Dismantling system for nuclear facility and methods of extending and shortening mast of dismantling system

Abstract

This dismantling system (1) for a nuclear installation comprises a fixed part (2), configured to be connected to the nuclear installation, a mast (4) supported by the fixed part and extending downwards along a vertical axis from the fixed part, the mast having at least two modules (41, 43) assembled together, a tool (8), carried by the lowest module (41) of the mast, and a handling system (6), adapted to add an additional module (43) to the top of the mast and then lower the mast, so as to lengthen the mast, and to raise and then remove the highest module (43) of the mast, so as to shorten the mast. The handling system comprises a lifting beam intended to be attached to the highest module of the mast, and two actuators on which the lifting beam is intended to rest. The deployment of the actuators causes the lifting beam to move between an upper and a lower position.

Description

[0001] The present invention relates to a dismantling system for a nuclear installation, a method of extending a mast of such a system and a method of shortening a mast of such a system.

[0002] Nuclear facilities generally have a sealed enclosure, inside which radioactive material, such as fuel rods or irradiated materials, is located.

[0003] In the field of dismantling nuclear installations, it is known that access to the interior of such a sealed enclosure is required in order to carry out dismantling operations, for example to remove radioactive material, using a tool. For this purpose, it is known to make an opening in the top of a sealed enclosure, and to pass a mast through the opening, the mast then extending downwards into the sealed enclosure, from outside the enclosure, and carrying at its lowest end a tool to be able to carry out the dismantling operations.

[0004] Such a mast generally comprises a frame formed by a tubular assembly. This frame is either single-piece or formed of several sections assembled together, for example by bolting.

[0005] When such a structure is a single-piece structure, it is very bulky, which makes its use difficult in cramped nuclear installations and reduces the tool's range of action, as the mast dimensions must then be reduced. Such a structure therefore cannot meet all the dismantling needs encountered in nuclear installations.

[0006] Conversely, when such a framework is formed from several sections assembled together, there is no system for simply assembling these sections.

[0007] GB 2 176 924 A describes a dismantling system comprising a mast formed of modules assembled together and a hoist allowing the mast to be raised and lowered. The mast forms a guide for a tool, which is movable along the mast. Such a dismantling system has the disadvantage of being complex to operate, the use of a hoist to raise or lower the mast being also imprecise and unsafe.

[0008] It is these drawbacks that the invention aims to remedy more specifically by proposing a nuclear installation dismantling system that is particularly simpler to assemble.

[0009] 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 tool, carried by the lowest module of the mast, and a handling system, adapted to add an additional module at the top of the mast then lower the mast relative to the fixed part, along the vertical axis, so as to extend the mast, and raise the mast relative to the fixed part, along the vertical axis, then remove the highest module of the mast from the mast, so as to shorten the mast.

[0010] According to the invention, the handling system comprises a spreader, configured to be connected to lifting means and to be fixed to the additional module to add it to the top of the mast and to the highest module of the mast to remove it from the mast, and two actuators, each actuator being deployable along the vertical axis and having a stroke which is at least equal to a height of the modules. In addition, the spreader is configured to be placed on the actuators, so that the deployment of the actuators causes the spreader to move between a high position and a low position.

[0011] Thanks to the invention, the handling system allows the mast to be extended by adding modules one by one, and the mast to be shortened by removing modules one by one.

[0012] 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: Each module of the mast is a straight cylinder section. Each module comprises at least one groove, and the fixed part comprises at least one finger, movable between a locking position, in which the finger extends into one of the grooves of the modules, so as to prevent the mast from moving relative to the fixed part, and an unlocking position, in which the finger does not extend into the grooves of the modules. The fixed part comprises two stops, the stops being configured to retain the spreader and prevent the mast from falling when the spreader is connected to the highest module of the mast, in particular in the event of failure of the actuators. The handling system comprises, for each actuator, a guide structure which supports and guides the actuator, and, when the spreader is moved between its high position and its low position, the spreader is guided by the guide structures, in particular when the spreader is not connected to the additional module.The handling system includes a handling flange, attached to the spreader beam and configured to be assembled to an additional module to be added to the mast or to the highest module of the mast to be removed from the mast.

[0013] According to another aspect, the invention also relates to a method of extending the mast of a dismantling system as described above. This method comprises at least the following steps: a) attaching an additional module to the spreader bar and bringing the additional module closer to the mast using the spreader bar; b) attaching the additional module to the highest module of the mast and bringing the spreader bar into contact with the actuators; c) using the actuators, lowering the spreader bar from its high position to its low position; and d) separating the spreader bar from the additional module, then, using the actuators, raising the spreader bar from its low position to its high position.

[0014] This extension method induces the same advantages as those mentioned above regarding the dismantling system of the invention.

[0015] Advantageously, during steps a), b) and d), the mast is locked onto the fixed part using the or each finger in the locking position.

