STEAM-COOLED FAST BREEDER REACTORS.

Although most development work on Fast Breeder Reactors has been devoted to the use of liquid metal cooling, in the early 1960'8 several studies were begun concerning the use of edternate coolants as a means of circumventing some of the problems associated with liquid metal systems.Among t)}e concepts considered since that time, several have involved using steam as coolant.Proponents of steam cooling recognized that breeding ratios somewhat lower than in other fast reactor concepts could be expected, due to the softer neutron spectrum resulting from the steam.The interest, however, was to introduce fast breeder economics into the nuclear power economy by utilizing the large backgrotmd of light water reactor technology and utility experience with steam systems.In general, steam coolant technology was felt t< "• e -LmDler than sodium.The super heat p|g(£)gram had gpwn that steam-cooled reactors could operat on a direct cycle, thus eliminating the primary heat exchangers and offering a more economical steam supply system.Some strong additional incentives for considering stea pooling included the f 5 , ity of flooding the reactor with a transparent meaiu.a(water) during rt ..ig and maintenance operations, and the possibility of using water E systems for emergency cooling.Early studies involved the use of super critical pressure steam a coolant.There were two outstanding reasons for the selection of tn^s T! ^'ftl*'^"" 1 •• Pewific