Analyses of Ibscth tests using thermal-hydraulics and fluid dynamic codes

Numerous computational tools have been developed worldwide to design and evaluate advanced reactor concepts. For Supercritical Water Reactors (SCWRs), various heat transfer correlations have been developed and integrated into codes like AC2 2021. Concerning Computational Fluid Dynamic (CFD), the available models seem suitable for normal heat transfer conditions while several limitations were observed for Deteriorated Heat Transfer (DHT) conditions. Finally, regarding the subchannel codes, as for an example ASSERT-PV, the developed correlation was tested with refined nodalization. Within the collaborative efforts of China, Canada, and the European Union, under the Joint European Canadian Chinese Development of Small Modular Reactor Technology (ECC-SMART) project and Generation IV Forum (GIF) activities, multiple system and CFD codes are employed to analyse heat transfer simulations in international benchmark on SCWR thermal-hydraulics characteristics (IBSCTH) tests. These tests encompass three configurations: Bare Rod, Local Wire Rod, and Full-Length Wired Rod experiments. This paper presents the work conducted by the University of Pisa using STAR-CCM+, by CNL with ASSERT-PV and the Research Centre Řež (CVR) employing AC2 2021 to simulate the three configurations. The primary objective is to demonstrate a practical combination of computer codes applicable to further SCW technology design. The simulations showed similar prediction of global heat-transfer behaviour across the three configurations, while notable discrepancies emerged in DHT, typically resulting in conservative overprediction of cladding temperatures. STAR-CCM+ generally yields a certain deviation in DHT regions, while ASSERT-PV demonstrates similar consistency with AC2 2021, particularly under conditions closest to SCWR operation.