Overview of the projects sponsored within the EU-R&D Framework Programme

Assuming that preventive measures to avoid reactor pressure vessel (RPV) fa ilure under core degradation scenarios have failed, the stabilisation of th e core melts after its release from the RPV is a key issue. Adequate coolin g of the ex-vessel cerium and the control of its interactions with the cool ant and structures are the main challenges to mitigate and stabilise the si tuation preserving the containment integrity. In this regard, the on-going Fourth Euratom Framework Programme (4(th) EFP) contributes with experimental and theoretical research activities aimed at responding to the main challenges mentioned, by satisfying three objective s: to improve the understanding of the basic physics related to ex-vessel ceri um behaviour from the phenomenological and technological viewpoints, as wel l as to provide a methodology for investigating it and setting up joint mul ti-partner projects to be co-sponsored and co-ordinated by the EC; to quantify and reduce the uncertainties associated with the risk issues by conducting experimental and numerical investigations and eventually to ach ieve a European consensus on the phenomenology and on accident mitigation s trategies; to provide a technological response to the risk issues by developing engine ered safety systems (e.g. core-catchers) and severe accident management str ategies (e.g, guidelines), and to discuss such a technological response wit h the end users of these technologies, i.e. designers and licensers. th To fulfil these objectives, the 4(th) EFP co-sponsors a total of five projects within the cluster "Ex-Vessel Cerium Behaviour and Coolability" of the Nuc lear Fission Safety Programme. The research undertaken addresses the main d ifferent aspects such as the determination of the composition and thermodyn amic data of the melt; experiments on spreading behaviour on various types of surfaces, as well as on cerium coolability by flooding or water injectio n; investigation of cerium stratification, crust and heat transfer related phenomena; analyses of scaling effects; and code validation.