Patent Number: 053135067
Section: description

DESCRIPTION OF THE PREFERRED EMBODIMENT Referring to FIG. 1, a typical prior art fuel bundle B is shown. The fuel bundle B includes a lower tie plate 14, and upper tie plate 16 and a plurality of fuel rods F in a matrix extending between the respective tie plates. The tie plates 14, 16 as well as the fuel rods F are surrounded by a channel C, which channel C is broken away so that a single spacer S can be seen. Spacer S is the subject of this invention. More particularly, a spacer S of the ferrule type is the subject of this patent application. FIG. 2 is an illustration of a particularly advantageous spring 12. This spring is taken from Johansson et. al. U.S. Pat. application Ser. No. 07/623,828 entitled Self Locating Springs for Ferrule Spacer filed Dec. 6, 1990 at FIG. 17. The content of this patent application is herein incorporated by reference. This loop spring, illustrated in the attached specification at FIG. 2, includes first and second vertical legs 14 and 16 containing rod contacting portions 15, 17. One vertical leg at one rod contacting portion extends interior of a first ferrule of a ferrule spacer to bias a fuel rod within that ferrule. The other vertical leg at the other rod contacting portion extends interior of an adjacent second ferrule of a ferrule spacer to bias the adjacent fuel rod within that adjacent ferrule. This disclosed spring has a shortened construction. This shortened construction is provided by two horizontal loops 20, 24; these horizontal loops being positioned one loop 20 at the top of the spring and the remaining loop 24 at the bottom of the spring. The first and top horizontal loop is connected at its central portion to the top of each of the spring legs 14, 16. The second and bottom horizontal loop is connected at its central portion to the bottom of each of the spring legs 14, 16. Thus, the spring when compressed flexes over the vertical length of the spring legs 14, 16 as well as the horizontal length of the top and bottom loops 20, 24. The respective top and bottom horizontal loops 20, 24 are provided with expanded loop ends 21, 22 in loop 20 and 25, 26 in loop 24. This expansion is labeled in an exemplary fashion at expanded sections 28, 30 in expanded end 25 of loop 24. A spring having a reduced vertical dimension with a superior deflection range results. As will hereinafter become more apparent, I prefer to trap this spring at the expanded ends 25 between opposing ferrules for the construction of the preferred spacer of this invention. Referring to FIGS. 3A and 3B the first embodiment of a ferrule pair 40 can be seen and understood. With reference to FIG. 3B, ferrule 42 includes solid section 42A and apertured section 42B having aperture 60 therein. Likes wise ferrule 44 includes solid section 44A and apertured section 44B. It will be appreciated that in each of the apertured sections, four apertures 60 appear. Appropriate stops 70 are configured interior of the ferrules. It will be further understood that between each ferrule pair 42, 44, there is defined a spring capturing window. Spring 12 (See FIG. 2) is first place within the aperture 62 of partially confronted ferrules and thereafter confrontation occurs. There results the composite construction which is the essential building element of the spacer construction of this invention. Referring to FIG. 4, a completed spacer S is shown using the ferrules of FIGS. 3A and 3B. This spacer S defines intervals for water rods W1 and W2. As the bracing of these water rods W1 and W2, and the exterior band are conventional, they are not shown. Referring to FIGS. 3A and 3B, the preferred embodiment of a ferrule pair 40 can be seen and understood. Referring to FIG. 3B, first ferrule section 42 is shown confronted to second ferrule section 44. Examining FIG. 3B further, it can be seen that a centerline 46 divides each ferrule of the ferrule pair 42, 44 into respective halves. Ferrule 42 has halves 42A and 42B; ferrule 44 has halves 44A and 44B. Provision must be made for the confrontation of the respective ferrule halves so as to define only one ferrule wall even though two ferrules are confronted. Accordingly, ferrule halves 42B and 44B have four portions of their respective walls milled away. Specifically, a milling tool is utilized which has two characteristics. First, the milling tool has a diameter slightly exceeding the diameter of the adjacent ferrules. Secondly, the milling tool when cutting away the wall is centered just as the adjacent ferrule would be centered. The result is milled intervals 60. Four such intervals are placed in ferrule halves 42B and four such intervals are milled in ferrule halves 44B. In order to accommodate the subsequent fit, it will be observed that the milling process exceeds in vertical dimension slightly the half dimension of the spacer halves 42B and 44B. The fit between the respective ferrule halves is as shown in FIGS. 3A and 3B. Referring to FIG. 3B, it can be seen that ferrule half 42A fits adjacent ferrule half 44B; likewise it can be seen that ferrule half 42B fits adjacent ferrule half 44A. As is shown in the plan view of FIG. 3A, with such an arrangement, the contiguous and tangent portions of ferrule halves 42A and 44B define only one ferrule wall between adjacent fuel rods F1, F2. That is, as best seen in FIG. 3A, the ferrule half 42a with walls present includes a wall portion which extends within the slot 60 of the ferrule half 44b and consequently only a single wall lies between adjacent fuel rods along a line extending parallel to the axes of the ferrules and along a tangency between the ferrule pair 40. The rest of the construction is conventional. A ferrule spring 12 is trapped between ferrule aperture 62 in ferrule 42 and ferrule aperture 64 in ferrule 44. As has been illustrated in Johansson et al. U.S. Pat. application Ser. No. 07/623,828 entitled Self Locating Springs for Ferrule Spacer filed Dec. 6, 1990, spring 12 is captured at the respective loops interior of the confronted ferrules. As is further conventional, the respective ferrule halves 42A, 42B, 44A and 44B define respective stops 70 into which fuel rods F1 and F2 are biased by spring 12. Turning to FIG. 4, a spacer S constructed of the ferrules is illustrated. In the plan view of FIG. 6, the orientation of two water rods W1 and W2 is shown. As bracing of the water rods at the spacer S is conventional, it is not shown. This invention can be applied to spacers. S having octagon shaped sections. Such is shown in FIGS. 5, 6A, 6B and 7. Referring to FIG. 5, a Zircaloy metal sheet is shown immediately before being bent into an octagon shape. As before, the cell 80 is divided into halves 80A and 80B. In the upper half 80B of spacer 80, four walls are removed at 82, 84, 86, and 88. These removals slightly intrude upon half 80A of the ferrule cell metal sheet. Conventional apertures 90A and 90B are configured for trapping spring 12. Referring to FIGS. 6A and 6B, two respective cells 80 are assembled. Assembly is by stamping and bending using conventional manufacturing techniques. Consequently, a detailed explanation of the cell formation of the octagon shaped cell will not be offered here. Referring to FIG. 6B, cells 80 are shown juxtaposed with sections 80A of one cell 80 juxtaposed to section 80B of an adjacent cell 80. Spring 12 is trapped between the cells at apertures formed by 90A and 90B between the respective cells. Referring to FIG. 6A, fuel rods F1 and F2 are shown biased into conventionally constructed stops 70 by spring 12. It will be observed that only one cell wall is present between fuel rods F1 and F2 Referring to FIG. 7, a completed spacer S is shown assembled. This spacer S defines intervals for water rods W1 and W2. As the bracing of these water rods W1 and W2 at the spacer and the exterior band are conventional, they are not shown. The reader will appreciate that the construction technique and process here shown will find applicability in arrays other than the 10 by 10 arrays here illustrated. Further, we have shown one spacer cell half having all of the walls removed. Other combinations of wall removal may be utilized. We prefer the illustrated configuration as providing a reversible cell assembly with a minimum inventory of required parts for assembly of the spacer.