EP0281433A2 - Working system for primary pipes and water-chamber in a vapour generator of a nuclear plant - Google Patents

Abstract

System for carrying out work on the water box of a steam generator of a nuclear power station. The system comprises a first member (1) of substantially elongate shape, forming a first arm of the system, and a second member (2) of substantially elongate shape. The second member (2) is articulated at one of its ends to an end of the first member (1). The combination of the first and of the second arm (2) is capable of being introduced into the water box (BAE) of the steam generator through the manhole. The second member (2) can be placed in an extended position in relation to the first member (1). A vehicle (3) mounted movably in relation to the second arm (2) makes it possible to explore and to ensure the decontamination of the internal walls of the water box (BAE) of the steam generator. A means of carrying out work such as decontamination (30) is carried by the vehicle (3). It is capable of reaching a plurality of regions of the surface of the said inner walls. Means for remote control of the vehicle (3) and means for carrying out work (30) are provided. <IMAGE>

Description

The present invention relates to an intervention system on the primary pipes and on the water box of a nuclear power plant steam generator.

When replacing a nuclear power plant steam generator, operations such as cutting pipes, chamfering, welding must be carried out on the parts to be replaced and in particular on the water box. The radiation dose received by the operators during these operations is significant due to the contamination of radioactive substances which are deposited on the internal walls of the abovementioned parts.

One possibility of reducing the aforementioned doses received during this type of intervention may consist, before the interventions necessary for carrying out these operations, of decontaminating the primary piping of the water box, over a length of the order of a few meters for example, the internal wall of the water box and the partition plate for example.

This decontamination can be carried out by electrodecontamination for example and, advantageously, by intervention from the outside of the water box by the implementation of the system which is the subject of the invention.

The intervention system on the primary pipes and the water box of the steam generators of a nuclear power plant, object of the invention, is remarkable in that it comprises a first element having a substantially elongated shape and forming a first arm. of the system and a second element having a substantially elongated shape, articulated to one of its ends at one end of the first element, the second element forming a second arm of the system. The assembly of the first and second arms is capable of being introduced into the water box of the steam generator via the manhole and said second element can be put in the deployed position relative to the first element. A vehicle is mounted on the second arm, the vehicle being mounted movable relative to the second arm and a decontamination means is carried by the vehicle. The intervention means, due to its movement relative to the second arm and the relative opening between the first and the second arm, is capable of reaching a plurality of areas of the internal surface of the steam generator such as in particular the primary pipes, the partition plate and the internal wall of the spherical bowl of the steam generator water box. Means for remote control of the vehicle and intervention means are also provided.

The system which is the subject of the invention can advantageously be used prior to any intervention by an operator on or in the water box of a steam generator, operations such as plugging the tubes, checking the tubes, fitting types shutter.

It is remarkable in that the intervention such as decontamination can be carried out and controlled from outside the water box of the steam generator, any entry or exit of an operator in the water box of a steam generator. steam prior to decontamination implemented in accordance to the system according to the invention having the effect of subjecting it to a too high irradiation dose.

• - la figure 1a représente une vue en perspective éclatée d'un système selon l'invention plus particulièrement adapté à la décontamintion de la tuyauterie primaire de la boîte à eau d'un géné­rateur de vapeur,
• - la figure 1b représente une vue en coupe partielle selon un plan de symétrie commun au trou d'homme TH et à la tuyauterie primaire TP de la boîte à eau d'un générateur de vapeur et du système selon l'invention, tel que représenté en figure 1a,
• - la figure 2a représenté une vue en pers­pective d'un élément essentiel du système objet de l'invention représenté en figures 1a et 1b, cet élément essentiel étant constitué par le véhicule support de l'élément de décontamination,
• - la figure 2b représente en coupe par­tielle une vue selon un plan de symétrie longitudinal de la figure 2a,
• - les figures 3a, 3b, 3c, 3d, 3e, 3f, 3g, 3h, 3i, 3j représentent les étapes successives de mise en place du véhicule représenté en figures 2a et 2b dans la tuyauterie primaire de la boîte à eau d'un générateur de vapeur,
• - les figures 4a, 4b, 4c représentent le mode opératoire du véhicule dans la tuyauterie pri­maire pour assurer le déplacement de celui-ci dans la tuyauterie primaire,
• - la figure 5a représente une vue en pers­pective éclatée d'un système selon l'invention plus particulièrement adapté à la décontamination de la plaque de partition de la boîte à eau d'un générateur de vapeur de centrale nucléaire,
• - les figures 5b et 5c représentent une vue en coupe partielle relative aux étapes d'installation du système selon l'invention tel que représenté en fi­gure 5a,
• - les figures 6a et 6b représentent des schémas des différentes phases de déplacement du deu­xième élément formant bras, au moyen du véhicule, dans le mode de réalisation du système objet de l'in­vention représenté en figure 5a,
• - la figure 7 représente une vue de face d'un détail de réalisation de l'agencement du véhicule sur le deuxième élément formant deuxième bras dans le mode de réalisation du système objet de l'invention représenté en figure 5a,
• - la figure 8a représente une vue en pers­pective éclatée d'un système selon l'invention plus particulièrement adapté à la décontamination de la paroi interne du bol de la boîte à eau d'un générateur de vapeur de centrale nucléaire,
• - la figure 8b représente une vue partielle d'un détail de réalisation de l'agencement du véhicule sur le deuxième élément formant deuxième bras dans le mode de réalisation du système objet de l'invention représenté en figures 8a et 8b,
• - les figures 9a à 9e représentent des phases de mise en place du système selon l'invention,
• - les figures 10a, 10b, 10c représentent un schéma illustratif des moyens de commande et de leur utilisation en liaison avec un système de décon­tamination objet de l'invention tel que représenté en figures 1a, 5a,8a, respectivement,
• - les figures 11a et 11b représentent respectivement un schéma de principe illustratif des moyens de décontamination dans le cas où ces moyens de décontamination sont constitués par une cellule d'électropolissage et un schéma détaillé en coupe partielle d'un mode de réalisation avantageux d'une telle cellule.

The invention will be better understood on reading the description and on observing the drawings below in which:

• FIG. 1a represents an exploded perspective view of a system according to the invention more particularly suitable for decontaminating the primary piping of the water box of a steam generator,
• - Figure 1b shows a partial sectional view along a plane of symmetry common to the manhole TH and to the primary piping TP of the water box of a steam generator and of the system according to the invention, as shown in Figure 1a,
• FIG. 2a represents a perspective view of an essential element of the system which is the subject of the invention represented in FIGS. 1a and 1b, this essential element being constituted by the vehicle supporting the decontamination element,
• FIG. 2b represents in partial section a view according to a longitudinal plane of symmetry of FIG. 2a,
• - Figures 3a, 3b, 3c, 3d, 3e, 3f, 3g, 3h, 3i, 3j show the successive stages of setting up the vehicle shown in Figures 2a and 2b in the primary piping of the water box of a steam generator,
• FIGS. 4a, 4b, 4c represent the operating mode of the vehicle in the primary piping to ensure the displacement of the latter in the primary piping,
• FIG. 5a represents an exploded perspective view of a system according to the invention more particularly adapted to the decontamination of the partition plate of the water box of a steam generator of a nuclear power plant,
• FIGS. 5b and 5c represent a partial sectional view relating to the steps for installing the system according to the invention as shown in FIG. 5a,
• FIGS. 6a and 6b represent diagrams of the different phases of movement of the second arm-forming element, by means of the vehicle, in the embodiment of the system which is the subject of the invention represented in FIG. 5a,
• FIG. 7 represents a front view of a detail of the arrangement of the vehicle on the second element forming a second arm in the embodiment of the system which is the subject of the invention shown in FIG. 5a,
• FIG. 8a represents an exploded perspective view of a system according to the invention more particularly suitable for decontamination of the internal wall of the bowl of the water box of a steam generator of a nuclear power plant,
• - Figure 8b shows a partial view of a detail of the arrangement of the vehicle on the second element forming the second arm in the embodiment of the system which is the subject of the invention shown in FIGS. 8a and 8b,
• FIGS. 9a to 9e represent phases for setting up the system according to the invention,
• FIGS. 10a, 10b, 10c represent an illustrative diagram of the control means and their use in connection with a decontamination system which is the subject of the invention as shown in FIGS. 1a, 5a, 8a, respectively,
• - Figures 11a and 11b respectively show a block diagram illustrating the decontamination means in the case where these decontamination means consist of an electropolishing cell and a detailed diagram in partial section of an advantageous embodiment of a such cell.

