WO2012153032A1

WO2012153032A1 - Containment for a source element liable to generate a fluid contaminant

Info

Publication number: WO2012153032A1
Application number: PCT/FR2012/050930
Authority: WO
Inventors: James GAZEAU; Bruno Deletre; Rémy PRIOLEAU; Sébastien DURAND; Jérôme PELLE
Original assignee: Gaztransport Et Technigaz
Priority date: 2011-05-10
Filing date: 2012-04-26
Publication date: 2012-11-15
Also published as: FR2975214A1; FR2975214B1

Abstract

The containment according to the invention comprises a safety chamber (7) placed around the source element (1, 2) and bounded by a load-bearing wall (5) made of concrete, said wall being equipped with a metallic coating (7). This coating comprises a metallic membrane, peripheral anchoring structures, and intermediate anchoring members distributed over the surface of the metallic membrane. Pressure distributing means are securely fastened to fastening tabs anchored in the concrete.

Description

CONFINEMENT ENCLOSURE FOR A SOURCE-ELEMENT CAPABLE OF GENERATING A CONTAMINANT FLUID

The present invention relates to a containment chamber associated with a source element capable of generating a contaminating fluid emission in the event of malfunction. Such an enclosure proves to be an absolute necessity when the element capable of generating a contaminating emission is a nuclear reactor, the fluid emission being in this case a radioactive gas stream, for example a stream of vapor coming from the primary cooling circuit of the reactor. reactor.

It is known, in fact, that the reactor core produces a large amount of heat, which is transported by a primary coolant towards a heat exchanger, where the calories are transferred to the fluid of a secondary cooling circuit located at outside the area where there is a high level of radiation. The high-irradiation zone can, in the event of an operating incident, give rise to leaks of radioactive materials and is therefore placed in a containment chamber intended to block or brake the passage of irradiated materials to the environment. external atmosphere where the secondary cooling circuit is located as well as the other organs ensuring the recovery of thermal energy and its transformation into mechanical energy. The containment chamber is traversed by the inlet and outlet ducts of the heat exchanger; it is, in known manner, consisting of at least one, and often two, enclosure (s) security, whose walls are made of concrete. One of the difficulties encountered in the production of these safety enclosures is that the concrete walls are not sufficiently sealed and may, in particular, let radioactive vapor escape from a leak in the circuit. primary cooling. It has therefore already been proposed to cover the inner face of the concrete wall of a safety enclosure with a composite coating comprising a fiberglass-reinforced epoxy resin. Such a coating effectively improves the barrier qualities of the security enclosure that carries it, but it has been found that it deteriorates over time, in particular because of the temperature and pressure conditions to which it is subjected during the course of time. operation of the reactor: the temperature is high, especially for the primary safety enclosure, and the loading or recharging phases of the reactor obviously imply that the temperature and pressure are not constant over time. However, in France, for nuclear power plants of 1300 and 1450 MW, the creation authorization decree sets the permissible limit of the leakage rate of the primary safety enclosure in case of accident to 1.5% per day of the mass of gas contained in the primary safety cabinet.

According to one embodiment, the invention provides a confinement enclosure for a source element capable of generating a contaminant fluid emission, said confinement enclosure comprising a security enclosure placed around said source element to isolate said element from the source element. external atmosphere, said safety enclosure being delimited by a concrete supporting wall, which comprises a coating disposed of side of said wall where said source element is located and intended to limit the diffusion into the outside atmosphere of a possible flow of contaminating leakage from said source element, characterized in that said coating comprises:

a metal membrane covering at least a portion of said concrete wall;

- Perimeter anchoring structures arranged at the periphery of said metal membrane for anchoring the edges of said metal membrane to the concrete wall;

- Intermediate anchoring members distributed on the surface of the metal membrane, each intermediate anchoring member comprising:

- On the one hand, a fixing rod fixed in the concrete wall so as to project on the surface of said wall in the direction of the element, each rod passing through the metal membrane by a bore provided through said membrane, and,

- On the other hand, a pressure distribution means, which is sealingly secured with its associated fastening rod and which rests, in a sealed manner, on an area of the metal membrane, so as to hold against the wall. concrete a corresponding portion of the metal membrane.

