CoreSOAR Core Degradation SOAR Update Status May 2017
Résumé
In 1991 the OECD Nuclear Energy Agency Committee on Safety of Nuclear Installations (NEA/CSNI) published the first State-of-the-Art Report (SOAR) on In-Vessel Core Degradation, NEA/CSNI/R(91)12 (1991) in water-cooled reactors, updated in 1995 under the European Union (EU) 3rd Framework programme, EUR16695EN (1996) . These reports covered phenomena, experiments, material data, main modelling codes and their assessments, identification of modelling needs, and conclusions with needs for further research. This is relevant to such safety issues as in-vessel melt retention of the core, recovery of the core by water reflood, hydrogen generation and fission product release.In the following 20 years, there has been much progress in understanding, with major experimental programmes finished, such as the integral Phebus FP tests, and others with many tests completed, e.g. QUENCH, on reflooding degraded rod bundles, and LIVE, on melt pool behaviour, and more generally in EU Framework projects such as COLOSS and ENTHALPY. A similar situation exists regarding integral modelling codes such as MELCOR (USA) and ASTEC (Europe) that encapsulate current knowledge in a quantitative way. After the two EU-funded projects in the SARNET network of excellence, now continuing in the NUGENIA association as Technical Area (TA) 2, it is timely to take stock of the knowledge gained.The NUGENIA/TA2 SARNET CoreSOAR project combines the experience of 11 European partners to update these SOARs over the two years to June 2018. At this, the roughly half-way stage of the project, data collection for the experimental side has now largely been completed, while that for the status of the main modelling codes is well under way. Following this review, research needs in the in-vessel core degradation area will be evaluated and main conclusions will be drawn. The main report will serve as a reference for ongoing research programmes in NUGENIA, in other EU research projects for example in Horizon2020 such as that on in-vessel melt retention (IVMR), and in OECD/NEA/CSNI, such as the Fukushima benchmark (BSAF).This paper outlines the general status of the project to date, with emphasis on experiments focusing on in-vessel cooling of a degraded core, related to the important safety issue of in-vessel melt retention, on fission product release, which would determine the source term to the environment if the lower head were to fail and the containment were likewise to fail, or be vented Examples are given of separate-effects experiments on materials interactions which determine the corium composition in the lower head, on melt pool behaviour, on debris bed quenching, on melt-water interactions and melt pool behaviour in-vessel, and on the material properties involved. Indications are given concerning the major computer codes which will be summarised. Finally, general conclusions to date are given.
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