Patent Number: 045377413
Section: description

DETAILED DESCRIPTION OF THE INVENTION This invention is directed to a funnel structure adapted to be arranged at the outer open end of a length of cladding which will ultimately contain fuel pellets as a nuclear fuel pin. It is utilized on a fuel pin subassembly which facilitates loading of fuel pellets within the cladding. A funnel is held in place by a length of shrink tubing that encircles both the funnel and cladding outer surfaces. The tubing serves as a protective cover about the encircled portion of the cladding outer surfaces. It also facilitates axial removal of the funnel after loading of the cladding. A completed fuel pin subassembly is shown in FIG. 2. The subassembly consists of a length of cladding 10 having a welded end cap 11, shown as the bottom end of the fuel pin, and internal non-contaminated fuel pin hardware (not shown) adjacent the welded end cap 11. A fuel loading funnel 12 is mounted to the remaining open end of the fuel cladding 10. As shown in FIG. 2, the funnel 12 has an enlarged outer open end that leads to a reduced diameter neck. A conical transition section connects the open end of funnel 12 to its neck. The smaller neck is at least partially inserted into the open axial end of the cladding as a coaxial extension of it. The fit between the funnel neck and the cladding interior should be reasonably close, and the thickness of the funnel neck should be minimal. The funnel 12 is held within the length of cladding 10 by a continuous length of plastic shrink tubing 4. After placement overlapping a portion of both the funnel and cladding, the tubing 14 is shrunk diametrically by proper application of heat. It tightly encircles and grips both the cladding 10 and funnel 12. It maintains them as a unit during reception of fuel into the cladding through the funnel 12. The funnel 12 is designed to be discarded after the length of cladding 10 has been charged with fuel pellets. Removal of the funnel is accomplished by pulling tubing 14 as cladding 10 is retracted axially. Removal is facilitated by providing a slidable collar or ring 13 that surrounds cladding 10 beneath the shrink tubing 14. The coaxial ring 13 presents a rear annular shoulder 19 which can be engaged to pull ring 13, tubing 14 and funnel 12 as a unit. If desired, the shoulder 19 could be presented as part of that portion of funnel 12 enveloped under the shrink tubing 14. The tubing 14 preferably extends along the outer surface of cladding 10 an an outer protective element. It provides a cylindrical surface for engagement by resilient or inflatable seals. Particles embedded in the tubing 14 as a result of such sealing will be discarded with the tubing when it is removed. This minimizes contamination of the cladding itself. It is to be understood that the funnel 12 could have many different interior or exterior configurations, so as to match the physical shape and requirements of particular pellet loading devices. These modifications are not believed to be pertinent to the present disclosure, since they will not change the manner by which the funnel is related to the length of cladding. The foregoing description of the preferred embodiments of the invention has been presented for purposes of illustration and description. It is not intended to be exhaustive or to limit the invention to the precise form disclosed, and obviously many modifications and variations are possible in light of the above teaching. The embodiments discussed in detail were chosen and described in order to best explain the principles of the invention and its practical application to thereby enable others skilled in the art to best utilize the invention in various embodiments and with various modifications as are suited to the particular use contemplated. It is intended that the scope of the invention be defined by the claims appended hereto.