The intervention system on the primary pipes and on the water box of a steam generator of a nuclear power plant will first be described in conjunction with FIG. 1a.

As shown in the aforementioned figure, the intervention system on the primary pipes and on the water box of steam generators of a nuclear power plant comprises a first element denoted 1 having a substantially elongated shape and forming a first arm of the system. It also comprises a second element denoted 2 having a shape which is also substantially elongated, this second element being articulated at 12 at one of its ends at one end of the first element denoted 1. The second element 2 forms a second arm of the system and the assembly of the first 1 and of the second arm 2 is capable of being introduced into the water box denoted BAE in FIG. 1a of the steam generator, via of the manhole noted TH. The second element 2 can thus be placed in the deployed position relative to the first element 1, the deployed position with an opening angle α shown in FIG. 1a.

In addition, as it appears in FIG. 1a, a vehicle denoted 3 is mounted on the second arm 2. The vehicle 3 is mounted movable relative to the second arm 2 as will be described in more detail below in the description.

An intervention means such as a decontamination means 30 is also carried by the vehicle 3. The intervention means 30, due to its movement relative to the second arm 2 and the relative opening between the first 1 and the second arm 2 is capable of reaching a plurality of zones of the internal surface of the steam generator, such as in particular the primary pipes denoted TP, the partition plate denoted PP, the internal wall of the spherical bowl of the water box marked BAE of the steam generator.

In addition, as shown in FIG. 1a, control means 6 are provided so as to allow remote control of the vehicle 3 and intervention means 30 from outside the water box BAE of the generator. steam. Auxiliary control means 6 are also associated with auxiliary elements such as an electrical energy supply system, noted 7, and a tank of decontaminating products noted 8. These two accessory auxiliary elements will be described more detailed later in the text of this description.

The axes of symmetry of the manhole, axes of symmetry denoted th in FIG. 1a, and of the primary piping, axes denoted tp in this same figure, lying in the same plane denoted P, the device object of the invention is based on the compass theory and thus allows, by deployment of the second arm noted 2 with respect to the first arm noted 1, to reach substantially all the points inside the water box BAE of the steam generator, which must be subjected to a decontamination process as described below in the description.

In accordance with a particularly advantageous embodiment represented in FIG. 1a, without limitation, the first element 1 is a hollow element of substantially semi-cylindrical shape so as to form a protective corset for the second element 2, when the latter is in position not deployed. The non-deployed position is understood to mean a value of the angle α which is substantially zero, This second element or second arm 2 then being brought back against the first element or first arm 1 and inside the hollow part of the latter.

A more specific description of the system which is the subject of the invention in the case where it makes it possible to ensure the decontamination of the primary pipes denoted TP of a steam generator, will be given in connection with FIGS. 1a, 1b, and 2a, 2b, below.

In the aforementioned case, the second arm denoted 2 is advantageously constituted by a teles arm copic noted 20 and the vehicle 3 is then removably mounted at the end of the second element 2 forming a second arm. The telescopic arm 20 can be constituted in a conventional manner, by an arm provided with a hydraulic cylinder controlled by the control means 6. The removable attachment of the vehicle 3 at the end of the telescopic arm 20 can advantageously be carried out by means of a jaw 21 controlled by the control means 6 and a corresponding fixing system 35, directly integral with the vehicle 3 as will be described later in the description.

Of course, the vehicle 3 having been placed in position at the inlet of the primary piping TP by means of the telescopic arm 20 controlled by the control means 6, the release of the jaw 21 is then controlled and the vehicle 3, a self-propelled vehicle as will be described later in the description can then move in the aforementioned primary piping TP.

FIG. 1b shows a partial sectional view along a plane of symmetry common to the manhole TH and to the primary piping TP of the water box of a steam generator and of the system according to the invention, the vehicle 3 having moved through the primary piping TP.

As will be seen in FIG. 1b above, the vehicle is mechanically secured to a tensor cable denoted 4, the tensor cable circulating during the movement of the removable vehicle 3 in the primary pipes TP by means of end pulleys denoted 200 of the second arm 2, of articulation pulleys noted 100 of the first and second arms for example. Of course, a pulley will be understood to mean any suitable guide means allowing movement of the cable without excessive wear of the latter and in particular possibly of guide grooves provided with a self-lubricating coating for example, such as a polytetrafluoroethylene coating. As has also been shown in FIG. 1b, the tensioning cable 4 is distributed by a balancing reel denoted 5 located near the free end of the first element 1 outside the manhole TH when the system and in particular the element 1 is in position, as will be described later in the description.

Thus, the vehicle 3 makes it possible to move the decontamination means 30 along the primary piping TP.

In general, the vehicle makes it possible to print, by means of decontamination 30, a rotational movement around the axis of the piping TP during decontamination and an incremental longitudinal movement allowing the progression of the vehicle assembly 3 - decontamination means 30, along the piping.

A more detailed description of the vehicle 3 will be given in conjunction with Figures 2a and 2b.

According to the aforementioned FIG. 2a, the vehicle 3 may advantageously include a vehicle body denoted 31 consisting of a longitudinal element arranged along the longitudinal axis Δ of the vehicle. The latter also comprises a chassis 32 rotatably mounted on the longitudinal element forming the vehicle body 31. The chassis 32 comprises a plate denoted 320, intended to support the decontamination means 30. In addition, as will be seen in FIG. 2a, means for supporting the vehicle 3 are provided. These lift means are constituted by a first denoted 33, and a second denoted 34, sets of jacks. Each set of jacks is integral with the vehicle body 31 and has a tripod configuration in a plane orthogonal to the longitudinal axis Δ of the vehicle. Each cylinder forming the sets of cylinders 33 and 34 are provided at their end with an application suction cup intended to bear on the internal wall of the primary wall TP. It will be noted in FIG. 2a that the set of jacks 33 has been shown with only two jacks, the third jack having been omitted so as not to unnecessarily overload the drawing.

According to an advantageous embodiment of the vehicle 3 shown in FIG. 2a, the chassis 32 is rotatably mounted on the longitudinal element 31 by means of a ring gear 310 and a motor 321 comprising a pinion meshing on the aforementioned toothed crown. The motor 321 is of course integral with the chassis 32. The rotation of the pinion of the motor 321 thus makes it possible to ensure the rotation of the chassis 32 and all the elements which are subject to it.

