FBR-type reactor

In an FBR type reactor, a flow guide comprising a toroidal plate disposed from the inner wall of a reactor container and a performed plate connected downwardly from the inner circumferential end of the plate is supported at a height of the inlet of a hot leg pipeline. Further, a dipped plate is disposed just below the surface of the liquid metal in a reactor container, and the dipped plate is disposed detachably covering the entire liquid surface by joining end portions of segment plates divided into a plurality of sections with each other with no gaps. As a result, the flow reaching the liquid metal in the upper plenum is suppressed, and the flow in the vicinity of the liquid flows from the reactor core upper mechanisms to the inner wall of the reactor container, causing less mutual interference of the flows to suppress involvement of gases. On the other hand, since the front surface just below the liquid is covered with the dipped plate, leaking flows especially elevating jet flows leaking from the gaps of the segment plates are reduced, thereby suppressing the flows reaching the free liquid surface. (N.H.)