GB2032329A - A shielding container - Google Patents

Abstract

A shielding container for transporting and/or storing burnt-up nuclear fuel elements comprises a jacket (1), a base (2) and a cover (3) flanged to the jacket, the base being screwed into the jacket. The container is made of cast iron or cast steel, and except when alloyed cast steel is used, is lined with fine steel. Prior to the base (2) being screwed in and the cover (3) attached, the interior of the jacket (1) is machined from both ends to the narrow tolerances required. <IMAGE>

Description

SPECIFICATION A shielding container for transporting and/or storing burnt-up fuel elements.

This invention relates to a shielding container for transporting and/or storing burnt-up nuclear fuel elements essentially consisting of a jacket, a base and a cover flanged to the jacket.

Burnt-up fuel elements from nuclear reactors have to be transported and stored in containers which safely contain the radioactivity of the material and which shield off from the outside the radioactive radiation which is released during the decay process. Accordingly, they have to be robust and thick-walled in construction.

At the same time, however, the containers also have to be able reliably to dissipate the heat of decay to the outside. Accordingly, the burnt-up fuel elements are generally accommodated inside the container in baskets of a highly-conductive material to enable the heat of decay of the fuel elements in the central region of the container as well to be dissipated to the inner wall of the container. To this end, the gap between the basket and the container has to be kept very narrow to avoid a build-up of heat in this air gap which is a poor conductor of heat.

Accordingly, the internal dimensions of the container are subject to very narrow tolerances.

in addition, the containers are required to have smooth, gap-free and corrosion-resistant inner surface, as is normal in the nuclear field, to enable the emptied container to be cleaned and decontaminated.

The transporting containers hitherto used generally satisfy these requirements. They are generally made of forged steel jacket with a welded-on base.

Their inner surface is normally lined with fine steel.

However, these known containers are attended by the disadvantage that their production is very timeconsuming and expensive which makes them uneconomical to use in particular as storage containers.

Accordingly, container constructions which are quicker and less expensive to manufacture have already been proposed. Thus, according to German Utility Model No. 77 28331 for example, the containers are directly cast from spherolitic cast iron or cast steel with an integrally cast base and a corrosionresistant metal layer is applied by electrodecomposition as the inner lining.

In this method of production, however, the internal dimensions are subject to the usual casting tolerances. In view of the length of the container determined by the shape of the fuel elements, and where the base is integrally formed, subsequent machining to the narrow tolerances required is only possible at very considerable expense.

Accordingly, an object of the present invention is to provide a shielding containerfortransporting and/or storing burnt-up fuel elements essentially consisting of a jacket, a base and a cover flanged to the jacket which combines the high precision of the known forged steel containers and the inexpensive production of the likewise known cast iron containers. In particular, the interior of the container is intended to be able to be readily machinable after production despite the considerable length of the container.

The present invention provides a shielding con tainer for transporting and/or storing burnt-up nuclear fuel elements comprising a jacket, a base and a cover flanged to the jacket, the base being screwed into the jacket.

The invention is illustrated in the accompanying drawing which is a diagrammatic longitudinal section through one example of an embodiment of a shielding container according to the invention. It consists of a jacket tube (1) initially open at its upper and lower ends, a base (2) screwed into this tube at its lower end and a cover (3) flanged to the top of the tube. The jacket tube (1) is preferably cast from cast steel or cast iron in the complete cylindrical length of the finished coritainer. The interior may then be machined to the narrow tolerances required from both ends using the tools. Only then is the base (2) screwed in and the cover (3) attached, both the base and the cover again preferably being made of cast steel or cast iron.

Where non-alloyed cast steel is used, the interior of the shielding container may readily be lined with fine steel in the same way as in the hitherto known transporting containers. In addition, before the cast base (2) is screwed in, a thin fine steel base may be welded gap-free to the fine steel lining. This produces a smooth, gap-free and decontaminatable inner surface which satisfies all requirements.

Where alloyed cast steel is used, there is no need for an internal lining provided that the machined inner surface is smoothed by standard techniques to such an extent that it is equivalent to a surface lined with fine steel and provided that the base screwed in is internally welded to the jacket without any gaps.

The shielding container according to the invention has the advantage over hitherto known containers that is combines the high precision of the the internal dimensions of the hitherto used transporting containers of forged steel with the rapid and inexpensive production of the transporting and/or storage containers of cast steel or cast iron.

1. Ashielding containerfortransporting and/or storing burnt-up nuclear fuel elements comprising a jacket, a base and a cover flanged to the jacket, the base being screwed into the jacket.

2. A shielding container as claimed in Claim 1, wherein one or more of the individual components consists of cast iron or cast steel.