As will also be noted in FIG. 2a, the decontamination means 30 are supported by the plate 320, by means of jacks denoted 3201, 3202. The jacks 3201, 3202 are each connected by a ball joint 3203, 3204 to the decontamination means. A radial translation of the assembly, that is to say in a direction orthogonal to the longitudinal axis Δ of the vehicle body 31, is controlled by a motor 3205 secured to the decontamination means 30, in order to allow docking of these means on the primary pipe wall to be treated. In FIGS. 2a and 2b in particular, it will be noted that the motor 3205 is mounted integral with the plate 320 and therefore with decontamination means 30, the motor 3205 meshing a transmission chain 3206, which drives two nuts 3207, 3208, driving the plate solidly 320 and the decontamination means 30, by means of two threaded rods 3209 secured to the chassis 32. The rotation of the motor 3205 thus makes it possible to set the transmission chain 3206 in motion, the movement in translation of the assembly of the crew formed by the plate 320, the motor 3205 and the decontamination means 30, in a direction perpendicular to the axis Δ. In FIGS. 2a and 2b, it will also be noted that the vehicle body 31 comprises at one of its ends a frustoconical part 35 provided with a groove 3500, and intended to come to engage in the fixing jaw disposed at the end of the telescopic arm 20.

A more detailed description of the vehicle shown in Figure 2a will be given in conjunction with Figure 2b in a sectional view along a longitudinal plane of symmetry passing through the axis Δ of the vehicle.

In FIG. 2b, it will be noted in particular the presence of an element denoted CA, which represents the power cord of the vehicle, this power cord being deemed to include a hose for supplying and discharging the liquid or fluid decontaminating towards the decontamination means 30, as will be described later in the description, as well as an electrical power supply pipe and a hydraulic fluid pipe allowing the actuation of the various cylinders constituting the vehicle 3.

As it also appears in FIG. 2b, the two sets of jacks, 33, 34, are, in order to allow the traction of the vehicle 3 to be ensured in the primary piping tp, mounted on a seat plate denoted 330, 340, the orientation of which relative to a plane orthogonal to the longitudinal axis Δ of the vehicle body is adjustable according to a value angle determined by means of ball joint fasteners denoted 331, 332 respectively 341, 342. The fasteners at ball joints can consist of lockable and unlockable ball joints. It will be noted that the support or seat plate 330 is in fact mechanically independent of the anchoring point of the tensor cable on the vehicle body 31. According to an advantageous characteristic of the system which is the subject of the invention, the seat plate 340 is movable in translation in a direction parallel to the longitudinal axis Δ of the vehicle 3, by means of traction jacks denoted 343 and 344. Thus, one or the other set of jacks 33 or 34 being placed in contact and as a fulcrum on the internal wall of the primary piping TP, the displacement of the set of jacks 34 relative to the body of the vehicle, then the fixing, that is to say the setting of the jacks of the game of cylinders 34 on the primary piping and the clearance of the set of cylinders 33, allows then the incremental translational movement of the vehicle 3 along the axis of symmetry of the primary piping TP, as will be described in more detail later in the description.

The vehicle 3 as shown in s s 2a and 2b allows in particular through the set of cylinders 33 and 34 having the above tripod configuration, centering and holding the vehicle 3 in the primary piping TP. The advance of the vehicle 3 is ensured by the aforementioned set of jacks 343, 344, articulated at their end so as to allow the angular offset of the set of jacks 34, with respect to the assembly constituted by the other set of jacks 33 and the vehicle body 31 and the chassis 32 during the progression of the assembly in the curved parts of the primary piping TP.

The entire vehicle 3 is held by the tensioning cables 4 mentioned above, the latter being actuated in order to prevent the fall of the vehicle 3, during the possible failure of one of the sets of jacks 33 or 34.

The decontamination process of the primary piping TP can then be carried out as follows. Vehicle 3 is lowered to the lowest point to be decontaminated from the primary piping TP. The decontamination of the walls of the primary piping TP is then ensured by means of the decontamination means 30, which are rotated around the longitudinal axis Δ of the vehicle, via the chassis 32 set in motion by the engine. 321 cited above. A side strip of the pipe TP primary land having been decontaminated, the vehicle is then moved by an increment and the ascent thereof is effected by means of the second set of jacks 34 previously described. It is at this point that the tensioning cables 4 fully play their role of means ensuring safety in the event of a failure in the aforementioned cylinders. The tensor cable or cables 4 being wound on the balancer 5, these facilitate the ascent of the vehicle 3, in particular when the vehicle and in particular the support jacks of the sets of jacks 33 or 34, pass in front of a decontaminated surface, that is to say a surface having a surface condition exhibiting adhesion difficulties.

A detailed description of the installation of the systems which are the subject of the invention in the BAE water box of a steam generator, installation from the outside thereof, will be described in conjunction with FIGS. 3a, 3b , 3c, 3d, 3e, 3f, 3g, 3h, 3i, 3d.

In FIGS. 3a and 3b, the installation of the system which is the subject of the invention is shown on an elevator marked 50 brought near the manhole marked TH. Of course it will be understood that Figure 3b shows a sectional view along a plane of symmetry of Figure 3a substantially. The elevator system 50 can consist, for example, of an inclined plane, the angle of inclination of which allows the assembly, that is to say of the system which is the subject of the invention, to position the articulation 12 of the first and second arms in the vicinity of the center of the tube plate denoted PT of the water box of the steam generator.

Figures 3c and 3d show in particular the position of the system which is the subject of the invention, after translation of the system on the elevator 50 and positioning of the articulation 12 in the vicinity of the center of the tube plate PT. The position of the assembly being as shown in Figure 3b for example, the vehicle 3 is then, as shown in Figure 3e and 3f, docked at the end of the telescopic arm 20 and locked at the end thereof. The telescopic arm can then be retracted so as to bring the vehicle inside the BAE water box. Of course, the power cord connections are also made beforehand.

Then, as shown in FIG. 3g, the second element noted² forming an arm, is then unlocked and put in the deployed position relative to the first element forming an arm noted 1. The second element forming an arm 2 is then deployed so as to bring this and the vehicle 3 in line with the primary piping TP as shown in Figure 3g. The deployment of the arm 2 can be carried out by means of a jack or by means of a motor driving the arm 2 in rotation in its deployed position.

Then, as shown in FIG. 3h, the telescopic arm is then actuated so as to introduce the vehicle 3 into the primary piping TP.

The jacks of the sets of jacks 33 and 34 of the vehicle 3 are then actuated in order to actuate the ac costing of the vehicle 3 on the walls of the primary piping TP as shown in FIG. 3i.

The vehicle 3 can then be disconnected from the telescopic arm 20 by means of the jaw previously described and the progression of the vehicle 3 in the primary piping can be achieved as already mentioned, by sequential progression along the axis piping.

A more detailed description of the progression of the vehicle 3, in particular in the curved part of the primary piping TP, will be given in connection with FIGS. 4a, 4b and 4c.

In Figure 4a, there is shown the two sets of cylinders 33 and 34 in the support position on the inner wall of the primary pipe TP in a curved part thereof. Note in particular that thanks to the ball joint of the traction cylinders 343 and 341 and the support plate 330 and 340, the system can easily move in the curved parts. In FIG. 4a, at point (1) the cylinders constituting the sets of cylinders 33 and 34 are under pressure and allow the application of the suction cups on the wall, in order to constitute a fulcrum. The ball joints can then be locked as shown by the letter V.

