Device for facilitating the insertion and withdrawal of fuel assemblies from a nuclear reactor

Claim 1

In combination a nuclear reactor and a fuel subassembly and isolating device for the reactor, said reactor including a vessel containing a coolant, a core surrounded by said coolant, said core containing a plurality of fuel subassemblies, said fuel subassemblies including handle means on the upper ends thereof, each of said handle means being configured to form a camming surface, and a closure head for said vessel containing an access port positionable above the various fuel subassembly locations; said centering and isolating device comprising: plug means for insertion into said access port, said plug having means for limiting penetration thereof into said port and further including a longitudinally extending opening therethrough of a size to permit passage of a fuel subassembly; an elongated structural tube attached to the lower end of and extending downwardly from said plug means; a downwardly extending camming tube vertically disposed under said structural tube; means for interconnecting said structural tube and said camming tube, said means permitting limited radial movement of said camming tube relative to said structural tube and being capable of raising and lowering said camming tube relative to said structural tube; said camming tube having a larger internal cross section than the external cross section of said fuel subassemblies and being configured to engage said camming surfaces of adjacent fuel subassemblies which lowered about a selected subassembly to bring said camming tube into axial alignment with said selected subassembly; whereby upon lowering said camming tube into said reactor core to isolate a selected fuel subassembly radial movement of said camming tube occurs if said tube is misaligned with said subassembly to thereby bring said tube and said subassembly into axial alignment with one another.