Patent Number: 054208998
Section: summary

TECHNICAL FIELD This invention relates to the field of nuclear reactors in general and to a tool used to lift a nuclear reactor fuel bundle channel from a fuel bundle assembly in particular. BACKGROUND Typically, BWR nuclear fuel bundles and channels are delivered to reactor sites in separate shipping containers. At the sites, the fuel bundles are removed from their shipping containers, inspected, and stored hanging on racks in a fuel preparation room. Before moving the fuel bundle to the reactor, the channel is installed over the bundle. There are occasions, however, when the channel must be removed from its associated fuel bundle. Once the channel has been installed on the fuel bundle, however, with the lower end of the channel fitted over the finger springs in the lower tie plate assembly, and with the top of the channel in place, snug against the upper tie plate, removal of the channel can be problematic. The channel is initially moved upwardly off the fuel bundle (about ten inches) so that a crane lift device can be attached to the channel. After the crane lift device has been attached, the crane hook is coupled to the lift device and the crane is then used to remove the channel from the fuel bundle. The initial upward movement of the channel currently is done manually to gain the approximate ten inches of elevation required to clear the upper tie plate. Typically, one or two people lift the channel and a third person then connects the crane lift device. If the channel is dropped during this procedure, however, the channel as well as the fuel bundle can be damaged. There is thus a need for a device which will permit a fuel bundle channel to be removed from a fuel bundle in a simpler, more reliable and less labor intensive manner. SUMMARY OF THE INVENTION This invention provides a locking channel grapple which permits channel removal from a fuel bundle to be accomplished reliably and safely by one person. The grapple device in accordance with this invention is adapted to attach to a crane lifting hook and then lowered over a fuel bundle. The grapple is designed to provide clearance so it can move down without interference over the upper tie plate bail and into position over the channel. The grapple includes screw actuated lifting feet fixed to a respective pair of lever arms. The lifting feet are positionable under the channel gussets at opposite corners of the channel. The grapple device has a central shaft to which the lever arms are pivotally mounted. The shaft is formed with screw threads at a lower end thereof, threadably receiving a cross piece pinned to the lever arms at locations between the ends of the latter. The pins are slideable within slots formed in the respective lever arms so that, when the shaft is turned by a serrated knob or handle, the lever arms are caused to swing outwardly moving the lifting feet under the channel gussets. The lifting feet on each lever arm are forked so that spaced lifting elements will fit around the upper tie plate boss or bosses on which the channel gussets rest, and which is formed with a threaded hole for receiving a bolt passing through the channel gusset. The screw action of the lever arms effectively holds the lifting feet under the channel gussets, preventing from slipping from under the channel gusset(s) during lifting. The lifting feet on each lever arm also have a secondary foot or slider which is captured in a slot between the spaced lifting elements, permitting the movable secondary foot to be located centrally under a respective channel gusset as described below. The secondary foot, unlike the forked lifting feet, has a hole in its end which, after the channel is lifted away from the tie plate boss, can be aligned with the bolt hole in the channel gusset by sliding the secondary foot to its extreme outside position. A pair of conventional ball lock pins are attached to the grapple device by chains or cables so they will be readily available for use with the sliders described above. Specifically, after the hole in the secondary foot of each pair of lifting feet is aligned under a respective channel gusset hole, the ball lock pin is inserted through the channel gusset hole and through the hole in the secondary foot, further insuring against relative lateral movement between the channel and the grapple. The ball lock pin will safely secure the channel to the grapple until the channel is securely back in its storage place, or until it is re-mounted on the fuel bundle. In its broader aspects, therefore, the present invention relates to a grapple for use with a fuel bundle channel of a nuclear reactor wherein the channel is provided with a pair of gussets in opposite diagonal comers of an upper end of the channel, each gusset having a hole therein, the grapple comprising a pair of lever arms, each provided with a channel lifting foot at a lower end of the respective lever arm, the lever arms movable to a channel lifting position wherein the channel lifting foot of each lever arm is located under a respective one of the pair of channel gussets, and wherein each lifting foot includes a pair of laterally spaced lifting elements such that the lifting foot may engage the underside of the gusset on either side of the gusset hole.