.At point (2) of FIG. 4a, the jacks of the jack set 34 are placed under vacuum in order to place them in the withdrawn position, the ball joints 341 and 342 being unlocked, position noted.

.

In FIG. 4b, at point 1, the set of jacks 33 is kept under pressure and constitutes a fulcrum for the vehicle 3. On the contrary, on the set of jacks 34, the pressure being removed and the traction jacks 343 and 344 are then put into action by pressurization, so as to move the second set of jacks 34 according to the arrow indicated in a direction substantially parallel to the tangent to the axis of the primary piping TP. Note that in Figures 4a to 4c the pipe axis TP is shown in phantom.

ainsi que représenté en figure 4b au point (2).The set of jacks 34 having translated with a length substantially equal to the stroke of the jacks 343 and 344, the pressure is restored at the jacks of the set of jacks 34, the vehicle 3 then being in its new equilibrium position , as shown in Figure 4b in point (2). The length of elongation of the rods of each cylinder of the cylinder set 34 can then be adjusted, by means of the control means, in order to obtain perfect centering of the central point of the ball joints 341, 342 on the axis of the primary pipe TP, the ball joints 331 , 332 having been placed in the unlocked position

as shown in Figure 4b in point (2).

In FIG. 4a at point (1), the pressure is then removed at the level of the jacks of the set of jacks 33 and the traction jacks 343 and 344 are then actuated so as to bring the entire vehicle 3 back to the set of jacks 34. Then, as shown in point (2), the pressure is restored at the level of the jacks of the set of jacks 33 and the vehicle 3 is in a new stable position offset by a displacement increment, along the longitudinal axis of the primary piping TP. Perfect centering of the central point of the ball joints 331, 332 on the axis of the primary pipe TP can be carried out in a similar manner to the corresponding centering of the central point of the ball joints 341, 342 shown in FIG. 4b (2). Of course, the cycle is thus restarted as many times as necessary, in order to cover the length of the primary piping TP to be decontaminated.

The progression of the vehicle 3 in the primary piping TP having been carried out from the lowest point of the treatment to the vicinity of the jaw for fixing the vehicle to the telescopic arm 20, the vehicle is then fixed to the telescopic arm 20. In order to facilitate the operation, a video camera can advantageously be fixed on the vehicle 3, so as to facilitate the maneuvers of approaching the vehicle and its fixing endpiece in the vicinity of the fixing jaw of the telescopic arm 20. The arm telescopic 20, when the vehicle 3 is again fixed at the end of the latter is then retracted and the element 2 forming an arm is then returned to its non-deployed position corresponding to the position of positioning of the start of the operations. The system which is the subject of the invention can then be removed by means of the elevator 50 as described above.

An advantageous variant of the system which is the subject of the invention will now be described in conjunction with FIG. 5a in the case where the system is more particularly adapted to an intervention such as the decontamination of the partition plate denoted PP of the water box of a nuclear power plant steam generator. It will be noted that the partition plate PP is a plate substantially orthogonal to the tube plate PT of the water box of the steam generator, the aforementioned partition plate dividing the water box into two half-hemispheres substantially.

As it appears in FIG. 5a, the second element 2 forming the second arm is articulated to the first arm 1 by means of a joint of the Cardan joint type denoted 120. Advantageously, the joint 120 comprises in position a first axis denoted D1, substantially parallel to the partition plate PP, and a second axis denoted D2 substantially perpendicular to the partition plate PP.

As will also be noted in FIG. 5a, the vehicle 3 is then mounted movable in translation along the second arm 2.

In order to maintain and move the second arm 2 on the partition plate PP, the second arm 2 advantageously comprises a first central cylinder denoted 200, which ensures the fixing in translation of the assembly constituted by the first denoted 1 and the second arm denoted 2 in the direction D2 perpendicular to the partition plate PP.

In addition, a plurality of jacks denoted 21, 22, respectively 23, 24 are arranged at the free end of the second arm 2 or in the vicinity thereof. According to another advantageous characteristic of the device which is the subject of the invention, at least two opposite jacks, for example jacks 21 and 23, form a moving element with respect to the second arm, this moving element being able to be moved perpendicular to the direction Δʹ, axis longitudinal of the second arm 2, this direction of movement being parallel to the partition plate PP. This movement ensures the movement corresponding to the second arm 2 relative to the axis D2 forming an axis of rotation for the second arm 2 relative to the fixed point formed by the central cylinder 200. Of course, all of the cylinders 21 , 22, 23 and 24 is provided at the end of their movable rod, with a fixing suction cup denoted 210, respectively 220, 230, 240. The fixing of the suction cups is of course carried out by placing them in depression. In the same way, the jack 200 forming the central jack is provided with a suction cup 201 allowing the system object of the invention to be supported at the joint 120 between the arms 1 and 2, in the vicinity of the central point of the tubular plate PT previously described.

Of course, the vehicle 3 is provided with decontamination means such as those described in connection with the previous embodiment.

A more detailed description of the installation of the system which is the subject of the invention in the case where it is more particularly suitable for an intervention such as the decontamination of the partition plate PP of the water box BAE of a generator steam will be described in connection with Figures 5b and 5c.

According to FIG. 5b, the system according to the invention is set up at the level of the manhole TH by means of an elevator 50, as has been previously described. It will be noted in FIG. 5b above that the articulation 120 is brought in the vicinity of the center of the tube plate PT of the steam generator. The system is then mounted by translation on the elevator 50 and engaged in the manhole TH, a locking on false studs fixed on the manhole flange being then carried out. The object of the invention system is in position as shown in Figure 5b. The element 2 forming an arm is then retracted into the hollow part of the arm 1 constituted, as described above, by a semi-cylindrical hollow part for example.

Then after fixing of the element 1 forming an arm on the flange of the manhole TH, the element 2 forming an arm is subjected, as shown in FIG. 5c, to a rotational movement around the axis D1 the element 2 forming an arm thus being brought into position substantially parallel to the partition plate PP, as shown in FIG. 5c. In order to achieve this operation, the assembly of the element 2 forming an arm and the articulation 120 has been brought into the deployed position around the axis D1. The central cylinder 200 is then docked, the suction cup 201 then being applied in the vicinity of the center of the tube plate PT, as shown in FIG. 5c. The jacks 21, 22, 23, 24 can then also be approached on the partition plate PP, as shown in FIG. 5c and the corresponding suction cups 210, 220, 230, 240 can then be put under vacuum to ensure the maintenance of the arm 2 in a position substantially parallel to the partition plate PP.

The principle of displacement of the element 2 forming an arm for the system which is the subject of the invention, as shown in FIG. 5a, will be described in conjunction with FIGS. 6a and 6b.

As it appears in FIG. 6a, the two opposite jacks 21 and 23 forming a moving assembly, are made mobile by means of a double-acting jack denoted 25, the body of which is mounted floating on the second arm 2, and recalled to an average position by means of an elastic system. In FIG. 6a, the elastic system is constituted by two return springs denoted 251 and 252, the jack 25 being guided in its movement to return it to its mean position by means of a light and pin system denoted 250 It will of course be understood that by the action of the double-acting cylinder 25, in one or the other direction of movement of the corresponding control rod, the mobile assembly constituted by the cylinders 21 and 23 and their corresponding suction cup 210 and 230 moves in a direction perpendicular to the longitudinal axis of the element 2 forming an arm of the system which is the subject of the invention, this movement being carried out in one or the other direction.

