Patent Number: 052415708
Section: claims

1. A method of removing a control rod from a boiling-water nuclear reactor, said control rod having plural blades, said method comprising: removing a top head of said reactor;  removing all fuel bundles from a fuel support having an aperture conforming to the cross section of said control rod through its blades;  positioning a control rod so that its blades clear said aperture sufficiently to permit decoupling of said control rod;  rotating said control rod so as to decouple it from a control-rod drive; and  lifting said control rod out of said reactor.  a control rod having a plurality of blades;  a control-rod guide tube for guiding vertical motion of said control rod;  a fuel support for supporting fuel bundles separated by said blades, said fuel support having an aperture conforming to a cross section of said control rod through said blades for preventing rotational movement of said control rod to a decoupling orientation when said control rod is between a maximum power position and a minimum power position, said minimum power position being above said maximum power position, said fuel support being supported by said control-rod guide tube;  control-rod drive means for controlling vertical motion of said control rod, said control-rod drive means providing for vertical motion between said maximum power position and said minimum power position, said control-rod drive means providing for vertical movement to a decoupling position, said decoupling position being no lower than said minimum power position, said decoupling position being at a level sufficient to permit said control rod to rotate to a decoupling orientation relative to said fuel support; and  coupling means for coupling said control rod to said control-rod drive means, said coupling means being releasable by rotational movement of said control rod to said decoupling orientation relative to said control-rod drive means. 2. A method as recited in claim 1 further comprising an initial step of inserting all control rods to respective minimum power positions, said positioning step involving moving said control rod to a decoupling position above its minimum power position. 3. A core-control assembly comprising: 4. An assembly as recited in claim 3 wherein said decoupling position is the same as said minimum power position. 5. An assembly as recited in claim 3 wherein said decoupling position is above said minimum power position. 6. An assembly as recited in claim 3 wherein said fuel support is welded to said control-rod guide tube.