Induced nuclear reactions: processes – systems – and elements – Handling of fission reactor component structure within... – Storage container systems for new and/or irradiated core...
Patent
1997-08-26
1998-11-10
Jordan, Charles T.
Induced nuclear reactions: processes, systems, and elements
Handling of fission reactor component structure within...
Storage container systems for new and/or irradiated core...
2505061, G21F 500, G21C 1900
Patent
active
058355480
DESCRIPTION:
BRIEF SUMMARY
The invention relates to a capsule for storing spent nuclear fuel, comprising a cylindrical part which includes a steel cylinder tightly embraced by a copper layer whose thickness is in the same order as the thickness of the cylinder wall. The invention also relates to a method of manufacturing such capsules for the storage of spent nuclear fuel.
It is necessary to finally store spent nuclear fuel deep in primary-rock cavities, with the fuel encapsulated or contained in capsules that are able to withstand all conceivable forms of corrosion and also be mechanically stable and prevent the emission of radio activity. Accordingly, it has been proposed in Sweden, among other countries, that the capsules shall be comprised of steel tubing embraced by a copper shell with a radiation-protective layer of lead on the inside thereof. The copper shell shall have a prescribed thickness of 50 mm and shall be capable of resisting any form of corrosion to which the capsules can conceivably be subjected over the period in which harmful quantities of radio activity still remain in the fuel. The copper shell shall also prevent the steel cylinder from being subjected to corrosion attack during this period. This requirement places very high demands on the fit between copper shell and steel cylinder and very strict specifications apply with regard to the steel-copper interface tolerances. This means that the outer surface of the steel cylinder and the inner surface of the copper cylinder that is to form the copper shell must be machined with great accuracy. Since each capsule is about 5 m in length and has a diameter of 0.9 m and weighs about 10 tonnes, the manufacture of such capsules presents significant problems with regard to the aforesaid requirements placed on the fit of the steel cylinder and copper shell and the tolerances relating thereto. The manufacture of such capsules from a steel cylinder and a copper shell as proposed in the aforesaid documents involves the following working operations: welded. degree of fineness (to meet the required steel-copper tolerance). mm. impervious cylinder. surface fineness that fulfills the prescribed steel-copper tolerance and so that the steel cylinder can be inserted into the copper cylinder.
It will readily be understood that these technical operations are difficult to carry out in view of the heavy weight concerned and that the operations are extremely onerous and also costly due to the fit required between steel and copper.
U.S. Pat. No. 4,527,065 proposes a spent nuclear fuel container made of cast steel or cast iron which is provided on its outer surface with a corrosion-resistant protective layer. The document proposes primarily a protected layer of ceramic, graphite or enamel because of the good corrosion properties of these materials, although it also mentions that a metal protective layer may be applied galvanically or with the aid of thermal spraying techniques. Because of the dissimilarity between the protective layer and the container body, leading to voltages between the mutually abutting surfaces, with the danger of cracks being formed and the protective layer loosening from the container body, the publication considers the application of a layer onto the large surface areas of the container to be a technically complicated and drawn-out procedure. It is therefore suggested in the document that the surface of the container is divided into several smaller sections that are partitioned-off with intermediate, outwardly projecting strips which are intended to take-up expansion stresses between protective layer and container and also to improve adhesion of the protective layer by virtue of each part surface of the protective layer being clamped firmly between the strips. Naturally, this proposed solution to the problem of storing radioactive material has not been given any weight by the authorities responsible for such storage, since protective layers that are comprised of the brittle materials referred to particularly in the proposal, for instance enamel, graphite and ceram
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patent: 895163 (1908-08-01), Cowper-Coles
patent: 4486512 (1984-12-01), Tozawa et al.
patent: 4527065 (1985-07-01), Popp et al.
patent: 4659540 (1987-04-01), Cheng et al.
Lindgren Per-Olov
Pettersson Joakim
Boliden Contech AB
Jordan Charles T.
Lattig M. J.
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