As has been explained above, the element capable of generating a contaminant fluid emission may be a nuclear reactor, the fluid emission then being a radioactive gas stream, for example a stream of steam from the primary cooling circuit of the reactor.

The containment chamber advantageously comprises two safety enclosures, a primary enclosure located in the vicinity of the source element and a secondary enclosure located in the vicinity of the external atmosphere; the structures constituting the two security enclosures may be identical; but it is also possible that only one of the two safety enclosures has a metal coating, whose structure comprises a metal membrane as previously indicated, the other comprising only, on a concrete wall, a coating consisting of a layer of resin epoxy reinforced with glass fibers; in such a case, it is preferred that the security enclosure which comprises a metal coating is the primary enclosure.

The concrete walls of the containment structure may be prestressed concrete having a metal reinforcement. Advantageously, the sealing at the level of fixing rods and pressure distribution means is obtained by welding. Preferably, between two adjacent pressure distributing means, the membrane comprises embossings giving it a mechanical flexibility between two intermediate anchoring members.

It can be provided that a peripheral anchoring structure is made by welding a membrane edge on a strip of metal plate positioned against the concrete wall with the interposition of a sealant, the maintenance of the metal plate being provided by a profile fixed on the concrete wall by fixing rods anchored in the concrete of the wall. In areas where the concrete wall passes the ducts required for normal operation of the source element, the metal membrane is removed and the edges defining the suppression zone are fixed to the wall by a peripheral anchoring structure as defined above.

It is preferred that the coating formed by a metal membrane is constituted, for the greater part of its surface, by the assembly of a plurality of rectangular sheets welded together; the sheets welded together are preferably stainless steel sheets.

The invention also relates to a method for coating a source element, capable of generating a contaminant fluid emission, of a confinement enclosure as defined above, in which:

- Fixing rods protruding from the surface of said wall towards the source element are fixed to the concrete supporting wall of a safety enclosure intended to receive a metal coating;

the metal diaphragm intended to constitute said metal coating is pierced at the locations of the fixing rods;

- The metal membrane is applied to the concrete wall portion for receiving the previously pierced metal membrane area, the fastening rods passing through said metal membrane by the holes of said membrane;

the edges of the metal membrane are anchored to the concrete wall by means of a peripheral anchoring structure; and

a pressure distributing means is securely fastened to each fastening rod, said means sealingly pressing against an area of the metal diaphragm, so as to hold against the wall; concrete a corresponding portion of the metal membrane.

In a preferred embodiment of the method defined above, the security enclosure for receiving a metal coating comprises a concrete carrying wall having a metal reinforcement, in which case, before the establishment of the fixing rods, said concrete wall is scanned to define the position of the reinforcing bars in the concrete wall and to prevent their contact with the fixing rods.

In such a method, it can be provided that, in order to anchor the edges of the metal membrane on the concrete wall, at the level of said edges, a putty is placed which is covered with a strip of metal plate and ensures the maintenance of the dish by means of a metal profile fixed on the concrete wall by fixing rods anchored in the concrete.

An idea underlying the invention is to set up metal coatings on the inner faces of the concrete load-bearing walls to maintain the sealing properties of the primary safety enclosure over time and to integrate the normative requirements of behavior in serious accident situations.