[0016] According to another aspect, the invention also relates to a method of shortening the mast of a dismantling system as described above. This shortening method comprises at least the following steps: a) place the spreader bar on the actuators, lower the spreader bar from its high position to its low position and attach the spreader bar to the highest module of the mast; b) using the actuators, raise the spreader bar from its low position to its high position; c) detach the highest module of the mast from the mast; and d) using the spreader bar, evacuate the detached module away from the mast.

[0017] This shortening method induces the same advantages as those mentioned above regarding the dismantling system of the invention.

[0018] Advantageously, during steps a), c) and d), the mast is locked onto the fixed part using the or each finger in the locking position.

[0019] 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, of a method of extending the mast of such a system and of a method of shortening the mast of such a system in accordance with its principle, given solely by way of example and 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 stage; [ Fig. 2 ] There figure 2 is a section of the dismantling system of the figure 1 , according to a plan comprising a vertical axis of the dismantling system, during the first extension stage; [ Fig. 3 ] There figure 3 is a perspective view of a mast of the dismantling system of the figures 1 And 2 ; [ Fig. 4 ] There figure 4 is a perspective view of a module of the mast of the figure 3 ; [ Fig. 5 ] There figure 5 is a perspective section of a support of the dismantling system of the figures 1 And 2 , the cut being made according to a plane comprising a vertical axis of the dismantling system; [ Fig. 6 ] There figure 6 is a perspective view of a guide of the support of the figure 5 ; [ Fig. 7 ] There figure 7 is a section of the dismantling system of the figures 1 And 2 , according to plan VII visible at the figure 2 ; [ Fig. 8 ] There figure 8 is a perspective view of a handling system belonging to the dismantling system of figures 1 And 2 ; [ Fig. 9 ] There figure 9 is a perspective view of the dismantling system of the figure 1 , represented in a second stage of extension; [ Fig. 10 ] There figure 10 is a section of the dismantling system of the figure 1 , during the second stage of extension, 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 stage of extension, the cut being similar to that of the figures 7 And 10 ; And [ Fig. 12 ] There figure 12 is a section of the dismantling system of the figure 1 , during a fourth stage of extension, the cut being analogous to that of the figures 7 , 10 And 11 .

[0020] On the figures 1 And 2a dismantling system 1 is presented comprising a fixed part 2, a mast 4, a handling system 6 and a tool 8.

[0021] The dismantling system 1 is used inside a nuclear installation 9 when an intervention, in particular dismantling, is carried out.

[0022] Nuclear facility 9 is only shown in the figure 2 , in a simplified way. At the figure 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 confinement vessel. In the example, the enclosure 91 is the enclosure protecting the core of the reactor 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 by a central conduit capable of accommodating a fuel cartridge or a control rod. In the example, the dismantling system 1 makes it possible to manipulate the graphite bricks so as to evacuate them from the stacks 93.

[0023] The interior volume V9 of enclosure 91 is therefore subject to significant radioactive activity, in the form of ionizing radiation and in the form of contamination, such as dust and radioactive materials.

[0024] The dismantling system 1 rests on the enclosure 91 of the nuclear installation 9, by means of its fixed part 2. The fixed part 2 carries the mast 4, which extends downwards, that is to say towards the interior 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 level of the upper end of the mast. In practice, the mast 4 extends through an opening 95, arranged in the enclosure 91 and opening into the interior volume V9. Preferably, the opening 95 is circular.

[0025] In the remainder of the description, the terms "up", "down", "upper", "lower", "up" and "down" are understood to refer to the vertical Z axis. In addition, the "horizontal" orientation refers to an orientation perpendicular to the vertical Z axis.

[0026] On the figure 3 , only mast 4 is shown.

[0027] 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 manipulate 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.

[0028] 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.

[0029] The interface module 41 is located at the lower end of the mast 4, and allows the tool 8 to be fixed 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, depending on the actual number, the height H4 of the mast 4 to be modified, the height H4 being measured along the vertical axis Z. In the example of the figure 3 , mast 4 includes three additional modules 43.

[0030] The interface module 41 is a section of a right circular cylinder, which is centered on an axis Z41, coincident 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 413 flanges thus extend in a plane perpendicular to the axis Z41 and are parallel to each other.

[0031] The cylindrical wall 411 of the interface module 41 is solid, and therefore watertight. 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.

[0032] 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.

[0033] 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 flat surface 414. Advantageously, the tapped holes of the upper flange 412 are regularly distributed around the vertical axis Z41. In the example, the upper flange 412 comprises eighteen tapped holes. In a variant not shown, the upper flange comprises a different number of tapped holes.

[0034] We note “D412” the internal diameter of the upper flange 412, measured perpendicular to the vertical axis Z41.

[0035] 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 example, the lower flange 413 comprises forty holes 417. In a variant not shown, the lower flange comprises a different number of holes 417.

[0036] The height of the interface module 41, measured parallel to the axis Z41 between the upper flange 412 and the lower flange 413, is noted “H41”. The height H41 is preferably between 1000 mm and 1500 mm, in the example equal to 1350 mm.

