Induced nuclear reactions: processes – systems – and elements – Handling of fission reactor component structure within... – Storage container systems for new and/or irradiated core...
Reexamination Certificate
2000-06-19
2002-05-14
Jordan, Charles T. (Department: 3644)
Induced nuclear reactions: processes, systems, and elements
Handling of fission reactor component structure within...
Storage container systems for new and/or irradiated core...
C250S506100
Reexamination Certificate
active
06389093
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates to a storage/transport container for nuclear elements. More particularly this invention concerns such a container for heat-evolving nuclear-fuel elements.
BACKGROUND OF THE INVENTION
A transport/storage container for spent nuclear-fuel elements normally has spaced steel inner and outer side walls defining an annular space extending along an axis, a cover at one end of the side walls, a floor at an opposite end of the side walls, and a filler such as concrete in the space between the inner and outer side walls. Normally such a container is cylindrical and its interior is filled with heat-evolving radioactive waste, normally spent fuel rods that may be held in special baskets as described in commonly owned patent application Ser. No. 09/550,742 (now U.S. Pat. No. 6,256,363 issued Jul. 3, 2001).
The contents of such a container evolve heat which must be dissipated. Accordingly it is known to install a first array of heat-conducting reinforcement rods inside the inner side wall extending parallel to the container axis, a second array of such rods in the concrete-filled space between the inner and outer side walls, and short connecting rods extending through the inner side wall between the first and second arrays. Such a system conducts the heat to the cover and floor, but little heat is transmitted to the outer side wall so that the container's contents can get excessively hot in center regions of the container.
OBJECTS OF THE INVENTION
It is therefore an object of the present invention to provide an improved transport/storage container for heat-evolving radioactive waste.
Another object is the provision of such an improved transport/storage container for heat-evolving radioactive waste which overcomes the above-given disadvantages, that is which surely and efficiently conducts heat from the contents of the container to the outer side wall which typically is immersed in a body of water designed to carry away such heat.
SUMMARY OF THE INVENTION
A transport/storage container for spent nuclear-fuel elements has according to the invention spaced inner and outer side walls defining an annular space extending along an axis, a cover at one end of the side walls, a floor at an opposite end of the side walls, and a plurality of heat-conducting elements in the space and each having one edge fixed, for instance by welding or bolting, to one of the side walls and an opposite edge bearing radially elastically on the other of the side walls.
According to the invention therefore one end of each metal element is firmly connected to the inner side wall or outer side wall and its other element abuts the opposite part of the container side wall, i.e. the inner side wall or outer side wall, under prestress without a firm connection. The metal elements therefore resiliently abut the opposite part of the container side wall. A “firm connection” to the inner side wall or outer side wall according to the invention means a connection which cannot be easily broken, particularly a connection by welding or screwing or bolting. “Abutting under prestress” according to the invention, on the other hand, means that there is no firm connection between the relevant end of the metal element and the inner side wall or outer side wall but that the end is simply pressed by the prestressing force.
Optionally according to the invention the metal elements are connected to metal elements for reinforcing the inner side wall and/or outer side wall. The reinforcing elements are preferably U-profiles, both arms of the U advantageously projecting into the space between the inner side wall and the outer side wall. In one embodiment of the invention the ends of the metal elements are connected to respective arms of the U-shaped reinforcing elements. Optionally according to the invention the reinforcing elements are of metal, preferably steel. The reinforcing elements, preferably U-profiles, stiffen the outer side wall and inner side wall and also bond the filler, preferably concrete. The reinforcing elements, preferably U-profiles, therefore have a strength-increasing effect. In a preferred embodiment U-profiles are provided at least on the inside of the outer side wall. Advantageously the spacing between the U-profiles is less than 15 cm.
In the last-mentioned preferred embodiment the reinforcing elements on the inner side wall need not be U-profiles. Alternatively according to the invention the reinforcing elements on the inner side wall are in the form of strips and are attached to the inner side wall, e.g. by screws. In a preferred embodiment the screw connection can be by nuts and bolts, the bolts being preferably directly welded to the outer side wall or inner side wall. Besides serving as stiffening elements, another function of the reinforcing elements is to transmit heat.
In a preferred embodiment of the invention one end of each metal element is firmly connected to the inner side wall and the other end abuts the outer side wall under prestress, thus forming a heat-conducting connection. Preferably each metal element is firmly connected to an element for reinforcing the inner side wall. In a highly preferred embodiment which is particularly important according to the invention, the metal elements are metal sheets. The firm connection is a welded connection or a screw connection. Optionally according to the invention the reinforcing elements are U-profiles mounted on the outer face of the inner side wall, and the metal elements or metal sheets are fastened to respective arms of the U-shaped profiles on the inner side wall.
The reinforcing elements provided on the outer face of the inner side wall may in principle have a different shape. For example according to the invention the reinforcing elements on the inner side wall may alternatively be reinforcing strips to which the metal elements or metal sheets can advantageously be screwed, or directly screwed to bolts welded to the inner side wall. According to a highly preferred embodiment of the invention the other ends of the metal elements, preferably metal sheets, abut under prestress against elements for reinforcing the outer side wall, the reinforcing elements being distributed over the periphery of the container on the inner surface of the outer side wall. Preferably according to the invention the reinforcing elements are U-profiles and advantageously the other end of each metal element or metal sheet abuts an arm of a U-profile under prestress. The reinforcing elements, preferably U-profiles, extend over the entire height of the container parallel to the central axis of the container.
With regard to the firm connection between one end of each metal element and the inner side wall, there are two preferred embodiments. In one preferred embodiment, use is made of steel metal sheets having a thickness of 6 mm to 8 mm. In a first option according to the invention, these metal sheets are welded to U-profiles on the inner container. The metal sheets can also be screwed to the inner container via reinforcing strips. Another possibility is to screw the metal sheets to bolts welded to the inner container. In the two last-mentioned embodiments with screwing, the metal sheets are advantageously bent before assembly, the bent arms being preferably drilled out for screwing. In another preferred embodiment of the invention, the metal sheets are of copper, preferably between 1 mm and 3 mm thick. According to a feature of this embodiment, the copper metal sheets are screwed to reinforcing strips on the inner container. According to another feature of this embodiment the copper metal sheets are screwed to bolts welded to the inner container.
According to another embodiment of the invention the metal elements, preferably metal sheets, are firmly connected alternately to the inner side wall or outer side wall, preferably by screwing. In a preferred embodiment of the invention the container according to the invention is manufactured as follows: first the metal elements, preferably metal sheets, are firmly connected at one end to t
Diersch Rudolf
Gluschke Konrad
Heidenreich Joachim
Methling Dieter
Dubno Herbert
GNB Gesellschaft fur Nuklear-Behalter mbH
Smith Kimberly S.
Wilford Andrew
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