An experimental study on in-vessel retention strategy by external reactor vessel cooling with liquid metal

The present work ultimately aims to develop the IVR-ERVC (In-Vessel Retention through External Reactor Vessel Cooling) system with enough thermal margin adopting liquid metal coolant as the severe accident mitigation system even for high power reactor. For the purpose, the conceptual design of IVR-ERVC with liquid metal is evaluated by performing an experimental campaign for a scaled facility. The specific geometry was devised to contain the liquid metal coolant facing with water through the container wall. Through this system, the heat transfer area is enlarged up to 2 times compared to the original area of the reactor vessel. This effect is also named as 'liquid metal fin' in the current study. Improved heat transfer or reduced heat flux including large drop of focusing effect was confirmed by experimental results for a small-scaled facility to simulate the boiling phenomena under IVR-ERVC condition. It was found that significant reduction of focusing effect by liquid metal and extended surface area guarantee enough margin of successful IVR-ERVC without CHF issue even for large-sized power reactors. (author)