Numerical investigations on the performance of passive heat removal system of small modular reactor under accidental conditions

The Small Modular Reactors (SMRs) play key role in sustainable energy supply. However, the challenge with them is the demonstration of passive safety systems. The SMART (system-integrated modular advanced reactor) is one such SMR with a coupled natural circulation loop (C-NCL) based passive heat removal system (PHRS) to keep the reactor safe under accidents. In this paper, vowing its safety significance and gap in the literature, performance of PHRS is investigated under accident induced conditions. As precise reactor details are unavailable, experimental PHRS in VISTA (Experimental Verification by Integral Simulation of Transients and Accidents) facility is chosen. A numerical code that can handle single-phase, two-phase and superheated flow is developed and employed. Evaluated the performance characteristics in terms of flow and heat transfer. The transient flow, pressure, temperature and heat sink conditions are predicted and analyzed. Investigated the influence of accident induced conditions and geometrical parameters. The performance is studied based on flow and PHRS performance factors, and quantified the effect of accident induced parameters based on sensitivity analyses. Fire, seismic deformations, leak in sink, loop diameter and surrounding temperature have shown considerable effect on PHRS performance. Further, it also identified the parameters that hamper PHRS performance of SMRs.