Study of the ablation consecutive to jet impingement on a meltable solid – Application to SFR core-catcher

Highlights: • Determination of a new experimental correlation for assessing the ablation rate in the jet axis in the first ablation regime. • The succession of two ablation regimes is reaffirmed (the initial constant ablation regime and the pooleffect). • Global phenomenological analysis of cavity shape evolution with time. • Measurements of cavity depth to jet's diameter ratio at onset of pool-effect (such measurements were never done before to the best of our knowledge). In the scope of safety studies for future sodium cooled fast reactors (SFR), the use of discharge tubes and in-vessel core-catcher are foreseen for severe accident mitigation. During relocation of corium onto the core-catcher, complex thermal hydraulics phenomena can occur. This work focuses on the ablation of the core-catcher by the jet of corium. For that purpose, as experiments using corium and Na are difficult to achieve, we performed experiments using simulant materials: water jet on transparent ice. Transparent ice allows for ablation cavity real-time recording. Two main regimes were identified: a film flowing regime and a pool regime. We also studied the influence of temperature (30, 50, 70 °C) and velocity ($1,2.5,5,7.5,10m/s$) of the jet. Comparison with existing data have been done and finally, a scaling law in the first regime, for which the ablation rate is constant, has been found.