Severe accidents pose a fatal threat to the safety of nuclear power plants and surrounding residents, such as TMI-2 accident, the Chernobyl accident and the Fukushima accident. A severe accident (SA) is defined as an incident involving the melting of the reactor core and the release of fission products from the fuel and the associated risks involved with these processes. The SA scenarios involve core melt from the beginning of core degradation to melt formation and relocation into the lower head and to the containment, the interactions of the molten corium with water and concrete, the behavior of fission products in- and ex-vessel, and finally, hydrogen-related phenomena. Fuel and coolant interaction (FCI) may lead to steam explosion in- and ex-vessel, which could damage the containment, then release the fission products into the atmosphere.
The phenomena during an LWR (PWR and BWR) SA are extremely complicated; thus, the progression of an LWR SA involves great uncertainty. Therefore, it is difficult to predict the behaviors of in- and ex-vessel core molten debris under accident conditions. Numerous experimental and analytical studies had been conducted on SAs, and SA research had provided sufficient information to resolve most of the issues that have been identified in a SA. However, many issues are still unresolved during in- and ex-vessel accident progression, such as narrow gap cooling, melt chemical interactions, steam explosion loads, molten debris coolability, and iodine chemistry. Experimental and numerical studies have been undertaken to acquire additional information to assist in developing the best possible models of in- and ex-vessel accident progression after the Fukushima accident.
This Research Topic aims to promote the experimental and numerical investigations on the severe accident (SA) phenomena in recent years and identify potential priority areas for research and development in SA. The topics involve new experimental and analytical investigations on severe accident phenomena, severe accident mitigation, prediction and prevention of environmental contamination for nuclear power plants, including but not limited to:
• Reactor core degradation process
• Molten core cooling: IVR, late phase injection, RV failure, etc.
• MCCI, FCI, Hydrogen
• Fission product behavior and SFP
• Environmental contamination
• Severe accident mitigation measures: core catcher, FCVS
• Lessons learned and experience with Fukushima accident
Keywords: nuclear safety, severe accident, phenomena and scenarios, mitigation strategies, nuclear power plants
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