JPH0149920B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a container for the storage of radioactive effluent and radioactive waste (hereinafter referred to as "radioactive effluent") embedded in a solid matrix.

With the development of nuclear energy, the amount of radioactive spills of all kinds is ever increasing. These radioactive spills must be separated and limited to as small amounts as possible and, after a period of decay or transmutation, must be stored under extremely strict safety conditions.

In the first stage of these operations, the radioactive effluent, if it is not already in solid form, is first converted into solid form and subjected to mechanical, physical or chemical attack from the radioactive material itself or from the external environment. embedded in a suitable solid matrix capable of withstanding

In the second stage, the radioactive effluent dispersed inside the solid matrix described above is "packed" and
The evolution of the radioactive material and, secondly, the storage itself ensures that it is retained for various lengths of time.

The invention consists in providing a container suitable for the storage of radioactive effluent embedded in a solid matrix.

Traditionally, the recommended material for storage containers for radioactive effluents embedded in such solid matrices has been steel, optionally coated with stainless steel alloys, concrete, wood or plastic. was. For example, in a container intended for immediate storage in a suitable location,
It has been recommended to use containers such as those described below to store the radioactive effluent embedded in a solid matrix.

(1) A black steel container with an internal volume of 50
~400 liters, the steel thickness is 0.6-2 mm.
The container is sealed with a cover provided with a rubber seal. The outside of said container is typically 30
Covered with a paint layer or special composition to a thickness of ~110μ. Approximately 100μ thick stainless steel
It has also been proposed to coat chrome steel.

(2) A black steel container with an internal concrete coating to improve biological protection against radiation.

(3) A black plate container, which can be up to 10 mm thick, has an internal volume of several m ³ , and is cylindrical or parallelepiped, depending on the case.

(4) A concrete container with a wall thickness of 100 to 350 mm, usually with an inner steel cladding and reinforcement in the concrete.

(5) A wooden container with a sealed plastic container inside.

(6) Containers molded from plastic, often with glass fiber reinforcement (reinforced polyester resin).

All of the above-mentioned conventional containers, even if modified, have the potential for deterioration over time (ageing), inadequate corrosion resistance, or
It has fatal technical flaws, such as excessive sensitivity to temperature or temperature changes, or excessive weight.

The present invention has been made to solve the above-mentioned problems and provides a container for the storage of radioactive effluent embedded in a solid matrix, said container being made of high-density asbestos cement. 30
a tube having a thickness of from 50 to 100 mm, said tube having means for holding a plug made of micro concrete with small particle size aggregate and having a thickness of from 50 to 100 mm. , at both ends of the tube and on its inner surface, the plugs comprising:
It is characterized by having on its outer surface a plate made of high-density asbestos cement, which is firmly fixed to the tube.

The high-density asbestos cement selected for this invention has a high proportion of cement (per ^m3 ,
1500 kg), 85% cement with a BLAINE specific surface area of 3000 to 4000 cm ² /g, and 15% asbestos with a BLAINE specific surface area of 20000 cm ² /g.
The particle size is small because it is a mixture of
Densities higher than 1.75 g/cm ³ have been obtained, which aids in the bonding and densification of each successive layer of material. The numbers listed above are average values. Any person skilled in the art can adapt the starting materials and conditions of use to obtain materials acceptable for the required application.

Furthermore, various techniques for using said high-density asbestos-cement materials, in particular for manufacturing pipes, are known and have already been industrialized, with diameters and thicknesses adapted to the storage problems mentioned above. A tube with the same characteristics and characteristics has been obtained.

Properties of this dense asbestos cement that may be particularly advantageous for storage of the radioactive effluents described above include:

(1) Must have appropriate density. For this reason, the thickness is 30
Biological protection can be achieved by using asbestos cement in the range ~100 mm (for βγ wastes with low specific activity, and for radioactive waste α).

(2) High mechanical strength. These properties are particularly important when products are shipped in asbestos-cement containers and when packaging is buried in layers underground, since said containers are exposed to various loads and potential This is because they must withstand severe shocks.

(3) It has stability over time proven by nearly 70 years of research.

(4) High corrosion resistance against various types of corrosion that may be encountered in underground storage (ground water, stray currents, bacteria, carbon dioxide, etc.).

(5) It has excellent gas and water resistance due to its extremely fine porosity and the gradual clogging of these pores over time due to the influence of external substances (for example, carbonation). .

(6) Very high resistance (and good stability) to temperature fluctuations. For example, asbestos cement can withstand temperature fluctuations between approximately -50°C and +300°C, and
It is believed that there are no major changes in its properties.