[0037] In practice, the tool 8 is attached to the interface module 41 via the lower flange 413. For this purpose, the tool 8 comprises a flange adapted to be attached to the lower flange 413. Advantageously, when the tool 8 is attached to the interface module 41, the tool completely and tightly closes the lower opening of the interface module, i.e. the opening of the lower flange 413. In other words, the interior volume V41 of the interface module 41 is not accessible through the lower flange 413 when the tool 8 is attached to the lower flange.

[0038] Each additional module 43 is a section of a right circular cylinder, which is centered on an axis Z43, coincident with the vertical axis Z in the assembled configuration of the mast 4, and which comprises a cylindrical wall 431. The cylindrical wall 431 is delimited, along 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 412 and lower 413 flanges thus extend in a plane perpendicular to the axis Z43 and are parallel to each other.

[0039] We denote “D4” the outside diameter of the mast 4, which corresponds to the outside diameter of the cylindrical walls 411 and 431 of the modules 41 and 43. Preferably, the diameter D4 also corresponds to the outside diameter of the upper flanges 412 and 432 as well as to the outside diameter of the lower flanges 433, which are therefore flush with the outside faces of the cylindrical walls 411 and 431. Advantageously, the outside 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 higher module 43.

[0040] The height of an additional module 43, measured parallel to the axis Z43 between the upper flange 432 and the lower flange 433, is denoted “H43”. 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.

[0041] The height H4 of mast 4 corresponds to the sum of the height of all modules 41 and 43. Thus, in the example of figures 1 à 3 , the height H4 is equal to three times the height H43 plus one time the height H41. In practice, the height of module 41 and the H43 modules are adapted according to the working environment of mast 4 within nuclear installation 9.

[0042] The cylindrical wall 431 of the additional modules 43 is solid, and therefore watertight. 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.

[0043] 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.

[0044] 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 upper flange 432 comprises eighteen tapped holes 435. In a variant not shown, the upper flange comprises a different number of tapped holes.

[0045] We denote "D432" the inside diameter of the upper flange 432, measured perpendicular to the vertical axis Z43. In practice, the diameter D432 is equal to the diameter D412.

[0046] The diameters D412 and D432 are preferably between 1200 mm and 1800 mm, in the example more preferably equal to 1550 mm. The diameter D4 is preferably between 1250 mm and 1850 mm, in the example more preferably equal to 1650 mm.

[0047] In practice, the upper flanges 432 of the additional modules 43 are identical to the upper flange 412 of the interface module 41.

[0048] 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 flat surface 436. In practice, the lower flange 433 comprises as many holes 437 as the upper flanges 412 and 432 comprise tapped 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.

[0049] Advantageously, each additional module 43 comprises 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 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 holes 437 which pass right through the lower flange, thus opening out opposite the flat surface 436. Thus, the holes 437 are through holes and open out into the recesses 438. In other words, the holes 437 of each additional module 43 are accessible from the outside of 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.

[0050] 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 upper flange 412 or into the tapped holes 435 of the upper flange 433, each screw having a head bearing 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 screws from the outside of the upper additional module 43. 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 together in a sealed manner, that is to say that there is no opening between two juxtaposed modules connecting their interior volume V41 and V43 with the exterior.

[0051] 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 cylinder section centered on the axis Z43 of the additional module, the outside diameter of which, measured perpendicular to the axis Z43 and noted “D439” on the figure 2 , is substantially equal to the diameters D412 and D432, with some clearances. As better visible on the figure 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 external diameter D439 of the centering skirt 439 is substantially equal to the diameters D412 and D432 makes it possible to center two juxtaposed modules between them, that is to say that their respective axes Z41, Z43 are merged, which is particularly advantageous for facilitating their assembly by screwed flanges, and thus reinforcing the sealing between two juxtaposed modules.

[0052] The interface module 41 and each additional module 43 comprise guide bars 45, which extend parallel to the axes Z41 and Z43 while being carried by their cylindrical wall 411, 413. In the example, the interface module 41 and each additional module 43 each comprise three guide bars 45, which are regularly spaced in a circumferential direction 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.

[0053] Each guide bar 45 comprises a high groove 451 and a low groove 453, each of which extends in a plane perpendicular to the vertical axis Z41.

[0054] 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 upper additional module 43. Similarly, for two juxtaposed additional modules 43, 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.

[0055] 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.

[0056] 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 cylindrical wall 411, 431, the closure plate 47 and the plane in which the upper flange 412, 432 extends is negligible in comparison with the internal volume V41, V43 of the module. Thus, in the remainder of the description, it is considered that the internal 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.

[0057] Furthermore, 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 sealed 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.

[0058] Furthermore, 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 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.

[0059] The fixed part 2 of the dismantling system 1 is better visible at the figure 5 , where it is represented alone and in section, according to the same plan as the section of the figure 2 .

[0060] 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.

[0061] 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, 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 enclosure.

[0062] The height of the guide cylinder 23, measured parallel to the central axis of the guide cylinder, is denoted “H23”. 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.

[0063] The fixed part 2 is designed to rest in a sealed manner on the enclosure 91, that is to say so that no opening is present between the exterior of the guide cylinder 23 and the enclosure 91. For example, this sealing is obtained by welding the fixed part to the enclosure, or by arranging a seal between the fixed part and the enclosure.

