EP4156206A1 - Dismantling system for nuclear facility - Google Patents

Abstract

This dismantling system (1) for a nuclear installation comprises a fixed part (2), configured to be connected to the nuclear installation and a mast (4) carried by the fixed part and extending along a vertical axis from the part fixed down. The mast comprises at least two modules (41, 43) assembled together and juxtaposed along the vertical axis. The dismantling system also comprises a handling system (6) configured to lower and raise the mast with respect to the fixed part, along the vertical axis, and a tool (8), carried by the module (41) furthest bottom of the mast. Each module of the mast is a straight cylinder section comprising a solid and sealed cylindrical wall, and defining an interior volume, the respective interior volumes of the modules jointly forming a sealed interior volume of the mast

Description

The present invention relates to a dismantling system for a nuclear installation.

Nuclear facilities generally have a sealed enclosure, in which there is radioactive material, such as fuel rods or irradiated materials.

In the field of the dismantling of nuclear installations, it is known to have to gain access to the interior of such a sealed enclosure in order to carry out dismantling operations, aimed for example at evacuating radioactive material, using a tool. For this, it is known to provide an opening in the top of a sealed enclosure, and to pass a mast through the opening, the mast then extending into the sealed enclosure downwards, from the outside the containment, and carrying at its lowest end a tool to be able to carry out the dismantling operations.

Such a mast generally comprises a framework formed by a tubular assembly. This frame is either one-piece or formed from several sections assembled together, for example by bolting.

However, such a mast has a complex framework, which is particularly disadvantageous in a nuclear environment. Indeed, during the dismantling operations, a large quantity of radioactive particles, such as dust for example, can be deposited on the tubes of the framework. When the mast has to be taken out of the sealed enclosure, its decontamination is then particularly long, complex and potentially incomplete. In addition, due to the open structure of such a frame, the mast does not protect against ionizing radiation, which can then easily pass through the opening made in the enclosure and expose a worker located outside the 'pregnant. Such a mast is therefore not suitable for an environment exposed to radioactivity.

In addition, a tubular assembly is not a symmetrical structure, and generally has a preferential direction for the recovery of the forces exerted there. Thus, such a mast is not suitable for working in all directions, which consequently reduces the field of action of the tool attached to it.

The document GB 2 176 924 A describes a dismantling system comprising a mast formed of modules assembled together, forming a guide for a tool, which is movable along the mast. The structure of the modules, adapted to allow the movement of the tool along the mast, makes the cleaning of the mast particularly complex and tedious, which makes the dismantling system unsuitable for an environment exposed to radioactive particles.

It is these drawbacks that the invention more particularly intends to remedy by proposing a nuclear installation dismantling system that is more suitable for managing the problems of irradiation and contamination, while being more resistant.

To this end, the invention relates to a dismantling system for a nuclear installation, comprising a fixed part, configured to be connected to the nuclear installation; a mast carried by the fixed part and extending along a vertical axis from the fixed part downwards, the mast comprising at least two modules assembled together and juxtaposed along the vertical axis; a handling system configured to lower and raise the mast relative to the fixed part, along the vertical axis; and a tool.

According to the invention, each module of the mast is a straight cylinder section comprising a solid and sealed cylindrical wall, and defining an interior volume, the respective interior volumes of the modules jointly forming a sealed interior volume of the mast. In addition, the tool is permanently carried by the lowest module of the mast.

Thanks to the invention, the solid cylindrical walls of the modules make the mast particularly easy to clean when it is polluted by radioactive particles and make it possible to block ionizing radiation, and the cylindrical geometry of the modules allows the mast to be more resistant and suitable for working in all directions.

• Au moins un des modules, voire chaque module, comprend une plaque de fermeture, qui est assemblée de manière étanche avec la paroi cylindrique de ce module.
• Chaque module comprend une bride supérieure et une bride inférieure, qui sont assemblées de manière étanche avec la paroi cylindrique de ce module, et qui permettent d'assembler les modules entre eux.
• Les modules incluent un module d'interface, qui est disposé en bas du mât et sur lequel l'outil est fixé, et au moins un module additionnel.
• La bride inférieure du ou de chaque module additionnel comprend une jupe de centrage, et un diamètre extérieur de la jupe de centrage est sensiblement égal à un diamètre intérieur des brides supérieures.
• La partie fixe comprend un cylindre de guidage, configuré pour s'étendre au travers d'une ouverture ménagée dans une enceinte de l'installation nucléaire, le cylindre de guidage permettant de guider le mât lorsque le mât descend ou remonte par rapport à la partie fixe.
• Le cylindre de guidage comprend au moins deux guides qui comprennent chacun au moins un patin, chaque module comprend au moins deux barres de guidage, et les patins des guides centrent et alignent le mât par rapport au cylindre de guidage, et guident le mât lorsque le mât descend ou remonte par rapport à la partie fixe, en coopérant avec les barres de guidage.
• Chaque guide comprend au moins deux patins qui exercent sur la barre de guidage associée des efforts qui permettent de centrer et d'aligner le mât par rapport au cylindre de guidage.
• Le ou chaque patin d'au moins un des guides comprend des ailettes entourant au moins une des barres de guidage des modules de manière à empêcher une rotation du mât autour de l'axe vertical.
• Le système de démantèlement forme un espace annulaire entre le mât et le cylindre de guidage, le système de démantèlement comprend des flexibles destinés à l'alimentation et/ou au contrôle de l'outil et disposés dans l'espace annulaire, et la partie fixe comprend un bouchon fermant de manière étanche le haut de l'espace annulaire.

According to advantageous, but not mandatory, aspects of the invention, this nuclear installation dismantling system incorporates one or more of the following characteristics, taken in isolation or in any technically admissible combination:

• At least one of the modules, or even each module, comprises a closure plate, which is assembled in a sealed manner with the cylindrical wall of this module.
• Each module comprises an upper flange and a lower flange, which are assembled in a sealed manner with the cylindrical wall of this module, and which make it possible to assemble the modules together.
• The modules include an interface module, which is placed at the bottom of the mast and on which the tool is fixed, and at least one additional module.
• The lower flange of the or each additional module comprises a centering skirt, and an outer diameter of the centering skirt is substantially equal to an inner diameter of the upper flanges.
• The fixed part comprises a guide cylinder, configured to extend through an opening made in an enclosure of the nuclear installation, the guide allowing the mast to be guided when the mast descends or rises relative to the fixed part.
• The guide cylinder includes at least two guides that each include at least one shoe, each module includes at least two guide bars, and the shoes of the guides center and align the mast with respect to the guide cylinder, and guide the mast when the mast descends or rises relative to the fixed part, cooperating with the guide bars.
• Each guide comprises at least two pads which exert forces on the associated guide bar which make it possible to center and align the mast with respect to the guide cylinder.
• The or each shoe of at least one of the guides comprises fins surrounding at least one of the guide bars of the modules so as to prevent rotation of the mast around the vertical axis.
• The dismantling system forms an annular space between the mast and the guide cylinder, the dismantling system comprises hoses intended for supplying and/or controlling the tool and arranged in the annular space, and the fixed part includes a plug sealingly closing the top of the annular space.

