WO2013030355A1

WO2013030355A1 - System for checking the position of a fuel assembly

Info

Publication number: WO2013030355A1
Application number: PCT/EP2012/066993
Authority: WO
Inventors: Philippe Berard; Eric MERKULOW
Original assignee: Bouygues Construction Services Nucleaires
Priority date: 2011-09-01
Filing date: 2012-08-31
Publication date: 2013-03-07
Also published as: FR2979740A1; FR2979740B1

Abstract

The invention relates to a system for checking the position of a fuel assembly and the associated method. The system comprises palpation members for the mechanical palpation of the head of the fuel assembly in order to determine an absolute position of the fuel assemblies, using mechanical devices for indicating the position of the fuel assembly. Preferably, the system comprises a SCARA-type articulated arm (30) and an instrumented shaft (40) mounted in translation on the articulated arm (30), with a measuring head (50) being disposed on the instrumented shaft (40).

Description

POSITION CONTROL SYSTEM OF AN ASSEMBLY

COMBUSTIBLE

GENERAL TECHNICAL FIELD AND PRIOR ART

The present invention relates to a system for controlling the position of a fuel assembly in the tank of a nuclear reactor.

The invention also relates to a method for controlling the position of a fuel assembly in the tank of a nuclear reactor.

Nuclear reactors with pressurized water are cooled by pressurized water. They comprise inside a tank, of which FIG. 1 is an overall diagram, a core consisting of fuel assemblies 2 arranged vertically in the tank 1.

Figure 2 is a diagram showing a partial sectional view of a fuel assembly 2. These fuel assemblies 2, generally prismatic, consist of a bundle of fuel rods 21 formed of a sheath filled with stacked fuel pellets. These fuel rods 21 are held by grids 23 surrounding the beam of rods. A head plate 24 and a foot plate 25 cover the respectively high and low ends of the bundle of rods 21. Usually, head and foot are respectively designated assemblies constituting the corresponding ends of the fuel assemblies.

A control cluster 22 caps the fuel assembly. This control cluster 22 is constituted by a control spider 27 carrying control rods 26. These control rods 26 are intended to slide along guide tubes 28 regularly distributed inside the beam of rods 21 in order to control the fission reactions by the absorption of neutron fluxes. A core of the nuclear reactor is for example composed of 157 fuel assemblies each comprising 264 rods containing the nuclear fuel, the number of fuel assemblies depending on the power of the reactor. The tank is closed by a tank lid. An example of arrangement of these fuel assemblies is illustrated in FIG.

Inside the vessel 1 are a top core plate 1 1 (PSC) above the fuel assemblies 2, as well as a bottom core plate 12 (PIC), on which the fuel assemblies 2 rest.

Above the upper core plate 1 1 (PSC) are arranged upper internal equipment 13 (EIS) comprising for example guide rods for handling control clusters. Likewise, below the lower core plate 12 are arranged lower internal equipment 14.

The fuel assemblies 2 are held in position by means of centering pins arranged at the upper core plate and the lower core plate. These centering pins cooperate with centering holes S placed on either side of the ends of a fuel assembly 2, in order to center them in the reactor vessel. These holes S are arranged in the head plate 24 and the foot plate 25.

A coolant circulating in the vessel 1 allows the transport of the energy generated by the fission reaction at the rods. In a pressurized water reactor, this heat transfer fluid is usually borated water.

In order to ensure a good circulation of the coolant along the fuel assemblies 2, they must be maintained in the tank 1 in perfectly defined positions, further allowing to homogenize the heat distribution of the reactor core.

Fuel assemblies must sometimes be handled during the maintenance phase. Handling usually occurs when replacing fuel assemblies, usually the third or quarter of the assemblies. The fuel assemblies no longer containing enough fissile material are removed from the tank, the remaining assemblies then being reorganized according to their respective richness of fissile material, and new assemblies being introduced.

These manipulations require the removal and removal of many fuel assemblies, usually all assemblies of a tank. However, the bad positioning of a fuel assembly can lead in particular to:

poor circulation of heat transfer fluid between fuel assemblies, leading to thermal anomalies;

a heterogeneity in the neutron flux, leading to fission behavior anomalies.

A more serious consequence of the poor positioning of fuel assemblies occurs during the establishment of the upper elements of the tank, when the centering holes S of a poorly positioned fuel assembly then no longer face the centering pins of the top plate of heart 11 corresponding.

