Fast reactor decay heat removal: approach to the safety system design in Japan and Europe

In the framework of the cooperation on fast reactor between the European an d Japanese electrical utilities, the design companies responsible for the d emonstration fast breeder reactor (DFBR) in Japan and the European fast rea ctor (EFR) have performed a comparative evaluation of the safety qualified decay heat removal systems of the two reactor designs. At the level of over all safety and concept design there is an obvious similarity between the tw o DHR systems. In both cases heat is removed directly from the reactor vess el primary sodium by systems designed according to a similar deterministic methodology, with a probabilistic assessment performed to demonstrate achie vement of the required reliability. Nevertheless, the evaluation revealed a number of differences resulting from different national practices. These i nclude the application of diversity and redundancy philosophy, the extent o f passivity taken into account, the consequences of postulated maintenance outage on the design and the decay heat curve. (C) 1999 Elsevier Science S. A. All rights reserved.