Patent Number: 063109301
Section: description

DETAILED DESCRIPTION OF THE INVENTION Referring now to the drawings, particularly to FIG. 1, there is illustrated a guide apparatus constructed in accordance with a preferred embodiment of the present invention and generally designated 10. Apparatus 10 as illustrated is employed to guide a fuel bundle, generally designated 12, into a fuel bundle channel 14. The fuel bundle 12 includes a plurality of elongated fuel rods 16 and at least one water rod 17 which pass through spacers 18 located at axially spaced positions along the length of the array of fuel rods 16. It will be appreciated that the spacers have a peripheral margin which extends laterally outwardly of the fuel rods in the fuel bundle and that the margins of the spacers 18 engage the interior wall surfaces of the channel 14 upon final assembly of the fuel bundle into the channel 14. As illustrated in FIG. 1, channel 14 has a nose piece 20 at its lower end, the channel 14 being secured by fasteners 21 to the nose piece 20. Consequently, it will be appreciated that the fuel bundle 12 comprised of the fuel rods and spacers must be inserted into the open upper end of the channel 14 because the channel cannot be lowered onto or about the fuel bundle as in the prior art. The guide assembly 10 includes a lower guide member or plate 22 and an upper guide member or plate 24 spaced one from the other by structural members 26 extending between the guide plates. The lower guide plate 22 has a plurality of depending channel locators 28 for positioning the guide assembly 10 on the upper end of the channel 14. Preferably, the channel locators 28 include four angle or corner members 30 secured to the underside of the lower guide plate 22 by screws 32. The inside surfaces of the channel corner members 30 are each provided with an elongated channel location slide or shim 34. The shims 34 are preferably formed of a plastic material such that their engagement about the external surfaces of the channel upon installation does not damage the channel. Also, the shims are provided in various sizes to accommodate dimensional variations in the channels thereby enabling accurate alignment of the guide assembly and channel even after channel irradiation. Consequently, the channel locators 28 precisely locate the guide assembly 10 on top of the channel 14. As illustrated in FIG. 6, the lower guide plate 22 has an interior opening 38 dimensioned to conform to the internal dimensions of the channel 14. Consequently, when the lower guide plate is disposed on top of the channel 14 with the channel locators 28 engaging the corners of the channel, the lower guide plate opening 38 is in alignment with the interior wall surfaces of the channel. The opening 38 also corresponds to the outer margins of the spacers 18 of the fuel bundle. Referring to FIG. 5, the upper guide plate 24 has an interior opening 40 dimensioned in excess of the lateral dimensions of the spacers 18. The opening is thus enlarged, for example, on the order of 7/8-inch larger than the opening 38 to the lower guide plate 22. The upper guide plate 24 is supported above the lower guide plate 22 by a plurality of structural members 26, preferably four, which maintain the upper and lower guide plates spaced from one another, with the openings 38 and 40 therethrough in spaced registration with one another. The structural members 26 are preferably angled members which extend from their lower ends upwardly and outwardly to diverge one from the other to the underside of guide plate 24. The members 26 are secured at opposite ends to the upper and lower guide plates 24 and 22, respectively, e.g., by welds on the underside of the corners of guide plate 24 and on the upper face of lower guide plates 22. Mounted on top of the upper guide plate 24 are a plurality of guide elements 44 (FIG. 3). Preferably, the guide elements comprise rollers 46 carried by clevis mounts 48 secured to the guide plate 24. The rollers 46 have surfaces corresponding in configuration to the configuration of the corners of the spacers 18 of the fuel bundle 12. Note also in FIG. 2 that the surfaces 50 of the rollers 46 register with the corners of the opening 38 through the lower guide plate 22. Additional sets of spring-biased rollers 70 (FIG. 7) may be mounted on the structural members 26 intermediate the upper and lower guide plates. The rollers 70 engage the corner fuel rods 73 of the fuel bundle 12 as the fuel bundle is lowered into the channel to maintain the alignment of the fuel bundle during its insertion into the channel. These additional rollers are displaced against the bias of the springs upon engagement with the spacers 18 as the spacers pass the spring-biased rollers 70 during downward travel of the fuel bundle into the channel 14. Also, the spacing between the corner rollers 46 and the top of the channel 14 corresponds to the spacing between the first and second fuel spacers of the bundle. This ensures that the first spacer 18 is properly aligned with the channel opening as it enters the channel. As an additional alignment aid, the guide apparatus has a pair of alignment indicators 60 and 62 (FIG. 3) disposed along the upper and lower guide plates 24 and 22, respectively. These alignment indicators may comprise V-notches on each of the four sides of each of the upper and lower plates. Consequently, as the fuel bundle is being lowered into the channel 14, visual inspection of the alignment of the fuel bundle with the V-notches 60 and 62 can indicate whether the fuel bundle 12 is out of alignment with the channel. In use, the guide apparatus 10 is first disposed on the upper end of a channel 14, the channel 14 being maintained in an upright position by fixturing, not shown. Particularly, the guide assembly 10 is lowered onto the upper end of the channel with the shims 34 of the channel locators 28 engaging sides of the channel adjacent the channel corners. With the locators 28 disposed along the corners of the channel and the lower guide plate 22 disposed on top of the channel, the guide apparatus is automatically aligned with the channel opening. The fuel bundle 12 is then disposed into the guide apparatus through the open upper end thereof. As the first spacer comes into engagement with the rollers 46, the fuel bundle is rotationally aligned with the channel. As the fuel bundle is lowered, its lower end enters the channel 14. Upon further lowering of the fuel bundle relative to the channel, the second spacer engages the rollers 46. Because of the dimensional relationship between the upper and lower guide plates, the first spacer enters the channel 14 at the time the second spacer engages the rollers 46. This ensures accurate alignment of the bundle and channel. As the fuel bundle is progressively lowered further or inserted into the channel, the spacers of the bundle engage one after another along the rollers to maintain alignment of the fuel bundle and channel. The additional rollers 70 between the upper and lower guide plates likewise maintain the alignment of the fuel bundle 12 when the spacers 18 pass below the rollers 46 until the next spacer engages rollers 46. Visual inspection of the alignment during the insertion process is also obtained. By visually aligning the V-notches 60 and 62 on each of the four sides of the guide apparatus with the bundle during bundle insertion, assurance is obtained that the bundle is not canted relative to the channel. After the fuel bundle is completely inserted into the channel 14, the guide apparatus 10 is lifted off the upper end of the channel. It may be desirable to locate further guides intermediate the lower and upper guide plates 22 and 24, respectively, to guide the fuel bundle 12 at times during the lowering of the fuel bundle when a spacer 18 is not guided by the rollers 46. For that purpose, the structural members 26 have additional guide rollers 70 (FIG. 7) at locations intermediate the upper and lower guide plates to engage the comer fuel rods 73. The rollers 70 are spring-biased inwardly to engage the comer fuel rods and are displaced outwardly against the bias of spring 72 when a spacer 18 is lowered past the rollers 70. To accomplish this, an opening 74 is provided through the structural member 26. A bracket 76 projects along the outside of member 26 and mounts a clevis 78 which, in turn, pivotally carries the roller 70. The clevis 78 is spring-biased by spring 72 toward the fuel bundle 12. While the fuel rods 16 are not normally considered as structural elements, the spacing between the spacers 18 is limited. Also, the fuel rods are captured by the spacers 18. Thus, the forces applied to the corner fuel rods by the rollers 70 at the four corners of the fuel bundle are sufficient to maintain alignment of the fuel bundle 12 and channel 14 while not causing undue stress on the fuel rods. 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.