Model Evaluation and Parallelization of Subchannel Analysis Code for Full-Core Pin-by-Pin Analysis

Abstract Subchannel analysis, as a common tool utilized in nuclear reactor core thermal-hydraulic calculation, is essential to establish high-fidelity high-resolution reactor core simulator which shows growing potential in nuclear reactor operation and monitoring. However, thermal-hydraulic models and correlations concerning the effect of spacer grids with mixing-vane currently employed in subchannel analysis codes are imprecise due to narrow applicability and insufficient accuracy, resulting in large calculation errors. Meanwhile, vast amount of data generated from pin-by-pin solution analysis brings challenge to current non-parallel calculation process which leads to low calculation efficiency. In this paper, an optimization for subchannel analysis program on the capability to run full-core scale subchannel analysis on existing PWRs with pin-by-pin resolution is carried out. Both OpenMP an MPI method is adopted to optimize the subchannel program and the result of adopting OpenMP is discussed. The correlation of single-phase turbulent mixing factor and transverse crossflow friction factor considering the effect of spacer grids are coded into the program. The evaluation and validation of the models are carried out through sensitivity analysis and results comparison with the reference database of subchannel benchmark PSBT. The new models’ effects on the flow field in the axial direction are also studied.