All of the above properties are the same for high-density asbestos.
Cement has proven to be the material of choice for storage containers for radioactive effluent embedded in a solid matrix.

The use of materials including asbestos and cement has all been proposed for various purposes involving radioactive elements. German patent 1136261
and French patent 1347402.
German Patent No. 1136261 discloses the use of a complex composition of refractory bonding materials mixed with asbestos, but does not disclose the use of high-density asbestos cement, as is the case in the present application. french patent
1347402 discloses the use of a filling material consisting of fibers impregnated with adhesive and compressed in the space located between two containers. Therefore, the material used in French patent 1347402 is not a dense asbestos cement as in the present application and does not exhibit the same behavior with respect to radiation.

High-density asbestos cement can be used in the manufacture of "containers" used for the transport and/or storage (particularly underground storage) of radioactive effluents dispersed inside a solid matrix; is an effluent that comes directly from an industrial nuclear facility or from an intermediate storage facility.

This container has the following characteristics.

(1) Made from asbestos-cement pipes, cut to special lengths in special cases, preferably
Preferably, it is made by the MAZZA method, ie using very high pressure.

(2) The thickness is preferably 30 to 80 mm.

(3) Near each end of the tube, on its inner surface, the tube has at least one means designed to retain the plug, such as a soft retaining ring made of Silicon mastic to improve the seal. with grooves or threads lined with.

(4) It is desirable that a chamfered edge be provided on the inner surface of the end.

The container is designed to be closed at both ends by plugs. One of these closure means can advantageously be manufactured in a factory so that the container is delivered with one end closed by a plug and the other end open. It is therefore convenient to produce plugs with a thickness of 50 to 100 mm by pouring micro-concrete perpendicularly to the fixing means provided on the inner surface of the tube. The above-mentioned micro concrete refers to cement, sand, and aggregate, which are the constituent components of concrete, and the particle size of the aggregate is smaller than about 3 mm.

The properties of micro-concrete are well compatible with asbestos cement, and this material exhibits good adhesion on pipes due to the gripping means. A retaining ring made of silicone mastic or similar material prevents water from entering between the sleeve joint of the high-density asbestos cement container and that part of the micro-concrete plug, but this This is because the set back of micro concrete is extremely small.
Advantageously, the outer surface of the micro-concrete is constituted by a plate made of high-density asbestos cement glued onto the tube, for example with the chamfered edges described above. In addition, where necessary, joints made of materials such as tar, pitch, or plastic (between micro-concrete and pipes, and between micro-concrete, pipes, and asbestos-cement outer panels) may also be used. Thus, the air-tightness of this type of container can be reinforced.

These containers can be used in two ways:

The first method consists in placing a minimum amount of solid waste in the container and then directly filling it with active or inert potting material containing the waste to be packaged. The second method consists in repackaging the waste previously contained in containers of the type already used before, in particular cylindrical containers with thin walls of stainless steel or plastic material. In this case, measure the internal dimensions of the asbestos-cement container and place high-density asbestos on the outside of the container designed for repacking.
Allow 0.5 to 2 cm of play between it and the inside of the cement container. This play is intended to help position the first container (first
enclosure walls shall not be considered as shielding).
It is also intended that fluid be injected into said empty space. This fluid is
It fills any empty space and solidifies by polymerization or cooling (eg polyester or epoxy resins, bitumen, pitch).

According to a second embodiment, several drums can be stacked inside the asbestos cement container (the length of the container in this case is the usual length of the tube element, i.e. usually 5 m), and , a compound of asbestos cement and bitumen, or asbestos
The second technical shield can be reinforced by producing a compound of cement and plastic resin.

The high-density asbestos cement container according to the invention is advantageously provided with a device to facilitate its transportation. Such devices can be of various types and may consist of metal belts placed at each end of the container, connected by joint pieces with hook devices, or simply made of asbestos cement. You can just bolt it inside. These may consist of one or more belts placed in internal grooves (for example 5-6 mm deep) provided in the outer circumference of the container. With these various metal belts, the container can be gripped on its sides by fork lift trolleys or other conveying devices, thus protecting it from shocks that may occur during loading and transport. I can endure it.

If the containers described above are used for the conveyance of effluents embedded in a solid matrix, it is advantageous to provide these containers with suitable external protection means. This protective means is designed to strengthen the container against shocks and drops that may occur during transportation, and should preferably be removable to avoid unduly increasing storage capacity.