This may result in a depression of the centering pins in the head plate of the fuel assembly, the fuel assemblies then being hooked to the upper core plate 11. In a subsequent uplift, these fuel assemblies 2 hooked may be driven by the upper plate of heart 11 and be suspended there, with the risk of then falling into the tank, resulting in the degradation of fuel assemblies 2 chus and those they could touch in their fall. It may alternatively result in a crushing of the fuel assembly 2 incorrectly positioned, causing the twisting of the rods 21 constituting it. In these two examples, the degradation of the fuel assemblies 2 would result in the release of fission products in the heat transfer fluid of the vessel 1, and potentially outside the confinement chamber of the reactor

The misalignment of the fuel assemblies 2 may be caused by the presence of migrating bodies, which may be debris resulting from the breakage of handling elements, such as ball bearing balls or any other element. The breakage of elements is likely to go unnoticed. Indeed, the tank of a nuclear reactor is an imposing environment of strong constraints, especially in terms of radiation, resulting in a restriction of the monitoring means, a spacing in time of control opportunities and premature aging of materials . In addition, the instrumentation is restricted for reasons of space.

In addition, the fuel assemblies typically have a height of about 4 m and a width of 213 mm. Therefore, a 3.5 mm diameter migrating element positioned under a fuel assembly 3 mm from the edge thereof, would result in a gap of 67 mm from the position of the fuel assembly head plate 24 relative to to normal. Thus, even a small migrating element is sufficient to cause large positioning errors. In addition, the poor positioning of a fuel assembly causes the shifting of other assemblies that are repelled by the fuel assembly. An example is given in FIG. 4, on which are represented the displacements resulting from the bad positioning of the assembly 2 located in the middle. Such a domino effect can have serious consequences since the aforementioned degradations can then occur simultaneously on several fuel assemblies.

It is therefore necessary to verify the correct positioning of the fuel assemblies. There are known methods of verification based on images, fixed or video, fuel assemblies in the reactor vessel, by means of which are measured various quantities such as the gaps between two assemblies or the length of an alignment of several assemblies fuel from which an average spacing between fuel assemblies is estimated.

However, the environment in which these images are taken involves strong environmental constraints. In particular, the high level of radiation prohibits the use of precision electronics near fuel assemblies, preventing the use of sufficiently accurate image sensors.

In addition, the heat transfer fluid, usually borated water which bathes the fuel assemblies in the tank, is subject to strong currents of circulation and convection. These strong currents deteriorate the accuracy of the images because of the eddy they cause and the heterogeneity of the refractive indices of the heat transfer fluid from one current to another, especially because of the different temperatures of these currents. The turbulence caused by these currents is even stronger than the bad positioning of an assembly is likely to modify the flow of heat transfer fluid.

In addition, such methods only allow the determination of a relative position of the fuel assemblies, that is to say relative to each other. However, the relative position is not sufficiently precise in view of the need for absolute positioning with respect in particular to the elements of the set of upper internals arranged on the upper core plate which are intended to be inserted at specific locations. compared to a theoretical position of the fuel assemblies.

Therefore, these methods are not entirely satisfactory. An object of the invention is therefore to overcome the disadvantages mentioned above.

GENERAL PRESENTATION OF THE INVENTION

An object of the invention is to propose, in a first aspect, a system for controlling the position of a fuel assembly in the tank of a nuclear reactor, characterized in that it comprises palpation members for implementing a mechanical alpine head of a fuel assembly to determine an absolute position of said fuel assembly.

Preferably, the palpating members are determination pins adapted to cooperate with centering holes of the head of the fuel assembly. More precisely, according to a first aspect, the invention proposes a system comprising mechanical devices for copying the position of the fuel assembly. Preferably, the system comprises an articulated arm of SCARA type and an instrumented pole mounted in translation on said articulated arm, a measurement head being disposed on the instrumented pole.

The system may further comprise an extension mast attaching to the instrument pole, said extension mast being provided with image sensors and handling and / or suction means.

Preferably, the instrumented pole further comprises a flotation element and the measuring head comprises image sensors. According to a second aspect, the invention also proposes a method for controlling the position of a fuel assembly in the tank of a nuclear reactor, characterized in that an absolute position of the fuel assembly is determined by mechanical palpation of the head the fuel assembly by means of palpating members of a system for controlling the position of a fuel assembly in the vessel of a nuclear reactor core.

