Patent Number: 046613064
Section: claims

1. In a spectral shift pressurized water nuclear reactor employing a low neutron moderating fluid for the spectral shift including a reactor pressure vessel, a core comprising a plurality of fuel assemblies, a core support plate, apparatus comprising means for penetrating the reactor vessel for introducing said moderating fluid into said reactor vessel, means associated with the core support plate for directly distributing said moderating fluid to and from said fuel assemblies comprising at least one inlet flow channel in said core plate; a plurality of branch inlet feed lines connected to said inlet flow channel in said core plate; a plurality of vertical inlet flow lines flow connected to said branch inlet feed lines; each vertical flow line communicating with a fuel assembly; said distribution means further comprising a plurality of lines serving as return flow lines, each of which is connected to one of said fuel assemblies; a plurality of branch exit flow lines in said core plate flow connected to said return flow lines of the fuel assembly; and at least one outlet flow channel flow connected to said branch exit flow lines; and a flow port interposed between said penetration means and said distribution means for flow connecting said penetration means with said distribution means. 2. The apparatus of claim 1, including at least two separate flow regions associated with said core support plate with each region including an inlet channel, a branch inlet feed line, a vertical flow line from the core support plate to a fuel assembly, a return flow line from the fuel assembly to the core support plate, a branch exit flow line, and an outlet flow channel in the core support plate. 3. The apparatus of claim 1, wherein said means for penetrating the reactor vessel comprises a pipe passing through the wall of said reactor vessel, said pipe being seal welded to said reactor vessel, the end of said pipe within said reactor vessel having a flange thereon. 4. The apparatus of claim 3, wherein said penetration means includes a venturi orifice within said pipe. 5. The apparatus of claim 1, wherein said flow port comprises an elongated hollow pipe fixedly connected at one end to said pentration means, and fixedly connected at the second end thereof to the core support plate, said flow port having means between said ends for sealingly varying the length of said flow port between said ends. 6. The apparatus of claim 5, wherein said flow port comprises a first member attached to said core support plate, a second member attached to said penetration means and said sealing means comprises a bellows fixedly connected at one end to said first member and fixedly connected at its other end to said second member. 7. The apparatus of claim 6, wherein the unconnected ends of said first and second members are telescopically arranged with a slideable seal therebetween. 8. The apparatus of claim 7, wherein the unconnected ends of said first member comprises an elongated hollow tube portion, a flow channel is formed in the core support plate which communicates with said elongated hollow tube, with said elongated hollow tube partially closed at its end by an elongated solid rod portion connected thereto, at the intersection of the elongated hollow tube and the solid rod portion; a shank at the intersection of said elongated hollow tube and said solid rod portion extending into said flow channel of said core support plates, said shank having at least one hole therethrough which provides flow communication between the elongated hollow tube and the flow channel in said core support plate. 9. In a spectral shift pressurized water nuclear reactor employing a low neutron moderating fluid for the spectral shift including a reactor pressure vessel, a core comprising a plurality of fuel assemblies, a core support plate; at least one means for penetrating the reactor vessel and for introducing said moderating fluid into said reactor vessel; means associated with the core support plate for directly distributing said moderating fluid to and from said fuel assemblies comprising at least one inlet flow channel in said core plate; a plurality of branch inlet feed lines connected to said inlet flow channel in said core plate; a plurality of vertical flow lines flow connected to said branch inlet feed lines, each vertical flow line communicating with a fuel assembly; said distribution means further comprising a plurality of lines serving as return flow lines, each of which is connected to one of said fuel assemblies; a plurality of branch exit flow lines in said core plate flow connected to said return flow lines of the fuel assembly; and at least one outlet flow channel flow connected to said branch exit flow lines; and a flow port interposed between each said penetration means and said distribution means for flow connecting said penetration means with said distribution means.