Reactor

Purpose: In an FBR type reactor, to reduce the quantity of radioactive wastes generated with the fuel exchange thereby to prevent the erroneous loading of fuel assemblies. Constitution: Shielding blocks are arranged on the core support plate, and fuel assemblies are inserted in the blocks. The shielding blocks are constituted so that these blocks have lengths different in correspondence to the power region of the core, and those having the longer lengths have nozzle mounting holes having larger diameters. That is, since the nozzle at the central part has the largest and longest diameter, the fuel assembly is not mounted erroneously in the other block. Since the shielding block is independent from the fuel assembly, it is not necessary to exchange the same at every exchange of the fuel assembly. (Kamimura, M.)