More specifically, the method according to the second aspect of the invention comprises the steps according to which:

an instrumented pole mounted on an articulated arm of the SCARA type is positioned opposite a theoretical position of a fuel assembly, said instrumented pole is lowered until palpation members arranged on a measuring head of said instrumented pole cooperate with said fuel assembly,

the absolute position of said fuel assembly is determined by the position of the articulated arm and a displacement of the palpation members induced by their cooperation with said fuel assembly. PRESENTATION OF FIGURES

Other features and advantages of the invention will become apparent from the description which follows, which is purely illustrative and not limiting. This description should be read on the basis of the accompanying drawings, in which:

FIG. 1 shows an overall diagram of a nuclear reactor vessel, FIG. 2 is a diagram showing a partial sectional view of a fuel assembly,

FIG. 3 is a diagram showing a view from above of a reactor vessel containing fuel assemblies,

FIG. 4 is a top view of fuel assemblies illustrating the offset of fuel assemblies,

FIGS. 5 and 6 are general figures of a system according to the first aspect of the invention embodying the method according to the second aspect of the invention,

FIGS. 7 to 10 are close-up views of the approach and palpation of a fuel assembly by the system according to the first aspect of the invention,

FIG. 11 is a sectional view of an instrumented pole of the system according to the invention,

Figures 12 and 13 show the system according to the first aspect of the invention provided with an extension mast in a low and high position respectively thereof,

Fig. 14 is a diagram illustrating the steps of the method according to the second aspect of the invention.

DESCRIPTION OF ONE OR MORE MODES OF REALIZATION AND IMPLEMENTATION

FIGS. 5 and 6 are overall figures of a system according to the first aspect of the invention embodying the method according to the second aspect of the invention and FIGS. 7 to 8 are close-up views of the palpation of FIG. 'a fuel assembly by the system according to the first aspect of the invention. The following description will be made in particular with reference to these figures.

The system according to the invention is a system for controlling the position of a fuel assembly 2 in the tank 1 of the core of a nuclear reactor. The fuel assemblies 2 are immersed in borated water in the tank 1 of the core of a nuclear reactor. They are arranged according to a positioning mesh allowing good operating conditions and safety. Any deviation of a fuel assembly 2 with respect to this mesh must be able to be accurately detected.

To this end, the system comprises palpating members for implementing a mechanical probe of the head of the fuel assemblies 2 to determine an absolute position of the fuel assemblies 2. These palpating bodies will be detailed later.

The system comprises an articulated arm 30 of SCARA type and an instrumented pole 40 mounted in translation on said articulated arm, a measuring head 50 being disposed on the instrumented pole 40. An arm SCARA, acronym for English Selective-Compliance-Assembly -Robot-Arm for articulated robotic arm with selective compliance. It is an articulated arm in an X-Y plane but rigid in a Z direction orthogonal to this plane. The use of an SCARA arm improves the speed and accuracy of positioning. The second aspect of the invention relates to a method for determining the position of a fuel assembly 2 in the tank 1 of a nuclear reactor, according to which an absolute position of the fuel assembly 2 is determined by a mechanical palpation of the fuel assembly 2 by means of palpating members of the system according to the first aspect. Fig. 14 is a diagram illustrating the steps of said method.

Positioning (step S0) the instrumented pole 40 mounted on the articulated arm 30 of SCARA type facing a theoretical position of a fuel assembly 2. This step is illustrated in particular by FIG. 5, on which the instrumented pole 40 is in the up position to allow a movement of the system minimizing the risk of collision.

The articulated arm 30 has two length members, a first length member 31 and a second length member 32 connected by a hinge 33 on prestressed tapered roller bearings. This hinge 33 allows both a rotation such that the second length member 32 can be placed along the first length member 31, on each side thereof. Preferably, it is an articulation on tapered roller bearings mounted in prestressed and motorized by a servomotor equipped with a negative-action gearbox.

The system comprises securing means to a fixed part associated with the tank 1, and means for determining a marker associated with the tank 1. The articulated arm 30 comprises securing means by pneumatic clamping to the column 70 guide placed at the periphery of the reactor vessel 1. The articulated arm 30 further comprises indexing means ensuring the angular positioning of the pneumatic clamping system on said guide column 70. These indexing means make it possible to prevent rotation of the base of the articulated arm 30 around the axis of the guide column 70. These indexing means are, for example, abutments provided with protective pads bearing either on the flanges (inside or outside) of the top of the reactor vessel 1, or in a tapping adjacent to the tapping of the column 70. for guiding, said indexing means ensuring the angular positioning of the pneumatic clamping system on said column 70.