Some aspects of the invention start from the observation that, therefore, a difficulty is due to the fact that it is necessary to ensure a perfect holding in position of the metal coating on the concrete carrying wall of the security enclosure. This difficulty stems essentially from the fact that the coating is subjected, at the time of loading or reloading of the fissile material reactor, to a vacuum which tends to separate the metal coating from the concrete supporting wall. Certain aspects of the invention are based on the idea of proposing a method of fixing a metallic coating by means of which the good state of the metallic coating makes it possible to permanently seal the security enclosures with respect to a radioactive leakage flow from a malfunction of the reactor. Of course, given the extreme importance of the confinement of radioactive materials in the event of malfunction, embodiments of the invention also make it possible, as provided by certain normative texts, to use a containment enclosure consisting of two enclosures safety, one primary in the vicinity of the radioactive source element and the other secondary in the vicinity of the external atmosphere, these two safety enclosures adding their effects in series to improve the final result.

To better understand the object of the invention will now be described, by way of purely illustrative and non-limiting example, an embodiment and implementation shown in the accompanying drawing. On this drawing :

FIG. 1 schematically represents a confinement enclosure according to one embodiment of the invention comprising two safety enclosures, this confinement enclosure being associated with a pressurized water nuclear reactor;

FIG. 2 diagrammatically represents the method of fixing a metal membrane on the concrete supporting wall of the safety enclosure closest to the core of the nuclear reactor;

- Figure 3 shows an enlargement of the magnifying glass A of Figure 2. Referring to the drawing, it can be seen that 1 has designated a pressurized water nuclear reactor, the primary cooling circuit 2 of which passes through a heat exchanger 3. The exchanger 3 comprises a secondary cooling circuit of which the 4a inlet duct the secondary heat transfer fluid to the exchanger 3 while the outlet 4b evacuate secondary heat transfer fluid towards organs that will allow the transformation of thermal energy into mechanical energy, said bodies not being shown in the drawing .

The zone with high radioactivity is constituted by the reactor 1 itself and the cooling circuit 2. If a malfunction occurs in this zone, there may be emission of a radioactive gaseous fluid, especially radioactive water vapor and c This is why the standards have made it possible to impose the confinement of radioactive source elements 1 and 2 vis-à-vis the outside. There is therefore provided a containment enclosure consisting of two safety enclosures 5 and 6. The primary safety enclosure 5 is that which directly covers the source elements 1 and 2, which can generate a safety hazard. The secondary safety enclosure 6 covers the primary safety enclosure 5. The confinement effects of the safety enclosures 5 and 6 therefore occur in series and are added to obtain the safety generated by the containment enclosure.

The two safety enclosures 5 and 6 each consist of a prestressed concrete support wall comprising an inner metal frame; but, since the concrete does not constitute a perfectly gas-tight barrier, it has been provided that each safety enclosure comprises, on its face in look with the source element 1 and 2, a coating for constituting a blockage, or at least a braking, of the diffusion of a radioactive accidental flow from the source element 1 and 2 to the outside.

In the embodiment described, the coating of the primary safety enclosure 5 is a metal coating designated by 7 as a whole, while the internal lining of the secondary safety enclosure 6 is a coating of epoxy resin reinforced with glass. The coating 8 corresponds to the state of the art and will not be described further. The embodiment shown in Figures 2 and 3, allows the establishment of a metal coating 7 and its holding on the concrete carrier wall despite the pressure variations inside the primary safety enclosure. It is recalled that these variations are due to the fact that the loading or reloading of the reactor of fissile material takes place in depression.

Figure 2 shows schematically in section the structure of the metal coating. This coating is constituted by a metal membrane 7 of stainless steel having embossings 9. The membrane 7 is attached to the inner face of the concrete of the primary safety enclosure 5 by means of fixing rods 10 anchored in the concrete. The head 11 of these fixing rods 10 protrudes with respect to the supporting wall 5 and maintains a pressure distribution means 12, which has, for example, the shape of a conical cup traversed along its axis by the fixing rod 10 ; this cup 12 is supported by the head 11 against the metal diaphragm 7. In order to seal this system for holding the metal diaphragm 7 against the concrete wall 5, provision is made to weld the head 11 on the cup 12 after the establishment of the fixing rod 10. And after this implementation, it is also possible to weld the periphery of the cup 12 on the metal membrane 7. In this way, if the internal space of the safety enclosure 5 is in depression, the metal membrane 7 is perfectly retained on the concrete supporting wall. Retention systems 10, 11 and 12 are expected to be evenly distributed over the entire surface of the metal coating.

