Nuclear Engineering and Design 278 (2014) 199–208 Contents lists available at ScienceDirect Nuclear Engineering and Design jou rn al hom ep age: www.elsevier.com/locate/nucengdes Transient interface temperature on a vertical surface in multi-component solid–liquid systems with volume heating. Application to various severe accident situations J.M. Seiler a,∗ , H. Combeau b a CEA, DEN, DTN, F-38054 Grenoble, France b Institut Jean Lamour, UMR CNRS 7198, Lorraine University, Ecole des Mines de Nancy, Parc de Saurupt, 54042 Nancy Cedex, France h i g h l i g h t s • The approach aims to improve multi-phase and multi-component thermal-hydraulics. • Same interface relation applies for ceramic dissolution, MCCI and IVR. • Interface temperature depends on fluid and wall properties and on ablation rate. • We predict ablation instabilities when the melt interacts with two walls. a r t i c l e i n f o Article history: Received 8 May 2014 Received in revised form 8 July 2014 Accepted 10 July 2014 a b s t r a c t The question of the transient interface conditions in various severe accident situations, involving multi- component and multi-phase material mixtures has until now remained largely unresolved. The interface temperature controls melt temperature and transient heat-flux distribution. The present paper proposes a new approach to the transient interface temperature, drawing on the numerous past efforts. A single relation is proposed which applies to various severe accident situations: (i) thermal-hydraulic steady state for in-vessel retention (IVR); (ii) transient solidification; (iii) transient concrete abla- tion (MCCI); and (iv) refractory material (ceramic) ablation (core-catcher retention, liner design). This approach yields the following important conclusions: - When a thermal-hydraulic steady state can be reached (external cooling, in case of IVR and melt stabi- lization in an externally cooled core-catcher), the melt-solid interface temperature tends towards the liquidus temperature corresponding to the melt composition. - During the ablation transient: • the interface temperature is lower than the melt liquidus temperature if the wall-melting temperature is less than the melt liquidus temperature (MCCI), • the interface temperature is higher than the melt liquidus temperature if the melting temperature of the wall exceeds the melt liquidus (oxidic corium-refractory ceramic interaction). The new interface model also suggests that simultaneous ablation of two similar walls (for instance: two concrete walls) may be subject to instabilities which can potentially result in complete arrest of the ablation of one of the walls. In the case of simultaneous ablation of two walls of different nature, the wall with the lowest melting temperature is preferentially ablated during the transient phase. © 2014 Elsevier B.V. All rights reserved. ∗ Corresponding author. Tel.: +33 4 38 78 30 23. E-mail addresses: jean-marie.seiler@cea.fr, seiler.jm@wanadoo.fr (J.M. Seiler). http://dx.doi.org/10.1016/j.nucengdes.2014.07.008 0029-5493/© 2014 Elsevier B.V. All rights reserved.