A dimensional analysis for melt flow and heat transfer between corium and cooling tubes

During the severe accident of a light water reactor, the corium relocating into the lower head of the reactor pressurized vessel may fail the vessel and subsequently threaten the containment integrity. In order to avoid these occurrences, two severe accident management strategies were employed to arrest the corium in the lower head or in the reactor cavity, corresponding to so-called In-Vessel melt Retention (IVR) or Ex-Vessel melt Retention (EVR). The present study is motivated by the development of an EVR strategy for a pressurized water reactor design at power rating larger than 1000MWe. A core catcher is conceived to contain the corium after the vessel failure, which features cooling tubes installed inside the crucible of the core catcher, so as to increase the chances of coolability. To qualify the core catcher design, it is necessary to investigate the behavior of the cooling tubes under the corium's attack and their heat removal limits, which are important to demonstrate the survivability and cooling ability of the cooling tubes. This paper presents a dimensional analysis for melt flow and heat transfer between the corium and the cooling tubes, using Buckingham PI Theorem. The dominant dimensionless parameters obtained in this dimensional analysis are instrumental to forthcoming experimental studies (including scaling of test facilities and their operational parameters) since it ensures that the experimental results are applicable to the prototype. Finally, simulant material for the corium is also selected for experiment based on the dimensional analysis. (author)