STABILITY AND NEAR-OPTIMAL UNDERRELAXATION OF COUPLED REACTOR PHYSICS CALCULATIONS

摘要

Coupling reactor physics neutronics with thermal and hydraulic calculations provides the ability to model important feedback effects. It has been demonstrated, however, that using conventional operator-splitting, fixed-point iterations to solve such systems can lead to numerical instability when feedback effects are sufficiently strong. Such systems are analyzed in this work and a simple, closed form estimate of the spectral radius is obtained that requires no a priori information from the equilibrium (converged) solution. The principal benefit in estimating the spectral radius is that the iteration can be underrelaxed to convergence in a near optimal fashion.