Sodium experiments on natural circulation decay heat removal and 3D simulation of plenum thermal hydraulics

Conclusions: • Sodium Experiments for SFR Natural Circulation DHR. → Inter-wrapper Flow (IWF) in a Core: – High potential to remove heat from core fuel subassemblies; – Simulation of IWF is significant issue. → Onset of natural circulation in PRACS and primary loop: –Smooth increases of air and sodium flows in stack and loops; –Development of air flow is faster than that of PRACS sodium flow; – Slow and steadily increase of pressure loss coefficient prior to freezing in low temperature operation of Air Cooler. → 3D simulation method and application to sodium test: – 3D simulation method - Full 3D modeling of primary system including core and piping; Decay heat removal system including air stack is modeled. – Comparison with Sodium tests: - Bypass flow and thermal stratification in IHX plenum equipped with PRACS heat exchanger were well simulated by 3D simulation