EP0373997A1 - Container for storing radioactive waste - Google Patents

Abstract

To guarantee good sealing and good impact and corrosion resistance, without increasing their cost, radioactive waste storage containers are made entirely of concrete reinforced with metal fibers. This material is used to make by molding a barrel (210) and a cover (212), as well as a keying joint (224) by which the cover is fixed to the barrel. At least one dovetail keying groove is formed in the junction zone between the barrel and the cover. Advantageously, a filling material of the same kind as that in which the container is formed is injected into the latter, so as to form a homogeneous block.

Description

The invention relates to a storage container intended to receive radioactive waste of low or medium activity, embedded in a filling material.

Radioactive waste storage containers usually include a barrel and a lid capable of sealing this barrel. When the radioactive waste has been placed in the barrel, the cover is put in place and secured to the barrel, for example by means of a seal ensuring the containment of the container. The filling material is then injected into the container through an injection tube or passage provided for this purpose.

In the current state of the art, the storage containers are made of concrete, associated with metal reinforcements generally composed of concrete reinforcing iron at least 6 mm in diameter. In a structure of this type, the rods constituting the frame are located at a minimum distance, generally at least equal to 25 mm, from the surface of the barrel or of the cover. The connection zone between the barrel and the cover, comprising the seal which can be made for example of cement or resin, therefore forms a zone without reinforcement whose thickness is at least equal to 50 mm. This zone has a modulus of elasticity different from that of the other parts of the container made up of concrete and reinforcement, and less resistance. Consequently, cracks and fractures are likely to occur preferentially at this location, in particular under the effect of differential expansions or handling shock.

There are very dense concretes whose use would solve these problems. However, these concretes are too expensive for their use to be considered in this case.

Furthermore, we also know, for example, document EP-A-0 248 693, concretes including metallic fibers.

As illustrated in document GB-A-2 023 056, it is also known to coat a spent nuclear fuel rod in concrete reinforced with metallic fibers. However, it is a coating produced in a single operation, which does not solve the problem of the connection between the barrel and the cover, when the latter must be fixed on the barrel after the radioactive waste has been introduced therein. .

The subject of the invention is precisely a storage container for radioactive waste designed so as to have a homogeneous structure, even in the connection zone between the barrel and the cover, so as to resist impact and corrosion, while having satisfactory air and water tightness and a low cost price.

In accordance with the invention, this result is obtained by means of a storage container for radioactive waste, comprising a barrel provided with an opening for introducing the waste, and a sealed closure cover for said opening, this container being characterized in that it is made entirely of concrete reinforced with metallic fibers, including in the junction zone between the cover and the barrel, this junction zone comprising, around said opening, at least one keying groove.

The metallic fibers used to reinforce concrete are, for example, steel, cast iron, stainless steel or galvanized steel fibers.

Advantageously, a filling material is also used, made of concrete reinforced with metal fibers, so that the container filled with waste and this material constitutes a monolithic block.

In a first embodiment of the invention tion, the container comprises at least one keying joint, also made of concrete reinforced with metal fibers, which simultaneously penetrates keying grooves formed in the barrel and on the cover.

In a second embodiment of the invention, the cover is poured directly onto the barrel and enters a keying groove formed in the barrel.

In a third embodiment of the invention, there is provided, in the junction zone between the cover and the barrel, a concrete joint reinforcement reinforced with metal fibers, poured into a dovetail space formed between an outer peripheral edge of the cover and an inner peripheral edge of the barrel surrounding the opening of the latter.

This last embodiment simplifies the barrel closing procedure, since this closing can be carried out without the need for formwork.

Advantageously, the cover has at least one filling passage having internally a keying groove and through which concrete reinforced with metal fibers can be injected around the waste previously placed in the container.