[0064] 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 circumferential direction 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.

[0065] Each guide 25 comprises several pads 251 which are distributed along the guide. In the example, each guide comprises three pads 251.

[0066] 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.

[0067] Advantageously, the pads 251 of at least one of the guides 25 comprise fins 253. In the example, among the three guides 25, the pads 251 of two of the guides 25 do not comprise fins 253 and the pads of the third guide 25, shown in figure 6 , include 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.

[0068] Each guide 25 also comprises 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 an unlocking position, in which the finger is located closest to the guide cylinder 23, and a locking position, in which the finger is furthest from the guide cylinder 23, i.e. closest to the central axis of the guide cylinder 23.

[0069] 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 with a rectangular section. The stops 27 are rigidly fixed to the support 21, for example by bolting or by welding. Alternatively, each stop 27 is a profile, or a mechanically welded assembly.

[0070] 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 comprises a circular opening, of diameter D29.

[0071] When the fixed part 2 carries the mast 4, the mast extends into 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 to exert forces on the guide bars. These forces make it possible to center and align the mast 4 relative to the guide cylinder 23.

[0072] In practice, among the three pads 251 of each guide 25, the top pad and the bottom pad allow the forces exerted by the mast 4 to be taken up, by being in contact with the guide bar of the highest module 41, 43 and the lowest module among the three modules located in the guide cylinder. It is advantageous for this force take-up 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 strength of the dismantling system 1. In addition, among the three pads 251 of each guide 25, the central pad allows the mast 4 to be guided, when the mast 4 is made up only of the interface module 41 and an additional module 43.

[0073] Furthermore, for the guide 25 whose pads 251 comprise 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 circumferential direction to the vertical axis Z. The fins 253 thus prevent the rotation of the mast 4 around the vertical axis Z. In other words, the guide 25 whose pads 251 comprise fins 253 is an anti-rotation guide.

[0074] 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 highest along the mast 4, or of the interface module 41 during the phases of assembly and disassembly of the mast 4, when the mast 4 only comprises the interface module. Thus, the movement 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. The mast 4 is then suspended from the fixed part 2 by means of the fingers 255.

[0075] When the fingers 255 are in the unlocked position, they do not extend into the upper grooves 451 or 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 Z axis.

[0076] As best seen at the figure 7 , when the fixed part 2 carries the mast 4, the mast 4 extends into 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.

[0077] In addition, the plug 29 of the fixed part 2 makes it possible to seal the top of the annular space V24 in a sealed manner. For this, in practice, the diameter D29 of the opening of the plug 29 is substantially equal, to within a clearance, to the external 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 internal volume V9 of the nuclear installation 9.

[0078] Thus, the interior volume V9 of the nuclear installation 9 is isolated 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 outside 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. Furthermore, the mast 4 does not connect the interior volume V9 with the outside, thanks to the tool 8 and the closing plates 47, which segment the modules 41 and 43 in a sealed manner.

[0079] Advantageously, the dismantling system 1 comprises hoses 81, shown schematically only in figure 7 and to 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 may group together hydraulic or pneumatic flexible 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 data, for example from sensors belonging to the tool 8. In practice, a passage is provided in the plug 29 for the hoses 81, this passage being sealed.

[0080] On the figures 1 à 3 , the mast 4 is shown 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.

[0081] The handling system 6 is provided for this purpose, allowing additional modules 43 to be added to or removed from the mast 4.

[0082] As visible 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.

[0083] In the example, the actuators 61 are cylinders, preferably hydraulic cylinders. Alternatively, the cylinders 61 are pneumatic cylinders, or electric cylinders.

[0084] 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 actuable, that is to say it is designed to be actuated in a retraction-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 retraction-extension movement by a guide 615, fixed relative to the upper end 613 and which slides on the associated guide structure 63.

[0085] The cylinders 61 are thus actuable between a retraction 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 cylinders are in the retraction configuration, and 2100 mm, when the cylinders are in the extension configuration. Thus, in the example, the stroke of the cylinders 61 is equal to 1350 mm. On the figures 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.

[0086] Generally, the stroke of the jacks 61 is at least equal to the height H43 of the modules 41 and 43.

[0087] 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.

[0088] The handling system 6 comprises a lifting beam 65 and a handling flange 67.

[0089] The lifting beam 65 is intended to be connected to lifting means, such as for example an overhead crane or a crane, which are not shown in the figures. Thus, the lifting beam 65 is movable horizontally and vertically in the nuclear installation 9, outside the enclosure 91.

[0090] In the example, the spreader 65 is a single-beam spreader, comprising two lifting points 651 and two ends 653. The lifting points 651 are for example used for the passage of slings making it possible to connect the spreader to an overhead crane. In a variant not shown, the spreader 65 is of another type, for example a single-piece spreader or a multi-beam spreader.

