US3068035A - Unloading device, particularly for fuel elements of nuclear reactors - Google Patents

Description

Dec. 1l, 1962 s. FOG

UNLOADING DEVICE. PARTICULARLY LIA Figs

United States Patent O 3,068,035 UNLOADING DEVICE, PARTICULARLY FOR FUEL ELEMENTS F NUCLEAR REACTORS Sebastien Foglia, Verrieres Le Buisson, France, asslgnor to Commissariat a lEnergie Atomique, Paris, France Filed Feb. 5, 1960, Ser. No. 7,010 Claims priority, application France Feb. 18, 1959 2 Claims. (Cl. 294-102) Various types of heterogeneous nuclear reactors comprise an active core including a num-ber of rods of a ssile fuel such as uranium, located in vertical bores. Handling of the rods, particularly to remove them from the reactor, is carried out by means of suitable pinchers which grasp them at their upper end, which may or may not be previded with a special head.

If for any reason the upper end of the rod is broken off or damaged so badly as to make it impossible to use conventional pinchers, removal of the rod presents a difcult problem, all the more embarrassing to solve due to the radioactive medium. The same difficulties are met when it is desired to remove a sheath, for example a graphite sheath or even a broken control or safety rod.

The object of the present invention is to provide an unloading device for fuel elements of nuclear reactors, which makes it easy to remove from a reactor fuel rods, sheaths or control rods which have undergone such damage as to make it impossible to use conventional unloading means.

The device is essentially characterized in that it comprises a heavy cylindrical body provided at the bottom with three vertical fingers each of which has a recess on its face coming in contact with the element to be removed, a ball or roller located in each recess engaging the element when the device is raised.

The device according to the invention is very simple to manufacture and to use, and may be employed to unload not only fuel rods, but also the sheaths or sleeves. In effect all that is required is to provide recesses containing blocking balls on the desired faces of the fingers. By providing two recesses on the opposite operative faces of the fingers the device may even be used to unload simultaneously a fuel rod and its graphite sheath.

An embodiment of the unloading device according to the invention will be described hereinafter by way of nonlimiting example, with reference to the accompanying schematical FIGURES 1 to 3. The features which will be disclosed with reference to this embodiment shall be considered a part of the invention, it being understood that equivalent features may also be employed within the scope of the invention.

In the drawings:

FIG. 1 is a vertical longitudinal section of the unloading device according to the invention, shown in operative position with respect to a rod as well as to its sheath.

FIG. 2 is a view in detail of one of the fingers of the device.

FIG. 3 is a section on line a-a of FIG. 2.

In FIG. l it is seen that the unloading device according to the invention consists of a body 1 of circular cross-section provided at the top with a ring 2 for securing a lifting cable, and at the bottom with three vertical fingers 3. The fingers 3 are angularly spaced 120 from each other, and their internal faces 4 enclose a cylinder of diameter corresponding to the diameter of a rod 5 which is to be unloaded. In other words when the device is placed in position the faces 4 slide with some play on the peripheral surface of the rod. The width of the fingers in a radial direction is such that these can enter without hindrance between the rod 5 and the wall of the bore in which it is contained, or between the rod and a sheath 6 which surrounds it, if such a sheath is provided as shown. If the 3,068,035 Patented Dec. 11, 1962 device is to be used to lift out such a sheath 6, the external faces of the lingers are spaced from the axis of the device a distance such that they slide with some play on the inner wall of the sheath 6.

Each finger of the device has an elongated recess 7 on its inner face if the element to be removed is a rod or the like, or a recess 7' on its outer face if the element to be removed is, for example, a sheath. In the drawings two recesses, 7 and 7', have Ebeen shown on each finger, in which case the device may be used to remove simultaneously a rod and a sheath, but it is understood that only one set of recesses, 7 or 7', may be provided if it is desired to limit the use of the device to only one of these two types of elements.

FIGS. 2 and 3 illustrate in greater detail the construction of one of the fingers of the device. The finger is formed as a bar 8 of rectangular cross-section, pointed at its end, and of suitable length. At a short distance from its point the bar has a recess 7 on the inner face of the finger, and a recess 7 on the outer face. The recesses are at different horizontal levels to avoid excessive thinning of the section of the finger, and they are formed aS elongated triangles, as shown in FIG. 2. The recess 7 has located in it a Iball (or roller) 9 and the recess 7' a ball (or roller) 9. The balls or rollers are kept in place laterally by two strips 10 and 11 secured to the bar 8 forming the iinger. The strips, as shown in FIG. 3, have in cross-section the shape of a flattened T and comprise two flanges such as 12 and 13, each of which terminates in a small lip 14. Thus, for example, the ball 9 is free to move within the space formed by the recess 7 and strips 10 and 11, but it cannot fall out of this space. The same goes for the ball 9' and for the balls of the other fingers which are all mounted in the same way. The operation of the unloading device according to the lnvention is as follows. For example, a fuel rod 5 (FIG. l) and its graphite sheath 6 are to be removed from a lbore. Hung from a cable by the ring 2, the device is lowered by gravity into the bore wherein it is guided by the cylindrical surface of the body 1. The fingers 3 engage between the rod and the sheath, and the balls (or rollers) withdraw within the recesses by traveling inwardly therein. After the fingers are sufiiciently engaged the device is pulled back upwardly; the balls located n the recesses 7 are wedged in the cavities formed by the recesses and by the surface of the rod, thus securing together the rod and the fingers. Similarly the balls in recesses 7 are wedged in the lower part of their recesses, thus securing together the sheath 6 and the fingers 3. Therefore the device as it moves up carries along with it the rod 5 and its associated sheath 6. Once these elements are removed from the bore, and if they are not radioactive, it is sutiicient to turn them upside down, in order to release the device. If they are too radioactive the device is disposed of together with them, since its price is lower than the cost of decontaminating it.

As mentioned above the device according to the invention may comprise either a set of internal recesses for handling rods or the like, or a set of external recesses for handling sheaths or the like, or as in the embodiment described, both internal and external recesses. To ensure a better hold, more than one recess may be provided on each face of the fingers.

It can be seen from the foregoing description that the device is easy to manufacture and operate, which makes it widely applicable, it may be operated from a distance and is therefore of particular interest for the handling of radioactive elements.

Of course the invention is not limited to the embodiment illustrated and described, which has been given merely by way of example.

The embodiments of the invention in which an exclusive property or privilege is claimed are defined as follows:

1. In an unloading device for fuel elements having a core and a sheath spaced therefrom, a heavy cylindrical body, at least three fingers extending from said body parallel to the longest length thereof and spaced symmetrically with respect to each other for insertion between the sheath and the core of the fuel element, surfaces on each of said lingers disposed parallel to the adjacent surface of the sheath and of the core respectively, a groove in each of said surfaces, said grooves in each of said fingers being spaced apart along the length thereof, a bottom for each of said grooves inclined downwardly toward the adjacent surface on the nger and a ball mounted in each of said grooves for movement into wedging engagement with the 15 2,514,760

4 adjacent surface of the fuel element when said device iS raised.

2. A device as described in-claim 1 in which each of said ngers comprises a bar of rectangular cross section, a plate secured to each of two opposed surfaces of said bar and extending beyond the other opposed surfaces of said bar and inturned edges on said plates, said balls being mounted between said plates and within said inturned edges.

References Cited in the tile of this patent UNITED STATES PATENTS 1,509,565 Oswald Sept. 23, 1924 1,618,851 Thunberg Feb. 22, 1927 Hanson et al July 11, 1950

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