A review on the external cooling of the pressure vessel lower head in nuclear power plant.

At the beginning of the new century, since nuclear energy received widespread attention due to its economy and environmental protection, the nuclear industry has developed rapidly. However, there are still some issues challenging the safety of nuclear power plants (NPPs) especially at extreme conditions. During a hypothetical severe accident in a light water reactor, the core fuel will be disrupted and melt-down resulting from the absence of coolant, and finally forms a high-temperature molten pool at the lower head of reactor pressure vessel (RPV), which threaten the integrity of RPV, one of the most important barriers to prevent radioactive fission product releasing to the environment. In this regard, the decay heat removal of the molten pool plays an essential role in the strategy of in-vessel retention (IVR)-external reactor vessel cooling (ERVC) to arrest the molten corium inside the RPV, as shown in Fig. 1. This paper examines the research work about experimental investigation, theoretical analysis, and numerical simulation conducted for ERVC and summarizes the different approaches proposed by scholars to strengthen ERVC capabilities. Those approaches are the replacement of the cooling work materials, the application of nanofluids, surface modification, and other methods. Finally, it concludes the deficiencies of the current study and the direction of future efforts. [ABSTRACT FROM AUTHOR]