Calculation of neutron fields in a reactor core using approximations maintaining materials mass balance in a finite-difference cell grid

Abstract

The possibility of using geometrical approximations, maintaining local materials mass balance in each spatial grid cell by introducing additional mixtures for the cells where several initial materials are present, in kinematic calculations of neutron fields in a reactor core is analyzed. To prescribe a 3D geometry of the core, combinatorial geometry methods, implemented in the MCU computer program for obtaining a Monte Carlo solution of the transport equation, are used to convert the combinatorial formulation of the geometry into a grid representation — the ray tracing method. Calculations of a VVER-1000 core and a model of a spent fuel repository show that the method considered here gives a severalfold computational gain over standard approximations of the geometry.