• [Fig. 1] La figure 1 est une vue en perspective d'un système de démantèlement d'installation nucléaire conforme à l'invention, représenté dans une première étape de prolongement ;
• [Fig. 2] La figure 2 est une coupe du système de démantèlement de la figure 1, selon un plan comprenant un axe vertical du système de démantèlement, au cours de la première étape de prolongement ;
• [Fig. 3] La figure 3 est une vue en perspective d'un mât du système de démantèlement des figures 1 et 2 ;
• [Fig. 4] La figure 4 est une vue en perspective d'un module du mât de la figure 3 ;
• [Fig. 5] La figure 5 est une coupe en perspective d'un support du système de démantèlement des figures 1 et 2, la coupe étant réalisée selon un plan comprenant un axe vertical du système de démantèlement ;
• [Fig. 6] La figure 6 est une vue en perspective d'un guide du support de la figure 5 ;
• [Fig. 7] La figure 7 est une coupe du système de démantèlement des figures 1 et 2, selon le plan VII visible à la figure 2 ;
• [Fig. 8] La figure 8 est une vue en perspective d'un système de manutention appartenant au système de démantèlement des figures 1 et 2 ;
• [Fig. 9] La figure 9 est une vue en perspective du système de démantèlement de la figure 1, représenté dans une deuxième étape de prolongement ;
• [Fig. 10] La figure 10 est une coupe du système de démantèlement de la figure 1, au cours de la deuxième étape de prolongement, la coupe étant analogue à celle de la figure 7 ;
• [Fig. 11] La figure 11 est une coupe du système de démantèlement de la figure 1, au cours d'une troisième étape de prolongement, la coupe étant analogue à celle des figures 7 et 10 ; et
• [Fig. 12] La figure 12 est une coupe du système de démantèlement de la figure 1, au cours d'une quatrième étape de prolongement, la coupe étant analogue à celle des figures 7, 10 et 11.

The invention will be better understood and other advantages thereof will appear more clearly in the light of the following description of an embodiment of a nuclear installation dismantling system, in accordance with its principle, given by way of example only and made with reference to the drawings in which:

• [ Fig. 1 ] There figure 1 is a perspective view of a nuclear installation dismantling system according to the invention, shown in a first extension step;
• [ Fig. 2 ] There figure 2 is a section of the dismantling system of the figure 1 , along a plane including a vertical axis of the dismantling system, during the first extension step;
• [ Fig. 3 ] There picture 3 is a perspective view of a mast of the dismantling system figure 1 And 2 ;
• [ Fig. 4 ] There figure 4 is a perspective view of a mast module of the picture 3 ;
• [ Fig. 5 ] There figure 5 is a perspective section of a support of the dismantling system of the figure 1 And 2 , the section being made along a plane comprising a vertical axis of the dismantling system;
• [ Fig. 6 ] There figure 6 is a perspective view of a support guide from the figure 5 ;
• [ Fig. 7 ] There figure 7 is a cross-section of the system for dismantling figure 1 And 2 , according to plan VII visible at picture 2 ;
• [ Fig. 8 ] There figure 8 is a perspective view of a handling system belonging to the dismantling system of figure 1 And 2 ;
• [ Fig. 9 ] There figure 9 is a perspective view of the dismantling system of the figure 1 , shown in a second extension step;
• [ Fig. 10 ] There figure 10 is a section of the dismantling system of the figure 1 , during the second extension step, the cut being similar to that of the figure 7 ;
• [ Fig. 11 ] There figure 11 is a section of the dismantling system of the figure 1 , during a third extension step, the cut being similar to that of the figure 7 And 10 ; And
• [ Fig. 12 ] There figure 12 is a section of the dismantling system of the figure 1 , during a fourth extension step, the cut being similar to that of the figure 7 , 10 And 11 .

On the figure 1 And 2 is presented a dismantling system 1 comprising a fixed part 2, a mast 4, a handling system 6 and a tool 8.

The dismantling system 1 is used inside a nuclear installation 9 when an intervention, in particular dismantling, is carried out.

Nuclear installation 9 is represented only at the figure 2 , in a simplified way. To the picture 2 , the dismantling system 1 and the nuclear installation 9 are shown in section along a plane comprising a vertical axis Z. In practice, the nuclear installation 9 comprises an enclosure 91 which delimits an interior volume V9 in a sealed manner. The enclosure 91 is for example the enclosure of a nuclear reactor, or a containment box. In the example, enclosure 91 is the enclosure protecting the reactor core of a Natural Uranium Graphite Gas (UNGG) nuclear power plant. Thus, in the example, several stacks 93 of graphite bricks are arranged in the interior volume V9 of the enclosure 91, most of the graphite bricks being pierced with a central duct which can accommodate a fuel cartridge or a rod of control. In the example, the dismantling system 1 makes it possible to manipulate the graphite bricks so as to evacuate them from the stacks 93.

The interior volume V9 of the enclosure 91 is therefore subjected to significant radioactive activity, in the form of ionizing radiation and in the form of contamination, such as for example dust and radioactive materials.

The dismantling system 1 rests on the enclosure 91 of the nuclear installation 9, via its fixed part 2. The fixed part 2 carries the mast 4, which extends downwards, i.e. i.e. towards the inside of the enclosure 91. The mast 4 is substantially vertical, and thus extends along the vertical axis Z, which is a main axis of the dismantling system 1. Thus, the mast 4 is carried by the fixed part 2 at the upper end of the mast. In practice, the mast 4 extends through an opening 95, made in the enclosure 91 and opening into the interior volume V9. Preferably, opening 95 is circular.

In the rest of the description, the terms "top", "bottom", "upper", "lower", "up" and "down" are understood by referring to the vertical axis Z. In addition, the orientation "horizontal" refers to an orientation perpendicular to the vertical Z axis.

On the picture 3 , only the mast 4 is shown.

The tool 8 is carried by the mast 4, so as to be able to carry out operations in the volume V9 necessary for the dismantling of the nuclear installation 1. For example, the tool 8 makes it possible to handle the bricks of the stacks 93. Preferably , the tool 8 comprises in practice a robotic arm fixed to the mast 4 and manipulating one or more tools to carry out the dismantling operations.

The mast 4 is formed of several modules, namely an interface module 41 and one or more additional modules 43. The interface module 41 and the additional module(s) 43 are assembled together by being juxtaposed along the vertical axis Z. At the figure 4 , one of the additional modules 43 is shown alone.

The interface module 41 is located at the lower end of the mast 4, and makes it possible to fix the tool 8 to the mast 4. The tool 8 is therefore fixed to the lower end of the mast 4. The additional module(s) 43 are therefore located above the interface module 41, and allow, according to the effective number, to modify the height H4 of the mast 4, the height H4 being measured along the vertical axis Z. On the example of the picture 3 , the mast 4 comprises three additional modules 43.

The interface module 41 is a straight circular cylinder section, which is centered on an axis Z41, coinciding with the vertical axis Z in the mounted configuration of the mast 4, and which comprises a cylindrical wall 411. The cylindrical wall 411 is delimited , along the axis Z41, by an upper flange 412 and by a lower flange 413, which form respective opposite edges of the cylindrical wall 411. The upper 412 and lower flanges 413 thus extend in a plane perpendicular to the axis Z41 and are parallel to each other.

The cylindrical wall 411 of the interface module 41 is solid, and therefore sealed. An interior volume V41 of the interface module 41 is defined as being the volume delimited radially by the cylindrical wall 411 and axially by the planes in which the flanges 412 and 413 extend.

The flanges 412 and 413 of the interface module 41 are assembled in a sealed manner with the cylindrical wall 411, for example by welding.

The upper flange 412 has a flat surface 414, of annular shape, perpendicular to the axis Z41 and oriented upwards, and several tapped holes not visible in the figures, extending parallel to the axis Z41 and opening onto the surface plane 414. Advantageously, the tapped holes of the upper flange 412 are regularly distributed around the vertical axis Z41. In the example, the top flange 412 includes eighteen tapped holes. In a variant not shown, the upper flange comprises a different number of tapped holes.

“D412” denotes the internal diameter of the upper flange 412, measured perpendicular to the vertical axis Z41.

