Nuclear Energy Agency Online Bulletin

May 2002

Nuclear safety news

Steam Explosion for Nuclear Accidents (SERENA programme)

In the hypothetical scenario of a nuclear reactor meltdown, a large breach in the lower head of a reactor pressure vessel could easily lead to ex-vessel energetic interactions between nuclear fuel and the reactor coolant in the flooded lower cavity. Should energetic fuel-coolant interactions (FCI) take place, the resulting in-vessel multiple jets of molten core through the reactor core support plate are potentially very dangerous for the primary coolant circuit. With the aim of alleviating this threat, the SERENA programme, sponsored by the CSNI Working Group on Analysis and Management of Accidents (GAMA), has been set up. The SERENA programme aims to promote international technical consensus on the understanding of FCI processes and energetics, and to standardise the methods for reliably estimating the core loadings under realistic reactor conditions. The programme, which consists of five consecutive tasks, will run from the beginning of 2002 until mid-2005.

Seven countries currently participate in the SERENA programme: Finland, France, Germany, Korea, Japan, the Russian Federation and the USA. The SERENA programme's first meeting was held at the Institut de Radioprotection et de Sûreté Nucléaire (IRSN), Fontenay-aux-Roses, France on 15-17 April 2002. During the meeting, the results of task one (the identification of relevant conditions for FCI) were discussed and task two (a comparison of various approaches to calculating jet break-up and pre-mixing) was launched. Close collaboration with the Korean Test for Real Corium Interaction with Water (TROI) programme has recently been established. It is expected that co-operation with other projects in the field of steam explosions and fuel-coolant interactions will be initiated in the coming months.

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