[0091] The handling flange 67 is attached to the spreader bar 65. In the example, the spreader bar comprises two attachment points 655, which allow the handling flange to be attached. In a variant not shown, the number of attachment points 655 is different, for example three or four.

[0092] The handling flange 67 is intended to be fixed to an additional module 43, by 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 figures 1 , 2 And 8 , an additional module 43 not forming part of the mast 4 is thus shown suspended from the handling system 6.

[0093] The spreader bar 65 is further provided to be placed on the upper ends 613 of the cylinders 61, by means of its ends 653. The actuation of the cylinders 61, for example to move from their extension configuration to their retraction configuration, then causes a vertical movement of the spreader bar 65. This defines a high position of the spreader bar, which corresponds to the extension configuration of the cylinders, and a low position of the spreader bar, which corresponds to the retraction configuration of the cylinders.

[0094] Preferably, when the spreader bar 65 is placed on the jacks 61, the lifting means remain connected to the spreader bar, but are not used, that is to say the lifting means do not carry the spreader bar. Keeping the lifting means connected to the spreader bar makes it possible to avoid a worker having to approach the dismantling system 1 to disconnect the lifting means from the lifting points 651.

[0095] Alternatively, when the spreader 65 is placed on the jacks 61, it is separated from the lifting means. Thus, the lifting means are used to place or remove the spreader 65 on the jacks 61, regardless of whether a module is attached to the handling system 6 or not.

[0096] The spreader 65 is shown placed on the jacks 61 at the figures 9 à 11 .

[0097] In practice, when the handling flange 67 is fixed to a module, the vertical movement of the spreader between its high and low positions is guided by the vertical movement of the mast 4, which is itself guided by the guide cylinder 23.

[0098] Advantageously, the guide structures 63 make it possible to guide the spreader 65, in particular when it is not fixed to a module. For this, the guide structures 63 are preferably “C” shaped 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 spreader 65 rests on the jacks 61, it extends between the two guide structures 63, and each guide structure surrounds one of the ends 653 of the spreader. Thus, the guide structures prevent any horizontal movement of the spreader 65, which makes it possible to secure the movement of the spreader between its high and low positions when it is not coupled to a module.

[0099] Dismantling system 1 is particularly suited to nuclear environments, which are subject to high constraints in terms of radiation protection, i.e. in terms of control of ionizing radiation and radioactive contamination.

[0100] In particular, it is particularly advantageous that the cylindrical walls 411 and 431 of the modules 41 and 43 are sealed and that the lower and upper ends of the modules are closed by the closing plates 47 and / or by the tool 8, because 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.

[0101] Furthermore, the fixed part 2 and the mast 4 make it possible to block ionizing radiation, so as to limit its escape through the opening 95 outside the enclosure 91. Indeed, ionizing radiation directed towards the opening 95 must necessarily, in order to pass through the opening 95, pass through at least the guide cylinder 23, the modules of the mast 4 or the plug 29, thus reducing its intensity and therefore its danger. The dismantling system 1 thus makes it possible, for workers located outside the enclosure 91, to limit exposure to ionizing radiation directed towards the opening 95.

[0102] Another advantage of the dismantling system 1 is the large diameter D4 of the mast 4, which allows the use of a large tool 8. Indeed, the tool 8 is designed to be able to pass into the guide cylinder 23, and its size in a horizontal plane is thus conditioned by the diameter of the guide cylinder 23, itself designed 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.

[0103] In addition, the fact that modules 41 and 43 are cylindrical increases the rigidity of mast 4 while controlling its mass, and since the mast is symmetrical, it does not have a preferential direction for receiving forces. In other words, the mast is suitable for working in all directions.

[0104] 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 guidance of the mast in all directions.

[0105] A method is now described for adding an additional module 43 to the mast 4, which, in the example, makes it possible to go from two additional modules to three additional modules. This method is therefore a method for extending the mast 4.

[0106] For this description, the highest additional module 43 of the mast 4 is designated “43n”, prior to the extension of the mast, and the additional module 43 added to the mast 4 to carry out its extension is designated “43n+1”. 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 may comprise a significant number of additional modules 43, for example up to fourteen additional modules 43.

[0107] The first step of the mast 4 extension method consists of approaching the additional 43n+1 module to the mast 4, using the handling system 6. This first step is shown on the figures 1 And 2. During this first step, the additional module 43n+1 is first 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 additional module 43n+1 is handled in the nuclear installation 9 using the spreader 65. During this first step, the mast 4 is locked on the fixed part 2 using the fingers 255, which extend into the upper grooves 451 of the guide bars 45 of the highest additional module 43, that is to say of the additional module 43n.

[0108] The second extension step consists of fixing the additional module 43n+1 to the mast 4. To do this, the spreader 65 is first positioned in the high position, being put in contact with the jacks 61, the jacks being in the extension configuration. This second step is shown on the figures 9 And 10. If necessary, at the beginning of the second stage, the cylinders are operated to their extension configuration.

[0109] When the spreader bar 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. In addition, the centering of the additional module 43n+1 on the additional module 43n is facilitated by the centering skirt 439 of the module 43n+1, which penetrates into the upper flange 432 of the module 43n.

