Ablation of a Solid Material by High-Temperature Liquid Jet Impingement: An Application to Corium Jet Impingement on a Sodium Fast Reactor Core-Catcher

This paper deals with the ablation of a solid by a high-temperature liquid jet. This phenomenon is a key issue to maintain the vessel integrity during the course of a nuclear reactor severe accident with melting of the core. Depending on the course of such an accident, high-temperature corium jets might impinge and ablate the vessel material leading to its potential failure. Since the Fukushima Daiichi accident, this severe accident scenario draws more concern in the nuclear safety policy and new mitigation measures are under study. As a designed safety feature of a future European sodium fast reactor (SFR), bearing the purpose of quickly draining the corium out of the core and protecting the reactor vessel against the attack of molten melt, the in-core corium is relocated via discharge tubes to an in-vessel core-catcher has been planned. The corecatcher design to withstand corium jet impingement demands the knowledge of very complex phenomena such as the dynamics of cavity formation and associated heat transfers. Even studied in the past, no complete data are available concerning the variation of jet parameters and solid structure materials. For a deep understanding of this phenomenon, new tests have been performed using both simulant and prototypical jet and core catcher materials. Part of these tests has been done at the University of Lorraine using hot liquid water impinging on transparent ice block allowing for the visualizations of the cavity formation. Other tests have been performed in Karlsruhe Institute of Technology (KIT) using liquid steel impinging on a steel block.