Optimal fuel management of CANDU reactors at approach to refuelling equilibrium: An investigation into the optimal use of advanced fuels in the CANDU-6 reactor

In this study, a simulation program was developed to investigate the optimum approach to refuelling equilibrium in a CANDU-6 Reactor. The program solves the neutron diffusion equations by finite differences to determine the fast and thermal fluxes. The lattice parameters are determined from various combinations of the group cross-sections, diffusion coefficients and the infinite multiplication factor and are dependent upon the cell thermal flux and fluence. A finite difference space of 80 x 80 x 26 mesh points yields 18 mesh points per bundle. An iterative technique converges the first eigenvalue, which is also the reactivity of the core. The lattice parameters are determined from interpolating flux and fluence from uniform parameter tables developed using the Transport Code WIMS-AECL with ENDF/B-V library. The reactor model does not include neutron absorbing materials reactivity control devices. Refuelling is conducted by setting the fluences at point to zero for bundles replaced and by adjusting the point fluences for those remaining and axially shifted. Channel selection is optimized by selecting a small group of channels based on maximum burnup and utilizing Perturbation Theory to determine which of these channels would yield the greatest time to zero reactivity. (Abstract shortened by UMI.)...