Object-Oriented Three-Dimensional Fine-Mesh Transport Calculation on Parallel/Distributed Environments for Advanced Reactor Core Analyses

This paper describes a comprehensive study on the feasibility of advanced reactor core analyses within the framework of pin-by-pin multigroup transport calculations using a prototype of the object-oriented parallel core calculation code SCOPE. The SCOPE code enables the coupling of the diffusion theory method and the SP_N transport theory method. The formulation of the method coupling and its verifications with benchmarks are presented.

Quantitative estimation of the pin-cell homogenization effects within the octant core geometry of a three-loop-type pressurized water reactor (PWR) was performed. Comparisons between results by heterogeneous and homogeneous calculations revealed the effects on pin-cell homogenization in large-scale geometry. In order to preserve the neutronic property in the heterogeneous calculation within the framework of pin-cell homogenized pin-by-pin calculations, the applicability of the homogenized cross section corrected by the superhomogénéisation SPH method was studied. It was found that the pin-by-pin nine-group calculation by the SP3 transport theory method with the SPH-corrected cross sections gave good accuracy for the pin power distribution approximately <1% of the root-mean-square error. The calculation accuracy of the transport calculation and the effectiveness of the method coupling were also demonstrated through analyses of the initial core of an identical three-loop-type PWR.

With fine-grained parallelism, the identical convergence property was obtained regardless of the number of processors. Parallel performance was almost scalable up to eight processors, 93% with eight processors in three-dimensional nine-group fine-mesh transport calculations with meshes of 180 × 180 × 30.