Nonoverlapping local/global iterations with 2-D/1-D fusion transport kernel and p-CMFD wrapper for transient reactor analysis—II: Parallelization and Predictor–Corrector Quasi-Static method application

• Nonoverlapping local/global (NLG) iteration is parallelized by MPI.
• Predictor–Corrector Quasi-Static (PCQS) method is applied to NLG iteration.
• Computational burden is distributed over parallel computers by parallelized NLG iteration.
• PCQS enables to use a large time-step size in transient calculations, if shape function does not change significantly.

As modern computing power grows, whole-core transport calculations become more viable with parallel computing architectures. Nonoverlapping local/global (NLG) iterative method has been recently developed for the whole-core transport calculation. The NLG iteration adopts the 2-D/1-D fusion transport kernel as the local solver, and the p-CMFD equation is used as the global wrapper. The NLG iteration is capable of solving 3-D transient heterogeneous problems, and it is naturally parallelizable. In this study, the computationally-expensive local problems in the NLG iteration are parallelized by MPI protocol, and the Predictor–Corrector Quasi-Static (PCQS) method is applied to the transient calculations to reduce the computing time further. The parallelized NLG iteration and the PCQS method have been implemented in an in-house code, CRX-2K. Several numerical problems are computed, and the numerical results reveal that the parallelized NLG iteration has high potential in the realistic whole-core transport calculation, and the computing time in the transient calculations can be reduced by the PCQS method if the reactivity behaves linearly in time for a given macro time-step size.