EP0479344B1 - Working system for internal walls of the 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 steam generator of a nuclear power plant.

As part of the replacement of 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 document EP-A-0 178 971 describes a tool-carrying robot making it possible to carry out various interventions inside a water box of a steam generator. This robot comprises a first arm and a second arm mounted pivoting at the free end of the first arm as well as a tool-carrying carriage mounted sliding on the second arm, this denier comprising two parts, and being capable of turning around its axis. longitudinal.

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 an excessive dose of irradiation.

• la figure 1a 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 1b 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,
• les figures 2a à 2e représentent des phases de mise en place du système selon l'invention,
• la figure 3 représente un schéma illustratif des moyens de commande et de leur utilisation en liaison avec un système de décontamination objet de l'invention,
• les figures 4a et 4b 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 adapted to the decontamination of the internal wall of the bowl of the water box of a steam generator of a nuclear power plant,
• FIG. 1b represents 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,
• FIGS. 2a to 2e represent phases for setting up the system according to the invention,
• FIG. 3 represents an illustrative diagram of the control means and their use in connection with a decontamination system which is the subject of the invention,
• FIGS. 4a and 4b respectively represent a schematic 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 such cell.

The system which is the subject of the invention will now be described in connection with FIGS. 1a and 1b, this embodiment being adapted to the decontamination of the internal wall of the bowl of the BAE water box of a nuclear power plant steam generator.

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

According to an advantageous characteristic of the system which is the subject of the invention, as shown in FIG. 1a, 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. 1a, 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 in order to secure the assembly. These elements are not shown in FIG. 1a, so as not to overload the drawing.

The adjustable hinge 1200 further comprises a turntable denoted 12001, this turntable freely around the bearing. The axis of rotation of the turntable constitutes the axis of rotation of orientation denoted D3, of the plane of movement of the orientable hinge 1200. The turntable 12001 has at its periphery an articulation denoted 12002 whose axis D4 is orthogonal to the axis of rotation of orientation 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. 1a.

In the embodiment of FIG. 1a, 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. 1a, the vehicle 3 is also movable in rotation relative to the longitudinal axis of the second arm, by means of a geared 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, thereby driving the element 2 forming the arm of the system, by means of a displacement system disposed on the vehicle 3. The displacement system mentioned above consists of a plurality of motorized drive rollers, the motorized drive rollers being denoted 331, 332, 333 in FIG. 1a.

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 1b, 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. 1b, 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, independent control of one or more rollers or of all the rollers, in order to ensure the displacement by traction of the assembly formed by the element 2 forming an arm and of the v 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. 1a and 1b, will be given in conjunction with FIGS. 2a, 2b 2c, 2d, 2e.

As will be seen in FIG. 2a, the system which is the subject of the invention is implemented 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 tubular plate PT and on the flange of the manhole TH is shown in FIG. 2b. The formation of the positioning position of the support plate on the tube plate is given for example by three proximity detectors arranged on the support plate for this purpose.

The system having been fixed at the level of the manhole flange 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 ensured 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 2c.

The drive movement of the rollers then ensures the work 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. 2c to the vertical position, folding the element 2 forming an arm, 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 recalling 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 2d and 2e 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 by means of 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 l hinge 1200.

The axis of rotation D3 allows the element 2 forming an arm to bypass the structure as shown in particular in FIG. 2e. 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. 2e, 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 the reduction in 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 control means of the system of the invention will be described in conjunction with FIG. 3.

In the case where the system which is the subject of the invention is 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 desk control means 6 shown on the FIG. 2d, the elementary movement commands such as the displacement and the orientation of the traction rollers, the orientation of the vehicle as well as the commands emergency stop. 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, the 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. 4 a and 4 b.

In Figure 4a, there is shown schematically an electropolishing cell denoted 30, which comprises a suction cup formed of 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 denoted 304 is disposed at the periphery of the suction cup body 300. The electrolyte contained in an electrolyte reservoir circulates through the cathode 301 pierced with small diameter holes, the assembly formed by the body of suction cup 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. 4 b, a set of rollers 305 is integral with the suction cup body 300, the rollers being intended to form abutment for supporting the suction cup on the surface S in order to keep the distance from l 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, constituted by castors made of polytetrafluoroethylene 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 chattering phenomenon 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 above-mentioned 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 plane 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. 4b, 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 secured to the suction cup body 300 and arranged according to a diameter thereof. As will be noted in particular in FIG. 4b, 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 the 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 subject 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. This is advantageously mounted on the rod of the electrode and is denoted 312. The dispenser can advantageously include a brush system, it can include a cooling circuit by air circulation making it possible to limit the heating of the dispenser. 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 an intervention system on the walls of the bowl of the water box of a steam generator, particularly advantageous in that the system, by its basic design, makes it possible to ensure the decontamination of the all of the previously cited parts.

