Patent Number: 046769455
Section: description

DETAILED DESCRIPTION OF THE INVENTION Referring to the drawings and, in particular to FIGS. 4, 5, and 6, a fuel bundle assembly which may be of the same general type described in U.S. Pat. Nos. 3,379,619 and 3,255,091 and includes a plurality of individual fuel rods 12, a lower grid spacer 13, an upper tie plate 14, and a lower tie plate 16. The upper tie plate 14 will be understood to be connected to the remainder of the fuel bundle assembly therebelow in the conventional manner as typically employed and shown in the aforesaid U.S. patents. Each of the upper tie plates 14 includes a pair of alignment holes or aperatures 18 for receiving a pair of stepped tapered dowel pins 20 disposed on diagonally opposite corners of a centering device generally designated 22. [See FIG. 1] Each of the centering devices 22 disposed on top of its respective fuel bundle upper tie plate 14 includes a top plate 26 and a pair of vertical side walls 28 weldably secured along their upper edges to the undersurface of the top plates 26. Also secured to the top plate 26 is a front inclined or sloping working face 30, while at the opposite end of the side walls 28, is a rear or bottom plate 31 weldably secured to said side walls. At the corner junctures or intersections of these respective side plates 28, working face 30, and bottom plate 31 are attached as by welding four legs or mounting pads 32. Each of the mounting pads 32 is arranged to mount upon four corresponding upstanding shoulders or corners 33 of the upper tie plate 14. The top plate 26 of each centering device 22 includes a socket 34 welded in an aperature therein and braced by a cross-plate 36 attached to the outer periphery of the socket 34 as well as to the sloping working face 30 and side walls 28. The socket 34 includes a receiving aperature 42 having a conical lower face 44. Disposed within the receiving aperature 42 is the lower end of an elongated handling pole 38 which is provided with a ball 40 to engage the inner diameter of aperature 42. On the underside of the ball 40 is an extending pin member 46 which mounts a chamfer plate 48 secured thereto by a nut 50. It can be seen that the angle on the outer peripheral edge of the chamfer plate 48 is similar to the angle of chamfer on a bottom cone portion 52 formed in the underside of the socket 34. Referring to FIGS. 1 and 2, it can be seen that the arrangement and cooperation between the box-like centering device 22 as disposed on top of a representative fuel assembly 14 is such as to provide for four lateral side openings 56 defined between the upper edge of the tie plate 14 and the lower arched recess portion of each of the two opposed side walls 28, the inclined working face 30, and the rear bottom plate 31. These side openings 56 are intended to provide free passageway of any reactor core cooling liquid flowing upwardly between the fuel rods 12 that may be present during fuel reloading. Such upward flow could be convection induced or alternatively result from the downward insertion of the fuel assembly 10 displacement of liquid from the empty core space 24. Those skilled in the art will understand that such reloading of a nuclear reactor core is accomplished while all the fuel bundles are submerged in the reactor coolant liquid and that thermal gradients within such cooling liquid will induce convection currents generally flowing upwardly in the liquid in each of the fuel bundles. The presence of the four side openings 56, along with a rectangular opening designated 54 defined between the upper edge of plate 31 and the undersurface of top plate 26, provide a large fluid flow area for any such convection or displacement liquid flowing upwardly within the fuel bundle so that the tendency and force of such fluid will not raise the centering device 22 off the top end of each fuel bundle. In any event, the weight of the handling pole 38 against the surface 44 will ordinarily assist in keeping the centering device 22 well seated on its respective fuel bundle. It should be appreciated that the handling poles may be as long as 20 to 30 feet and that only the lower portion thereof has been shown for drawing convenience herein. However, these handling poles may readily be inclined out of the immediate work area as shown by the position of the chamfer plate 48 in dotted lines in FIG. 3. When the handling pole 38 is in such position the ball 40 will necessarily rest against the conical lower face 34 and the pole 38 will be free to pivot in a conical envelope. Accordingly, it may readily be placed out of the way so that interference with the fuel bundle being loaded into the empty core position 24 and with the fuel loading equipment is avoided. In operation and in particular with reference to FIG. 6, it may be seen and appreciated that as the fuel assembly loading equipment [not shown] is operated to gradually lower, the assembly 10 into the empty core position 24 that even though one of the fuel bundles 12 is bowed at its upper end to diminish the amount of space for receiving the lower end of the bundle that the lower tie plate 16 of the bundle being lowered is effective to contact the inclined face 30 of the centering device and thereby laterally displace the bowed upper end of the fuel bundle assembly outwardly as the bundle is lowered so that it may readily slide and be inserted into the empty core position 12. While a specific embodiment of the invention has been shown and described in detail to illustrate the application of the inventive principals, it will be understood that the invention may be embodied otherwise without departing from such principals.