• - la figure 1 est une vue en coupe verticale selon la ligne I-I de la figure 2, représentant le fût et le couvercle d'un conteneur réalisé conformément à un premier mode de réalisation de l'invention, avant la mise en place d'un joint de clavage reliant ces deux par­ties ;
• - la figure 2 est une vue de dessus du fût représenté sur la figure 1 ;
• - la figure 3 est une vue en coupe verticale représentant à plus grande échelle la zone de jonction entre le fût et le couvercle du conteneur des figures 1 et 2, après mise en place du joint de clavage ;
• - la figure 4 est une vue en coupe verticale représentant un conteneur réalisé selon un deuxième mode de réalisation ;
• - la figure 5 est une vue en perspective écor­chée de la plaque anti-envol du conteneur de la figure 4 ; et
• - la figure 6 est une vue en coupe verticale d'un conteneur conforme à un troisième mode de réalisa­tion de l'invention.

Three embodiments of the invention will now be described, by way of nonlimiting examples, with reference to the appended drawings, in which:

• - Figure 1 is a vertical sectional view along line II of Figure 2, showing the barrel and the lid of a container made according to a first embodiment of the invention, before the establishment of a keying joint connecting these two parts;
• - Figure 2 is a top view of the barrel shown in Figure 1;
• - Figure 3 is a vertical sectional view showing on a larger scale the junction zone between the barrel and the cover of the container of Figures 1 and 2, after placement of the keying joint;
• - Figure 4 is a vertical sectional view showing a container made according to a second embodiment;
• - Figure 5 is a cutaway perspective view of the anti-theft plate of the container of Figure 4; and
• - Figure 6 is a vertical sectional view of a container according to a third embodiment of the invention.

In Figures 1 and 2, the reference 10 generally designates a barrel which in this case has the shape of a parallelepiped of square section. This barrel 10 comprises a side wall 10a and a bottom 10b. At its upper end, the side wall 10a defines an opening capable of being sealed off by a cover generally designated by the reference 12 in FIG. 1.

The barrel 10 associated with the cover 12 constitutes, when they are tightly connected in a manner which will be described in detail below, a storage container in which are placed radioactive waste of low or medium activity.

In accordance with an essential characteristic of the invention, the entire container, that is to say in particular the barrel 10 and the cover 12, is made of concrete reinforced with metallic fibers. The metallic fibers, which can in particular be fibers of cast iron, steel or stainless steel, are distributed uniformly and randomly inside the concrete, which makes it possible to reinforce the latter while giving it a homogeneous character. to the surface. The modulus of elasticity of the container is therefore perfectly identical at all points, so that the cracks which usually appear on concrete containers reinforced internally by reinforcement are eliminated and that the risks of breakage in the event of the container falling fall away.

The barrel 10 and the cover 12 are manufactured by molding, which allows them to be given any suitable shape.

In particular, it can be seen in FIG. 1 that the bottom 10b of the barrel 10 has support pads 14, possibly removable, which protrude beyond the outer surface of the bottom, in order to allow the container to be handled by means of 'a lifting device.

In addition, the molding of the barrel 10 and the cover 12 are carried out so that the interior surfaces of the container are rough and include, for example, cells. The upper edge 16 of the side wall 10a of the barrel as well as the peripheral edge 18 of the cover 12 also have rough surfaces. In addition, keying grooves 20 and 22 are formed on the edges 16 and 18, respectively around the opening of the barrel and around the cover. The width of the keying grooves 20 and 22 increases with increasing distance from the surfaces of the edges in which these grooves are formed, so that these grooves have in section trapezoidal or dovetail shapes.

As illustrated in FIGS. 1 and 3, the dimensions and the shape of the cover 12 are such that a lower part 12a of the latter enters the opening formed at the top of the barrel 10 to ensure the positioning and centering of the cover on the barrel. Above this part 12a of the cover 12, the peripheral edge 18 of the latter in which the key groove is formed vage 22 has a dimension slightly greater than that of the opening formed in the barrel.

The tight connection of the barrel to the cover is ensured by a keying joint 24, also made of concrete reinforced with metallic fibers of the same kind as those of the barrel 10 and of the cover 12. The keying joint 24 is formed by molding and penetrates in the keying grooves 20 and 22 as illustrated in FIG. 3. It is located both in the extension of the side wall 10a of the barrel and in the extension of the cover 12, and it adheres perfectly to their edges 16 and 18 , thanks to the roughness of these.

