Patent Number: 055263879
Section: description

BEST MODE FOR CARRYING OUT THE INVENTION The modified and improved spacer 38 in accordance with this invention includes a peripheral band 40 having an uppermost edge 42. At intervals spaced about the periphery, as best seen in FIGS. 7 and 8, modified flow tabs 44 are provided which extend upwardly from the edge 42. Each flow tab 44 has a substantially vertical lower portion 46 and an upper portion 48 which extends upwardly and inwardly toward the fuel bundle. The substantially vertical portion 46 (a part of which is formed within the peripheral band itself) includes a vertical center line or crease 50 which lies to the outside of the peripheral band 40, as best seen in FIG. 6. This substantially vertical portion 46 of the flow tab 44 includes a pair of substantially planar portions 52 and 54 which are bent outwardly from the side edges of the flow tab such that the center line or crease 50 lies outside the peripheral band. A third substantially planar portion 56 having a substantially triangular configuration, also extends from the plane of the band 40 at the lowermost edge of the tab, outwardly and upwardly to the center line or crease 50. The upper bent portion 48 of the flow tab 44 includes an inclined center line or crease 50' which extends from the vertical center line 50 and extends upwardly and inwardly toward the fuel bundle. A pair of substantially planar portions 58 and 60 are bent inwardly from the side edges 62 and 64 so that the center line or crease 50' lies below and inwardly of the side edges 58 and 60. In other words, the upper and lower portions 46, 48 of the flow tab 44 are characterized by reverse bends about a pair of contiguous center lines 50 and 50'. The bent upper portion 48 of the flow tab projects into the region between the fuel rods 12' as best appreciated from FIG. 7 and FIG. 8. Because of the secondary bend along the upper center line or crease 50', velocity components are imparted to the flow which are parallel to the band 40 and away from the flow tab 44. Thus, coolant flow is diverted in opposite directions away from the crease 50' to thereby impact directly on fuel rods 12' on either side of the flow tab. Thus, more water droplets are directed to the surfaces of the outer fuel rods 12' than in the conventional arrangement. In addition, this shape provides less flow resistance to flow generally through the bundle. At the same time, the outward bend in the lower tab portion 46 rigidities the flow tab 44 and facilitates the manufacturing process. With reference specifically to FIG. 5 and FIG. 7a, if the bend angle A is equal to angle B, the top portion 48 of the flow tab 44 can be bent without any stretching of the material. 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.