Severe accident research in the United Kingdom

The United Kingdom position on severe accidents reflects two essential facts. First, the large potential social impact of such events makes their avoidance and control a matter of special concern. Second, their rarity means that world-wide experience of them is very limited. Understanding of severe accidents must therefore be based on predictive models, validated against a wide variety of experiments, and of course, against such accident experience as is available. In this paper, in order to provide a background to the UK research program, the general principles are explained on which control and avoidance of severe accidents are based in the UK. How these principles have developed in practice in the UK PWR program is then discussed, using as an example the Sizewell B Public Inquiry. Finally two examples of the UK severe accident research are described: the work on steam explosions and on fission product chemistry