The lower flange 413 has a flat surface 416, of annular shape, perpendicular to the axis Z41 and oriented downwards, and several holes 417, extending parallel to the axis Z41 and opening onto the flat surface 416. In the For example, the lower flange 413 comprises forty holes 417. In a variant not shown, the lower flange comprises a different number of holes 417.

We note “H41” the height of the interface module 41, measured parallel to the axis Z41 between the upper flange 412 and the lower flange 413. The height H41 is preferably between 1000 mm and 1500 mm, in the example equal to 1350 mm.

In practice, the tool 8 is fixed to the interface module 41 via the lower flange 413. For this purpose, the tool 8 comprises a flange adapted to be fixed to the lower flange 413. Advantageously, when the tool 8 is fixed to the interface module 41, the tool completely and in a sealed manner closes the lower opening of the interface module, that is to say the opening of the lower flange 413. other words, the interior volume V41 of the interface module 41 is not accessible through the lower flange 413 when the tool 8 is fixed to the lower flange.

In summary, the tool 8 is permanently fixed to the lowest module of the mast 4. In other words, the tool 8 is permanently carried by the lowest module of the mast.

Each additional module 43 is a right circular cylinder section, which is centered on an axis Z43, coinciding with the vertical axis Z in the mounted configuration of the mast 4, and which comprises a cylindrical wall 431. The cylindrical wall 431 is delimited, according to the axis Z43, by an upper flange 432 and by a lower flange 433, which form respective opposite edges of the cylindrical wall 431. The upper flanges 412 and lower 413 thus extend in a plane perpendicular to the axis Z43 and are parallel to each other.

We denote "D4" the outer diameter of the mast 4, which corresponds to the outer diameter of the cylindrical walls 411 and 431 of the modules 41 and 43. Preferably, the diameter D4 also corresponds to the outer diameter of the upper flanges 412 and 432 as well as to the outer diameter of the lower flanges 433, which are therefore flush with the faces outer diameter of the cylindrical walls 411 and 431. Advantageously, the outer diameter D4 of the mast 4 is constant over the entire height of the mast, that is to say from the bottom of the cylindrical wall 411 of the module 41, to the top of the cylindrical wall 431 of the module 43 above.

We note "H43" the height of an additional module 43, measured parallel to the axis Z43 between the upper flange 432 and the lower flange 433. The height H43 is preferably between 1000 mm and 1500 mm, in the example equal to 1250 mm. Alternatively, the heights H41 and H43 are equal.

The height H4 of the mast 4 corresponds to the sum of the height of all the modules 41 and 43. Thus, in the example of the figures 1 to 3 , the height H4 is equal to three times the height H43 plus one time the height H41. In practice, the height of the module 41 and of the modules H43 are adapted according to the working environment of the mast 4 within the nuclear installation 9.

The cylindrical wall 431 of the additional modules 43 is solid, and therefore sealed. An interior volume V43 of an additional module 43 is defined as being the volume delimited radially by the cylindrical wall 431 and axially by the planes in which the flanges 432 and 433 extend.

The flanges 432, 433 of each additional module 43 are assembled in a sealed manner with the cylindrical wall 431 of this module, for example by welding.

The upper flange 432 of each additional module 43 has a flat surface 434, of annular shape, perpendicular to the axis Z43 and oriented upwards, and several tapped holes 435, extending parallel to the axis Z43 and opening onto the flat surface 434. Advantageously, the tapped holes 435 are regularly distributed around the vertical axis Z43. In the example, the top flange 432 includes eighteen tapped holes 435. As a variant not shown, the top flange includes a different number of tapped holes.

“D432” denotes the inner diameter of the upper flange 432, measured perpendicular to the vertical axis Z43. In practice, diameter D432 is equal to diameter D412.

The diameters D412 and D432 are preferably between 1200 mm and 1800 mm, in the example still preferably equal to 1550 mm. The diameter D4 is preferably between 1250 mm and 1850 mm, in the example still preferably equal to 1650 mm.

In practice, the upper flanges 432 of the additional modules 43 are identical to the upper flange 412 of the interface module 41.

The lower flange 433 of each additional module 43 has a flat surface 436, of annular shape, perpendicular to the axis Z43 and oriented downwards, and several holes 437, extending parallel to the axis Z43 and opening onto the surface plane 436. In practice, the lower flange 433 comprises as many holes 437 as the upper flanges 412 and 432 comprise threaded holes. Advantageously, the holes 437 of the lower flange 433 of each additional module 43 are aligned with the tapped holes 435 of the upper flange 432 of this module.

Advantageously, each additional module 43 includes recesses 438. The recesses 438 of each additional module 43 extend from the cylindrical wall 431 towards the vertical axis Z43, so as to form niches. The recesses 438 of each additional module 43 are arranged at the level of the lower end of the cylindrical wall 431, so that the lower flange 433 of this module is partially visible in the recesses 438, at the level of the holes 437 which pass through the flange bottom right through, thus opening out opposite the flat surface 436. Thus, the holes 437 are through and open into the recesses 438. In other words, the holes 437 of each additional module 43 are accessible from outside the additional module, that is to say from the outside of the cylindrical wall 431, via the recesses. Thus, the holes 437 of an additional module 43 do not open into the interior volume V43 of this additional module.

Two modules juxtaposed to each other along the vertical axis Z among the modules 41 and 43, that is to say an additional module 43 arranged above another additional module 43 or above the interface module 41, are assembled together by means of their flanges. More precisely, the lower flange 433 of the upper module is fixed to the upper flange 412 or 433 of the lower module, using screws passing through the holes 437 of the lower flange 433 and being screwed into the tapped holes of the flange 412 or in the tapped holes 435 of the upper flange 433, each screw having a head resting against the lower flange 433. In addition, the heads of the screws are accessible in the recesses 438 of the upper module, which makes it possible to screw the screw from the outside of the additional module 43 higher. The assembly of two juxtaposed modules is therefore carried out by flanges screwed together. Such an assembly is particularly advantageous, because it makes it possible to assemble a module 41 with a module 43 or two modules 43 between them in a sealed manner, that is to say that there is no opening between two modules. juxtaposed connecting their interior volume V41 and V43 with the exterior.

Advantageously, the lower flange 433 of each additional module 43 has a centering skirt 439, which extends from the flat surface 436 of the flange, parallel to the axis Z43, moving away from the cylindrical wall 431. The centering skirt 439 therefore forms a section of cylinder centered on the axis Z43 of the additional module, the outer diameter of which, measured perpendicular to the axis Z43 and marked "D439" on the figure 2 , is substantially equal to the diameters D412 and D432, except for games. As best seen on the picture 2 , when an additional module 43 is juxtaposed above another additional module 43 or the interface module 41, the centering skirt 439 of the upper module extends through the upper flange 412 or 432 of the lower module , being in contact with the upper flange, and thus extends into the interior volume V41 or V43 of the lowest module. The fact that the outer diameter D439 of the centering skirt 439 is substantially equal to the diameters D412 and D432 makes it possible to center between them two juxtaposed modules, that is to say that their respective axes Z41, Z43 coincide, which is particularly advantageous for facilitating their assembly by screwed flanges, and thus reinforcing the seal between two juxtaposed modules.

The interface module 41 and each additional module 43 comprises guide bars 45, which extend parallel to the axes Z41 and Z43 being carried by their cylindrical wall 411, 413. In the example, the interface module 41 and each additional module 43 each comprises three guide bars 45, which are regularly spaced in a direction circumferential to the axis Z41, Z43. In a variant not shown, a different number of guide bars is provided, for example one guide bar or four guide bars.

Each guide bar 45 comprises an upper groove 451 and a lower groove 453, which each extend in a plane perpendicular to the vertical axis Z41.

