Severe accident design approach for the ESBWR - a balanced approach to cost and safety

The European Simplified Boiling Water Reactor (ESBWR), currently being designed by a steam consisting of European members and General Electric, maximizes safety and minimizes cost in the goal prevent the occurrence and mitigate the consequences of a severe accident (SA). This paper outlines the optimal safety/cost philosophy of the ESBWR and provides a general description of the severe accident design methodology that is being followed. Features incorporated into the ESBWR for the both prevention and mitigation of severe accidents are summarized. The ESBWR approach to severe accidents is matched with the European Utility Requirements (EUR). This is done so as to give the approach an international perspective in a rapidly changing design area. Special attention is given in the paper to the management of the core-on-the-floor issue. Sizing of the lower drywell floor area in the ESBWR design ensures that core debris coolability is achieved in the event of a complete core melt. The ESBWR lower drywell design includes provisions for a core catcher. One potential core catcher design concept is described briefly in the paper along with some severe accidents are also mentioned. In summary, the ESBWR approach emphasizes the harmony between safety and cost. (authors)