A nested FGMRES method for parallel calculation of nuclear reactor transients (Q1264571)

A semi-iterative method based on a nested application of flexible generalized minimum residual (FGMRES) is developed to solve the linear systems resulting from the application of the discretized two-phase hydrodynamics equations to nuclear reactor transient problems. The complex three-dimensional reactor problem is decomposed into simpler, more manageable problems which are then recombined sequentially by GMRES algorithms. Mathematically, the method consists of using an ``inner'' level GMRES to solve the preconditioner equation for an ``outer'' level GMRES. Applications are performed on practical, three-dimensional models of operating pressurized water reactors.