Patent Number: 047327294
Section: abstract

In the fast breeder reactor according to this invention, a medium-pressure plenum and a high-pressure plenum are disposed, in the mentioned order from above in a reactor core. Sodium is filled in the medium- and high-pressure plenums. The pressure in the medium-pressure plenum is lower than that in the high-pressure plenum. The lower ends of the entrance nozzles of a multiplicity of fuel assemblies loaded in the reactor core are supported by a supporting plate which forms a boundary between the medium- and high-pressure plenums. The entrance nozzles of control rod guide pipes disposed among the multiplicity of fuel assemblies are also supported by said supporting plate. The sodium in the medium-pressure plenum is supplied into each control rod guide pipe through a first opening provided in the lateral surface of the entrance nozzle of each control rod guide pipe. The sodium in the high-pressure plenum is supplied into each fuel assembly from the lower end of the entrance nozzle of each fuel assembly through a second opening provided piercing through the supporting plate. The sodium in the high-pressure plenum is supplied to the medium-pressure plenum through a pressure-reducing orifice.