Patent Number: 050911465
Section: description

IN THE SPECIFICATIONS Referring to FIG. 1, a fuel bundle B utilizing this invention is illustrated. The fuel bundle is, for the most part, conventional. The reader will note that the preferred embodiment of the invention as set forth in FIG. 1 does not include water rods. As will hereinafter more fully be developed, the presence of the steam vent tubes of this invention may well obviate the need for such water rods. The fuel bundle here illustrated includes full length fuel rods 20 and part length fuel rods 22. Full length fuel rods 20 are conventional and extend the full distance between lower tie plate 14 to upper tie plate 16. The reader will understand that the channel C has been broken away so that the fuel rods are exposed. Part length rods 22 are also present. These part length rods extend from lower tie plate 14 and terminate short of upper tie plate 16. Spacers are also utilized. Typically, as here shown, seven such spacers are evenly placed throughout the fuel bundle. Part length rods 22 are here shown terminating just above spacer 5. Thereafter, at spacer 6 and 7, a steam vent volume is defined overlying the end of the part length rods. It is into this steam vent volumes that the steam vent tubes T1-T4 of this invention are placed. The reader will understand that the length of fuel rod used here is exemplary; lengths of fuel rods other than those specifically shown may be used. Referring to FIG. 2, this type of steam vent tubes placed within the fuel bundle B of FIG. 1 are illustrated. Specifically, paired full length rods 20 are shown sectioned from an interior portion of the bundle extending upwardly on either side of a part length rod 22. Part length rod 22 terminates at spacer S5 just above the spacer at end 40. Overlying, or connected to end 40 of the part length rod is steam vent tube T1 having a deflector 19 which is here shown conical in shape. Deflector 19 is separated a small interval from steam vent tube T1 for the purpose of deflecting water off the end of the rod and permitting the preferential entry of steam into vent tube T1. Tube T1 includes a lower opening 42 for receiving steam off the end of part length rod 22 at end 40. The tube extends upwardly and through the upper tie plate 16 at a discharge end 44 for venting steam through the upper tie plate. Suspension of the steam vent tube occurs from upper tie plate 16 and spacers S6 and S7 (see FIG. 1). Optimally, and adjacent the end 40 of partial length rod 22 in the steam vent tube, there can be provided openings 44, 46. These openings can have functions for either ejecting water from the interior of the steam vent tube T1, or for admitting steam. The function of these openings will hereinafter be described with respect to FIGS. 7 and 8. Referring to FIG. 3, an alternate embodiment of the steam vent tubes is illustrated at T5. A partial length rod 22 is again shown between full length rods 20 terminating at end 40. Overlying the part length rod 22, there is provided a steam vent tube 25 and deflector 19. Comparing this view with that shown in FIG. 2, it can be seen that the diameter of the tube T5 exceeds the diameter illustrated of both the rods 20, full length rods 20, and the part length rods 22. All other constructions remain, including lower opening 42, upper opening 44, and vents 44,46. Referring to FIG. 4, an additional steam vent tube T6 is illustrated. Tube T6 is shown at its lower end only between lower spacer S5 and upper spacer S6. As can be seen in the view of FIG. 4, four part length rods 22A, 22B, 22C and 22D are placed inside in a side-by-side array. Rods all terminate at an upper end 40 which end 40 is clustered interior of the fuel bundle. Thus, the volume overlying the ends of the part length rods 40 and the upper tie plate constitutes an interval which would normally be occupied by four full length rods 20. A steam trapping entry is provided by a first complete cone 50 and a second cone truncated at the apex, this second cone being designated 52. Portions of the complete cone 50 are broken away to expose the truncated apex 54. As before, apertures 44,46 interrupt and manifold the sidewalls of the steam vent tube T6. An explanation of the entry of steam and the rejection of water at the respective cones 50,52 is instructive. As is well known, in a two-phase liquid vapor mixture, the liquid occupies a higher density. Therefore, upon impact with lower cone 50, liquid will typically continue along the outside of the tube T6 (see the schematically illustrated liquid at vector 60). The low density steam is another matter. Typically, the steam will find its way around and into the truncated apex 54 of truncated cone 52 (see schematic vectors 62). Stated in ordinary terms, the steam has a density which will admit of its following circuitous flow paths. Once the steam is interior of the steam vent tube T6, upward flow will continue. Thus far, all steam vent tubes illustrated have been of circular section. Referring to FIG. 5, a square section T7 steam vent tube is illustrated. Referring to FIG. 5, a plurality of full length rods 20 surrounds a cluster of nine partial length rods 22. Partial length rods 22 all terminate at upper ends 40. Since the rods 22 are in a 3.times.3 array, it will be understood that overlying the ends 40 of the part length rods there exists a steam vent volume that may be suitably occupied by a square sectioned steam vent tube T7. Steam vent tube T7 has a generally conical bottom 70 flaring to a square sectioned tube structure 72. As before, tube structure 72 continues upwardly through the upper tie plate, it being realized that the top portion of the tube T7 is not illustrated. As before, apertures 44,46 are present. Referring to FIG. 6A, a steam vent tube placed within a generally conical void within a fuel bundle is shown. A plan view of the steam vent tube T8 is illustrated in FIG. 6B. Referring to FIG. 6B, a 9.times.9 array of full length rods is illustrated. This 9.times.9 array has 21 part length rods 22 terminating underlying the steam vent tube T8. Referring to FIG. 6A, it can be seen that the central length rod 22 terminates at a first elevation 91. Second part length rods 22 terminate at second elevations 92. Finally, third groups of path length rods 22 terminate at third elevations 93. The rods are placed in a stepped configuration similar to that illustrated in Ueda, Japanese Patent Showa 52-50489 so as to define from lower spacer S5 to upper tie plate 16, a generally conical volume. This volume is filled with a step tapered tube T8. Tube T8 includes a flare portion 100 at the upper end of short partial length rod 22. Thereafter, a cylinder 102 connected by truncated cone 104, connects to cylinder 106. A second truncated cone 108 connects to cylinder 110. Cylinder 110 extends upwardly to and possibly through tie plate 16. As before, alternating openings 46,48 are shown utilized. Referring to FIG. 7, a vent 46 is illustrated which vent 46 in the side of a vent tube T permits the preferential entry of vapor along an illustrated path 120. Aperture 46 includes an upper opening 122 and is disposed outwardly from the linear wall 124. As can be seen, vapor with its low density can follow the circuitous path 120. Water with its higher density will pass by aperture 122 as illustrated in vector 126. It will be realized that the aperture shown in FIG. 7 is shown in a planar wall. This aperture can just as easily be adapted to circular walls. Referring to FIG. 8, a vent 48 is illustrated which vent 48 is for the ejection of water interior of the wall 124. Specifically, water will normally flow against the wall. Since aperture 132 of opening 48 is downwardly disposed, water tracking along wall 124 will be ejected from the interior of the steam vent tube T. It will be realized that the placement of the respective apertures 46,48 and their respective dimensions will be a function of the size of the steam vent tube, the total volume of vapor to flow within the tube as well as the total volume of water to be ejected from the tube. Thus, the designer will place these apertures and dimension them in accordance with the design parameters of the fuel bundle involved. It will be realized that I have shown my preferred embodiment without a water rod. Those having skill in the art will understand that a water rod can be added. Further, I have shown the steam vent tubes of my invention fastened to the spacers and tie plates. The steam vent tube can as well be fastened to the end of the part length rod.