In FIG. 6b, the different stages corresponding to the movement of the movable assembly constituted by the jacks 21 and 23 and by the element 2 forming an arm, are shown respectively 1, 2, 3, 4, 5, 6, 7.

• - position 1 : les ventouses 210, 220 sont mises en dépression,
• - position 2 : la dépression dans la ventouse 210 est supprimée,
• - position 3 : le vérin 25 est actionné de façon à déplacer l'équipage mobile formé par les vérins 21 et 23, le vérin 21 et la ventouse 210 étant décollés de l'élément 2 formant bras,
• - position 4 : mise en dépression de la ventouse 210 et arrêt de la dépression dans la ven­touse 220,
• - position 5 : action sur le vérin 25 lequel entraîne en translation l'élément 2 formant bras vers la ventouse 210 et le vérin 21,
• - position 6 : mise en dépression de la ventouse 220 et arrêt de la dépression dans la ven­touse 210, le vérin 25 est en outre ramené dans sa position moyenne par les moyens élastiques 251 et 252 représentés en figure 6a.
• - position 7 : mise en dépression de la ventouse 210.

From a given position of the element 2 forming an arm, the displacement procedure is as follows in accordance with the 7 positions represented in FIG. 6b:

• - position 1: the suction cups 210, 220 are placed under vacuum,
• position 2: the vacuum in the suction cup 210 is eliminated,
• position 3: the jack 25 is actuated so as to move the mobile assembly formed by the jacks 21 and 23, the jack 21 and the suction cup 210 being detached from the element 2 forming an arm,
• position 4: depression of the suction cup 210 and stop of the depression in the suction cup 220,
• position 5: action on the jack 25 which drives in translation the element 2 forming an arm towards the suction cup 210 and the jack 21,
• - Position 6: depression of the suction cup 220 and stop of the vacuum in the suction cup 210, the jack 25 is also brought back to its middle position by the elastic means 251 and 252 shown in Figure 6a.
• - position 7: vacuum suction of the suction cup 210.

Position 7 corresponds substantially to the initial position 1 after displacement of the element 2 forming an arm with an increment of displacement in rotation corresponding to the movement of the element 2 forming an arm relative to the movable assembly constituted by the jacks 21 and 23 actuated by the jack 25.

Of course, the vehicle 3 supporting the decontamination means 30 can move parallel to the element 2 forming an arm thanks to a motor driving a worm screw housed in the element 2 forming an arm. Such an arrangement will not be described in detail since it is within the reach of those skilled in the art.

In addition, the decontamination means can advantageously be rotatable along an axis perpendicular to the axis of the element 2 forming an arm and to the partition plate PP, as will be described later in the description.

In addition, a so-called safety cylinder denoted 26 may be provided at the free end of the element 2 forming an arm. This cylinder is directed in the direction of the longitudinal axis Δʹ of the second element 2 forming an arm. In the event of a power supply fault, it makes it possible to block the second elements 2 forming arms in its current position.

There is shown in Figure 7, a partial sectional view of the arm member 2, front view in a direction parallel to the axis Δʹ shown in Figure 5a. In this same figure 7, we have designated by G a circle surrounding the element 2 forming an arm, provided with its accessories, and representing the size of the manhole.

As shown in FIG. 7 above, the opposite jacks 21 and 23 form the above-mentioned mobile assembly and are, for this purpose, mounted so as to have a spacing greater than the pair of fixed jacks 22, 24, according to a direction perpendicular to the longitudinal axis Δʹ of the second arm 2 and parallel to the partition plate PP. The above-mentioned jacks 21 and 23 are mounted integral with the motor chuck of the jack 25 by means of arched arms denoted 2123 and 2321. As will be seen in FIG. 7, one of the jacks, the jack 21 by example, constituting the movable assembly, is retractable in order to allow the retraction of the assembly in the protective corset formed by the first arm 1, in order to allow the introduction of the assembly through the manhole TH . The retraction of the jack 21 is shown in FIG. 7, the assembly constituted by the element 2 forming an arm and its accessories being inscribed in the circle G representative of the size of the manhole TH. As shown in FIG. 7, the accessories may advantageously include a motor for orienting the decontamination means 30, this motor being denoted 400, the orientation of the decontamination means 30 being produced by a rotation about the perpendicular axis Δʺ to the longitudinal Δʹ axis of the element 2 forming an arm as previously mentioned. The accessories also include guide pins 4001, 4002 of the decontamination element carriage, the vehicle proper being noted in this embodiment 4003 and consisting of a carriage sliding on the guide pins 4001, 4002, a worm-type drive screw, denoted 4004 and a worm drive motor noted 4005.

The system as shown in accordance with the object of the invention in FIGS. 5a to 7 advantageously makes it possible to ensure the decontamination of the partition plate PP of the water box of a steam generator.

A particularly advantageous embodiment of the system which is the subject of the invention will now be described in connection with FIGS. 8a and 8b, this embodiment being more particularly suitable for decontamination of the internal wall of the bowl of the BAE water box. a nuclear power plant steam generator.

In the embodiment shown in FIG. 8a in particular, the second element 2 forming the second arm, is articulated to the first arm 1 by means of a hinge whose deflection plane is rotatable. In FIG. 8a, the deflection plane of the orientable hinge denoted 1200 is shown, by the longitudinal axis Δʹ of the second arm denoted 2 and the orientation rotation axis denoted D3, axis of rotation of the hinge 1200, the movement of the hinge, that is to say the orientation of the longitudinal axis Δʹ of the arm forming the second arm 2 in the plane of movement constituted by the axes D3 and Δʹ then takes place around an orthogonal axis D4 to the hinge 1200 travel plane.

According to an advantageous characteristic of the system which is the subject of the invention, as shown in FIG. 8a, the deflection plane of the hinge 1200 constitutes in operation, the first element denoted 1 and the second element denoted 2 forming an arm being in the deployed position, a diametral plane of the hemispherical bowl of the BAE water box of the steam generator.

As will be seen in FIG. 8a, the orientable hinge 1200 may advantageously include a bearing denoted 12000 fixed at the end of the first arm 1. The bearing is provided with a contact plate denoted 12000 with the tubular plate PT of the generator. steam. The contact plate can advantageously be made of a material conforming to the profile of the tube plate or tube plate of a set of retractable fingers distributed on the contact plate or not of tubes on the tube plate and coming to engage in these to ensure the fixing of the assembly. These elements are not shown in FIG. 8a, so as not to overload the drawing.

The orientable hinge 1200 further comprises a turntable denoted 12001, this turntable freely around the bearing. The axis of rotation of the turntable constitutes the orientation axis of rotation denoted D3, of the deflection plane of the orientable hinge 1200. The turntable 12001 has at its periphery an articulation denoted 12002 whose axis D4 is orthogonal to the orientation rotation axis D3 of the hinge 1200 and thus forms the aforementioned orientable hinge. The second element 2 forming an arm is articulated around the joint 12002, as shown in FIG. 8a.

In the embodiment of FIG. 8a, the vehicle 3 is mounted at the end of the second arm 2, by means of a pusher member denoted 2000, allowing the vehicle 3 to press against the internal wall of the bowl in operation. hemispherical of the steam generator BAE water box. The pusher member 2000 can be produced by a hydraulic cylinder for example. The stroke of the aforementioned hydraulic cylinder advantageously makes it possible to compensate for the variations in the radius of action of the assembly constituted by the second element 2 forming an arm and the vehicle, these variations in the radius of action being due to the slight offset from the center of rotation of the hinge 1200, axis of rotation D3, with respect to the axis of symmetry of the hemispherical bowl of the water box of the steam generator.

