Patent Number: 054815797
Section: claims

1. In a fuel bundle assembly for a nuclear reactor wherein a plurality of fuel rods and at least one water rod extend between an upper tie plate and a lower tie plate, the improvement comprising: an upper end plug secured to the at least one water rod and having a recessed portion defined by upper and lower shoulders; and  a latching mechanism for securing the at least one water rod to the upper tie plate comprising a latch bar mounted on an upper surface of the upper tie plate and rotatable into and out of said recess portion in said end plug when said end plug extends above said upper surface of said tie plate upon installation of said upper tie plate on the fuel bundle assembly. 2. The improvement of claim 1 wherein said at least one water rod comprises a pair of water rods and respective end plugs in side-by-side relationship, and wherein said upper tie plate includes a double water rod boss having a pair of apertures enabling at least said end plugs of said pair of water rods to pass through and extend above said upper tie plate, and wherein said latch bar includes laterally opposite portions simultaneously rotatable into and out of opposed recessed portions on the end plugs of said pair of water rods. 3. The improvement of claim 2 wherein said latch bar is free to rock from side to side when the latch bar is rotated into said cut-outs to thereby accommodate radiation growth of said pair of water rods. 4. The improvement of claim 3 wherein a lower surface of said latch bar is formed with a projecting rib extending perpendicular to a centerline between centers of said pair of water rods, said rib in engagement with said upper surface of said tie plate thereby serving as a pivot axis for said latch bar. 5. The improvement of claim 1 and further including a locking pin engageable between said latch bar and said upper tie plate to prevent said latch bar from rotating out of said cut-out. 6. The improvement of claim 2 and further including a locking pin engageable between said latch bar and said upper tie plate to prevent said latch bar from rotating out of said recessed portions. 7. The improvement of claim 5 wherein said locking pin is spring loaded. 8. The improvement of claim 5 wherein said locking pin includes a pair of spring fingers. 9. The improvement of claim 2 wherein said water rod double boss includes a hole located between said apertures for receiving a centering post passing through said latch bar, thereby enabling rotation of said latch bar relative to said upper tie plate. 10. The improvement of claim 2 wherein said water rod double boss includes a projection and a first through hole therein extending parallel to said apertures, and wherein said latch bar includes a second through hole alignable with said first through hole when said latch bar is rotated into said recessed portions: and a locking pin insertable within said first and second through holes to thereby prevent rotation of said latch bar out of said recessed portions. 11. The improvement of claim 1 wherein said at least one water rod comprises a pair of water rods and respective end plugs in side-by-side relationship, and wherein said upper tie plate includes a double water rod boss having a pair of apertures enabling at least said end plugs of said pair of water rods to pass through and extend above said upper tie plate, said laterally opposed recessed portions comprise circumferential grooves in the respective end plugs, and further wherein said latch bar includes a pair of hooks facing in opposite directions and simultaneously rotatable into engagement with said circumferential grooves. 12. The improvement of claim 11 wherein said pair of hooks are provided with rounded water rod engagement surfaces. 13. The improvement of claim 11 wherein said circumferential grooves are each defined by a square base and each hook has a corresponding generally square shaped water rod engagement surface. 14. A fuel bundle assembly for a nuclear reactor including a plurality of fuel rods and a pair of water rods extending between upper and lower tie plates, said fuel rods and said water rods passing through said upper tie plate; a latch bar mounted on said upper tie plate for securing said pair of water rods to said upper tie plate, said latch bar including means for accommodating differential thermal growth of said pair of water rods. 15. The fuel bundle of claim 14 wherein said water rods include end plugs having laterally recessed opposed portions located above said upper tie plate, and wherein said latch bar includes laterally opposite portions simultaneously rotatable into and out of said opposed recessed portions. 16. The fuel bundle of claim 15 wherein said means includes an elongated rib on a lower surface of said latch bar in engagement with said upper tie plate and forming a pivot axis for said latch bar. 17. The fuel bundle of claim 15 and including means for locking said latch bar in a locked position when said laterally opposite portions are located within said opposed recessed portions. 18. The fuel bundle of claim 14 and including means for biasing said upper tie plate away from said plurality of fuel rods and said pair of water rods. 19. The fuel bundle of claim 15 wherein said laterally opposed recessed portions comprise 360.degree. circumferential grooves, and wherein said latch bar is formed with a pair of hooks having rounded water rod engagement surfaces facing in opposite directions. 20. The fuel bundle of claim 15 wherein said laterally opposed recessed portions comprise 360.degree. circumferential grooves, a base of each groove having a substantially square profile, and wherein said latch bar is formed with a pair of hooks having substantially squared slob opening in opposite directions.