Integration of the subchannel thermal-hydraulic code SubChanFlow into the reactor dynamics code PARCS: Development and testing based on a computational benchmark

This paper describes the coupling of the subchannel code SubChanFlow developed at the Karlsruhe Institute of Technology (KIT) with the reactor dynamics diffusion code PARCS. The coupling aims to improve the description of the physical models involved in the core analysis by enhancing the prediction accuracy. In addition, using SubChanFlow enables the detailed prediction of local thermal-hydraulics parameters. The extended capabilities of PARCS-SubChanFlow are demonstrated by the analysis of a PWR minicore, where the importance of considering the crossflow in the simulations is shown. The prediction capabilities of PARCS-SubChanFlow are shown by the analysis of the OECD/NEA PWR MOX/UO₂ core REA transient benchmark, where the results of PARCS-SubChanFlow are compared against the results of other benchmark participants. Moreover, a methodology was developed for the determination of local safety parameters e.g. DNBR at pin/subchannel level. A comparison against a higher order solution obtained with the coupled code SERPENT2/SubChanFlow is presented.