PARALLEL AND SERIAL APPLICATIONS OF THE RETRAN-03 POWER-PLANT SIMULATION CODE USING DOMAIN DECOMPOSITION AND KRYLOV SUBSPACE METHODS

High-fidelity simulation of nuclear reactor accidents such as the rupt ure of a main steam line in a pressurized water reactor (PWR) requires three-dimensional core hydrodynamics modeling because of the strong e ffect channel cross flow has on reactor kinetics. A parallel nested Kr ylov linear solver was developed and implemented in the RETRAN-03 reac tor systems analysis code to make such high-fidelity core modeling pra ctical on engineering workstations. Domain decomposition techniques we re also applied to the RETRAN-03 solution algorithm and demonstrated u sing a distributed memory parallel computer. Applications were perform ed for a four-loop Westinghouse PWR steam-line-break accident, and per formance improvements of over a factor of 30 were achieved for models with 25 flow channels in the core. Larger models (e.g., 104-core chann els), previously inaccessible because of memory limitations, were also solved with practical execution times.