LMR core temperature calculation based on implicit formulation of the ENERGY model and a Krylov subspace method

A computational method was developed for predicting the steady-state temperature field in an LMR core based on the simplified energy equation mixing model and the subchannel analysis method. The -method was employed for discretizing the energy equation in the axial direction, and the interassembly coupling was achieved by interassembly gapflow. For an implicit scheme, a Krylov subspace method based on the BiCGSTAB algorithm and the MILU preconditioning was employed to solve the resulting linear system at each axial level. Numerical test results suggest that at least an order of magnitude reduction in the computing time can be achieved with the implicit solution scheme employing the Krylov subspace method when compared to the explicit scheme