A three-dimensional BWR core simulation has been attempted with the use of PACS-32, a newly developed parallel microcomputer system. The PACS system is an MIMD-type microprocessor complex, consisting of 32 processors, that was specially designed for the numerical analysis of the partial differential equations.
The neutron diffusion model in the simulation is based on the modified two-group finite-difference coarse-mesh method, and the thermo-hydraulic model assumes the energy balance in the stationary state.
The analysis of the parallel processing program revealed that the system overheads, i.e. the loss of computation power pertinent to the parallel processing, is independent of the number of processors, and that the efficiency of processors,
i.e. the ratio of the effective calculation over the total calculation, amounts to 70%, and even upto 88% if the computation is limited to the reactor core region.
By the measurement of the execution time, it has been demonstrated that the computation speed of nearly twice as fast as a middle size general purpose machine is realized, with 20 times better cost-performance ratio. The PACS system could be used as the practical BWR core simulator for more complicated core models.
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