Design advances in the achievement of high reliability in the decay heat rejection systems for the CDFR

The UK overall reliability criterion for decay heat rejection on a commercial size Fast Breeder Reactor is that no single accident should exceed a failure frequency of 10-7 per reactor operating year and the way in which the CDFR design meets this criterion is discussed in detail. The avoidance of common cause failure necessarily implies the use of reliable and redundant NaK loop thermal syphon system for emergency cooling of the reactor and employs parts of the conventional steam plant to meet all operational requirements, which if augmented by a few additional components also provides a method for emergency cooling of the reactor. The latter system is described in detail and its diversity and high reliability demonstrated