Patent Number: 047327308
Section: description

DESCRIPTION OF THE PREFERRED EMBODIMENTS Referring in detail to the drawings, there is illustrated in FIGS. 1 and 2 a first embodiment of the stuck fuel rod capping sleeve 10 of the present invention. The stuck fuel rod capping sleeve 10 is made up of two cylindrical members fastened together with outer sleeve 12 surrounding a longer inner sleeve 14. The outer sleeve 12 is made of a moderately ductile material (e.g., 304 stainless steel), while the inner sleeve 14 is made of a low work hardening, highly ductile material (e.g., Inconel 600). As shown in FIG. 3, the stuck fuel rod capping sleeve 10 is placed on a spent cylindrical fuel rod 16, which has become stuck in a fuel assembly. After the capping sleeve is in place, the capping sleeve together with the fuel rod 16 are severed through the use of a bolt cutter device 18. The bi-metallic capping sleeve provides strength to permit fracturing of the ceramic fuel without severing the fuel rod cladding upon the initial application of pressure by the bolt cutter 18. During the continued application of pressure, the fractured surfaces separate and there is a closure of each of the rod ends since the ductile flow of the inner sleeve 14 results in a barrier that restricts the release of radioactive fuel material. The bolt cutter 18, with a final application of pressure, fractures the outer sleeve and results in a separation of the upper and lower portions of the fuel rod 16 as illustrated in FIG. 4. The capping sleeve 10 does not hermetically seal the ends of the severed fuel rod 16. However, it does prevent the gross release of radioactive fuel material by leaving only a small residual opening 20, as shown in FIG. 5, to communicate with the interior of a fuel rod 16 after the fuel rod has been severed into two pieces. FIGS. 6 and 7 illustrate a second embodiment of the present invention. In this embodiment, the outer sleeve 12 has threads 22 at each end thereof. The inner sleeve 14 is provided with a tapered and split portion 24 at each end. Locking sleeves 26, each of which has interior threads 28, are threaded onto the threads 22 located at each end of the outer sleeve 12 prior to placement of the stuck fuel rod capping sleeve over the stuck fuel rod. Each sleeve 26 also has a tapered portion 30 which cooperates with the tapered and split portion 24 of the inner sleeve 14. The tapered portion 30 contracts the split portion 24 so that it grasps the fuel rod 16 when the locking sleeve 26 is threaded onto the outer sleeve in the manner shown in FIG. 7 with a fuel rod present in the stuck fuel rod capping sleeve. With this arrangement, the inner sleeve 14 provides a seal around the fuel rod 16. Each locking sleeve 26 also has threads 32 located on its outer surface. After the fuel rod 16 has been severed, the end of the rod may be completely sealed off through the use of a cap 34. As shown in FIG. 7, cap 34 has threads 36 on its interior surface which mate with the threads 32 on the exterior of the locking sleeve 26. Thus, after severing the fuel rod, the cap 34 is threaded onto each locking sleeve 26 to seal the severed end of the fuel rod 16. As noted previously, advancement of locking sleeve 26 through the engagement of threads 22 and 28 seals the shank of the fuel rod 16 to the inner sleeve. Through the use of this embodiment, a severed fuel rod can be completely sealed off so that release of radioactive debris is prevented. FIG. 8 illustrates a third embodiment of the present invention. In this embodiment, the outer sleeve 12 has an internal recess 37. The inner sleeve 14 is not utilized in this embodiment. An underwater epoxy 38 is packed into the recess prior to placement of the sleeve 12 on the stuck fuel rod 16. The sleeve 12 is placed on the fuel rod 16 and the rod is then severed before the epoxy hardens. The epoxy reduces the amount of fission product released by capturing fuel debris and locks the capping sleeve on the fuel rod when it hardens. The invention being thus described, it will be obvious that the same may be varied in many ways. Such variations are not to be regarded as a departure from the spirit and scope of the invention, and all such modifications as would be obvious to one skilled in the art are intended to be included within the scope of the following claims.