[0110] 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 held on the one hand by being fixed to the fixed part 2 by means of the additional module 43n, the upper grooves 451 of which receive the fingers 255, and on the other hand by being suspended under the spreader bar 65, which rests on the jacks 61, by means of the handling flange 67.

[0111] The third extension step consists of lowering the mast 4, relative to the fixed part 2, so that the mast is fixed on the fixed part 2 by means of the additional module 43n+1. For this, the fingers 255 of the guides 25 are tilted into the unlocked position, so that the mast 4 is only held in position by the handling flange 67 while being suspended under the spreader 65. Then, the jacks 61 are retracted from their extension configuration to their retraction configuration, causing the descent, along the vertical axis Z, of the spreader 65 and the mast 4. The spreader 65 is thus lowered from its high position to its low position. From the extension configuration to the retraction configuration of the jacks, the mast 4 descends, along the vertical axis Z, by a height equal to the height H43.At the end of the descent of the mast 4, the high 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 tilted 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 extension of the mast 4.

[0112] Furthermore, 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 both cylinders 61. Furthermore, if the stroke of the cylinders 61 is greater than the height H43, the stops 27 make it possible to precisely define the low position of the spreader bar 65, including when the upper end 611 of the cylinders descends can descend lower than the stops 27.

[0113] 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.

[0114] The fourth and final step of extending the mast 4 consists of separating the mast 4 from the handling system 6. To do this, the handling flange 67 is separated from the additional module 43n+1, by removing the screws connecting the upper flange 432 of the additional module to the handling flange. The jacks 61 are then deployed from their retracted configuration to their extended configuration, so as to raise the spreader 65 and the handling flange 67 to the high position. This configuration is illustrated in figure 12 .

[0115] At the end of the fourth step of extending the mast 4, the spreader bar 65 is either kept placed on the jacks 61, or moved away from the fixed part 2 and the mast 4, using the lifting means, to a secure parking position within the nuclear installation 9. When the spreader bar 65 is kept placed on the jacks 61, the jacks are either kept in the extension configuration, or retracted in the retracted configuration, so that the spreader bar 65 also rests on the stops 27, in a stable manner.

[0116] This method of extending the mast 4 also applies to the installation of the first additional module 43, i.e. the lowest additional module, on the interface module 41. 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.

[0117] A method is now described for removing an additional module 43 from the mast 4. This method is therefore a method for shortening the mast 4.

[0118] For this description, the additional module 43 located immediately below the additional module 43n+1 on the mast 4 is designated "43n+1", prior to shortening the mast, and the additional module 43 located immediately below the additional module 43n+1 is designated "43n". The additional module 43n+1 therefore corresponds to the module removed from the mast 4 by this method.

[0119] The first step of the method for shortening the mast 4 consists of suspending the mast 4 from the handling system 6. This step is substantially similar to the fourth step of the method for extending the mast 4, carried out in reverse. Thus, succinctly, during this step, the spreader 65 is, if necessary, placed on the jacks 61, then the jacks are lowered into the retracted configuration, allowing the spreader 65 to be lowered from its high position to its low position, and the handling flange 67 is screwed to the upper flange 432 of the additional module 43n+1. Alternatively, during this step, the jacks are first lowered into the retracted configuration, then the spreader is placed on the jacks, being 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.

[0120] The second step of the method for shortening the mast 4 consists of raising the mast 4, relative to the fixed part 2. This step is substantially similar to the third step of the method for extending the mast 4, carried out in reverse. Thus, succinctly, during this step, the fingers 255 are tilted into the unlocking position to release the additional module 43n+1 and allow the deployment of the jacks 61 in the extension configuration, then the fingers are tilted into the locking position, so as to fix the mast 4 relative to the fixed part 2, via the additional module 43n.

[0121] During the raising 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.

[0122] The third step of the method for shortening mast 4 is to detach the additional module 43n+1 from the mast 4. To do this, the screws holding 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 spreader bar 65.

[0123] The fourth step of the method for shortening the mast 4 consists of removing the additional module 43n+1. For this, the lifting beam 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 to a storage area of ​​the nuclear installation 9. During this step, the lifting beam 65 is therefore separated from the jacks 61.

[0124] This method of shortening the mast 4 also applies to the removal of the first additional module 43, i.e. 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.

[0125] During the extension of the mast 4 and during the shortening of the mast 4, as well as during the use of the dismantling system 1, for example in the case of maintenance operations, the mast can be raised or lowered by a height less than the height of a module, thanks to the lower grooves 453. For example, during the second step of the shortening method, the raising of the mast can be carried out in two operations. A first operation consists of removing the fingers 255 from the upper grooves 451 of the additional module 43n+1 by tilting the fingers into the unlocking position, then deploying the jacks 61 to an intermediate configuration between the withdrawal configuration and the extension configuration, then tilting the fingers into the locking position, so that they are inserted into the lower grooves 453 of the module 43n+1.The mast 4 is then held in this intermediate position, which makes it easier, for example, to clean the top of the module 43n+1. A second operation then consists of tilting the fingers 255 into the unlocked position, out of the lower grooves 453, then deploying the jacks 61 to their extension configuration, then tilting the fingers into the locked position, so as to complete the raising of the mast 4.