When the keying joint 24 is formed, the container according to the invention constitutes a homogeneous and sealed assembly, in which no discontinuity exists, even in the junction zone between the cover and the barrel. This observation has been confirmed by tests which have shown that in the event of the container falling on a corner, in the junction zone, there occurs with the container according to the invention only a slight crumbling on the surface, without consequence on air and water tightness or on the preservation of containment.

In the embodiment shown in Figures 1 to 3, the waste to be stored is placed in the barrel 10, then the cover 12 is put in place. A filling material is then injected inside the container, preferably consisting of concrete reinforced with metal fibers, of the same composition as the concrete forming the container.

This injection is carried out, in the example shown, by at least one of two vertical tubes 26 embedded in the concrete of the barrel 10, in two opposite angles thereof. These two tubes 26 open onto the upper edge of the side wall 10a of the barrel and inside the latter, immediately above the bottom 10b.

During the injection, the air and gases are evacuated by a vent 28 (FIG. 1) formed for example in the center of the cover 12.

On the inside-facing side of the container, the tubes 26 like the vent 28 are protected by grids 30 and 32 preventing the waste from entering it.

The keying joint 24 is put in place in order to seal the cover 12 to the barrel 10, as described above, then the filling is carried out.

As shown in particular in Figures 1 and 3, the barrel 10 and the cover 12 respectively comprise, on their upper faces, rods 34 and 36 allowing their handling by means of a suitable installation.

In the embodiment shown in FIGS. 4 and 5, the storage container according to the invention comprises a barrel 110, of cylindrical shape, and a cover 112 poured into the upper opening of the barrel after the latter has been filled.

More specifically, the opening formed in the upper part of the cylindrical lateral partition 110a of the barrel 110 comprises a keying groove 120 of semi-circular section.

In this embodiment, the barrel 110 is first produced by molding a concrete reinforced with metallic fibers, in the same manner as in the first embodiment. This molding provides the groove 120, as well as a groove 123 formed on the outer peripheral surface of the side wall 110a, to allow the handling of the barrel.

Low or medium activity radioactive waste is then placed in the barrel 110. In the illustrated embodiment, this waste is less dense than the filling material, so that an anti-theft plate generally designated by the reference 140 is snapped into the groove 120, by means of springs 142, or equivalent members. This anti-theft plate 140 is also made of concrete reinforced with metallic fibers and has a composition identical to that of the concrete constituting the barrel 110.

As illustrated more precisely in FIG. 5, the anti-theft plate 140 generally has the form of a disc 141 whose outside diameter is less than the diameter of the opening formed in the upper part of the cylindrical partition 110a of the barrel. This disc 141 is pierced in its center with a circular passage 144 through which the filling material is injected inside the barrel. As before, this filling material is preferably made up of concrete reinforced with metallic fibers, of the same composition as the concrete in barrel 110.

So that the filling takes place satisfactorily, the barrel 110 is then placed on a vibrating table.

The underside of the disc 141 is slightly inclined upward as it approaches its outer peripheral edge, to facilitate when filling the exhaust of air and gases by passages 146 formed at the periphery of the disc, between parts radial 143 of the anti-theft plate 140. These parts 143 ensure in particular the centering of the plate in the barrel 110. In addition, one in two of the radial parts 143 has lateral grooves 145 serving to fix by interlocking one of the springs 142.

Each of the springs 142 is in the form of an elastic metal wire comprising two parts in the form of an isosceles trapezium connected by their small base. One of these parts, of relatively small dimen sions, is fitted onto the projecting end of one of the radial parts 143 of the anti-take-off plate, so that its lateral branches penetrate into the grooves 145. The second part in the form of an isosceles trapezium of the spring 142, larger, is located in a plane which is then inclined outward, so that the large base of this second part is housed in the groove 120 of the barrel.

When the part of the barrel located below the anti-theft plate 140 is filled with concrete, the cover 112 is molded directly above this plate, so as to come flush with the upper edge of the lateral partition 110a of the barrel, filling the keyway 120 and coming into close contact with the interior surface of the barrel opening.

