Multi-physics multi-scale thermal-hydraulic analysis of the steam line break accident for the SMART small modular reactor with TRACE/PARCS/OpenFOAM

Within the framework of the EU McSAFER project, advanced multi-physics and multi-scale thermal-hydraulic codes have been developed and validated for the safety analysis of innovative Small Modular Reactors (SMRs). This paper concentrates on modeling and analyzing a Steam Line Break (SLB) accident for the SMART reactor using the coupling code TRACE/PARCS/OpenFOAM developed at KIT. Specifically, OpenFOAM is employed to describe the flow characteristics within the downcomer and lower plenum, while TRACE simulates the Thermal-Hydraulic (TH) phenomena in other regions of the reactor pressure vessel (RPV) as well as in the steam lines and passive heat removal system. PARCS is utilized for core neutronics simulations. Starting from normal operating conditions, a double-ended break in one of the eight steam lines, resulted in a sudden pressure drop within that tube consequently triggering a SCRAM signal. In addition, a coincident loss of offsite power is assumed that leads to the coast-down of the four main pumps. Throughout this transient event, the coupled code successfully predicts global phenomena, such as the transition from forced convection to natural convection within the reactor vessel, thereby validating the inherent passive safety features of the SMART reactor. Moreover, the couple code is able to capture the three-dimensional asymmetrical coolant mixing in the downcomer, lower plenum, and its impact on the core behavior in great detail.