The articulation of the arm SCARA 30 around the axis of the guide column 70 is provided with tapered roller bearings mounted in prestressing and motorized by a servomotor equipped with a negative-action gearbox. Thus, preferably, the two length members 31, 32 of the articulated arm 30 each comprise at their end a hinge on tapered roller bearings mounted motor-biased by a negative-action servomotor. The structure of the SCARA articulated arm 30 preferably takes the form of a large hollow box structure. The large transverse dimensions of the articulated arm 30 make it possible in particular to stiffen the holding of the instrumented pole 40 on the articulated arm 30, as well as the holding of the articulated arm 30 on the guide column 70. Preferably, the structure comprises perforations to allow passing the flow of heat transfer fluid to reduce the bearing surface facing said flow.

A hollow structure makes it possible to lighten the weight (in immersion in the borated water) of the articulated arm SCARA 30 and to pass the wiring inside. Preferably, the electrical connecting cables are embedded in the structure, and a single electropneumatic connecting cable connects the flanged system on the guide column 70 to a remote control / control station.

The structural materials, both of the articulated arm and of the entire system according to the invention, are chosen from the products and materials that can be used in power plants (commonly referred to by the acronym PMUC) and resistant to the radiation of a reactor core. nuclear - charged or discharged.

The articulated arm 30 is chosen to have longitudinal dimensions sufficient to be able to scan the surface of the tank 1 in the plane of evolution of the articulated arm 30 of the SCARA type, so that the system according to the invention can reach each of the fuel assemblies without requiring the displacement of the hitching of the articulated arm 30. The drive torques of the SCARA arm 40 are controlled to reduce the consequences of a collision. In addition, proximity sensors may be provided to add security redundancy to software positioning for collision avoidance. Once the SCARA arm 30 is positioned, steps (S2 and S4) are lowered to said instrumented pole 40 until palpating members 51 arranged on a measuring head 50 of said instrumented pole 40 cooperate (step S5) with said assembly. 2. This step is illustrated in particular in Figure 6 which shows the boom instrumented 40 being lowered opposite the fuel assembly 2 whose absolute position is to be determined.

The instrumented pole 40 consists of a honeycombed tube and has a diameter less than or equal to the pitch of the fuel assemblies (215 mm for example), that is to say at the center distance of the fuel assemblies to optimize its bulk in the air. internal space of the tank 1 of the reactor and minimize its bearing surface facing the flow of water. The honeycombed tube structure allows to combine strength and lightness, while allowing the passage of wiring and instrumentation inside said tube.

Preferably, the instrumented pole 40 is mounted in translation on the articulated arm 30 by means of an oversized rack driven by a servomotor equipped with a negative-clearance reducer. It is also guided by prestressing rollers. The instrumented pole 40 can rotate 360 ° about its axis. This axis of rotation is mounted on tapered roller bearings prestressed and motorized by a servomotor equipped with a gearbox with negative clearance.

The instrumented pole 40 also comprises a buoyancy element 60. The buoyancy element allows a balancing and adjustment of the buoyancy of the system to facilitate its implementation on the guide column. Preferably, the flotation element is arranged in the upper part of the instrumented pole.

In the illustrated embodiment, the buoyancy element is a buoy whose buoyancy is sufficient to ensure the floatation of the instrumented rod in the heat transfer fluid of the tank. In this way, a rapid rise of the pole 40 can be provided in degraded mode or in case of breakage, avoiding a deposit of the pole 40 at the bottom of the tank 1. Alternatively, the floating element can be of variable size, such as a balloon whose inflation and / or deflation are remotely controllable to adjust the buoyancy of the pole in the heat transfer fluid of the tank. This inflation can for example be provided by a cylinder of gas under pressure, or by a gas supply with an intake valve and a controlled exhaust valve to control inflation of the balloon. The buoyancy of the system can then be chosen to bring it up to the surface, float it between two waters to facilitate its implementation, or sink it to ensure the establishment.

Figures 8 and 9 are close-up views illustrating the approach of the palpating members of the fuel assembly 2, while Figures 10 and 11 are close-up views illustrating the palpation of a fuel assembly by the system according to the first aspect of the invention.

In the embodiment illustrated in FIG. 8, the palpating members are determination pins 51 adapted to cooperate with centering holes S of the fuel assemblies 2. However, the palpation members could take other forms, in the to the extent that it would allow them to perform a palpation of the fuel assembly by the cooperation of said palpating members with the fuel assembly. For example, it could be flanges partially surrounding the head of the fuel assembly or a recess, such as the recess 56 cooperating with the control cluster 22 disposed on the head of the fuel assembly.

