FBR type reactor

An opening for inlet and outlet of coolants is disposed in the vicinity of at least one of both ends of a pipeline present between a reactor container and a heat exchanger in an FBR type reactor for transporting coolants and a reversing portion for substantially reversing the circulating direction of the coolants is disposed at a position lower than the opening. Even if vibrations including long period components are applied and sloshing is caused at the surface of the coolants contained in a reactor vessel or the like to expose the end portion of the pipeline out of the coolants, the coolants are kept between the opening and the reversing portion disposed at a lower position, thereby enabling to prevent surrounding gases from intruding into the pipeline. Then, there is no worry that transportation of the coolants is stopped or temporarily interrupted transportation is not restored, but there can be provided advantageous effects capable of avoiding remarkable temperature elevation or reactor scram accompanying therewith. (I.S.)