Evaluation on core melt retention in core catcher of Toshiba's EU-ABWR

Toshiba's EU-ABWR includes some mitigation systems to assure the containment integrity during severe accidents. The core catcher is a key system in them and has an important role to arrest and stabilize the core melt. The core catcher features a round basin structure with underneath inclined cooling channels arranged in an axisymmetrical way. The core catcher is in a dry condition initially, and flooded after collecting the core melt by the water injection from the suppression pool via the passive flooders. Boiling in the cooling channels brings natural circulation of water. After the core catcher flooding, the core melt is cooled by both the overlaying water and the lower cooling channels in a passive manner. Some analytical and experimental works including heat transfer test with the full-scale cooling channel are conducted to qualify the core catcher performance. The goal is to show that the core catcher withstands all thermal loads and structural loads in short term and long term. Some estimations to the key loads in them have been conducted, including jet impingement, fuel-coolant interaction, jet impaction during relocation and thermal load in long term. This paper outlines the estimation results. Through these works, we concluded that the core catcher has the capability of core melt retention. (authors)