Nuclear-waste transport and storage container and method of drying same

Abstract

A transport or storage container holding radioactive waste and a body of water is dried by the steps of first draining or pumping out the body of water and thereby leaving residual water in the container. Then at least one solid drying agent is introduced into an interior the container for removing from the interior of the container for removing the physically or chemically bonded residual water. The solid drying agent is an alkaline earth salt, particularly an alkaline earth oxide.

Claims

1. A transport or storage container holding radioactive waste and a body of water is dried by the steps of: a) draining or pumping out the body of water, leaving residual water in the container; and thereafter b) introducing at least one solid drying agent consisting essentially of an alkaline earth salt into an interior the container for removing physically or chemically bonded residual water.

2. The method according to claim 1, wherein the solid drying agent is at least 80 wt % calcium oxide.

3. The method according to claim 1, further comprising, between steps a) and b), the steps of: a′) vacuum-drying an interior of the container; and, after step c), the step of: d) removing the residual water from an interior of the container with the solid drying agent.

4. The method according to claim 3, wherein step a′ is carried out after step a″).

5. The method according to claim 1, further comprising the step after step a′) and before step c) of: a″) filling the interior of the container with helium gas after vacuum drying.

6. The method according to claim 5, wherein the interior of the container is filled with helium gas up to an internal pressure of 400 hPa to 1000 hPa.

7. The method according to claim 1, wherein the drying agent or the calcium oxide is introduced into the interior of the container as at least one candle.

8. The method according to claim 7 wherein the candle with the drying agent is introduced into an upper third of the interior of the container.

9. A transport or storage container for radioactive spent fuel elements, the container: a vessel constructed to hold the spent fuel elements; a lid hermetically closing the vessel and defining therewith an interior holding the fuel elements and adapted to be vacuum dried; and a drying device comprising drying agent consisting essentially of an alkaline earth oxide.

10. The transport or storage container according to claim 9, wherein the drying agent is calcium oxide.

11. The transport or storage container according to claim 9, wherein the drying agent is powder form.

12. The transport or storage container according to claim 9 wherein the drying agent is held in a candle that is suspended in an upper third of the interior of the container.

13. The transport or storage container according to claim 12, wherein the candle has walls defining a chamber for the drying agent, the walls being made at least partially of a sintered metal and being permeable to water vapor.

14. The transport or storage container according to claim 13, wherein the walls permeable to water vapor of the filter candle have a wall thickness of 0.5 mm to 6 mm.

Description

BRIEF DESCRIPTION OF THE DRAWING

(1) The above and other objects, features, and advantages will become more readily apparent from the following description, reference being made to the accompanying drawing in which:

(2) FIG. 1 is a schematic side-view section through the transport and/or storage container according to the invention; and

(3) FIG. 2 is a schematic side-view section through a filter candle for the method according to the invention or for the container according to the invention.

SPECIFIC DESCRIPTION OF THE INVENTION

(4) As seen in FIG.

(5) FIG. 1 shows a transport and/or storage container 1 according to the invention that was loaded with a carrying basket (not showed) with spent fuel elements. The loading took place under water and the container 1 was first drained or pumped out. Expediently and here, a primary lid 2 for closing the container 1 closes the container 1. Preferably and here, the interior of the container 3 of the container 1 was first vacuum-dried.

(6) For removing the residual water from the interior of the container 3, a solid drying agent 4 is used according to the invention that, according to a preferred embodiment, is calcium oxide in powder form. It is recommended that, also in the embodiment, this drying agent 4 or the calcium oxide in powder form is held in a chamber 5 of a filter candle 6. This filter candle 6 is shown in more detail in FIG. 2.

(7) Preferably and here, the filter candle 6 is positioned in the upper fifth of the interior of the container 3 of the container 1. Effectively and here, the filter candle 6 is suspended from the underside of the primary lid 2 via a hanger 7. It is within the scope of the invention that the walls delimiting the chamber 5 of the filter candle 6 are permeable to water vapor. Expediently and here, these walls permeable to water vapor are made of a sintered metal. According to a design variation of the invention, this can be austenitic stainless steel. According to a preferred embodiment, the walls 8 permeable to water vapor of the filter candle 6 have a wall thickness between 1 and 5 mm and are recommended to have a pore size between 2 and 12 μm. Effectively and here, the filter candle 6, including the hanger 7, has a length of approximately 800 to 1200 mm, particularly from 900 to 1100 mm.

(8) The free volume of the interior of the container 3 of the container 1 according to the invention is expediently 2 to 8 m.sup.3, particularly 3 to 6 m.sup.3. In this case, free volume of the container 1 refers particularly to the interior volume of the container 1 without the carrying basket and without fuel elements. The diameter or the outside diameter of the filter candle 6 corresponds to only a fraction of the inside diameter of the interior of the container 3. Expediently, the diameters are measured in the horizontal direction of the propped up container 1. According to a recommended design variation of the invention, the outer diameter of the filter candle 6 is less than one sixth and preferably less than one eighth of the inner diameter of the interior of the container 3.