CROSS-REFERENCE TO RELATED APPLICATIONS

This application is the U.S. national phase of International Application No. PCT/FR2020/050184 filed Feb. 4, 2020 which designated the U.S. and claims priority to French Application No. 1901123 filed Feb. 5, 2019, the entire contents of each of which are hereby incorporated by reference.

BACKGROUND OF THE INVENTION

Field of the Invention

The present invention relates to the technical field of protection against ionising radiations.

More particularly, it relates to a radio-protective shield intended to be fastened on the periphery of an opening formed in a wall separating a space subjected to ionising radiations (called hot space), and a space that is not subjected to ionising radiations (called cold space).

It also relates to a shielded cell enclosing a space subjected to ionising radiations, comprising a metallic internal coating and at least one anti-radiation window enabling visual access from the outside to the inside of said shielded cell, which anti-radiation window comprises a sheath embedded in a concrete wall, which sheath receives a shielded porthole which is associated to a radio-protective shield fastened on the periphery of an opening formed in said metallic internal coating.

Description of the Related Art

In some waste reprocessing plants, or some laboratories, there are shielded cells within which operations on radioactive materials are carried out.

These shielded cells are surrounded by walls adapted to ensure an effective protection against ionising radiations, and they generally comprise at least one window enabling visual monitoring from outside of the operations carried out inside (cf. for example U.S. Pat. No. 7,257,927, EP 0 430 687, U.S. Pat. No. 3,505,525, FR 1 333 746).

Such windows (called anti-radiation windows) may comprise a sheath, embedded in a concrete wall, which sheath receives a shielded porthole composed by a mount made of cast iron integrating a plurality of anti-radiation glass slabs.

In addition, on the internal side (also called “hot space”), the shielded enclosure may include a radio-protective shield, positioned opposite the shielded porthole. This radio-protective shield (also called “alpha glass”), is fastened on the periphery of an opening formed in a metallic internal coating which covers the walls of the shielded enclosure.

The considered radio-protective shield comprises a wall made of a transparent material whose periphery is sandwiched in a carrier set composed by a fastening frame and by a counter-frame, enabling fastening by welding with the internal coating of the shielded enclosure.

The wall made of a radiation-shielding transparent material is delimited by a first face, intended to be directed on the external “cold space” side, and by a second face intended to be directed on the internal “hot space” side. A peripheral edge of this first wall face bears against a bearing face of the counter-frame through a seal made of an organic material (in general EPDM or neoprene). And the fastening frame is provided with bearing means, with a seal, against a peripheral edge of the second face of the wall made of a transparent material.

However, the seals interposed between the wall made of a transparent material of the radio-protective shield and the counter-frame and fastening frame deteriorate quite rapidly over time, because of the high amounts of radiations to which they are subjected, and it is necessary to replace them on a regular basis, which, in this context, is not easy to carry out and generate considerable costs.

SUMMARY OF THE INVENTION

In order to overcome the aforementioned drawback if the state of the art, the present invention provides a radio-protective shield intended to be fastened on the periphery of an opening formed in a wall separating a space subjected to ionising radiations, called hot space, and a space not subjected to ionising radiations, called cold space, which radio-protective shield comprises a wall made of a transparent material, said wall made of a transparent material comprising a first face intended to be directed on said cold space side, and a second face intended to be directed on said hot space side,

a peripheral edge of one of said first face or second face of said wall made of a transparent material bearing against a bearing face of a counter-frame through a seal,

said radio-protective shield comprising a fastening frame provided with means for bearing against a peripheral edge of the other one of said first face or second face of said wall made of a transparent material,

which bearing means comprise a longitudinal bearing structure comprising a contact surface with the peripheral edge of the first face or of the second face opposite said wall made of a transparent material,

which radio-protective shield also comprises securing means for securing together said counter-frame and said fastening frame,

this radio-protective shield being characterised by the fact that said bearing means comprise elastic return means adapted to apply a pressure against said longitudinal bearing structure in the direction of said wall made of a transparent material.

Such a particularity enables the use of seals that resist ionising radiations very well, in particular gaskets made of an inorganic material (advantageously gaskets made of a soft metal, that is to say malleable or ductile, selected from lead, copper, tin or cadmium, in the pure state or in an alloyed form), or gaskets made of graphite.

Other non-limiting and advantageous features of the radio-protective shield in accordance with the invention, considered separately or according to any technically-feasible combinations, are as follows:the elastic return means consist of a plurality of spring members evenly, or at least almost evenly, distributed over the periphery of said fastening frame;said spring members consist of Belleville washers;the longitudinal bearing structure comprises a pressure metallic profile associated to an affixed bearing profile forming said surface of contact with the peripheral edge of the face opposite the wall made of a transparent material and forming a seal;said affixed bearing profile is made of a material selected from (i) soft metals, preferably lead, copper, tin and cadmium, in the pure state or in an alloyed form, and (ii) graphite;at least some of the elastic return means are associated to pressure setting screws adapted to enable setting of the pressure applied by said elastic return means on said longitudinal bearing structure;each of at least some of said Belleville washers is associated to a pressure setting screw.

The present invention also relates to a shielded cell enclosing a space subjected to ionising radiations, comprising a metallic internal coating and at least one anti-radiation window enabling visual access from the outside to the inside of said shielded cell, which anti-radiation window comprises a sheath embedded in a concrete wall, which sheath receives a shielded porthole which is associated to a radio-protective shield as defined hereinabove, fastened on the periphery of an opening formed in said metallic internal coating.

Of course, the different features, variants and embodiments of the invention may be associated with one another according to various combinations provided that they are not incompatible or do not exclude each other.