In accordance with the invention, the cover 110 is also made of concrete reinforced with metal fibers, so that the container constitutes, as in the previous embodiment, a homogeneous and sealed assembly having a uniform modulus of elasticity and, therefore, in which cracks and fractures appearing with the containers of the prior art are removed. The structure of the container also gives it good resistance to corrosion.

Preferably, as in the embodiment described above, the interior surfaces of the drum 110 as well as the surfaces of the anti-theft plate 140 are rough in order to allow good adhesion of the concrete which is then poured against these surfaces.

A third embodiment of the invention will now be described with reference to FIG. 6.

In FIG. 6, the reference 210 generally designates a barrel intended to be sealed in a sealed manner by a cover 212, to form a container storage intended to receive radioactive waste of low or medium activity, coated in a filling material. In the embodiment shown, the container is of parallelepiped shape and the tank 210a has a flat bottom 210b and a side wall 210a of square section, the upper end of which defines an opening capable of being sealed by the cover. 212.

According to the invention, the entire container, that is to say in particular the barrel 210 and the cover 212, is made of concrete reinforced with metallic fibers.

The barrel 210 as the cover 212 are manufactured by molding and have for example the shapes shown in FIG. 5.

In particular, the upper end of the side wall 210a of the barrel has a stepped shape defining successively, going from the outside towards the inside of the barrel, a flat end face 250 and a flat surface 252 parallel to the face 250 and set back with respect thereto. The surface 252 is connected to the end face 250 by an inclined inner peripheral edge 254 forming a Z in section with the surface 252 and the face 250. The inclined edge 254 progressively deviates towards the outside as it approaches the surface 252, so that this inclined edge forms an angle β of at least 10 ° with the axis of the barrel.

The cover 212 also has a peripheral zone in steps comprising, starting from its upper face, an inclined external peripheral edge 256 and a vertical edge 258 set back from the inclined edge 256. These edges 256 and 258 are connected by a surface plane 260 parallel to the upper and lower faces of the cover. The inclined edge 256 deviates progressively outward towards the surface 260, so that this inclined edge forms with the axis of the cover 212 an angle α of at least 10 °. This angle α formed by the surface 256 with the axis of the cover 212 is less than the angle β formed by the surface 254 with the axis of the barrel.

When the cover 212 is placed on the barrel, the lower part of the cover delimited by the edge 258 fits into the opening formed at the top of the barrel, until the surface 260 comes to bear on the surface 252. As can be seen in FIG. 5, the inclined edges 254 and 256, which have the same height, are then opposite one another and delimit between them an annular space in the shape of a tail dovetail whose width is substantially constant from the upper face of the container to the surface 252. This annular space constitutes a keying groove.

In order to seal the cover 212 on the barrel 210, a keying joint 224 is poured into the abovementioned annular space. According to the invention, this keying joint 224 is made of the same material as the rest of the container. , i.e. concrete reinforced with metallic fibers.

The creation of the keying joint 224 in an annular space open upwards makes it possible to ensure the sealed closure of the container without the need to use a formwork. In addition, the shape of the keying joint makes it possible to avoid any risk of the cover taking off when this joint is made.

Advantageously, the lid 212 has in its center one or more opening (s) 228 in which a keying groove 229 is formed. In this way, the filling of the container can be carried out after sealing the lid 212 on the barrel. 210 by means of the keying joint 224. When the waste has been introduced through the opening 228, the filling material is introduced in turn until the opening 228 is completely closed. By using concrete fiber-reinforced concrete as filling material identical to that which forms the container proper, a homogeneous assembly is produced in which the risks of cracking and breakage are eliminated.

As in the previous embodiments, the interior surfaces of the container as well as the interior surfaces of the groove intended to receive the keying joint 224 and of the central opening 228 are made rough by any suitable means, for example by stripping these surfaces by means of a brushing or bush hammering device or high pressure water jets.

Tubes for injecting the filling material into the bottom of the tank can, if necessary, be embedded in the side wall 210a of the tank, in the case where the filling is carried out under pressure, in accordance with the teachings of the request for main patent.

