FBR type reactor system

When a reactor core is wholly exchanged together ten years later in an FBR type reactor, it is necessary for reactor structures and primary cooling systems to remove a great amount of after-heat from the exchanged reactor core. Then in the present invention, the reactor core is wholly taken out together ten years later and it is utilized as a heat supply device using it as a heat supply source for further ten years. For this purpose, a reactor core burnt in the FBR reactor for a predetermined period is hung up by a cask together with an intermediate heat exchanger and a hanger body, and the hanger body is immersed in a liquid metal pool of a heat supply reactor. A secondary pipeline of the intermediate heat exchanger is connected to a water/liquid metal type heat exchanger in the liquid metal pool. After-heat of the reactor core is taken out by using the heat exchanger to cool the reactor core. With such a constitution, spent fuels can be reutilized as a heat supply reactor. Further, fresh fuels and a new intermediate heat exchanger are inserted again to the reactor after withdrawing former fuels, to utilize it again as a reactor. (T.M.)