According to another advantageous characteristic of the embodiment of the system which is the subject of the invention shown in FIG. 8a, the vehicle 3 is also movable in rotation relative to the longitudinal axis of the second arm, by means of a gear motor noted 2001.

The vehicle 3 on the action of the jack or pusher member 2000 is thus pressed against the internal wall of the hemispherical bowl of the water box of the steam generator. The vehicle 3 can then be moved, causing the element 2 forming the system arm to be cel, by means of a displacement system disposed on the vehicle 3. The displacement system The aforementioned cement consists of a plurality of motorized drive rollers, the motorized drive rollers being denoted 331, 332, 333 in FIG. 8a.

According to another advantageous characteristic, the motorized rollers 331, 332, 333 form a tripod system. The drive control of each roller can advantageously be provided independently.

As shown in Figure 8b, a single motorized roller being shown in this figure so as not to overload the drawing, each roller can advantageously include a drive motor noted 3310, consisting of a gear motor coupled to a drive system by pinion and chain 3311 of the drive wheel of the roller 3312. In addition, and advantageously, each roller such as the roller 331 shown in FIG. 8b, can be oriented by means of an orientation motor 3313, coupled by a gear 3314, to the axis integral with the body of the roller 331. Of course, advantageously, the rollers forming the tripod system can then be oriented simultaneously in the same direction and the independent traction control of the roller can allow, if necessary, the independent control of one or more rollers or of all of the rollers, in order to ensure the displacement by traction of the assembly formed by the element 2 forming an arm and of the vehicle 3.

A more detailed description of the installation of the system which is the subject of the invention, in its embodiment as shown in FIG. 8a and 8b, will be given in conjunction with FIGS. 9a, 9b 9c, 9d, 9th.

As will be seen in FIG. 9a, the system which is the subject of the invention is set up by means of an elevator 50 as previously described. The system is slid by translation on the inclined plane of the elevator and the contact plate is brought in the vicinity of the tubular plate, in order to ensure the fixing thereon. The system thus fixed both on the tube plate PT and on the flange of the manhole TH is shown in FIG. 9b. The formation of the positioning position of the support plate on the tubular plate is given for example by three proximity sensors arranged on the support plate for this purpose.

The system having been fixed at the flange of the manhole TH by locking the lock nut provided for this purpose, the element 2 forming an arm is then deployed, the vehicle 3 is then lowered so as to bring the latter at the bottom of the bowl of the BAE water box of the steam generator. A suitable thrust is provided by the thrust cylinder 2000 on the vehicle, in order to allow good adhesion of the rollers on the internal wall of the bowl of the steam generator. The corresponding position is shown in Figure 9c.

The drive movement of the rollers then ensures the working movements to ensure decontamination by means of decontamination means 30 carried by the vehicle 3 and of sector change so as to pass from a decontaminated zone to an uncontaminated zone , to be subjected to the decontamination process.

The extraction of the system which is the subject of the invention can then, after the end of the decontamination process, be carried out by returning the element 2 forming an arm shown in FIG. vehicle having been brought back by the thrust element 2000 to its position furthest from the internal wall of the bowl of the steam generator, folding of the arm 2 inside the element 1 forming an arm by return of a cable recall for example or any other suitable means for this purpose. The system which is the subject of the invention can then be brought back to the elevator as described above.

Figures 9d and 9e provide a better understanding of the principle of monitoring the arm 2 during its movement in the hemispherical bowl of the water box BAE of the steam generator.

When the vehicle 3 moves, the pusher arm 2 via the jack 2000, applies the vehicle 3 against the spherical surface of the water box and follows the movements of the vehicle 3 thanks to the two degrees of freedom present at the joint 1200.

The axis of rotation D3 allows the element 2 forming an arm to bypass the structure as shown in particular in FIG. 9e. This system advantageously makes it possible to ensure the passage of the vehicle around the manhole as will be readily understood on observation of FIG. 9e, only a substantially circular zone denoted ZE cannot be reached by the vehicle and by the decontamination means 30.

The pusher arm interface 20 - vehicle 3 consists of a geared motor assembly allowing the orientation of the decontamination means 30 in order to respect the direction of arrival and exit of the decontamination fluid. The element 2 forming an arm can then advantageously be linked to the vehicle 3 by means of a ball joint of the Cardan type. This type of connection makes it possible to transmit the orientation command to the vehicle 3 while guaranteeing the transmission of the force from the pusher arm 20 and an application of the vehicle 3 to the surface to be decontaminated.

In the event of a failure of the supply fluids, the pusher arm 20 retains its pusher function and maintains the position of the vehicle 3. This is made possible in particular by reducing the range of action of the pusher arm 20 from top to bottom. the steam generator water box.

Finally, the upper plate 12001 of the joint 1200 can be mechanically oriented from the outside of the water box BAE of the steam generator in order to reposition the element 2 forming the arm and the vehicle 2 in the fold axis of the element 2 forming an arm in the event of a major breakdown.

A more detailed description of the control means 6 shown in particular in Figure 1a will be described in conjunction with Figures 10a, 10b and 10c.

As it appears in FIG. 10a in particular in the case of the decontamination of the primary piping of the water box of a steam generator of a nuclear power plant, the control means 6 comprise a control console having the controls vehicle movement, viewing spots on a double screen and safety controls. Advantageously, as shown in FIG. 10a, the double screen allows the display of the sectors of the primary piping TP on which the decontamination must be carried out and an analogical representation of the decontamination passes to be carried out for each sector.

In the case where the system which is the subject of the invention is more particularly suitable for the decontamination of the PP partition plate of the water box of the steam generator, the system is controlled by an operator having on the control desk means of command 6, the commands for elementary movements of rotation of the decontamination means 30, working movement of the vehicle 3 and pendular movement of the arm 2, as shown in FIG. 10b. The different axes of movement are instrumented in order to give on the desk with two screens previously described, on the one hand the image of the partition plate with the bands already subjected to decontamination and the bands to be subjected to decontamination and on the other the image of the strip being decontaminated with a visualization of the passes made.

In the case where the system which is the subject of the invention is more particularly suitable for decontaminating the bowl of the water box BAE of the steam generator, the system is controlled by an operator having on the control console control means 6, the basic movement controls such as the movement and orientation of the traction rollers, the orientation of the vehicle as well as the emergency stop orders. A display assembly mounted on a turret fixed to the element 2 forming an arm makes it possible to follow the vehicle 3 during its evolutions.

In order to ensure the decontamination of the various parts such as the primary piping TP of the water box of a steam generator, the partition plate PP of this same water box and the hemispherical bowl thereof, the object system of the invention can advantageously make it possible to ensure decontamination by electrodecontamination. In this case, as will be explained in detail below in the description, decontamination can be carried out by electrodecontamination from outside the water box of the steam generator.

In the case where the decontamination is carried out by electrodecontamination, the decontamination means 30 may advantageously comprise an electropolishing cell as shown in FIG. 11a.

A more detailed description of an electropolishing cell which is particularly suitable for the decontamination system which is the subject of the invention will be given in conjunction with FIGS. 11a and 11b.