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 1200, this articulation being able to be fixed on an arm or element 1 forming a universal arm, capable of 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 decontamination is ensured by electrodecontamination, the means of supplying electrical energy 7 are advantageously constituted by a battery of controlled rectifiers, in order to allow the supply of electrical energy to the vehicle and, in particular, electrodecontamination means previously described.

Claims (8)

1. A system for working on the water tank of a steam generator in a nuclear power station, the system comprising:
      a first element (1) of substantially elongate shape and forming a first arm of the system;
      a second element (2) of substantially elongate shape, hinged at one of its ends to one end of the first element, said second element (2) forming a second arm of the system, and the assembly comprising both the first arm (1) and the second arm (2) being suitable for being inserted into the water tank (BAE) of the steam generator (GV) via a manhole (TH), and said second element (2) being capable of being put into a deployed position relative to the first element (1);
      a vehicle (3) mounted on said second arm (2), said vehicle (3) being mounted to move relative to said second arm (2); and
      working means (30) carried by said vehicle (3), the working means being capable, by virtue of moving relative to said second arm and because of the relative angle between said first and second arms (1, 2), of reaching a plurality of inside surface zones of the steam generator such as, in particular, the primary tubes (TP), the partition plate (PP), and the inside wall of the spherical end of the water tank (BAE) of the steam generator;
      the system being characterized in that in order to work on the inside walls of the spherical end of the water tank (BAE) of a steam generator, e.g. for decontamination purposes, said second element (2) forming the second arm is hinged to said first arm via a hinge that is fixed to a tube plate (PT) of the steam generator to swing in a plane that can be swivelled (1200), said plane defined by the longitudinal axis (Δ′) of the second arm and the swivel axis of rotation (D3) constituting, in operation, a diametral plane of the hemispherical end wall, and in that said swivellable hinge (1200) includes:
      a bearing (12000) fixed at the end of the first arm (1) and provided with a plate for making contact with said tube plate (PT) of the steam generator; and
      a turntable (12001) mounted to rotate freely relative to the bearing, its axis of rotation constituting the swivel axis of rotation (D3) of said plane in which the swivellable hinge (1200) can swing, said turntable (12001) including at its periphery a hinge (12002) having an axis (D4) orthogonal to the swivel axis of rotation (D3) and forming the swivellable hinge, said second arm (2) being hinged about said hinge (12002).
2. A system according to claim 1, characterized in that said vehicle (3) is mounted at the end of said second arm (2) by means of a thrust member (2000) making it possible, in operation, to urge said vehicle (3) against the inside wall of the hemispherical end of the water tank of the steam generator.
3. A system according to claim 2, characterized in that said vehicle (3) is also rotatable about the longitudinal axis of said second arm by means of a motor and gear box unit (2001).
4. A system according to claim 3, characterized in that said vehicle (3) is provided with a displacement system consisting in a plurality of motor-driven drive wheels (331, 332, 333).
5. A system according to claim 4, characterized in that said wheels (331, 332, 333) form a tripod system, with drive control of each wheel being independent.
6. A system according to any one of claims 1 to 5, characterized in that in order to insert and position the assembly constituted by the first and second arms (1, 2) in the manhole (TH), said system further comprises a sloping plane type lift system (50) with the angle of inclination of the sloping plane making it possible by mere translation of said assembly to position the hinge (1200) of the first and second arms in the vicinity of the center of the tube plate (PT) of the steam generator.
7. A system according to any one of claims 1 to 6, characterized in that said work means (30) include an electrolytic polishing cell.
8. A system according to claim 7, characterized in that said cell (30) comprises:
      a suction cup constituted by a suction cup body (300) that is substantially a body of revolution;
      a permeable electrode (301) situated in the suction cup body (300) and defining therein an electrolyte admission chamber (302) and an electrolyte suction chamber (303) when the suction cup body is applied against the wall of the surface to be treated;
      a gasket (304) disposed at the periphery of the suction cup body; and
      a set of wheels (305) secured to the suction cup body (300), said wheels being designed to form a thrust abutment of said suction cup against said surface in order to keep the distance between the electrode and the surface to be treated constant.

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