3. A shielding container as claimed in Claim 1 or 2, wherein the inner walls of the individual components are lined with fine steel.

4. A shielding container for transporting and/or storing burnt-up nuclear fuel elements substantially as described with particular reference to the accompanying drawing.

**WARNING** end of DESC field may overlap start of CLMS **.

Claims (4)

**WARNING** start of CLMS field may overlap end of DESC **. SPECIFICATION A shielding container for transporting and/or storing burnt-up fuel elements. This invention relates to a shielding container for transporting and/or storing burnt-up nuclear fuel elements essentially consisting of a jacket, a base and a cover flanged to the jacket. Burnt-up fuel elements from nuclear reactors have to be transported and stored in containers which safely contain the radioactivity of the material and which shield off from the outside the radioactive radiation which is released during the decay process. Accordingly, they have to be robust and thick-walled in construction. At the same time, however, the containers also have to be able reliably to dissipate the heat of decay to the outside. Accordingly, the burnt-up fuel elements are generally accommodated inside the container in baskets of a highly-conductive material to enable the heat of decay of the fuel elements in the central region of the container as well to be dissipated to the inner wall of the container. To this end, the gap between the basket and the container has to be kept very narrow to avoid a build-up of heat in this air gap which is a poor conductor of heat. Accordingly, the internal dimensions of the container are subject to very narrow tolerances. in addition, the containers are required to have smooth, gap-free and corrosion-resistant inner surface, as is normal in the nuclear field, to enable the emptied container to be cleaned and decontaminated. The transporting containers hitherto used generally satisfy these requirements. They are generally made of forged steel jacket with a welded-on base. Their inner surface is normally lined with fine steel. However, these known containers are attended by the disadvantage that their production is very timeconsuming and expensive which makes them uneconomical to use in particular as storage containers. Accordingly, container constructions which are quicker and less expensive to manufacture have already been proposed. Thus, according to German Utility Model No. 77 28331 for example, the containers are directly cast from spherolitic cast iron or cast steel with an integrally cast base and a corrosionresistant metal layer is applied by electrodecomposition as the inner lining. In this method of production, however, the internal dimensions are subject to the usual casting tolerances. In view of the length of the container determined by the shape of the fuel elements, and where the base is integrally formed, subsequent machining to the narrow tolerances required is only possible at very considerable expense. Accordingly, an object of the present invention is to provide a shielding containerfortransporting and/or storing burnt-up fuel elements essentially consisting of a jacket, a base and a cover flanged to the jacket which combines the high precision of the known forged steel containers and the inexpensive production of the likewise known cast iron containers. In particular, the interior of the container is intended to be able to be readily machinable after production despite the considerable length of the container. The present invention provides a shielding con tainer for transporting and/or storing burnt-up nuclear fuel elements comprising a jacket, a base and a cover flanged to the jacket, the base being screwed into the jacket. The invention is illustrated in the accompanying drawing which is a diagrammatic longitudinal section through one example of an embodiment of a shielding container according to the invention. It consists of a jacket tube (1) initially open at its upper and lower ends, a base (2) screwed into this tube at its lower end and a cover (3) flanged to the top of the tube. The jacket tube (1) is preferably cast from cast steel or cast iron in the complete cylindrical length of the finished coritainer. The interior may then be machined to the narrow tolerances required from both ends using the tools. Only then is the base (2) screwed in and the cover (3) attached, both the base and the cover again preferably being made of cast steel or cast iron. Where non-alloyed cast steel is used, the interior of the shielding container may readily be lined with fine steel in the same way as in the hitherto known transporting containers. In addition, before the cast base (2) is screwed in, a thin fine steel base may be welded gap-free to the fine steel lining. This produces a smooth, gap-free and decontaminatable inner surface which satisfies all requirements. Where alloyed cast steel is used, there is no need for an internal lining provided that the machined inner surface is smoothed by standard techniques to such an extent that it is equivalent to a surface lined with fine steel and provided that the base screwed in is internally welded to the jacket without any gaps. The shielding container according to the invention has the advantage over hitherto known containers that is combines the high precision of the the internal dimensions of the hitherto used transporting containers of forged steel with the rapid and inexpensive production of the transporting and/or storage containers of cast steel or cast iron. CLAIMS

1. Ashielding containerfortransporting and/or storing burnt-up nuclear fuel elements comprising a jacket, a base and a cover flanged to the jacket, the base being screwed into the jacket.

2. A shielding container as claimed in Claim 1, wherein one or more of the individual components consists of cast iron or cast steel.

3. A shielding container as claimed in Claim 1 or 2, wherein the inner walls of the individual components are lined with fine steel.

4. A shielding container for transporting and/or storing burnt-up nuclear fuel elements substantially as described with particular reference to the accompanying drawing.