JPS5840000A - Container for storing radioactive waste for long time - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention provides a container body and an outer surface for long-term storage of radioactive waste, particularly spent fuel elements, in a suitable geological formation.
and a protective layer applied to the container.

The irradiated fuel elements are previously stored in a pool and then post-processed immediately or after intermediate storage for a certain period of time.

In this case, the nuclear fuel and the parent material are separated from the fission products and fed back into the fuel cycle. The fission products are conditioned according to known methods using large quantities of materials, such as lead and copper, and are finally stored in suitable geological formations in a virtually irretrievable manner.

Furthermore, the irradiated fuel element was not post-treated in the near term, but the fuel and parent material present in the fuel element were abandoned for the time being and the fuel element was allowed to sedate for a period of time in a reservoir configured for it. It may also be conceivable to take it out again later, if necessary.
des Kernforschungs-zentrum
Karlsruhe) KFK2535 and 265
0). The storage period can be from several generations to several thousand years, during which the dangerous level of the radioactive inventory decreases significantly during this period, depending on the known physical laws and in accordance with its composition.

Containers suitable for long-term storage containers of this type, which should have a service life several times longer than known transport and storage containers, have special demands due to the variable storage times. Furthermore, the container storage must be difficult to access and thus monitoring methods are limited.

Some very expensive methods are known for storing irradiated fuel elements in salt, sand or rock caves using containers made of metal or concrete.

Containers made of alloyed and unalloyed steel, copper and corundum have been proposed as packaging devices for radioactive materials and irradiated fuel elements. Containers made of steel are not sufficiently corrosion resistant and containers made of random material, although suitable in principle, lack the experience necessary to manufacture them. Additionally, manufacturing requirements require that the fuel element be crushed for packaging into small corundum containers.

This is associated with significant costs. Containers of this type must only partially satisfy the conditions of long-term storage, such as tightness at the pressures and temperatures that may occur and corrosion resistance against salt water, or must be constructed with a significant wall thickness. be. Moreover, these containers are often unsuitable for simultaneous use as transport containers, so that the waste must be transferred from the transport container to the final storage container at great expense.

A final storage container for spent fuel has also been proposed consisting of alloyed and unalloyed steel with a plated protective layer selected on the basis of an electrochemical voltage sequence. These known externally applied protective layers are often sensitive to mechanical loads, can be partially destroyed and, in the event of an accident, corrosion starts from the points of damage. It may progress.

The object of the invention therefore consists of a container body and a protective layer applied to its outer surface, which protective layer is suitable and possible for any possible inexpensive container body. A storage medium for the long-term storage of radioactive waste, especially spent fuel elements, in suitable geological formations that has limited corrosion resistance and protection against mechanical damage and prevents leakage of fission products from the final storage container. The aim was to provide containers for

According to the invention, the protective layer consists of a well-adhering plastic, in which is embedded a filler which is swellable in the presence of water and has ion-exchangeable and adsorptive properties. This is solved by the fact that In particular, sheet silicates of the montmorillonite type have proven suitable as fillers. For this purpose it has been found to be advantageous to use bentonite, and polyurethane has proven particularly suitable as plastic component. However, as a plastic component, e.g. It is also possible to use litertrafluoroethylene, polycarbonate, Evoquin resin, phenol formaldehyde F resin or acrylate synthetic rubber.

On the outside of the sealed final container containing the spent fuel elements or fuel rods, e.g.
? The IJ urethane layer is applied, in this case a two-component system of polyurethane containing bentonite as a filler in its components.

After reacting on the surface, the container has uniform mechanical stability of the bentonite, thus reliably preventing damage to the container body. At the same time, it is absolutely corrosion-resistant against salt water, which can occur in the event of an accident within this polyurethane.

Bentonite, which is advantageously contained as a filler in the polyurethane, provides additional protection and forms a secondary barrier. If the plastic layer is damaged 1, for example if cracks occur, the filler is exposed. It swells to 4-7 times its volume in the presence of water, thus resealing the cracks that have formed. Furthermore, the phyllosilicate filling prevents the leakage of fission products from a damaged final storage vessel.

Bentonite has adsorption as well as ion exchange properties. Therefore, the fission products leaking from the final storage container are
It is bound to bentonite by adsorption or ion exchange and prevents it from entering the living space.

In this way, the protective layer of the present invention provides multiple protection and significantly increases the safety of the final storage of spent fuel.

The invention will now be explained with reference to the illustrated embodiment.

A protective layer 2 consisting of well-adhered plastic and a swellable filler is applied onto the container body 1.

[Brief explanation of drawings]

The drawing is a cross-sectional view of one embodiment of the invention. 1... Container body, 2°°° protective layer

Claims (1)

[Scope of Claims] 1. In a container consisting of a container body and a protective layer applied to the outer surface for storing radioactive waste in a suitable geological formation for a long period of time, the protective layer (2) has good adhesion. for long-term storage of radioactive waste, characterized in that a filler with ion exchange and adsorptive properties, which is swellable in the presence of water, is embedded in the plastic. A container for storage. 2. The container according to claim 1, wherein a montmorillonite-type layered silicate is embedded in plastic. 3. The container according to claim 1 or 12, characterized in that the layered silicate is 4tonite. 4. The device according to any one of claims 1 to 3, characterized in that the plastic is polyurethane.