In the assembled state of the mast 4, each of the bars 45 of the interface module 41 is aligned, in a direction parallel to the vertical axis Z, with one of the bars 45 of the additional module 43 above. Similarly, for two additional modules 43 juxtaposed, each of the bars 45 of the lower module is aligned, in a direction parallel to the vertical axis, with one of the bars 45 of the upper additional module. Thus, the guide bars 45 of the modules 41 and 43 together form three guide bars of the mast 4.

Advantageously, the interface module 41 and each additional module 43 each comprise a closure plate 47. The closure plate 47 is in practice a disc extending in a plane perpendicular to the vertical axis Z41, Z43 of diameter equal to the diameter D412, D432 and arranged in the interior volume V41, V43 of the module. The closure plate 47 is assembled in a sealed manner with the side wall 411, 431, for example by welding.

Preferably, the closure plate 47 of each module 41, 43 is arranged close to the upper flange 412, 432, so that the volume between the wall cylindrical 411, 431, the closure plate 47 and the plane in which the upper flange 412, 432 extends is negligible compared to the internal volume V41, V43 of the module. Thus, in the rest of the description, it is considered that the interior volume V41, V43 of each module is delimited radially by the cylindrical wall 411, 431 and axially on the one hand by the closure plate 47 and on the other hand by the plane in which the lower flange 413, 433 extends.

In addition, the interior volume V41 of the interface module 41 is a closed and sealed volume, when the tool 8 is fixed to the interface module 41. Indeed, this volume is closed in a sealed manner by the cylindrical wall 411, by the closing plate 47 of the interface module 41 and by the tool 8, which completely closes, in a sealed manner, the lower opening of the interface module.

Moreover, in the assembled state of the mast, the interior volume V43 of each additional module 43 is a closed and sealed volume. Indeed, this volume is sealed off by the cylindrical wall 431 of this additional module, by the closing plate 47 of this additional module and by the closing plate 47 of the additional module or of the interface module, located under this additional module.

The fixed part 2 of the dismantling system 1 is better visible at the figure 5 , where it is represented alone and in section, on the same plane as the section of the picture 2 .

The fixed part 2 comprises a support 21, which rests on the enclosure 91 of the nuclear installation 9, and a guide cylinder 23. The support 21 and the guide cylinder 23 are assembled together, for example by welding. In practice, the support 21 is arranged outside the enclosure 91.

The guide cylinder 23 is a hollow tube, forming an interior volume V23 and extending along a central axis which coincides with the vertical axis Z, from the support 21 towards the interior volume V9 of the nuclear installation 9, at the through the opening 95 of the enclosure 91. Thus, the top of the guide cylinder 23 is located outside the enclosure 91 and the bottom of the guide cylinder is located in the interior volume V9 delimited by the pregnant.

We note “H23” the height of the guide cylinder 23, measured parallel to the central axis of the guide cylinder. Advantageously, the height H23 is substantially equal to three times the height H43. Thus, the guide cylinder 23 surrounds and makes it possible to simultaneously guide three juxtaposed modules among the modules 41 and 43.

The fixed part 2 is provided to rest in a sealed manner on the enclosure 91, that is to say so that no opening is present between the outside of the guide cylinder 23 and the enclosure 91. For example, this tightness is obtained by welding the fixed part to the enclosure, or by arranging a joint between the fixed part and the enclosure.

The guide cylinder 23 of the fixed part 2 comprises several guides 25, which are arranged inside the interior volume V23. Each guide 25 is elongated and extends parallel to the central axis of the guide cylinder 23. In the example, the fixed part 2 comprises three guides 25, which are regularly distributed around a direction circumferential to the central axis of the guide cylinder. In a variant not shown, the fixed part 2 comprises a different number of guides 25, such as for example one guide or four guides. In practice, the fixed part comprises as many guides 25 as each module 41 and 43 comprises guide bars 45.

Each guide 25 comprises several pads 251 which are distributed along the guide. In the example, each guide comprises three pads 251.

The pads 251 of each guide 25 are movable in translation along an axis radial to the central axis of the guide cylinder 23 and are actuated by hydraulic cylinders 257. All the pads of the same guide 25 are actuated by hydraulic cylinders 257 connected to the same hydraulic line, so that all the hydraulic cylinders of the same guide exert equal pressure on the pads 251 of this guide.

Advantageously, the pads 251 of at least one of the guides 25 include fins 253. In the example, among the three guides 25, the pads 251 of two of the guides 25 do not include fins 253 and the pads of the third guide 25, shown in figure 6 , comprise the fins 253. The fins 253 extend towards the central axis of the guide cylinder 23, giving each of the pads 251 a "U" shape in a plane perpendicular to the central axis.

Each guide 25 also includes a finger 255, actuated by a hydraulic cylinder 259. In the example, each finger 255 is movable in translation along an axis radial to the central axis of the guide cylinder 23. Each finger 255 is movable between a unlocking position, in which the finger is located closest to the guide cylinder 23, and a locking position, in which the finger is farthest from the guide cylinder 23, that is to say closest to the central axis of the guide cylinder 23.

Advantageously, the fixed part 2 also comprises two stops 27, which extend upwards from the upper side of the support 21 parallel to the vertical axis Z. In practice, each stop 27 is a tube, in the example a tube rectangular in section. The stops 27 are rigidly fixed to the support 21, for example by bolting or by welding. Alternatively, each abutment 27 is a section, or a mechanically welded assembly.

Advantageously, the fixed part 2 comprises a plug 29. The plug 29 is annular in shape and is fixed to the top of the support 21, partially covering the guide cylinder 23. The plug 29 includes a circular opening, of diameter D29.

When the fixed part 2 carries the mast 4, the mast extends in the guide cylinder 23 so that the guide bars 45 of the modules 41 and 43 are in contact with the pads 251 of the guides 25 of the guide cylinder. Thus, each guide bar 45 is associated with one of the guides 25. In practice, the pads 251 of each guide are actuated by the aforementioned jacks until they are in contact with the guide bars 45, and guide bars. These efforts make it possible to center and align the mast 4 with respect to the guide cylinder 23.

In practice, among the three pads 251 of each guide 25, the top pad and the bottom pad make it possible to take up the forces exerted by the mast 4, by being in contact with the guide bar of the highest module 41, 43 and of the lowest module among the three modules located in the guide cylinder. It is advantageous for this resumption of the forces to be carried out using two pads separated by a significant vertical distance, because the guiding performance of the mast 4 is improved, as well as the resistance of the dismantling system 1. In addition, among the three pads 251 of each guide 25, the central pad ensures the guiding of the mast 4, when the mast 4 consists only of the interface module 41 and an additional module 43.

In addition, for the guide 25 whose pads 251 include the fins 253, the latter surround the guide bars 45 associated with the guide, so as to angularly position the guide bars 45 in a direction circumferential to the vertical axis Z. fins 253 thus prevent the mast 4 from rotating about the vertical axis Z. In other words, the guide 25 whose pads 251 include fins 253 is an anti-rotation guide.

In addition, when the fixed part 2 carries the mast 4, the fingers 255 are in the locking position, so as to extend into the upper grooves 451 or into the lower grooves 453 of the guide bars 45 of the additional module 43 located the higher along the mast 4, or the interface module 41 during the assembly and dismantling phases of the mast 4, when the mast 4 includes only the interface module. Thus, the displacement of the mast 4 along the Z axis, upwards or downwards, is prevented, by blocking the guide bars against the fingers 255, when they are in the locking position. Mast 4 is then suspended from fixed part 2 via fingers 255.

