Container for radioactive inventory and method of making same

Abstract

A container for radioactive inventory has an end wall, a side wall, and a container lid that form a closed chamber for the radioactive inventory. A plastically deformable layer is provided between the container lid and the inventory and is of such a composition that, in the event of an impact of the inventory against the container lid, at least a majority of the impact forces are uniformly distributable over at least a majority of a surface of the plastically deformable layer.

Claims

1. A container for radioactive inventory comprising: an end wall, a side wall, and a container lid that form a closed chamber for the radioactive inventory; a plastically deformable layer between the container lid and the inventory and of such composition that, in the event of an impact of the inventory against the container lid, at least a majority of the impact forces are uniformly distributable over at least a majority of a surface of the plastically deformable layer.

2. The container defined in claim 1, wherein the plastically deformable layer has a specific energy absorption of 10 to 50 J/cm.sup.3 in a vertical direction.

3. The container defined in claim 1, wherein the plastically deformable layer is isotropically deformable.

4. The container defined in claim 1, wherein the plastically deformable layer is a metal foam.

5. The container defined in claim 4, wherein the plastically deformable layer contains aluminum.

6. The container defined in claim 1, wherein the plastically deformable layer is encapsulated or coated.

7. The container defined in claim 1, wherein the plastically deformable layer has a thickness of 30 to 200 mm.

8. The container defined in claim 1, wherein the plastically deformable layer is of circular shape.

9. The container defined in claim 1, wherein the plastically deformable layer is attached directly to an inner face of the container lid.

10. The container defined in claim 9, wherein the plastically deformable layer is bonded unitarily to the inner face of the container lid.

11. The container defined in claim 1, further comprising: a lead shield lining the side wall and end wall; a shield lid lining the container lid; and a flat holding element for the shield lid interposed between the plastically deformable layer and the shield lid, the plastically deformable layer being attached directly to the lead shielding lid or to the flat holding element.

12. The container defined in claim 1, wherein edges of the plastically deformable layer at least in areas border a fluid.

13. The container defined in claim 1, further comprising: a load distributor between the plastically deformable layer and the inventory.

14. The container defined in claim 12, wherein the load distributor is a plate.

15. The container defined in claim 1, further comprising: a reversible fastener securing the container lid to the side wall.

16. The container defined in claim 1, wherein the side wall has a thickness of 100 to 350 mm.

17. A method of making a container for radioactive inventory comprising the steps of: providing an end wall, a side wall, and a lid together forming a closed chamber for the radioactive inventory; interposing between the lid and the inventory at least one plastically deformable layer of such composition that impact forces of at least a majority of the inventory are uniformly distributable over at least a majority of a surface of the plastically deformable layer in the event of the container being dropped.

18. The method defined in claim 17, wherein the plastically deformable layer is formed by in situ foaming of aluminum in the container between the container lid and the inventory such that the layer bonds unitarily to the container lid.

Description

BRIEF DESCRIPTION OF THE DRAWING

(1) The above and other objects, features, and advantages will become more readily apparent from the following description, it being understood that any feature described with reference to one embodiment of the invention can be used where possible with any other embodiment and that reference numerals or letters not specifically mentioned with reference to one figure but identical to those of another refer to structure that is functionally if not structurally identical. In the accompanying drawing:

(2) FIG. 1 is a schematic cross-section of the container according to the present invention;

(3) FIG. 2 is a schematic view of another embodiment of the container according to FIG. 1;

(4) FIG. 3 is a schematic view of yet another embodiment of the container according to FIG. 1.

SPECIFIC DESCRIPTION OF THE INVENTION

(5) FIG. 1 shows a container according to the present invention having an end wall 2, a tubularly cylindrical side wall 3 centered on a normally vertical axis A, and a lid 4 here shown closing the open bottom end of the side wall 2. The container is hollow and cylindrical and forms a closed chamber 5 in which an only schematically represented radioactive inventory 1 is located. The lid 4 is connected via screw connections 8 in the form of 24 M36 screws to the side wall 3. The container walls 2, 3, and 4 are made out of cast iron of quality GGG 40. The side wall 3 has a thickness of 160 mm; in contrast, the end wall 2 and the lid 4 each have a thickness of 180 mm. The hollow cylindrical interior space 5 has a height of 1140 mm and a diameter of 740 mm. The side wall 3 and 3 end wall are unitarily cast with each other.

(6) The container is shown upside down to illustrate a lid flat fall. At the time of lid-first impact onto a solid base, the inventory 1 strikes the lid 4 with a time delay so that significant forces act upon the lid 4.

(7) According to the invention a plastically deformable layer 6 is attached to the inner face of the lid 4 in the form of a block of aluminum foam here formed as a cylindrical plinth of a diameter smaller than the inside diameter of the side wall 3. The aluminum foam has been foamed by use of the foaming agent titanium hydride. The thermal energy expended during foaming results in a liquefying of the aluminum and, when the aluminum foam cools, it bonds to the lid 4. During foaming, the aluminum foam of the deformable plastic layer 6 is limited in the upward direction by a load distributor 7 in the form of a load distribution plate of cylindrical shape and a diameter equal substantially to the inside diameter of the side wall 3. The load distributor 7 is bonded to the aluminum foam just like the lid 4.

(8) The aluminum foam is plastically deformable to an approximately equal extent in all spatial directions and, for this reason, is isotropic. The aluminum foam is closed cell and is encapsulated for the purposes of water-tightness. The aluminum foam has a density of 0.7 g/cm.sup.3, a thickness of 70 mm and a diameter of 585 mm when circular. The 0.2% yield point of the load distributor 7 in the form of a circular load distribution plate made from fine-grain construction steel is 1100 MPa. The thickness of the load distributor 7 is 20 mm.

(9) FIG. 2 illustrates a different embodiment of the container according to the present invention. The same components of FIG. 1 are here provided with the same reference characters. Compared to the embodiment of FIG. 1, the container according to FIG. 2 has an additional inner lead shield 9 entirely lining and delaminating the chamber 5. Here, this lead shield 9 is inside the container at the end wall 2 as well as also on the side wall 3 and a lead shielding lid 10 is provided on the lid 4. In the embodiment according to FIG. 2, the lead shielding lid 10 is kept and fixed to the lid 4 by a holding plate 11 itself fixed to the lid 4 by screws 12 that extend through the lead shield lid 10. Thus, advantageously and in the illustrated embodiment according to FIG. 2, the assembly of the lead shielding lid 10 and holding plate 11 is interposed between the deformable plastic layer 6 of aluminum foam and the lid 4.

(10) In the embodiment according to FIG. 3, the holding plate 11 is omitted. Instead, the lead shielding lid 10 is fixed to the lid 4 by the load distributor 7 or by the load distribution plate. The screws 12 in FIG. 3 reach here from the load distributor 7 or the load distribution plate 7 through the force-distribution layer 5 and the lead shield lid 10 into the lid 4.