A Review of the CFD Modeling Progress Triggered by ISP-47 on Containment Thermal Hydraulics

The Organisation for Economic Co-operation and Development (OECD)/Nuclear Energy Agency International Standard Problem 47 (ISP-47) was aimed at assessing the predictive capabilities of computational fluid dynamics (CFD) and lumped-parameter codes regarding hydrogen mixing under representative thermal-hydraulic conditions of a loss-of-coolant-accident. The benchmark consisted of two systematic steps. The first step was a fundamental model assessment based on quasi-steady-state separate-effects tests in the French TOSQAN facility (7 m³, IRSN, Saclay) and MISTRA facility (100 m³, CEA, Saclay) regarding steam condensation, buoyant turbulent flows, and mixed atmospheric conditions. The second step was based on a more realistic experimental transient in the multicompartmented German Thermal-hydraulics, Hydrogen, Aerosols and Iodine (THAI) facility (60 m³, Becker Technologies, Eschborn). At that time, the blind and open analysis revealed that CFD codes needed further improvement regarding modeling of turbulence in buoyant flows, steam condensation, temperature and species concentration, and stratification buildup as well as their dissolution. This result triggered a comprehensive experimental and analytical effort, e.g., within the German national THAI, the OECD-THAI, and the OECD-SETH-1 and OECD-SETH-2 projects. Now, 10 years later, this paper aims to benchmark the state-of-the-art containment CFD model, developed at Forschungszentrum Juelich and RWTH Aachen University, and to highlight the progress made and the remaining open issues.