When the fingers 255 are in the unlocked position, they do not extend into the upper grooves 451 nor into the lower grooves 453 of the guide bars 45, and the movement of the mast 4 along the Z axis is then not prevented. . The movement of the mast along the Z axis is then advantageously guided by the pads 251 of the set of guides 25, against which the guide bars 45 slide, which makes it possible to constrain the position of the guide bars perpendicular to the axis. Z.

As best seen at the figure 7 , when the fixed part 2 carries the mast 4, the mast 4 extends in the volume V23 of the guide cylinder 23 but does not occupy the entire volume V23. Thus, an annular space V24 is formed between the mast 4 and the guide cylinder 23. In practice, the guides 25 of the fixed part 2 are arranged in the annular space V24.

In addition, the cap 29 of the fixed part 2 makes it possible to seal the top of the annular space V24 in a leaktight manner. For this, in practice, the diameter D29 of the opening of the plug 29 is substantially equal, to within one clearance, to the outer diameter D4 of the mast 4. In addition, a seal is advantageously provided between the plug 29 and the mast 4. Thus, the annular space is delimited radially by the mast 4 and by the guide cylinder 23, and is delimited vertically upwards by the plug 29, while being open, downwards, to the interior volume V9 of the nuclear facility 9.

Thus, the interior volume V9 of the nuclear installation 9 is insulated from the outside, that is to say that the enclosure 91 is sealed, despite the presence of the opening 95 through which the guide cylinder 23 passes. Indeed, no opening is present between the exterior of the guide cylinder 23 and the enclosure 91, thanks to the fixed part 2 which rests in a sealed manner on the enclosure. In addition, no opening is present between the guide cylinder 23 and the mast 4, thanks to the plug 29. In addition, the mast 4 does not connect the interior volume V9 with the exterior, thanks to the tool 8 and to the closure plates 47, which segment the modules 41 and 43 in a sealed manner.

Advantageously, the dismantling system 1 comprises flexible hoses 81, shown schematically only in figure 7 and at the figure 12 , arranged in the annular space V24. The hoses 81 are intended for supplying the tool 8 with energy and/or for controlling it. In practice, the hoses 81 can combine flexible hydraulic or pneumatic pipes and/or conductive cables making it possible to deliver an electrical power supply and/or to transmit electrical signals corresponding to control signals or to data, for example coming from sensors belonging to the tool 8. In practice, a passage is made in the cap 29 for the hoses 81, this passage being sealed.

On the figures 1 to 3 , the mast 4 is represented with the interface module 41 and three additional modules 43. However, the number of additional modules 43 can be reduced, to lower the height H4 of the mast, or increased, to increase the height H4.

The handling system 6 is provided for this purpose, allowing additional modules 43 to be added or removed from the mast 4.

As seen on the figure 8 , the handling system 6 comprises two actuators 61, extending vertically upwards. Each actuator 61 is supported and guided by a guide structure 63.

In the example, the actuators 61 are cylinders, preferably hydraulic cylinders. As a variant, the jacks 61 are pneumatic jacks, or electric jacks.

Each cylinder 61 comprises a lower end 611, fixed to the guide structure 63, and an upper end 613, movable relative to the guide structure 63. Each cylinder 61 is operable, that is to say it is intended to be actuated in a withdrawal-extension movement, making it possible to vary its length L61, which corresponds to the distance, measured parallel to the vertical axis Z, between its ends 611 and 613. In practice, the upper end 613 of each cylinder 61 is guided in its withdrawal-extension movement by a guide 615, fixed with respect to the upper end 613 and which slides on the associated guide structure 63.

The cylinders 61 are thus operable between a retracted configuration, in which the upper ends 613 are closest to the lower ends 611, and an extension configuration, in which the upper ends are furthest from the lower ends. In the example, the length L61 varies between 750 mm, when the jacks are in the retracted configuration, and 2100 mm, when the jacks are in the extended configuration. Thus, in the example, the stroke of the cylinders 61 is equal to 1350 mm. On the figure 1 , 2 , 8 , 9 , 10 And 12 , the cylinders 61 are shown in the extended configuration. On the figure 11 , the cylinders are shown in the retracted configuration.

In general, the stroke of the cylinders 61 is at least equal to the height H43 of the modules 41 and 43.

The guide structures 63 are fixed to the fixed part 2, more precisely to the support 21, and extend from the fixed part 2 upwards. The guide structures 63 are for example welded to the support 21. In practice, the guide structures 63 are located on either side of the guide cylinder 23.

The handling system 6 comprises a lifting beam 65 and a handling clamp 67.

The spreader bar 65 is designed to be connected to lifting means, such as for example a traveling crane or a crane, which are not shown in the figures. Thus, the lifter 65 is movable horizontally and vertically in the nuclear installation 9, outside the enclosure 91.

In the example, the lifter 65 is a single-beam lifter, comprising two lifting points 651 and two ends 653. The lifting points 651 are for example used for the passage of slings to connect the lifting beam to an overhead crane. As a variant not shown, the lifter 65 is of another type, for example a one-piece lifter or a multi-beam lifter.

The handling flange 67 is fixed to the lifting beam 65. In the example, the lifting beam comprises two attachment points 655, which make it possible to fix the handling flange. In a variant not shown, the number of attachment points 655 is different, for example three or four.

The handling flange 67 is designed to be fixed to an additional module 43, being fixed to the upper flange 432 of the additional module. Thus, the handling system 6 makes it possible, in cooperation with lifting means not shown, to handle an additional module 43 in the nuclear installation 9. In practice, an additional module 43 handled by the handling system 6 is suspended under the handling flange 67. On the figure 1 , 2 And 8 , an additional module 43 not forming part of the mast 4 is thus shown suspended from the handling system 6.

The lifter 65 is further provided to be placed on the upper ends 613 of the cylinders 61, via its ends 653. The actuation of the cylinders 61, for example to pass from their extended configuration to their retracted configuration , then causes a vertical displacement of the lifting beam 65. A high position of the lifting beam is thus defined, which corresponds to the extension configuration of the cylinders, and a low position of the lifting beam, which corresponds to the retraction configuration of the cylinders.

Preferably, when the lifter 65 is placed on the cylinders 61, the lifting means remain connected to the lifter, but are not used, that is to say the lifting means do not carry the lifter. Maintaining the lifting means connected to the lifting beam makes it possible to prevent a worker from approaching the dismantling system 1 to disconnect the lifting means from the lifting points 651.

Alternatively, when the lifter 65 is placed on the cylinders 61, it is separated from the lifting means. Thus, the lifting means are used to place or remove the lifter 65 on the cylinders 61, regardless of whether a module is attached to the handling system 6 or not.

The lifter 65 is shown resting on the jacks 61 at the figures 9 to 11 .

In practice, when the handling flange 67 is fixed to a module, the vertical displacement of the lifter between its high and low positions is guided by the vertical displacement of the mast 4, which is itself guided by the guide cylinder 23.

Advantageously, the guide structures 63 make it possible to guide the lifter 65, in particular when it is not attached to a module. For this, the guide structures 63 are preferably in the shape of a "C" in a horizontal plane, the opening of which is directed towards the Z axis. Thus, the openings of the guide structures 63 are directed towards each other. When the lifter 65 rests on the cylinders 61, it extends between the two guide structures 63, and each guide structure surrounds one of the ends 653 of the lifter. Thus, the guide structures prevent any horizontal movement of the lifter 65, which makes it possible to secure the movement of the lifter between its high and low positions when it is not coupled to a module.

The dismantling system 1 is particularly suitable for nuclear environments, which are subject to strong constraints in terms of radiation protection, that is to say in terms of controlling ionizing radiation and radioactive contamination.