Finally, to allow handling of the container, various means can be provided. Among these means, mention will only be made, by way of example, of rods or rings 234 sealed on the flat end face 250 of the barrel. A handling groove or groove 223 can also be formed by molding on the outer peripheral surface of the barrel 210, near the end face 250.

Of course, the invention is not limited to the embodiments which have just been described by way of examples, but covers all the variants thereof. In particular, it will be observed that the three modes of reaction The described descriptions can be combined in different ways.

Thus, the technique of molding the lid directly into the opening of the barrel described with reference to FIG. 4 could be applied to non-cylindrical containers. Conversely, the use of keying joints as shown in Figures 3 and 5 can also apply to cylindrical containers.

In a comparable manner, the shapes of the keying grooves can be reversed. In addition, cylindrical containers can be fitted with support pads and / or lifting rods.

Finally, in the embodiment of Figure 4, the anti-theft cover 140 can be removed when the waste is denser than the filling material.

Claims (18)

1. Storage container for radioactive waste, comprising a barrel (10,110,210) provided with a waste introduction opening, and a cover (12,112,212) for sealing said opening, this container being characterized in that it is made entirely of concrete reinforced with metal fibers, including in the junction zone between the cover and the barrel, this junction zone comprising, around said opening, at least one keying groove (20, 120). 2. Container according to claim 1, characterized in that it comprises at least one keying joint (24) of concrete reinforced with metallic fibers, simultaneously penetrating into a keying groove (20) formed on an upper edge of the barrel and in at least one keying groove (22) formed on a peripheral edge (18) of the cover. 3. Container according to claim 2, characterized in that the keying joint (24) is formed both in the extension of a side wall (10a) of the barrel and in the extension of the cover (12). 4. Container according to claim 3, characterized in that the cover (12) has a centering part (12a) which penetrates into said opening of the barrel. 5. Container according to any one of the preceding claims, characterized in that each keying groove (20, 22) has a width which increases as it moves away from the surface on which this groove opens. 6. Container according to claim 1, characterized in that the cover (112) is poured directly into the keying groove (120) of the barrel. 7. Container according to claim 6, character rized by the fact that the keying groove (120) is formed in said opening. 8. Container according to any one of claims 6 and 7, characterized in that an anti-take-off plate (140) of concrete reinforced with metal fibers is snapped into the groove (120) formed in said opening of the barrel, set back from the cover (112). 9. Container according to claim 1, characterized in that it comprises a keying groove constituted by a dovetail space formed between an outer peripheral edge (256) of the cover and an inner peripheral edge (254) of the barrel surrounding said opening, a keying joint (224) of concrete reinforced with metallic fibers being poured into this space. 10. Container according to claim 9, characterized in that the outer peripheral edge (256) of the cover and the inner peripheral edge (254) of the barrel gradually move outward away from an upper face of the cover and an end face (250) of the barrel, so as to produce a self-locking of the cover by the keying joint (224). 11. Container according to any one of the preceding claims, characterized in that it comprises at least one filling passage (26,144,228) by which concrete reinforced with metal fibers can be injected around the waste contained in the container. 12. Container according to claim 11, characterized in that the filling passage (26) is formed in a side wall (10a) of the barrel and opens near the bottom of the latter. 13. Container according to claims 8 and 11 combined, characterized in that the passage of rem pleating (144) being formed in the anti-theft plate 140). 14. Container according to any one of the preceding claims, characterized in that the barrel (12) comprises support pads (14) made of concrete reinforced with metal fibers, projecting from the outer surface of the bottom of the was. 15. Container according to any one of the preceding claims, characterized in that the interior surfaces of the barrel and of the cover, as well as the surfaces defining the junction zone, are rough surfaces. 16. Container according to any one of the preceding claims, characterized in that the metallic fibers are fibers chosen from the group comprising cast iron, steel, stainless steel, or galvanized steel. 17. Container according to any one of the preceding claims, characterized in that lifting means (34, 234) are mounted on an upper edge of the barrel. 18. Container according to any one of the preceding claims, characterized in that a handling groove (123,223) is formed on an external peripheral surface of the barrel.

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