Patent Number: 
Section: description

Referring now to the drawings, particularly to FIG. 1, there is illustrated a spacer for use in a fuel bundle or assembly in a nuclear reactor, the spacer being generally designated 10. The spacer includes a plurality of cylindrical ferrules 12 having stops 13 projecting from interior wall surfaces thereof and springs 16 for bearing against fuel rods 18 extending through the spacer in each of the ferrules 12. The springs 16 impart a lateral force to the fuel rods to maintain the fuel rods in bearing engagement against the stops 13. The spacer 10 also has a surrounding band 20 laterally encompassing the ferrules. As illustrated, a pair of water rods 22 pass through enlarged openings in the spacer 10. A clip 24 is secured to the ferrules, for example, by welding, and has a vertical extent corresponding to the vertical extent of the ferrules. One of the water rods 22 carries upper and lower tabs 26 which engage upper and lower margins, respectively, of the clip 24 to prevent relative axial displacement of the spacer and one water rod. As previously stated, in unchanneled bundles, the twist of the water rods and spacers may be sufficient to misalign the tabs 26 with the clip, enabling the spacer and water rod for relative axial displacement. Referring to FIGS. 2A-2C, there is illustrated in a preferred form of the present invention, a spacer/water rod connecting structure or retention assembly, generally designated 30, for use in a spacer of the type illustrated in FIG. 1 but having a different clip and water rod retention tab arrangement, as will now be explained. As best illustrated in FIG. 2C, the clip 32 is generally U-shaped with laterally outwardly directed flanges 34 to facilitate welding to adjoining ferrules 12 (FIG. 1). The base of the U-shaped clip 32 defines a slot or opening 36 bounded by axially opposite structural portions 38 and 40, as well as lateral or side structural portions 42 and 44 (FIG. 2B). Thus, the portions 38, 40, 42 and 44 perimetrically enclose the slot 36. Along the side portion 42 of clip 32, there is provided a clip tab 45 which projects toward the opposite side portion 44 of slot 36. The metal material from which the clip 32 is made enables the clip tab 45 to be resiliently deflected. A water rod tab 46 projects generally radially outwardly from the water rod and is sized for reception in the slot 36. To secure the spacer and water rod relative to one another, the water rod is disposed through the opening in the spacer with the tab 46 outside of the opening or slot 36 as illustrated in FIG. 2B. By rotating the spacer and water rod relative to one another, for example, by rotating the water rod in a counterclockwise direction as illustrated in FIG. 2B, the water rod tab 46 engages the tab 45 of the clip 32, resiliently deflecting tab 45 such that the water rod tab 46 obtains the position illustrated in FIG. 3B within slot 36. The clip tab 45, once the water rod tab 46 passes by out of engagement with tab 45 and into slot 36, resiliently deforms back to its initial position, generally within the slot 36. As a consequence, the side portion 44 of clip 32 and tab 45 lie on opposite sides of the water rod tab 46, preventing relative rotation between the spacer and water rod. Even with a twist of an unchanneled fuel bundle assembly, the water rod tab 46 remains captured in the slot between the side portion 44 and clip tab 45. To disassemble the water rod and spacer, a tool, not shown, may be used to deflect the spring in the same direction as in the initial assembly whereby the tab 46 can be rotated out of the slot past the tab 45. Referring now to the embodiment of the present invention illustrated in FIGS. 4A-4B and 5A-5C, wherein like reference numerals as in the prior embodiment apply to like parts followed by suffix xe2x80x9ca,xe2x80x9d the water rod 22a includes a tab 46a. The clip 32a includes a slot 36a which is perimetrically bounded by axially opposite end portions 38a and 40a, as well as bounded on its sides by side portions 50 and 52. The clip 32a is secured to the spacer similarly as in the prior embodiment. In this form, however, the tab 45 projecting from one side portion of the clip is omitted. To secure the spacer and one water rod against axial displacement relative to one another, the tab 46a is rotated into the slot 36a by relative rotation of the spacer and water rod. The tab 46a is thus prevented from rotational movement by one side portion 50 of the slot 36a. To prevent rotational movement of the tab in a direction displacing the tab from the slot, a second water rod 23 is disposed through an opening in the spacer adjacent the first water rod. The second water rod prevents rotation of the tab out of the slot 36a. The water rod does not rely on a square lower end plug and tie plate hole to prevent water rod rotation as in certain current designs. Thus, the present spacer/water rod retention assembly not only prevents relative rotation of the water rod and spacer to an extent permitting axial displacement of the water rod and spacer, particularly when installed in unchanneled fuel bundle assemblies, but also permits the less costly fabrication of a round water rod end plug and round openings in the lower tie plate of the fuel assembly. While the invention has been described in connection with what is presently considered to be the most practical and preferred embodiment, it is to be understood that the invention is not to be limited to the disclosed embodiment, but on the contrary, is intended to cover various modifications and equivalent arrangements included within the spirit and scope of the appended claims.