In particular, it is particularly advantageous for the cylindrical walls 411 and 431 of the modules 41 and 43 to be sealed and for the lower and upper ends of the modules to be closed by the closure plates 47 and/or by the tool 8, since the interior volumes V41 and V43 of the modules are thus isolated from the interior volume V9 of the nuclear installation, and thus cannot be subjected to radioactive contaminants, such as for example dust. Thus, the mast 4 has a sealed interior volume, formed jointly by the volumes V41 and V43.

In addition, the fixed part 2 and the mast 4 make it possible to block ionizing radiation, so as to limit their escape through the opening 95 outside the enclosure 91. Indeed, an ionizing radiation directed towards the opening 95 must necessarily, to cross the opening 95, cross at least the guide cylinder 23, the modules of the mast 4 or the stopper 29, thus reducing its intensity and therefore its dangerousness. The dismantling system 1 thus allows, for workers located outside the enclosure 91, to limit exposure to ionizing radiation directed towards the opening 95.

Another advantage of the dismantling system 1 is the large diameter D4 of the mast 4, which allows the use of a tool 8 of large size. Indeed, the tool 8 is provided to be able to pass through the guide cylinder 23, and its size in a horizontal plane is thus conditioned by the diameter of the guide cylinder 23, itself provided according to the diameter of the mast 4. The mast 4 having a large diameter D4, the tool 8 can have a large size in a horizontal plane. The tool 8 can thus be more efficient, which facilitates the dismantling operations of the nuclear installation 9.

In addition, the fact that the modules 41 and 43 are cylindrical increases the rigidity of the mast 4 while controlling its mass, and the mast being symmetrical, it has no preferential direction for receiving forces. In other words, the mast is suitable for working in all directions.

This advantage also comes from the presence of three guides 25, which take up the forces exerted by the mast 4 on the fixed part 2 with a good distribution of the forces, while allowing constant guiding of the mast in all directions.

A method is now described which makes it possible to add an additional additional module 43 to the mast 4, which, in the example, makes it possible to pass from two additional modules to three additional modules. This method is therefore a mast extension method 4.

For this description, “43n” designates the highest additional module 43 of the mast 4, prior to the extension of the mast, and “43n+1” designates the additional additional module 43 added to the mast 4 to achieve its extension. It is thus understood that this extension method applies regardless of the number of additional modules 43 that the mast 4 comprises. In practice, the mast 4 can comprise a large number of additional modules 43, for example up to fourteen additional modules 43.

The first step of the mast 4 extension method consists of bringing the additional module 43n+1 closer to the mast 4, using the handling system 6. This first step is shown on the figure 1 And 2 . During this first step, the additional module 43n+1 is first of all fixed to the handling flange 67 of the handling system 6, by screwing the upper flange 432 of the additional module with the handling flange, then the module additional 43n+1 is handled in the nuclear installation 9 using the lifting beam 65. During this first stage, the mast 4 is locked on the fixed part 2 using the fingers 255, which extend into the grooves high 451 of the guide bars 45 of the highest additional module 43, that is to say of the additional module 43n.

The second extension step consists in fixing the additional module 43n+1 to the mast 4. For this, the lifter 65 is first of all positioned in the high position, by being brought into contact with the cylinders 61, the cylinders being in the configuration of 'extension. This second step is shown on the figure 9 And 10 . If necessary, at the start of the second stage, the jacks are actuated to their extended configuration.

When the crossbar 65 is placed on the jacks 61 in the high position, the axis Z43 of the additional module 43n+1 coincides with the axis Z43 of the additional module 43n and the lower flange 433 of the additional module 43n+1 is in contact with the upper flange 432 of the additional module 43n. The lower flange 433 of the additional module 43n+1 is then fixed to the upper flange 432 of the additional module 43n, by screwing. The additional module 43n+1 is then fixed to the mast 4, and thus corresponds to the highest additional module 43 of the mast. Moreover, the centering of the additional module 43n+1 on the module additional 43n is facilitated by the centering skirt 439 of the module 43n+1, which penetrates into the upper flange 432 of the module 43n.

At the end of the second extension step, the additional module 43n+1 is arranged, along the vertical axis Z, above the fixed part 2, and the mast 4 is maintained on the one hand by being fixed on the fixed part 2 via the additional module 43n, whose high grooves 451 receive the fingers 255, and on the other hand by being suspended under the crossbar 65, which rests on the jacks 61, via the flange handling 67.

The third extension step consists of lowering the mast 4, relative to the fixed part 2, so that the mast is fixed to the fixed part 2 via the additional module 43n+1. For this, the fingers 255 of the guides 25 are tilted into the unlocking position, so that the mast 4 is only held in position by the handling flange 67 while being suspended under the spreader bar 65. Then, the cylinders 61 are retracted from their extension configuration to their retracted configuration, causing the descent, along the vertical axis Z, of the lifter 65 and of the mast 4. The lifter 65 is thus lowered from its high position to its low position. From the extension configuration to the cylinder withdrawal configuration, the mast 4 descends, along the vertical axis Z, by a height equal to the height H43. After the mast 4 has been lowered, the upper grooves 451 of the additional module 43n+1 are aligned, along the vertical axis Z, with the fingers 255 of the guides 25. The fingers 255 are then swung into the locking position, so as to fix the mast 4 on the fixed part 2. At the figure 11 , the dismantling system 1 is shown at the end of the third stage of extending the mast 4.

In addition, when the spreader bar 65 is in the low position, its ends 655 rest on the stops 27 of the fixed part 2. Thus, the low position of the spreader bar 65 is stable, including in the event of failure of one or more two cylinders 61. In addition, if the stroke of the cylinders 61 is greater than the height H43, the stops 27 make it possible to precisely define the lower position of the lifter 65, including when the upper end 611 of the cylinders descends can descend lower than the stops 27.

During the descent of the mast 4, the mast is guided by the guide cylinder 23, by cooperation of the guide bars 45 with the pads 251 of the guides 25.

The fourth and final step of extending the mast 4 consists in separating the mast 4 from the handling system 6. For this, the handling flange 67 is separated from the additional module 43n+1, by removing the screws connecting the upper flange 432 of the module additional to the handling flange. The jacks 61 are then deployed from their retracted configuration to their extended configuration, so as to raise the lifter 65 and the handling flange 67 in the high position. This configuration is shown in figure 12 .

At the end of the fourth stage of extension of the mast 4, the lifting beam 65 is either kept placed on the jacks 61, or moved away from the fixed part 2 and from the mast 4, using the lifting means, until a secure parking position within the nuclear installation 9. When the lifter 65 is kept placed on the jacks 61, the jacks are either kept in the extended configuration, or retracted in the retracted configuration, so that the lifter 65 also rests on the stops 27, in a stable manner.

This method of extending the mast 4 also applies to the installation of the first additional module 43, that is to say the lowest additional module, on the interface module 41. In this case, the module additional module 43 corresponds to the additional module 43n+1 previously described and the interface module 41 corresponds to the additional module 43n previously described, the reference signs being adapted accordingly.

A method is now described which makes it possible to remove an additional module 43 from the mast 4. This method is therefore a method of shortening the mast 4.

For this description, “43n+1” designates the highest additional module 43 of the mast 4, prior to the shortening of the mast, and “43n” designates the additional module 43 located immediately below the additional module 43n+1. The additional module 43n+1 therefore corresponds to the module removed from the mast 4 by this method.

The first step of the method of shortening the mast 4 consists in suspending the mast 4 from the handling system 6. This step is substantially similar to the fourth step of the method of extending the mast 4, carried out in reverse. Thus, briefly, during this step, the lifter 65 is, if necessary, placed on the jacks 61, then the jacks are lowered in the retracted configuration, allowing the lifter 65 to be lowered from its high position to its position low, and the handling flange 67 is screwed to the upper flange 432 of the additional module 43n+1. As a variant, during this step, the jacks are lowered beforehand in the retracted configuration, then the spreader bar is placed on the jacks, having been lowered by the lifting means from its high position to its low position, then the handling flange 67 is screwed to the additional module 43n+1.

