Patent Number: 049960199
Section: summary

The invention relates to a storage container for receiving low or medium activity radioactive waste embedded in a filling material. Radioactive waste storage containers generally comprise a drum and a cover able to seal said drum. When the radioactive waste has been placed in the drum, the cover is put into place and joined to the drum, e.g. by means of a joint ensuring the confinement of the container. The filling material is then injected into the container by an injection tube or passage provided for this purpose. In the present state of the art, the storage containers are made from concrete, combined with metal fittings generally made from iron-reinforced concrete with a thickness of at least 6 mm. In a structure of this type, the rods constituting the fitting are located at a minimum distance, generally at least equal to 25 mm, from the surface of the drum or cover. The connecting zone between the drum and the cover, which has a joint which can e.g. be made from cement or resin, consequently forms a fitting-free zone, 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 constituted by concrete and fittings and a reduced strenght. Therefore cracks and fractures may occur in this zone, particularly under the effect of differential expansions or handling shocks. Very dense concrete types exist, whose use would make it possible to solve these problems. However, such concrete types are too expensive for their use to be envisaged in this case. In addition, e.g. EP-A-0 248 693 discloses concretes incorporating metal fibers. As illustrated by GB-A-2 023 056, an irradiated nuclear fuel rod can be coated with a metal fiber-reinforced concrete. However, this is a coating produced in a single operation, which does not solve the problem of the connection between the drum and the cover, when the latter has to be fixed to the drum following the introduction of the radioactive waste into it. The invention specifically relates to a container for the storage of radioactive waste designed in such a way as to have a homogeneous structure, even in the connection zone between the drum and the cover, so that it is resistant to shocks and corrosion, while still having a satisfactory seal with respect to air and water and having a relatively low cost. According to the invention, this result is obtained by means of a radioactive waste storage container comprising a drum having a waste introduction opening and a cover for the tight sealing of said opening, said container being characterized in that it is completely made from concrete reinforced by metal fibers, including in the junction zone between the cover and the drum, said junction zone having, around said opening, at least one keying groove. The metal fibers used for reinforcing the concrete are, for example, steel, cast iron, stainless steel or galvanized steel fibers. It is advantageous to use a filling material formed by metal fiber-reinforced concrete, so that the container filled with waste and said material constitute a monolithic block. In a first embodiment of the invention, the container comprises at least one keying joint, which is also made from metal fiber-reinforced concrete and which simultaneously penetrates the keying grooves formed in the drum and on the cover. In a second embodiment of the invention, the cover is directly cast on the drum and penetrates a keying groove formed in the drum. In a third embodiment of the invention, in the junction zone between the cover and the drum, there is a metal fiber-reinforced concrete keying joint, cast into a dovetail space formed between an outer peripheral edge of the cover and an inner peripheral edge of the drum surrounding the opening of the latter. The latter embodiment simplifies the procedure of sealing the drum, because sealing can be carried out without it being necessary to produce a formwork. Advantageously, the cover has at least one filling passage internally provided with a keying groove and by which the metal fiber-reinforced concrete can be injected around the waste previously placed in the container.