In Figure 11a, there is shown schematically an electropolishing cell denoted 30, which comprises a suction cup formed by a suction cup body 300, substantially of revolution. A permeable electrode denoted 301 is located in the suction cup body 300 and delimits therein a chamber. electrolyte intake denoted 302 and an electrolyte suction chamber denoted 303 when the suction cup body is applied to the wall of the surface to be treated. A seal noted 304 is disposed at the periphery of the suction cup body 300. The electrolyte contained in an electrolyte reservoir, constituted by the decontaminating fluid tank noted 8 in FIG. 1a in particular, flows through the cathode 301 pierced with small diameter holes, the assembly constituted by the suction cup body and the cathode moving along the wall and the sealing of the electropolishing cell is ensured by the aforementioned seal 304.

As it further appears in FIG. 11b, a set of rollers 305 is integral with the suction cup body 300, the rollers being intended to form a bearing stop for the suction cup on the surface S in order to keep the distance from the electrode 301 at the surface S to be treated. Under the effect of the vacuum induced by the suction of the electrolyte, the seal 304 is normally crushed. In order to control this crushing, the aforementioned set of rollers, consisting of polytetrafluoroethylene rollers for example, is mounted on ball bearings with pivoting axis fixed on the body of the suction cup. This set of rollers has the function of ensuring and facilitating the sliding of the suction cup on the surface S, and prevents the phenomenon of chattering which appears when the seal 304 is too crushed.

In accordance with an advantageous characteristic of the electropolishing cell in accordance with the object of the invention, the intake chamber 302 and the suction chamber 303 respectively comprise an intake tank 306 and a suction nozzle 307 of the above-mentioned electrolyte. In accordance with another particularly advantageous aspect of the electropolishing cell according to the present invention, the electropolishing suction cup is made integral with the vehicle 3 by means of an indexing table 308 mounted movable in rotation relative to a axis perpendicular to the direction formed by the intake nozzle 306 and the suction nozzle 307 of the electrolyte. The indexing table 308 is provided with adjustment means 3080 making it possible, when the vehicle 3 is moving, to maintain the plane containing the axis of the electrolyte intake and suction nozzles, nozzles denoted 306, 307, substantially vertical. . Of course, for a given path, the adjustment of the orientation of the aforementioned plane can be adjusted once and for all. In particular when the surface to be treated is constituted by a spherical surface, in particular in the case of decontamination of the bowl of the water box BAE of the steam generator, the path of movement of the vehicle can be constituted by a large circle of the sphere for example, and the orientation of the plan can thus be established for a given path. The aforementioned adjustment means 3080 can then be constituted by a stepping motor secured to the indexing table and allowing remote adjustment of the latter as a function of the path chosen.

According to another advantageous characteristic of the electropolishing cell conforming to the object of the present invention, the suction cup body 300 is made integral with the indexing table 308 by means of an elastic suspension 309.

According to an advantageous embodiment of the above-mentioned elastic suspension, the latter comprises at least two spring jacks denoted 3091, 3092 in FIG. 2b, the mandrel of which is made integral with the suction cup body 300 by means of an articulation with ball joint noted 3100, 3110. The above-mentioned ball joint 3100, 3110 is mounted on two fixing lugs 3101, 3111, integral with the suction cup body 300 and arranged according to a diameter thereof. As will be noted in particular in FIG. 11b, each ball joint 3100, 3110 is mounted to slide according to the aforementioned diameter. The spring jacks 3091, 3092 are mounted fixed on the table or indexing table and are arranged so that the force exerted by the springs of the jack or pressing force ensures permanent contact of the suction cup with the wall to be treated. The aforementioned cylinders make it possible to compensate for any variations in level of the wall by allowing a movement back and forth along the axis previously described. The connection of the jacks or suction cup body 300 by the sliding ball joints 3100, 3110 allows the suction cup to take any angular position without introducing bending stress in the jack rods and in the fixing lugs 3101, 3111 previously described. When mounting the electropolishing suction cup on the vehicle, in accordance with the object of the invention, two flanges fixed on the body of the cylinders 3091, 3092 make it possible to ensure compressing them while maintaining the suction cup body and the suction cup in the high position.

Because the suction cup is rotated for angular corrections, it is advantageous to supply the electrode 301 with electrical energy by a distributor system. The latter is advantageously mounted on the rod of the electrode and is denoted 312. The distributor can advantageously include a brush system, it can comprise a cooling circuit by air circulation making it possible to limit the heating of the distributor. The suction cup body 300 can advantageously be made of a synthetic material such as hydrogenated polypropylene, PPH, or difluorinated polyvinyl denoted PVDH.

We have thus described a system of intervention on the primary pipes, on the partition plate and the walls of the bowl of the water box of a steam generator, particularly advantageous in that the system, by its basic design , ensures the decontamination of all the parts previously mentioned.

Of course, the system which is the subject of the invention is particularly suitable for ensuring decontamination by electrodecontamination, as has been described previously in the description.

In particular, each element 2 forming an arm can be directly associated as a function of the zone to be decontaminated from the water box of the steam generator with a corresponding articulation 12, 120 or 1200, this articulation being able to be fixed on an arm or element 1 forming universal arm, susceptible to receive the corresponding joint. Thus, the elements 2 forming arms constitute a set of arms capable of being adapted to the element 1 forming a single arm.

Of course, the different forms of vehicle are then associated with the element 2 forming the corresponding arm.

Of course, in the case where the decontamination is ensured by electrodecontamination, the electrical energy supply means 7 are advantageously constituted by a battery of controlled rectifiers, in order to allow the electrical energy supply to the vehicle and, in particular, electrodecontamination means previously described.

Claims (25)