The second step of the method of shortening the mast 4 consists in raising the mast 4, with respect to the fixed part 2. This step is substantially similar to the third step of the method of extending the mast 4, carried out in an inverted manner. Thus, briefly, during this step, the fingers 255 are swung into the unlocking position to release the additional module 43n+1 and allow the deployment of the cylinders 61 in the extended configuration, then the fingers are swung into the locking position, so as to fix the mast 4 with respect to the fixed part 2, via the additional module 43n.

During the ascent of the mast 4, the mast is guided by the guide cylinder 23, by cooperation of the guide bars 45 with the pads 251 of the guides 25.

The third step of the mast 4 shortening method consists in detaching the additional module 43n+1 from the mast 4. To do this, the screws now fixed together the upper flange 432 of the additional module 43n and the lower flange 433 of the additional module 43n+ 1 are removed. At the end of this step, the additional module 43n+1 is no longer part of the mast 4 and the mast is no longer suspended from the crossbar 65.

The fourth step of the mast 4 shortening method consists in removing the additional module 43n+1. For this, the lifter 65 is used, with the help of the lifting means, to move the additional module 43n+1 away from the mast 4 and the fixed part 2, for example up to a storage area of the nuclear facility 9. During this step, the lifter 65 is therefore separated from the jacks 61.

This method of shortening the mast 4 also applies for removing the first additional module 43, that is to say the lowest additional module. In this case, the additional module 43 corresponds to the additional module 43n+1 previously described and the interface module 41 corresponds to the additional module 43n previously described, the reference signs being adapted accordingly.

During the extension of the mast 4 and during the shortening of the mast 4, just as during the use of the dismantling system 1, for example in the event of maintenance operations, the mast can be raised or lowered by one height less than the height of a module, thanks to the low grooves 453. For example, during the second step of the shortening method, raising the mast can be done in two operations. A first operation consists in removing the fingers 255 from the high grooves 451 of the additional module 43n+1 by tilting the fingers into the unlocking position, then in deploying the cylinders 61 to an intermediate configuration between the withdrawal configuration and the configuration of extension, then to switch the fingers into the locking position, so that they fit into the lower grooves 453 of the module 43n+1. The mast 4 is then maintained in this intermediate position, which makes it possible, for example, to facilitate the cleaning of the top of the module 43n+1. A second operation then consists in tilting the fingers 255 into the unlocking position, out of the lower grooves 453, then in deploying the cylinders 61 to their extended configuration, then in tilting the fingers in the locking position, so as to complete the rise of the mast 4.

The methods for extending and shortening the mast 4 are particularly simple to implement, which is very advantageous for varying the height H4 of the mast 4. It is thus simple to adjust the vertical position of the tool 8, which depends on the height of the mast, depending on the operations to be carried out by the tool.

Furthermore, the methods of extending and shortening the mast 4 are particularly advantageous, because they are secure and reliable. Indeed, at each step of these methods, the mast 4 is held in a secure manner, by the fixed part 2 and/or by the lifter 65. The risks of accident, such as for example the mast 4 falling, are therefore controlled. , which is crucial in a nuclear environment.

When the mast 4 is suspended from the lifter 65 and the mast is raised or lowered using the jacks 61, the safety of the dismantling system 1 is also improved by the presence of the stops 27. Indeed, in the event of failure of one of the two cylinders 61, or of the two cylinders 61, the lifter 65 bears on the stops 27, which prevents its uncontrolled fall into the interior volume V9 of the nuclear installation 9. The stops 27 thus make it possible to retain the spreader bar 65 and to prevent mast 4 from falling.

Moreover, the method of shortening the mast 4 makes it possible to control the radioactive risks during the removal of an additional module 43n+1. Indeed, no manipulation of the additional module is carried out until the module is reassembled outside of volume V9, that is to say until the module is located above the part fixed 2. Thus, the workers unscrewing the module 43n+1 from the module 43n are protected from ionizing radiation by the fixed part 2 and by the mast 4, as explained above.

In addition, controlling radioactive pollution, in particular radioactive dust, is particularly easy when removing an additional module 43n+1. In particular, when the module 43n+1 is located above the fixed part 2 and before this module is separated from the module 43n, it is very easy to decontaminate by mechanical cleaning, for example using impregnated wipes. Indeed, thanks to the fact that the volume V43 is sealed, only the outer surface of the module must be cleaned, which is simple to achieve. This cleaning is all the more simple to carry out when the additional module 43n+1 is located at working height for a worker positioned standing on the enclosure 91 of the nuclear installation 9. Indeed, the height between the enclosure 91 , at the level of the opening 95, and the bottom of the additional module 43n+1, corresponds approximately to the height H43 of the modules 41 and 43. The height H43 being preferably between 1000 mm and 1500 mm, the module 43n+1 is accessible at head height, which allows easier intervention on the part of a worker, including when this worker is wearing nuclear protection clothing, which is generally cumbersome.

In a variant not shown, the fixed part 2 comprises a different number of guides 25, for example one guide, or four guides. The number of guide bars 45 of the modules 41 and 43 is then adapted accordingly. In a variant where the fixed part 2 comprises a single guide 25, then the mast 4 is also centered with respect to the guide cylinder 23 by one or more slideways.

In a variant not shown, among the pads 251 of a guide 25, some are movable in translation by being actuated by the hydraulic cylinders 257, and others are fixed. For example, each guide comprises a fixed pad and two mobile pads. The distribution between fixed runners and mobile runners can be identical between all the guides, or vary between the guides.

In a variant not shown, among the guides 25, some comprise only pads 251 movable in translation being actuated by the hydraulic cylinders 257, and others comprise only fixed pads

In a variant not shown, the height H23 is substantially equal to a multiple of the height H43 different from three, for example once the height H43, or four times the height H43. The guides 25 then comprise a different number of pads 251, for example one or four pads 251. Thus, in this variant, the guide cylinder 23 makes it possible to simultaneously guide a number of modules 41 and 43 different from three, such as one or four mods.

In a variant not shown, the guide bars 45 do not include a lower groove 453, or intermediate grooves, arranged between the upper grooves and the lower grooves.

In a variant not shown, the jacks 257 and/or the jacks 259 are actuators other than hydraulic jacks, such as for example pneumatic jacks, electric jacks or linear electromagnets.

As a variant, the cylinders 61 are replaced by other actuators, such as for example systems with helical columns, systems with winches and cables, racks, endless screw systems, or else push chains.

In a variant not shown, the interface module 41 is identical to the additional modules 43. In such a variant, the tool 8 is then adapted to be able to be fixed to the lower flanges of the modules.

In a variant not shown, the modules 41 and 43 are non-circular straight cylinder sections, such as straight prism sections, for example.

In a variant not shown, all the modules 41 and 43 do not include a closing plate 47. For example, only the lowest module of the mast 4 includes a closing plate.

In a variant not shown, the lower flange 413 of the interface module 41 comprises a centering skirt 439, making it possible to center the tool 8 with respect to the interface module.

In the example, the connections between modules 41 and 43, as well as the connection of the modules with the handling flange 67, are screwed connections. As a variant of the invention, not shown, the connections between modules 41 and 43, and/or the connection of the modules with the handling flange, are made using other types of removable rigid connections. For example, the modules are assembled together, and with the handling flange, by bolted, pinned or assembly collar type connections. Preferably, the connection between the modules and the connection of a module with the handling flange are of the same type.

