Optimal Thorium-Fueled CANDU Nuclear Reactor Fuel Management

The optimization of in-core fuel management for a thorium-fueled Canada deuterium uranium (CANDU) nuclear reactor was investigated by minimizing the total refueling rate at equilibrium with respect to criticality and power-peaking constraints. The computer code ASTERIX was written to solve the optimization problem, using a steepest descent technique with a moderate number of diffusion calculations required. Because of the presence of ²³³Pa in the fuel, the diffusion calculations are nonlinear and are solved numerically by the specially written program CALYPSO. Simulation was performed on simple models of a CANDU 600-MW reactor, with the core divided into two or four refueling zones. Results indicated that the optimization method investigated did work out well and that potential savings of up to 14% in the feed rate are possible for the self-sufficient equilibrium thorium cycle fuel, with an optimum refueling rate of 1.372 × 10⁻⁴ MgHE (heavy elements)/MWd. Sensitivity of the optimal discharge burnups to the value of the power-peaking constraint was significant.