1. Intervention system on the primary pipes and on the water box of the steam generators of a nuclear power plant, characterized in that it comprises:
- a mechanically removable vehicle (3) secured to a tensioning cable (4) circulating, during the movement of the removable vehicle in the primary pipes (TP) on idler pulleys (200), the tensioning cable being distributed by a balancing reel (5) located near the free end of an element (1) outside the manhole (TH) when said element is in position,
- a means (30) of intervention carried by said vehicle (3). 2. Intervention system on the primary pipes and on the water box of the steam generators of a nuclear power plant, characterized in that it comprises:
- a first element (1) having a substantially elongated shape and forming a first arm of the system,
- a second element (2) having a substantially elongated shape, articulated (12) at one of its ends at one end of the first element, said second element (2) forming a second arm of the system, and the whole of the first (1 ) and the second arm (2) being capable of being introduced into the water box (BAE) of the steam generator via a manhole (TH) and said second element (2) being able to be put in the deployed position relative to the first element (1),
a vehicle (3) mounted on said second arm (2), said vehicle (3) being mounted movable relative to said second arm (2),
- an intervention means (30) carried by said vehicle (3), the intervention means (30), due to its movement relative to said second arm and the relative opening between the first (1) and the second arm (2), being capable of reaching a plurality of zones of the internal surface of the steam generator such as in particular the primary pipes (TP), the partition plate (PP), the internal wall of the spherical bowl of the box steam generator (BAE),
- means (6) for remote control of the vehicle and intervention means. 3. System according to claim 2, characterized in that said first element (1) is a hollow element, of substantially semi-cylindrical shape so as to form a protective corset of said second element (2) when the latter is in the non-deployed position. . 4. System according to claim 2, characterized in that, in order to ensure intervention on the primary pipes (TP) of a steam generator, said second element (2) forming a second arm consists of a telescopic arm (20 ), said vehicle being removably mounted at the end of the latter. 5. System according to claim 4, characterized in that said vehicle is mechanically integral with a tensioning cable (4) circulating, during the movement of the removable vehicle in the primary pipes (TP) on end pulleys (200) of the second arm, pulleys (100) for articulation of the first and second arms, the tensioning cable (4) being distributed by a balancing reel (5) located near the free end of the first element (1) outside the manhole (TH) when said element is in position. 6. System according to one of claims 1, 4 or 5, characterized in that said vehicle (3) comprises:
- a vehicle body (31) consisting of a longitudinal element arranged along the longitudinal axis (Δ) of the vehicle,
a chassis (32) rotatably mounted on the longitudinal element forming the vehicle body (31), said chassis (32) comprising a plate (320) intended to support said intervention means (30),
means for supporting said vehicle constituted by a first (33) and a second (34) set of jacks, each set of jacks secured to the body (31) having in a plane orthogonal to the longitudinal axis (Δ) of the vehicle, a tripod configuration. 7. System according to claim 6, characterized in that said frame (32) is rotatably mounted on the longitudinal element (31) by means of a ring gear (310) and a motor (321). 8. System according to claims 6 and 7, characterized in that the intervention means are constituted by decontamination means and are supported by the plate (320) by means of jacks (3201,3202), each fixed by a ball joint (3203,3201) to the latter, the radial translation of the assembly relative to the longitudinal axis (Δ) of the vehicle body (31) being controlled by a motor (3205) integral with the decontamination means (30) to allow docking of the decontamination means (30) on the wall of the primary piping. 9. System according to one of claims 6 to 8, characterized in that the first (33) and the second set of jacks (34) are mounted on a seat plate (330,340) whose orientation relative to a plane orthogonal to the longitudinal axis of the vehicle body is adjustable according to an angle of value determined by means of fastening with ball joints (331,332,341,342), one of the seat plates (340) being movable in transition in a direction parallel to the longitudinal axis (Δ) of the vehicle by the intermediate traction cylinders (343,344) to provide incremental movement of the entire vehicle in this direction. 10. System according to one of claims 2 or 3, characterized in that, in order to ensure an intervention such as the decontamination of the partition plate (PP) of the water box of a steam generator, said second element (2) forming a second arm is articulated to said first arm (1) by means of a Cardan joint (120), said articulation (120) comprising, in the operating position, a first axis (D1) substantially parallel to the partition plate and a second axis (D2) substantially perpendicular to the partition plate (PP), said vehicle (3) being mounted movable in translation along said second arm (2). 11. System according to claim 10, characterized in that, in order to maintain and move said second arm (2) on the partition plate (PP), said second arm (2) comprises:
- A first central cylinder (200) arranged in the vicinity of the articulation provided with a suction cup (201), said first cylinder ensuring the fixing in translation of the assembly constituted by the first (1) and the second arm ( 2) in the direction (D2) perpendicular to the partition plate,
- a plurality of jacks (21,22) (23,24) arranged at the free end of the second arm (2), at least two opposite jacks (21,23), forming a movable assembly with respect to said second arm (2) , which can be moved perpendicular to the longitudinal direction (Δʹ) of the second arm (2) in a direction parallel to the partition plate (PP) to ensure the corresponding movement of said second arm (2), the axis (D2) forming an axis of rotation, relative to the fixed point formed by the central cylinder (200), all of the cylinders (21,22,23,24) being provided at the end of their movable rod with a suction cup (210,220,230,240) by depression. 12. System according to claim 11, characterized in that the two opposite jacks (21, 23) forming mobile assembly are made mobile by means of a double-acting jack (25) whose body is mounted floating on said second arm and brought back to a medium position via an elastic system. 13. The system of claim 12, characterized in that a safety cylinder (26) directed in the direction of the longitudinal axis of said second arm is further provided at the end thereof, this cylinder allowing, in in the event of a power supply fault, ensuring that said second arm (2) is locked in its current position. 14. The system as claimed in claim 11, characterized in that said opposite jacks (21, 23) forming a moving assembly are mounted so as to have a spacing greater than the pair of fixed jacks (22, 24) in a direction perpendicular to the longitudinal axis (Δʹ) of the second arm and parallel to the partition plate (PP), one of said jacks (21) constituting the movable assembly being retractable so as to allow retraction of the assembly in the protective corset formed by the first arm (1) to allow the introduction of the assembly through the manhole (TH). 15. System according to one of claims 2 or 3, characterized in that in order to ensure an intervention such as the decontamination of the internal walls of the spherical bowl of the water box (BAE) of a steam generator, said second element (2) forming a second arm is articulated to said first arm by means of a hinge, the plane of movement of which is rotatable (1200), said plane formed by the longitudinal axis (Δʹ) of the second arm and the orientation rotation axis (D3) constituting, in operation, a diametrical plane of the hemispherical bowl. 16. System according to claim 15, characterized in that said orientable hinge (1200) comprises:
- a bearing (12000) fixed at the end of the first arm (1) provided with a contact plate with the tubular plate (PT) of the steam generator,
- a turntable (12001) freely around the bearing, the axis of rotation of which constitutes the orientation rotation axis (D3) of said plane of movement of the orientable hinge (1200), said turntable (12001) comprising its periphery an articulation (12002) of axis (D4) orthogonal to the axis of orientation rotation (D3) and forming orientable hinge, said second arm (2) being articulated around said articulation (12002). 17. System according to one of claims 15 or 16, characterized in that said vehicle (3) is mounted at the end of said second arm (2) via a pusher member (2000) allowing, in operation , pressing said vehicle (3) against the internal wall of the hemispherical bowl of the water box of the steam generator. 18. System according to claim 17, characterized in that said vehicle (3) is also movable in rotation relative to the longitudinal axis of said second arm by means of a geared motor group (2001). 19. The system of claim 18, characterized in that said vehicle (3) is provided with a displacement system consisting of a plurality of motorized drive rollers (331,332,333). 20. The system of claim 19, characterized in that said rollers (331,332,333) form a tripod system, the drive control of each roller being independent. 21. System according to one of claims 2 to 20, characterized in that in order to ensure the introduction and the establishment in the manhole (TH) of the assembly constituted by the first (1) and the second arm (2) said system further comprises an elevator system (50) of the inclined plane type, the angle of inclination of the inclined plane allowing, by single translation of said assembly, the positioning of the articulation (12,120,1200 ) from the first and second arms near the center of the steam generator tube plate (PT). 22. System according to one of the preceding claims, characterized in that said means intervention (30) comprise an electropolishing cell. 23. System according to claim 22, characterized in that said cell (30) comprises:
- a suction cup formed by a suction cup body (300) substantially of revolution,
- a pre-electrode (301) located in the suction cup body (300) and delimiting therein an electrolyte admission chamber (302) and an electrolyte suction chamber (303) when the suction cup body is applied to the wall of the surface to be treated,
- a seal placed at the periphery of the suction cup body,
- A set of rollers (305) integral with the suction cup body (300), said rollers being intended to form a support stop for said suction cup on said surface in order to maintain constant the distance from the electrode to the surface to be treated. 24. A method of decontamination of primary piping and of the water box of a nuclear power plant steam generator, characterized in that the decontamination is carried out by electrodecontamination. 25. The method of claim 24, characterized in that the decontamination is carried out by electrodecontamination from outside the water box of the steam generator.

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