In the example, when the crossbar 65 is in the low position, it rests on the stops 27. Thus, in the configuration of the figure 11 , the mast 4 is both held by the fingers 255 which fit into the upper grooves 451 and by the lifter 65 which rests on the stops. In a variant not shown, the stops are arranged lower than the lower position of the lifter, so that the lifter does not rest on the stops. The stops 27 are then safety devices making it possible to retain the lifting beam 65 and to prevent the fall of the mast 4 in the event of failure of the fingers 255 or the cylinders 61, and facilitate the maintenance of the mast by allowing it to be maintained during operations. specific maintenance.

In the example, the fixed part 2 of the dismantling system 1 rests directly on the enclosure 91 of the nuclear installation 9. The dismantling system is therefore fixedly connected to the nuclear installation. In a non-represented variant of the invention, the fixed part 2 rests on a platform, this platform itself resting on the enclosure 91. In such a variant, the platform seals off the opening 95 of the enclosure 91, and the platform itself comprises a passage opening for the guide cylinder 23 and the mast 4, this passage opening being itself closed in a sealed manner by the dismantling system 1. The guide cylinder 23 of the part fixed 2 then always extends through the opening 95 of the enclosure 91, since it extends through the opening of the platform itself placed in the opening 95 of the enclosure. Such a platform is either fixed or mobile in rotation on itself, relative to the nuclear installation and relative to the enclosure 91, around a vertical axis of rotation. Thus, the dismantling system is connected to the nuclear installation via the platform, either in a fixed manner or in a mobile manner. Preferably, when such a platform is mobile in rotation on itself, the axis of rotation of the platform is offset from the main axis Z of the dismantling system 1. Thus, the rotation of the platform on itself leads to a displacement of the dismantling system and therefore of the mast 4 in a plane perpendicular to the main axis Z, which makes it possible to increase the field of action of the tool 8 fixed at the bottom of the mast, thus facilitating dismantling operations. Furthermore, the mobile platform is not driven in rotation during the extension or the shortening of the mast 4. In practice, the fixed part 2 can rest on any structure, fixed or mobile, arranged intermediate between the fixed part and the pregnant 91.

In the second step of the mast extension method described above, the spreader bar 65 is first placed in the high position on the jacks 61, the jacks being in the extended configuration, then the additional module 43n+1 is fixed to the additional module 43n. Alternatively, at the start of the second step, the jacks are in the retracted configuration. Thus, during the second step, the additional module 43n+1 is first of all put in place on the additional module 43n using the lifter 65, the centering of the two modules being facilitated by the insertion of the skirt centering 439 of the module 43n+1 in the upper flange 432 of the module 43n, then the additional module 43n+1 is fixed to the module 43n, thus extending the mast 4. Once the modules 43n+1 and 43n fixed together, still in the second step, the cylinders 61 are raised in the extended configuration, so as to come into contact with the spreader bar 65. An advantage of this variant is to facilitate the installation of the module 43n+1, and more particularly its alignment with the module 43n, because the lifter 65 is not placed on the cylinders 61 before the installation of the module 43n+1, it is free to be moved by the lifting means.

In the method of extending the mast 4 described above, the last step consists in separating the mast 4 from the handling system 6. Similarly, at the end of the method of shortening the mast described above, the spreader beam 65 is no longer connected to the mast 4. Thus, when the tool 8 is in operation, the spreader bar 65 is not connected to the mast. As a variant, when the tool 8 is in operation, the spreader bar 65 is connected to the mast, that is to say the handling flange 67 is fixed to the highest module of the mast. In such a variant, the lifter is thus in the low position. In practice, this configuration then corresponds to the configuration shown in figure 11 . In such a variant, the order of the steps of the mast extension method then differs: the extension method begins with the fourth step, which consists of separating the mast from the handling system, then the method continues with the first step , which consists in approaching the additional module 43n+1, by the second step, which consists in fixing the additional module to the mast, then ends with the third step, which consists in lowering the mast 4. Similarly, the order of the steps mast shortening method also differs: the shortening method begins with the second step, which consists of raising the mast 4, then continues with the third step, which consists in detaching the additional module 43n+1, then with the fourth step, which consists in evacuating the additional module using the lifting beam, then ends with the first step, which consists in fixing the handling flange 67 to the shortened mast 4. The advantage of this variant is that, when the tool 8 is in operation to carry out dismantling operations, the mast 4 remains connected to the lifter 65, which then serves as a safety device: in the event of failure of the guide cylinder 23, by example of the fingers 255, the fall of the mast 4 is prevented by the lifter.

Any feature described for one variant in the foregoing can be implemented for the other variants described previously, as far as technically feasible.

Part of the project that led to the present invention received funding from the Euratom 2019-2020 research and training program under grant agreement No. 945273.

Claims (10)

Dismantling system (1) for a nuclear installation (9), comprising: - a fixed part (2), configured to be connected to the nuclear installation (9); - a mast (4) carried by the fixed part and extending along a vertical axis (Z) from the fixed part downwards, the mast comprising at least two modules (41, 43) assembled together and juxtaposed according to the vertical axis; - a handling system (6) configured to lower and raise the mast relative to the fixed part, along the vertical axis; And - a tool (8), characterized in that each module (41, 43) of the mast (4) is a straight cylinder section comprising a solid and sealed cylindrical wall (411, 431), and defining an interior volume (V41, V43), the respective interior volumes modules jointly forming a sealed interior volume of the mast, and in that the tool (8) is carried by the lowest module (41) of the mast (4). Dismantling system (1) according to claim 1, in which at least one of the modules (41, 43), or even each module, comprises a closing plate (47), which is assembled in a sealed manner with the cylindrical wall (411, 431) of this module. Dismantling system (1) according to any one of the preceding claims, in which each module (41, 43) comprises an upper flange (412, 432) and a lower flange (413, 433), which are sealed together with the cylindrical wall (411, 433) of this module, and which make it possible to assemble the modules together. Dismantling system (1) according to any one of the preceding claims, in which the modules (41, 43) include an interface module (41), which is arranged at the bottom of the mast and on which the tool (8) is fixed, and at least one additional module (43). Dismantling system (1) according to claims 3 and 4 considered in combination, in which the lower flange (433) of the or each additional module (43) comprises a centering skirt (439), and in which an outside diameter (D439) of the centering skirt is substantially equal to an inside diameter (D412, D432) of the upper flanges (412, 432). Dismantling system (1) according to any one of the preceding claims, in which the fixed part (2) comprises a guide cylinder (23), configured to extend through an opening (95) formed in an enclosure (91) of the nuclear installation (9), the guide cylinder making it possible to guide the mast (4) when the mast descends or rises relative to the fixed part. Dismantling system (1) according to Claim 6, in which the guide cylinder (23) comprises at least two guides (25) which each comprise at least one shoe (251), in which each module (41, 43) comprises at at least two guide bars (45), and in which the pads of the guides center and align the mast (4) with respect to the guide cylinder, and guide the mast when the mast descends or rises with respect to the fixed part, cooperating with the guide bars. Dismantling system (1) according to claim 7, in which each guide (25) comprises at least two pads (251) which exert forces on the associated guide bar (45) which make it possible to center and align the mast ( 4) relative to the guide cylinder (23). Dismantling system (1) according to one of Claims 7 and 8, in which the or each shoe (251) of at least one of the guides (25) comprises fins (253) surrounding at least one of the guide bars ( 45) of the modules so as to prevent rotation of the mast (4) around the vertical axis (Z). Dismantling system (1) according to one of Claims 6 to 9, in which the dismantling system (1) forms an annular space (V24) between the mast (4) and the guide cylinder (23), in which the dismantling system comprises hoses (81) intended for supplying and/or controlling the tool (8) and arranged in the annular space, and in which the fixed part (2) comprises a closing cap (29) sealingly the top of the annular space.

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