It is clear that the metal membrane used must necessarily be pierced before the place where it is desired to set up a fastening rod 10. This metal membrane consists of sheets welded together overlap. The embossings 9 are positioned between the holes corresponding to the fixing rods 10: they make it possible to give a deformation flexibility for the metal membrane 7, which is subjected to significant temperature variations and must consequently be able to expand and contract. between the fixed points constituting the fixing rods 10.

The free edges of the metal membrane 7 must also be sealed to the concrete wall 5. It should also be noted that a zone of the concrete supporting wall will not be as easily protected as the others, since the metal membrane 7 must be traversed by the ducts 4a, 4b of the secondary cooling circuit. All the edge regions of the metal membrane 7 are held tightly on the concrete wall of the security enclosure 5 by the device which. is surrounded by the magnifying glass A of FIG. 2 and which is shown in detail in FIG. At the level of the edge of the metal membrane 7, a strip of metal plate 13 has been put in place, which is supported on the concrete of the safety enclosure 5 by a mastic bead 1. The metal plate 13 is held on the concrete by means of a metal profile 15 fixed on the concrete by a fixing rod 10a anchored in the concrete; the fixing rod 10a has a head 11a, which rests on the profile 15 and holds it on the bearing wall 5. To ensure the seal, a weld 16 is made between the metal membrane 7 and the flat strip 13. The fixing rods 10a and 11a are similar to the fixing rods 10 and 11 and are distributed all along the edges of the metal membrane 7.

It is clear that the implementation of the metal coating, which has just been described, must be made at a time when the nuclear reactor is not in operation. For the installation of a metallic coating of the type just described, the concrete bearing wall 5 is first scanned to define the position of the reinforcing bars in the wall, and then the rods are laid down. fixing 10, 10a in their anchoring locations. Prepositioning the metal sheets of the metal coating and marking on the sheets the position of the fixing rods 10; the sheets are then punched to obtain the bores, which will be traversed by the fixing rods 10; is then positioned on the face of the metal membrane 7 which will face the concrete carrier wall 5, the flat strips 13 and mastic flanges 14; after which, we put in place the metal membrane 7 on all fixing rods 10. We lock the membrane in the final position by positioning the heads 11 on the fixing rods 10. Along the edges of the metal diaphragm 7, the fixing rods 10a and the metal sections 15 are positioned and the edges of the metal membrane 7 are locked by placing in place heads lia.

It is clear that a containment chamber of the type just described, allows a considerable improvement in safety in case of malfunction of the nuclear reactor 1 and / or the primary cooling circuit 2.

Although the invention has been described in connection with several particular embodiments, it is obvious that it is not limited thereto and that it comprises all the technical equivalents of the means described and their combinations if they are within the scope of the invention.

The use of the verb "to include", "to understand" or "to include" and its conjugated forms does not exclude the presence of other elements or steps other than those set out in a claim. The use of the indefinite article "a" or "an" for an element or a step does not exclude, unless otherwise stated, the presence of a plurality of such elements or steps. Several means or modules can be represented by the same hardware element.

In the claims, any reference sign in parentheses can not be interpreted as a limitation of the claim.

Claims

1. containment vessel for a source element (1,2) capable of generating a contaminating fluid transmission, said containment vessel comprising a safety enclosure placed around said source element _(1/2) to isolate said element- source (1,2) of the external atmosphere, said safety enclosure being delimited by a concrete carrying wall, which comprises a coating disposed on the side of said wall where said source element (1,2) is located and intended to limiting the diffusion into the outside atmosphere of a possible flow of contaminating leakage from said source element (1,2), characterized in that said coating comprises:

