Treatment of Circular Boundary Conditions in Neutron Diffusion CaJculations

Abstract

The treatment of circular boundary conditions is incorporated in neutron diffusion calculations that are done using a rectangular mesh, where thephysical properties are homogeneous on parallelepipeds. This inclusion is done after transformation of the albedos at the external boundary, to take into accountt he volume corrections implied by a circular boundary. Numerical results of various orders for the nodal collocation option in TWAC are given for a bare cylindrical core and comparisons of results for circular-corrected boundary conditions in SMEX and in FMDP are also presented, showing that this model preserves the overall accuracy.