Patent Number: 063209225
Section: description

DETAILED DESCRIPTION OF THE INVENTION Referring now to the drawings, particularly to FIGS. 1 and 2, there is illustrated a preferred embodiment of a tool, generally designated 10, constructed in accordance with the present invention. Tool 10 is useful both as an extractor tool for extracting fuel rods from a fuel assembly and as an insertion tool for inserting fuel rods into the fuel assembly. Tool 10 includes an inner rod 12 mounting a handle H at one end and which rod 12 is, in part surrounded by a coaxially extending outer tube 14. An externally threaded portion or locking sleeve 16 is secured to the inner rod 12 by a pinned connection at an intermediate location along the rod. A cover sleeve 18 is secured to the proximal end of the outer tube 14, for example, by welding. The opposite end of the cover sleeve 18 includes a flange 20 (FIG. 3A) rotatably received within an internal recess of a retaining ring 22 secured by bolts to a locking tube nut 24. It will be appreciated that, with the flange 20 locked by the retaining ring 22 to the locking tube nut 24, the outer tube 14, cover sleeve 18 and locking tube nut 24 are jointly axially displaceable while the locking tube nut 24 is rotatable relative to the cover sleeve 18, outer tube 14 and threaded locking sleeve 16. The locking tube nut 24 is internally threaded for threaded engagement with the locking sleeve 16 and serves as a drive element as described below. Inner rod 12 also includes a laterally extending pin 26. The pin 26 is received in a slot 28 formed through a side wall of the outer tube 14. The outer sleeve 18 overlies the end of the pin 26 received in the slot 28 but is not connected to the pin 26. As a consequence, it will be appreciated that the pin 26 prevents relative rotation between the inner rod 12 and outer tube 14 while enabling relative axial movement of the inner rod 12 and outer tube 14 to the limited extent of the slot 28. With the above described arrangement, it will be appreciated that rotating the locking tube nut 24 in a direction to cause the locking sleeve 16 to thread relative to the tube nut 24 for movement to the right in FIG. 1 the pin 26 will advance to the opposite of the slot, i.e., as illustrated in FIG. 3B. Rotation of the locking tube nut 24 in the opposite direction causes relative displacement of the inner rod 12 and outer tube 14 to the position illustrated in FIG. 3A, locating the locking pin 26 in the left-hand end of slot 28 as illustrated. Consequently, the inner rod 12 and outer tube 14 are axially displaceable relative to one another for the full extent of the length of the slot 28. Referring to FIG. 2, the outer tube 14 terminates in an outer sleeve 30 having a split inwardly directed flange 32 at its distal end. The end of inner rod 12 is reduced in diameter at 34 and has a transitional outwardly tapered section 36 between its end 34 and the inner rod proper. The end of the inner rod 12 terminates in a flat end face 38. An opening 40 extends laterally through the end of inner rod 12 adjacent to the transition between the reduced diameter section 34 and tapered section 36. Referring to FIGS. 2, 4 and 4A, there is provided at the end of tool 10 a collet, generally designated 42, having split collet sections 44 which are the mirror images of one another. The split collet sections 44 have generally semi-circular aligned openings at lateral sides thereof for receiving the pin 46 extending through the opening 40 of the inner rod 12. The proximal ends of the split collet sections 44 are tapered at 48 (FIG. 4) to permit the collet sections to pivot about pin 46 between opened and closed positions with a clearance along a diametrical plane. The proximal end of the collet sections also have split flanges 49 for reception in the open areas between the split flanges 32 of the outer sleeve 30 to facilitate assembly of the collet sections 44, distal end of inner rod 12 and the outer sleeve 30. The distal ends of collet sections 44 include jaws 50. Referring to FIG. 2, a first end plug 52 of a nuclear fuel rod F.R. includes a barbed end cap 54 having a flat end face 55 and a tapered distal end portion defining a groove or neck portion 56 with the body 58 of the end plug 52. The tapered and neck portions 54 and 56 are circular in configuration and form a barbed end on the end plug 52. The jaws 50 of the split collet sections are geometrically sized for reception about the neck portion 56 between the tapered section 54 and the main body 58 of the end plug 52. With this design, capture and retention of end plug 52 by barbed area 54 and neck 56 is fully mechanical and does not rely on springs or other ancillary moving parts. The opposite end of the nuclear fuel rod F.R. mounts a second or lower end plug 60 which is generally cylindrical in shape for reception in or a snap fit with a complementary-sized opening 61 in the lower tie plate L.T.P. To use the tool of the present invention to extract a fuel rod from a nuclear fuel bundle, the collet end of the extractor tool 10 is initially closed. With the collet closed, the extractor tool 10 is inserted axially into the fuel bundle through the spacer openings or ferrules in axial alignment with the end plug mounted on the fuel rod desired to be removed. The tool 10 may be inserted to the extent that the collet, i.e., the end faces of jaws 50, butts the end face 55 of the end plug 52. The tool may then be slightly backed off the end plug 52. The locking tube nut 24 is then rotated in a direction causing the outer tube 14 to be withdrawn relative to the inner rod 12. Upon withdrawal of the outer tube 14, the flanges 32 of the outer sleeve 30 cam against the split flanges 49 of the collet sections 44 to pivot the collet sections 44 about pin 46, displacing the jaws 50 away from one another into a collet-open position. Once opened, the extractor tool can be axially advanced to butt the end face 38 of the inner rod 12 against the end face of the end cap surface 55. With this abutting arrangement, the jaws 50 straddle the neck portion 56 of the end cap. By rotating the locking tube nut 24 in an opposite direction threading on locking sleeve 16, the outer tube 14 is advanced relative to the inner rod 12 whereby flanges 32 cam along the outer surfaces 43 of collet sections 44, displacing the sections 44 toward one another and the jaws 50 into the annular slot straddling neck portion 56. With the end cap thus engaged by the collet, the extractor tool and fuel rod can be withdrawn axially from the fuel bundle. In the event the fuel rod is stuck or cannot be readily axially withdrawn, a slide hammer 62 on the inner rod 12 can be impacted upwardly against the handle H or downwardly against the end 64 of the locking sleeve 16, the locking sleeve end or handle in effect forming anvils for the hammer. In this manner, the fuel rod can be jarred loose such that the extractor tool can then withdraw the fuel rod from the fuel bundle. It will be appreciated that a fuel rod can be disposed in a bundle using the tool hereof as an insertion tool. With the collet engaged about the upper end cap of the fuel rod, the fuel rod and extractor tool can be inserted into the bundle with the fuel rod passing through the openings or ferrules of the spacers. Because of the tapered end of the lower end plug 60, the fuel rod end plug 60 can be inserted or snapped into a complementary opening in the lower tie plate. The hammer and anvil arrangement can be employed to drive or further insert the fuel rod into the tie plate opening by impacting hammer 62 against sleeve 16. Upon final insertion of the fuel rod, the locking tube nut 24 can be threaded on sleeve 16 to withdraw the outer tube 14 relative to the inner rod 12 to displace the collet sections to a collet-open position whereby the tool can be displaced upwardly above the end plug. Once disposed above the end plug and before the collet can be withdrawn through the opening or ferrule of the spacers above the fuel rod end plug, the locking tube nut 24 is threaded on sleeve 16 to close the collet sections, thereby reducing the diameter of the collet to a size for reception through the spacer openings or ferrules to facilitate withdrawal of the tool 10 from the fuel bundle assembly. 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.