- a metal membrane (7) covering at least a portion of said concrete wall;

peripheral anchoring structures (10a, 11a, 13, 14, 15, 16) arranged at the periphery of said metal membrane (7) for anchoring the edges of said metal membrane (7) to the concrete wall;

intermediate anchoring members distributed on the surface of the metal membrane (7), each intermediate anchoring member comprising:

- on the one hand, a fixing rod (10) fixed in the concrete wall so as to project on the surface of said wall towards the source element (1, 2), each rod (10) passing through the metal membrane (7) by a bore provided through said membrane (7), and

- On the other hand, a pressure distribution means (12), which is sealingly secured with its associated fixing rod (10) and which is supported, so that sealing, on an area of the metal membrane (7), so as to maintain against the concrete wall (5) a corresponding portion of the metal membrane (7).

2. Enclosure according to claim 1, characterized in that the source element (1,2) capable of generating a contaminating fluid emission is a nuclear reactor, the fluid emission being a radioactive gas stream.

3. Enclosure according to one of claims 1 to 2, characterized in that the sealing at the fixing rods (10) and means (12) pressure distributing is obtained by welding.

4. Enclosure according to one of claims 1 to 3, characterized in that between two adjacent distributor means (12), the membrane (7) comprises embossments (9) conferring a mechanical flexibility between two intermediate anchoring members adjacent.

5. Enclosure according to one of claims 1 to 4, characterized in that a peripheral anchoring structure is formed by welding a membrane edge on a metal plate strip (13) positioned against the concrete wall with interposition d a putty (14), the maintenance of the metal plate (13) being provided by a profile (15) fixed on the concrete wall by fixing rods (10a) anchored in the concrete of the wall.

6. Enclosure according to one of claims 1 to 5, characterized in that the coating formed by a metal membrane (7) is constituted, for most of its surface, by the assembly of a plurality of welded rectangular sheets between them overlapping.

7. Enclosure according to claim 6, characterized in that the sheets welded together are stainless steel sheets.

8. Enclosure according to one of claims 1 to 7, characterized in that the containment chamber comprises two safety enclosures (5,6), a primary enclosure (5) located in the vicinity of the source element (1). , 2) and a secondary enclosure (6) located in the vicinity of the external atmosphere.

9. Enclosure according to one of claims 1 to 8, characterized in that the structures constituting the two enclosures (5,6) security are identical.

10. Enclosure according to one of claims 1 to 9, characterized in that the concrete concrete walls of the containment is a prestressed concrete having a metal frame.

11. A method for coating a source element (1,2), capable of generating a radioactive fluid emission, of a confinement enclosure, characterized in that:

- Fixing rods (10) protruding on the surface of said wall, in the direction of the wall, are fixed on a concrete support wall of a safety enclosure (5) intended to receive a metal coating (7). source element (1,2);

- piercing at the locations of the fixing rods

(10), the metal membrane (7) intended to constitute said metal coating;

the metal membrane (7) is applied to the concrete wall portion intended to receive the previously pierced metal membrane zone (7), the fixing rods (10) passing through said metal membrane (7) through the bores of said membrane; anchoring the edges of the metal membrane to the concrete wall by means of a peripheral anchoring structure; and

a pressure distribution means (12) is sealingly secured to each fastening rod (10), said means sealingly pressing against an area of the metal diaphragm (7) so as to hold against the concrete wall a corresponding portion of the metal membrane (7).

12. The method of claim 11, wherein the security enclosure (5) for receiving a metal coating (7) comprises a concrete supporting wall having a metal frame, characterized in that before the establishment of rods. fixing (10), said concrete wall is scanned to define the position of the reinforcing bars in the concrete wall and to prevent their contact with the fixing rods (10).

13. Method according to one of claims 11 to 12, characterized in that, to anchor the edges of the metal membrane (7) on the concrete wall, is put in place at said edges, a putty (14) that covered with a strip of metal plate (13), and that the dish (13) is maintained by means of a metal section (15) fixed to the concrete wall by fixing rods ( 10a) anchored in the concrete.