Patent Number: 053696760
Section: claims

1. A reactor refueling mechanism positionable above a nuclear reactor core disposed in a cylindrical core shroud, comprising: a bridge positionable above said core;  a trolley disposed on said bridge;  an elevator disposed on said trolley and including a vertically movable mast having a grapple at a lower end thereof for releasably holding a load;  means for rotating said bridge around said core;  means for translating said trolley along said bridge;  means for rotating said elevator on said trolley;  means for vertically moving said mast to position said grapple; and  an annular rail positionable on said core shroud for supporting said bridge thereon above said core, wherein:  said bridge comprises a center frame extending diametrally across said rail, and first and second end frames fixedly joined transversely on opposite ends of said center frame and disposed on said rail; and  said bridge rotating means comprise a plurality of spaced wheels rotatably joined to said first and second end frames and supported on said rail, with a motor driving at least one of said wheels on said rail to rotate said bridge.  said trolley is disposed on said center frame for translation therealong; and  said trolley translating means comprises a rack gear fixedly joined to said center frame and a trolley pinion gear operatively joined thereto, with a motor joined to said trolley for driving said trolley pinion gear on said rack gear to translate said trolley along said center frame between said first and second end frames.  said elevator further comprises an elongate, vertical housing containing therein said mast and rotatably supported on said trolley; and  said elevator rotating means comprises a ring gear fixedly joined to said elevator housing and a pinion gear operatively joined thereto, with a motor joined to said trolley for driving said elevator pinion gear to rotate said elevator housing and said mast therein.  said elevator further comprises an elongate, vertical housing containing therein said mast and rotatably supported on said trolley; and  said elevator rotating means comprises a ring gear fixedly joined to said elevator housing and a pinion gear operatively joined thereto, with a motor joined to said trolley for driving said elevator pinion gear to rotate said elevator housing and said mast therein.  means for coupling to a fuel bundle assembly located in said core;  first moving means for raising said coupling means in a direction parallel to a longitudinal axis of said fuel bundle;  second moving means for rotating said raised coupling means about said longitudinal axis;  third moving means for displacing said raised coupling means horizontally along a diameter of said core shroud; and  fourth moving means for displacing said raised coupling means along a circular path concentric with a centerline axis of said core shroud and having a diameter less than said core shroud diameter,  wherein said first moving means are supported by said second moving means, said second moving means are supported by said third moving means, said third moving means are supported by said fourth moving means, and said fourth moving means are supported by said core shroud or a reactor pressure vessel surrounding said core shroud. 2. A mechanism according to claim 1 wherein: 3. A mechanism according to claim 2 wherein: 4. A mechanism according to claim 1 wherein: 5. A mechanism according to claim 1 further comprising means for selectively controlling said bridge rotating means, said trolley translating means, and said elevator rotating means for positioning said grapple at a selected location in a horizontal plane above said core, and at a selected elevation at said location, and at a selected rotated position at said location. 6. A mechanism according to claim 1 further comprising a pair of said trolleys and said elevators disposed on said center frame and independently controllable. 7. A reactor refueling mechanism positionable above a nuclear reactor core having a plurality of fuel bundle assemblies inside a cylindrical core shroud, comprising: 8. The reactor refueling mechanism as defined in claim 7, wherein said fourth moving means comprise a bridge mounted on said core shroud via rolling means, said third moving means comprise a trolley translatable along said bridge; said second moving means comprise a platform rotatably mounted on said trolley, said first moving means comprise an elevator supported on said platform, and said coupling means comprise a grapple supported by said elevator. 9. The reactor refueling mechanism as defined in claim 8, wherein said fourth moving means are supported by said core shroud via an annular rail positionable on said core shroud for supporting said fourth moving means thereon. 10. The reactor refueling mechanism as defined in claim 9, wherein said bridge comprises a center frame extending diametrally across said rail, and first and second end frames fixedly joined transversely on opposite ends of said center frame, and said rolling means comprise a plurality of spaced wheels rotatably joined to said first and second end frames and supported on said rail, and a motor coupled to drive at least one of said wheels on said rail to rotate said bridge. 11. The reactor refueling mechanism as defined in claim 10, wherein trolley is disposed on said center frame for translation therealong, and said third moving means further comprises a rack gear fixedly joined to said center frame, a trolley pinion gear mounted on said trolley for operatively coupling with said rack gear, and a motor coupled to drive said trolley pinion gear on said rack gear to translate said trolley along said center frame between said first and second end frames. 12. The reactor refueling mechanism as defined in claim 11, wherein said elevator comprises an elongated vertical housing rotatably supported by said trolley, a mast which is vertically displaceable relative to said housing, and a motor coupled to vertically displace said mast relative to said housing, said grapple being connected to an end of said mast. 13. The reactor refueling mechanism as defined in claim 11, wherein said second moving means further comprises a ring gear connected to said platform, a worm gear mounted on said trolley for operatively coupling with said ring gear, and a motor coupled to drive said trolley worm gear on said ring gear to rotate said elevator about said longitudinal axis. 14. The reactor refueling mechanism as defined in claim 8, wherein said rolling means comprises first and second guide rollers means positioned to bear against and roll along a circular cylindrical inner circumferential surface. 15. The reactor refueling mechanism as defined in claim 7, further comprising means for selectively controlling said first through fourth moving means. 16. The reactor refueling mechanism as defined in claim 7, wherein said fourth moving means comprise a bridge mounted on said core shroud via rolling means, said third moving means comprise first and second trolleys translatable along said bridge; said second moving means comprise first and second platforms rotatably mounted on said first and second trolleys respectively, said first moving means comprise first and second elevators supported on said first and second platforms respectively, and said coupling means comprise first and second grapples supported by said first and second elevators respectively.