Basket for radioactive-waste container

Abstract

A radioactive waste container according to the invention has a waste-holding basket formed of two layers of respective dissimilar materials. The layers have faces engaging each other and are bonded together over their entire engaged faces.

Description

FIELD OF THE INVENTION

[0001] The present invention relates to a radioactive-waste container. More particularly this invention concerns a basket adapted to hold spent fuel rods or the like in a radioactive-waste container.

BACKGROUND OF THE INVENTION

[0002] As described in U.S. Pat. No. 6,256,363 a transport/storage container for spent nuclear-fuel elements has a vessel having a side wall with an inner surface defining an interior extending along an axis and a plurality of like sections forming a basket extending substantially a full axial length of the interior and forming a plurality of axial full-length rectangular-section wells adapted to receive the spent fuel elements. Each of the sections is formed of two long light-metal neutron-absorbing plates crossing each other, each having a pair of outer ends directly engaging the inner surface of the side wall in heat-transmitting contact therewith, and subdividing the interior at the respective section into a plurality of segments. A plurality of short light-metal neutron absorbing plates are fitted together in each of the segments and form with the main plates of the respective section rectangular-section axially throughgoing openings forming the wells with the plates of the other sections.

[0003] Such a basket fulfills several functions. First of all it physically contains and separates the radioactive elements being stored or transport from one another, to which end it must be fairly strong as these rods are very heavy. Furthermore it must have good neutron-shielding capacity for obvious shielding purposes. Finally the basket must be able to conduct heat readily from the decaying elements to the outer wall of the container.

[0004] As a result the basket is typically made of sheet or plate material having at least two layers. One layer is selected for strength and heat transmission and typically is high-strength stainless steel. The other layer is typically a boron-alloyed or boron-containing metal whose primary function is maintaining subcriticality, or shielding. In addition it is possible to use also copper or aluminum to maximize heat transmission.

[0005] These layers are very difficult to join together. Typically welds are used, which means that there are gaps or spaces between the layers. As a result, heat transmission is reduces because of the spaces. Furthermore these spaces can trap water and create subsequent corrosion problems. Finally the welding invariably weakens at least the boron-containing layer, reducing the overall strength of the basket. The only way to make such a multilayer basket strong enough is to use fairly thick plate material, increasing the weight of the basket and reducing the space available for the radioactive material being stored.

[0006] Another disadvantage of the known systems is that they are fairly expensive to manufacture. The techniques for welding together such disparate materials are somewhat complex, and at best yield poor results.

OBJECTS OF THE INVENTION

[0007] It is therefore an object of the present invention to provide an improved basket for a radioactive-waste container.

[0008] Another object is the provision of such an improved basket for a radioactive-waste container which overcomes the above-given disadvantages, that is which shields and conducts heat well and that is quite strong.

SUMMARY OF THE INVENTION

[0009] A radioactive waste container according to the invention has a waste-holding basket formed of two layers of respective dissimilar materials. The layers have faces engaging each other and are bonded together over their entire engaged faces.

[0010] Joining the two layers of the basket over their entire surfaces ensures that there are no air gaps between them, greatly increasing the strength of the assembly even though it might include a relatively weak boron-containing metal. Furthermore the elimination of any air spaces between the layers ensures that heat will be efficiently transmitted by them to the surrounding container. The layer of radiation-blocking material is also continuous and of uniform thickness so it offers maximum shielding with no leak spots.

[0011] The surface bond with no spacing according to the invention can be done by roller plating, that is rolling together two sheets of metal under very high pressure with or without an intermediate bonding layer, by high-pressure hydroforming in particular when nonflat shapes are needed, or even by explosive plating. What is important in accordance with the invention is that the confronting surfaces of the two layers are joined together at the molecular level over their entire abutting surfaces, with or without the interposition of an intermediate bonding layer with which both layers are molecularly bonded.

[0012] In accordance with the invention one of the layers is made of copper, a copper alloy, aluminum, an aluminum alloy, borated stainless steel and/or a boron-containing metal alloy and the other layer is made of high-strength stainless steel. The high-strength steel layer acts as the support and supplies most of the strength to the basket while the other layer functions more for shielding. Both layers can conduct heat away and, since they are intimately joined together, will conduct between each other very efficiently.

BRIEF DESCRIPTION OF THE DRAWING

[0013] The above and other objects, features, and advantages will become more readily apparent from the following description, reference being made to the accompanying drawing whose sole figure is a largely diagrammatic representation of the invention.

SPECIFIC DESCRIPTION

[0014] As seen in the drawing a spent radioactive fuel rod shown partly at 3 is held in a container shown partly at 4 in a similarly partially shown basket comprised of a pair of layers 1 and 2. The layers 1 and 2 have confronting faces 1′ and 2′ that are secured molecularly together at a bond 5 that extends over the entire areas of these faces 1′ and 2′. This bond 5 is produced here by roller plating, that is pressing two sheets or plates together between rollers with such force that they bond together.

[0015] In accordance with the invention the layer or lamina 1 is made of copper, a copper alloy, aluminum, an aluminum alloy, borated stainless steel and/or a boron-containing metal alloy. The other layer or lamina 2 is made of high-strength stainless steel. The two layers 1 and 2 are unitarily joined together at the faces 1′ and 2′ in surface contact, that is bonded on a molecular level.

[0016] The bond 5 can also be a sheet bonding layer between the faces 1′ and 2′ unitarily bonding same together.

Claims

1. In a radioactive waste container, a waste-holding basket formed of two layers of respective dissimilar materials, the layers having faces engaging each other and being bonded together over their entire engaged faces.

2. The basket defined in claim 1 wherein one of the layers is made of copper, a copper alloy, aluminum, an aluminum alloy, borated stainless steel or a boron-containing metal alloy and the other layer is made of high-strength stainless steel.

3. The basket defined in claim 1 wherein the layers are joined unitarily in surface contact.

4. The basket defined in claim 1, further comprising

a layer of bonding material between the faces unitarily bonding the layers together.