[0126] The methods of 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, according to the operations to be carried out by the tool.

[0127] Furthermore, the methods of extending and shortening mast 4 are particularly advantageous, as they are safe and reliable. Indeed, at each stage of these methods, mast 4 is held securely, by the fixed part 2 and / or by the spreader bar 65. The risks of accidents, such as for example the fall of mast 4, are therefore controlled, which is crucial in a nuclear environment.

[0128] When the mast 4 is suspended from the spreader bar 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 jacks 61, or of the two jacks 61, the spreader bar 65 rests 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 prevent the mast 4 from falling.

[0129] In addition, the method of shortening mast 4 makes it possible to control radioactive risks when removing an additional module 43n+1. Indeed, no handling of the additional module is carried out until the module is reassembled outside of volume V9, i.e. until the module is located above fixed part 2. Thus, the operators unscrewing the module 43n+1 from the module 43n are protected from ionizing radiation by fixed part 2 and by mast 4, as explained above.

[0130] Furthermore, the control of 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 simple to decontaminate by mechanical cleaning, for example using impregnated wipes. Indeed, thanks to the fact that the volume V43 is sealed, only the external surface of the module needs to be cleaned, which is simple to carry out. This cleaning is all the simpler to carry out since 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 43n+1 module is accessible at man height, which allows for easier intervention by a worker, even when this worker is wearing nuclear protection clothing, which is generally bulky.

[0131] 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 further centered relative to the guide cylinder 23 by one or more slides.

[0132] 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 movable pads. The distribution between fixed pads and movable pads may be identical between all the guides, or vary between the guides.

[0133] In a variant not shown, among the guides 25, some comprise only pads 251 movable in translation while being actuated by the hydraulic cylinders 257, and others comprise only fixed pads.

[0134] In a variant not shown, the height H23 is substantially equal to a multiple of the height H43 other than three, for example one times 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 other than three, such as one or four modules.

[0135] In a variant not shown, the guide bars 45 do not include a low groove 453, or intermediate grooves, arranged between the high grooves and the low grooves.

[0136] In a variant not shown, the cylinders 257 and / or the cylinders 259 are actuators other than hydraulic cylinders, such as for example pneumatic cylinders, electric cylinders or linear electromagnets.

[0137] Alternatively, the cylinders 61 are replaced by other actuators, such as helical column systems, systems with winches and cables, racks, worm screw systems, or even push chains.

[0138] 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.

[0139] In a variant not shown, modules 41 and 43 are non-circular sections of right cylinders, such as sections of right prisms.

[0140] In a variant not shown, all modules 41 and 43 do not include a closing plate 47. For example, only the lowest module of mast 4 includes a closing plate.

[0141] 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 relative to the interface module.

[0142] 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. In 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.

[0143] In the example, when the lever 65 is in the low position, it rests on the stops 27. Thus, in the configuration of the figure 11 , the mast 4 is held both by the fingers 255 which are inserted into the upper grooves 451 and by the spreader bar 65 which rests on the stops. In a variant not shown, the stops are arranged lower than the low position of the spreader bar, so that the spreader bar does not rest on the stops. The stops 27 are then safety members making it possible to retain the spreader bar 65 and to prevent the mast 4 from falling in the event of failure of the fingers 255 or the jacks 61, and facilitate maintenance of the mast by allowing it to be held during specific maintenance operations.

[0144] 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 variant of the invention that is not shown, the fixed part 2 rests on a platform, this platform itself resting on the enclosure 91. In such a variant, the platform seals the opening 95 of the enclosure 91, and the platform itself comprises an opening for the passage of the guide cylinder 23 and the mast 4, this passage opening itself being sealed by the dismantling system 1. The guide cylinder 23 of the fixed part 2 then always extends through the opening 95 of the enclosure 91, since it extends through the opening of the platform itself arranged 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 causes 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 the dismantling operations. Furthermore, the mobile platform is not driven in rotation during the extension or shortening of the mast 4.In practice, the fixed part 2 can rest on any structure, fixed or mobile, arranged intermediately between the fixed part and the enclosure 91.

[0145] In the second step of the mast extension method described above, the spreader 65 is first placed in the upper position on the cylinders 61, the cylinders being in the extension configuration, then the additional module 43n+1 is fixed to the additional module 43n. Alternatively, at the start of the second step, the cylinders are in the retracted configuration. Thus, during the second step, the additional module 43n+1 is first put in place on the additional module 43n using the spreader bar 65, the centering of the two modules being facilitated by the insertion of the centering skirt 439 of the module 43n+1 into 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 are fixed together, still in the second step, the jacks 61 are raised in the extension 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 lifting beam 65 is not placed on the jacks 61 before the installation of the module 43n+1, it is free to be moved by the lifting means.

