Core disruptive accidents in fast reactors

The nuclear safety of fast reactors is important in determining the feasibility of the large scale introduction of fast power reactors. The core disruptive accidents, involving the attainment of super promt criticality, are often the severest accidents which can be hypothesized. Although the possibility of such accidents in a well designed reactor is small, they are studied due to their severe consequences. The core disruptive accidents can be initiated among other causes, by the loss of cooling, uncontrolled reactivity addition and the propagation of an abnormal local condition. The detailed sequence of events leading to such an accident is often difficult to identify in a unique manner. Most of the physical processes involved in this initiating phase are not very well understood. A study of the severe accidents involves many interacting phenomena and disciplines. The current status of the study of the physics of core disruptive accidents, the available computational tools and the problem areas are discussed. Some recent work done in this field, including the development of space-time codes and the relevant thermodynamic data, is summarised. (author)