The following non-limiting examples use high density asbestos cement to manufacture containers according to the invention.

Figures 1, 2, 3 and 4 illustrate containers in which the shielded material of the present invention can be used. FIG. 1 is a perspective view of a container according to the invention, one half of which is provided with external protection means and the other half provided with means simply to facilitate handling. Figure 2 shows the A-- of the container shown in Figure 1.
It is an A-line sectional view.

1 and 2, 1 is a high-density asbestos cement pipe, which has a diameter of, for example
It is 1000mm, height 1250mm, and thickness 50mm.

2, 2', 3, and 3' are two grooves provided on the inner surface of the tube near both ends thereof. Before filling the container, at the level of the grooves 2, 2', a micro-concrete 4 of approximately 60 mm thickness is glued to the asbestos cement tube 1, and at its periphery with a suitable adhesive. The lower plug is manufactured by a plate 5 made of asbestos cement, which is glued to the chamfered edge formed around the tube 1 (for example with a filled epoxy adhesive). The upper plug, which has a similar structure to the lower plug, is attached after filling the container with the solid material to be packaged.

6 is a lower belt, 7 is an upper belt, and the lower belt 6 and the upper belt 7 are connected to a band-shaped pad 8.
are connected by etc. Said metal belt is also connected by tabs 9 to outer belts 10, 11, also made of metal.

Welded below the lower belt 6 are two metal perforations 12 and 13 made of thick steel plate, these perforations having dimensions such that the forks of a fork lift trolley pass through them.

All spaces defined by the outer belts 10 and 11 and the container body are filled with polyurethane foam.

When the container thus packed was filled with concrete and some tests were conducted, the following results were obtained.

(1) The container was immersed in water and an air pressure of 0.5 bar was introduced into it, but no leakage was detected.

(2) The container was dropped from a height of 1.5 m onto a concrete slab, but apart from a considerable deformation of the circular metal belt, there was no obvious damage to the container itself; It was completely sealed with the same 0.5 bar pressure.

3 and 4 are cross-sectional views showing other embodiments of the container according to the present invention, which are suitable for transportation and/or
or have protective measures used for storage.

In the container shown in FIG. 3, protection is achieved by two circular angles 14 and 15 joined by a joining piece 16. A rubber member 17 is inserted between the angle and the container.

In the container shown in FIG. 4, protection is provided by appropriately placed delta-shaped rubber damping means. On the top side of the container, it is advantageous to arrange the damping means radially. On the underside of the container, the damping means are arranged in such a way as to leave sufficient room for the arms of the material handling device. Similar damping means are provided on the high and low parts of the outer circumference of the container. All of these damping means are held in place by suitable metal members, which can be removed to allow recovery of the damping means.

Although this invention has been described with a focus on high-density asbestos cement, in this type of material it is often possible to replace some of the asbestos fibers with other fibers, and this provides benefits. It is well known that the properties of composite materials do not change. This invention, of course, also covers the use of such similar materials.

[Brief explanation of drawings]

FIG. 1 is a perspective view of the container of the present invention, FIG. 2 is a cross-sectional view taken along the line A--A in FIG. 1, and FIGS. 3 and 4 are cross-sectional views showing other embodiments of the container of the present invention. . In the drawings, 1...high-density asbestos cement pipe, 2, 2', 3, 3'...groove, 4...micro-
Concrete, 5... Board, 6... Lower belt, 7... Upper belt, 8... Band-shaped padding, 9... Tab, 10,
11... Outer belt, 12, 13... Hole box, 14, 1
5...Circular angle, 16...Joint piece, 17...Rubber member.

Claims (1)

Claims: 1. Container for the storage of radioactive effluent embedded in a solid matrix, characterized in that: The tube is thus constructed with means for holding plugs made of micro-concrete with aggregate of small particle size and having a thickness of 50 to 100 mm at both ends of the tube and on its inner surface. The plug has on its outer surface a plate made of high-density asbestos cement, which is rigidly fixed to the tube. 2. The means for retaining the plug includes at least one formed on the inner surface of the tube.
Container for storage of radioactive effluent according to claim 1, characterized in that it consists of a circumferential groove and a soft retaining ring received in said at least one groove. . 3. The means for retaining the plug comprises a circumferential thread formed on the inner surface of the tube and a soft ring received within the thread. A container for storing radioactive effluent according to claim 1. 4. Container for storage of radioactive effluent according to claim 2 or 3, characterized in that the soft retaining ring is made of silicone mastic.