[0146] In the method of extending the mast 4 described above, the last step consists of separating the mast 4 from the handling system 6. Similarly, at the end of the method of shortening the mast described above, the spreader 65 is no longer connected to the mast 4. Thus, when the tool 8 is in operation, the spreader 65 is not connected to the mast. Alternatively, when the tool 8 is in operation, the spreader 65 is connected to the mast, that is to say the handling flange 67 is fixed on the highest module of the mast. In such a variant, the spreader 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 of approaching the additional module 43n+1, with the second step, which consists of fixing the additional module to the mast, then ends with the third step, which consists of lowering the mast 4. Similarly, the order of the steps of the 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 of detaching the additional module 43n+1, then with the fourth step, which consists of evacuating the additional module using the spreader, then ends with the first step, which consists of 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 spreader bar 65, which then serves as a safety device: in the event of failure of the guide cylinder 23, for example of the fingers 255, the fall of the mast 4 is prevented by the spreader bar.

[0147] Any feature described for one variant in the above may be implemented for the other variants described above, as long as technically feasible.

[0148] Part of the project leading to the present invention received funding from the Euratom 2019-2020 research and training programme under grant agreement No. 945273.

Claims

1. A decommissioning system (1) for a nuclear facility (9), comprising: - a fixed part (2), configured to be connected to the nuclear facility (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 along the vertical axis; - a tool (8), carried by the lowest module (41) of the mast (4); and - a handling system (6), adapted for: ∘ adding an additional module (43) at the top of the mast (4) and then lowering the mast relative to the fixed part, along the vertical axis, so as to extend the mast; and ∘ raising the mast relative to the fixed part, along the vertical axis, then removing the highest module (43) from the mast, so as to shorten the mast, characterised in that the handling system (6) comprises: - a spreader bar (65), configured to be connected to lifting means and to be attached to the additional module (43) to add it to the top of the mast and to the topmost module (43) of the mast to remove it from the mast; and - two actuators (61), each actuator being deployable along the vertical axis (Z) and having a stroke which is at least equal to a height (H43) of the modules (41, 43), and in that the spreader bar is configured to be placed on the actuators, so that the deployment of the actuators causes the spreader bar to move between a raised position and a lowered position.

2. The dismantling system (1) according to claim 1, wherein each module (41, 43) of the mast is a straight cylindrical segment.

3. The dismantling system (1) according to any one of the preceding claims, wherein each module (41, 43) comprises at least one groove (451), and wherein the fixed part (2) comprises at least one finger (255), movable between a locking position, wherein the finger extends into one of the grooves of the modules, so as to prevent movement of the mast (4) relative to the fixed part, and an unlocking position, wherein the finger does not extend into the grooves of the modules.

4. The dismantling system (1) according to any of the preceding claims, wherein the fixed part (2) comprises two stops (27), the stops being configured to retain the spreader bar (65) and prevent the mast (4) from falling when the spreader bar is connected to the highest module (43) of the mast, particularly in the event that the actuators (61) fail.

5. The dismantling system (1) according to any one of the preceding claims, wherein the handling system (6) comprises, for each actuator (61), a guide structure (63) which supports and guides the actuator, and wherein, when the spreader bar (65) is moved between its raised and lowered positions, the spreader bar is guided by the guide structures, in particular when the spreader bar is not connected to the additional module (43).

6. The dismantling system (1) according to any of the preceding claims, wherein the handling system (6) comprises a handling clamp (67), attached to the spreader bar (65) and configured to be assembled to an additional module (43) to be added to the mast (4) or to the highest module (43) of the mast to be removed from the mast.

7. A method of extending the mast (4) of a dismantling system (1) in accordance with any one of the preceding claims, the extension method comprising at least the following steps: a) attaching an additional module (43n+1) to the spreader bar (65) and moving the additional module towards the mast (4) using the spreader bar; b) attaching the additional module (43n+1) to the highest module (43n) on the mast and bringing the spreader bar into contact with the actuators (61); c) using the actuators (61), lowering the spreader bar from its raised position to its lowered position; and d) separating the spreader bar from the additional module, then, using the actuators, raising the spreader bar from its lowered position to its raised position.

8. The extension method according to claim 7, wherein the dismantling system (1) further complies with claim 3, and wherein, during steps a), b) and d), the mast (4) is locked to the fixed part (2) by means of the or each finger (255) in the locking position.

9. A method of shortening the mast (4) of a dismantling system (1) according to any one of claims 1 to 6, the shortening method comprising at least the following steps: a) placing the spreader bar (65) on the actuators (61), lowering the spreader bar from its raised position to its lowered position and attaching the spreader bar to the highest module (43n+1) of the mast (4); b) using the actuators, raising the spreader bar from its lowered position to its raised position; c) detaching the mast (4) from the highest module (43n+1) of the mast; and d) using the spreader bar (65), evacuating the detached module (43n+1) away from the mast.

10. The shortening method according to claim 9, wherein the dismantling system (1) further complies with claim 3, and wherein during steps a), c) and d) the mast (4) is locked to the fixed part (2) by means of the or each finger (255) in the locking position.

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