Patent Number: 060581549
Section: description

DESCRIPTION OF THE PREFERRED EMBODIMENTS As shown in FIG. 2, the invention appears particularly simple to construct and implement and the container assembly has a perfectly smooth, cylindrical outer surface and its entire length is free from rough projections. In FIG. 2, reference (1) is the thin wall of the tubular body of the multi-purpose canister, (2) is the inner cavity designed to house the irradiated fuel assemblies placed in an appropriate holder. The upper end (10) of the tubular body may have the same thickness as the body but here it has been welded on and has a slight additional thickness inside said tubular body. Like the tubular body it is circular in cross-section except for certain places, for example when the shoulder (11) does not run around the entire periphery of the inner wall of the tubular body, as will be seen below. The external walls of the tubular body (vertical in this example) and its upper end (10), which may be added on, are aligned so that there are no projections capable of causing an obstruction. The optional internal overthickness gives the upper end (10) of the unit increased rigidity so that the guaranteed leaktightness of the apparatus according to the invention is improved without reducing the capacity of said unit. The upper end (10) has a shoulder (11) cut into the inner wall; this shoulder may be cut into the entire periphery of said inner wall or only part thereof. The shoulder ensures that the support for the bearing disk or collar (12) is stable. The bearing disk or collar is circular and has an upper surface, a lower surface and a cylindrical lateral wall. On the upper surface of the circular bearing disk or collar (12) is placed a first solid disk (13). The periphery of said solid disk (13) essentially of circular shape comprises sealing means comprising a bevel (14) cut into the periphery of its lower edge and an O-ring (15) that is usually made of metal placed in the housing created by said bevel (14). The metal seal may be of the Helicoflex.TM. or any other type of metal seal having similar properties. In another embodiment the first solid disk (13), which is in the lower position, bears directly on the shoulder (11). Leaktightness is ensured by the O-ring (15) between the circular cross-section vertical cylindrical inner wall of the upper end (10), or the end of tubular body (1) where no specific end-piece has been added, and either the surface of the bevel or the upper horizontal surface of the support disk. This embodiment using a support disk is particularly advantageous since it compresses the O-ring (15) and ensures leaktightness when the shoulder (11) is not cut into the entire periphery of the inner wall. It achieves this in particular because said leaktight seal is partly obtained due to pressure of the seal on the vertical section of the inner wall. In order to both guarantee improved leaktightness and improve testing of the leaktightness obtained, a second solid disk (13') that is identical to first solid disk (13), complete with bevel (14') and metal seal (15') is placed on the upper surface of the disk (13). Seal (15') is also compressed due to the action of the upper surface of the first solid disk (13) in lower position on which it is placed. The gripping apparatus (16) is entirely located inside the upper end (10) of tubular body (1). This is normally of known type and comprises gripping means that operate in conjunction with the inner wall, thereby making the closure of the unit leaktight by compressing the seals (15, 15') and pressing vertically on the upper disk. It will be seen that, as the assembly is tightened, the seals (15, 15') are compressed to create a leaktight seal between the bevels of the first and second solid disks (13) and (13') and the inner wall of the upper end (10) of the end of the tubular body (1). The number of solid disks may simply be increased to give further improvements in the degree of leaktightness required. It will be seen that the reversible closure apparatus of the invention is easy to produce. It also allows a multi-purpose canister to pass all the way through an over-pack from one end to the other and also gives a high degree of leaktightness and mechanical resistance that meets the requirements of the safety regulations.