution of the neutrons-diffusion equation in two- and three-dimensional hexagonal geometries. The nodal scheme has been incorporated as an option in the finite-difference diffusion-theory code DIF3D, and is intended for use in the analysis of current LMFBR designs. The nodal equations are derived using higher-order polynomial approximations to the spatial dependence of the flux within the hexagonal-z node. The final equations, which are cast in the form of inhomogeneous response-matrix equations for each energy group, involve spatial moments of the node-interior flux distribution plus surface-averaged partial currents across the faces of the node. These equations are solved using a conventional fission source iteration accelerated by coarse-mesh rebalance and asymptotic source extrapolation.