Preferably, at least one centering pin 51 comprises at least one centering spring 52 intended to cooperate with walls of holes of centering fuel assembly 2. The centering spring 52 can for example take the form of a network flexible blades regularly distributed around said pin 51 or any other resilient shape. The centering spring 52 makes it possible to ensure that the centering pin 51, once inserted into the centering hole S, is centered in the centering hole S. The resilience of the spring 52 eliminates the risk of wedging the centering pin 51 in the S-hole. As shown in FIG. 9, the measuring head 50 has image sensors 55. These image sensors can be load-sensing circuit hardened cameras or hardened tube cameras. In addition, a recess 56 may be provided at the level of the measuring head 50 for housing the control cluster 22 of the fuel assembly 2, so that it does not interfere with palpation.

These image sensors may be used to identify a fuel assembly identifier 2 disposed thereon.

Preferably, image sensors 51 and palpating members, that is to say pins 51, are alternately arranged on the measuring head 50 at the vertices of an invariant rotary angle polygon Θ. In addition, the system according to the invention comprises actuators for rotating the instrumented pole 40 of the angle Θ. In the embodiment illustrated in FIG. 9, the polygon is a square and the angle Θ is equal to 90 °. Thus image sensors 55 and palpating members 51 are alternately arranged on the measuring head 50 at the vertices of a square.

More generally, at least one angle between on the one hand a first straight line passing through a palpating member 51 and a center of rotation of the measuring head 50 and, on the other hand, a second straight line passing through an image sensor 55 and the center of rotation of the measuring head 50 is equal to the angle Θ.

Thus, the instrumented pole 40 can be pivoted from said angle Θ so that the palpating member 51 is in the position previously occupied by the image sensor 55.

Thus the method according to the invention preferably comprises the steps according to which, during a first part of the descent of the instrumented pole 40, the image sensors 55 are opposite the centering holes S of the fuel assembly 2, then

the instrumented pole 40 is pivoted so that the palpating members 51 are facing the centering holes S of the fuel assembly 2 during a second part of the descent.

In this way, during the first part of the descent, we then check:

- cleanliness and integrity of centering holes of the fuel assemblies, - alignment of the measuring head with the fuel assembly.

When the centering pins 51 arrive at the level of the fuel assemblies 2, the pins 51 penetrate into the centering holes S of the fuel assemblies 2. The centering pins then cooperate, directly or by means of the centering springs 52 if they are present. provided, with the centering holes S. The cooperation of these palpating members with the fuel assemblies 2 is particularly illustrated by FIGS. 9 and 10.

The measuring head 50 is disposed on the instrumented pole 40 by means of a compilant link 59. This compilant link 59 is produced by an elastic device capable of being offset in a plane perpendicular to the axis of the instrumented pole 40. so that the compiler link 59 allows a limited travel of the measuring head 50 relative to the instrumented pole 40 with return to the initial alignment, in the axis of the instrumented pole 40, when the palpation operation is complete .

An offset of the longitudinal axis of the holes S relative to the alignment of the instrumented pole 40, and therefore with respect to the position of the mechanical arm 30, causes the displacement of the measuring head 50. This displacement is made possible by the compiler link 59. Thus, the offset of the measuring head 50 relative to the instrumented pole 40 is representative of the position of the fuel assembly 2 relative to the mechanical arm.

FIG. 11 illustrates in partial section the inside of the instrumented pole 40.

Within said instrumented pole 40, an amplifying rod 41 connecting the measuring head to a measuring system is mounted in pivot connection 44 on said amplifying rod 41 along a transverse axis perpendicular to the longitudinal axis of said rod 41. The amplifying rod 41 can also be mounted by means of a finger-joint connection. The rod 41 can rotate around this connection. Another position of the rod 41 and the measuring head 50 is illustrated by dotted lines in FIG. 11, in which the measuring head 50 is moved laterally to the right of the figure, with the shank 41 copying the position of the measuring head 50. Preferably, the pivot 44 is located at a fraction β of the length of the rod 41, from the end 42 connected to the measuring head 50, so that a displacement of said end 42 is amplified by a factor a = (l / p-1) at the opposite end of the rod 41, where the displacement will be measured by a measuring device 43. For example, if the pivot 44 of is at β = 1/6 of the length of the rod 41, then the displacement of the measuring head 50 will be amplified five times. The configuration of the fixing and pivoting points of the amplifying rod 41 makes it possible to transmit to the measuring device 50 the lateral and rotary displacements of the measuring head on a plane perpendicular to the axis of the instrumented pole 40 within the limits established by the elastic compliance device 59.

The amplification of the displacement of the measuring head 50 makes it possible to improve the accuracy of the measurement. In addition, the amplifying rod 41 moves the measuring device away from the measuring head. Thus, the measuring device 43 may be placed in the instrumented pole 40 at a distance greater than 1 m from the measuring head 50, in order to attenuate the radiation by a borated water mattress. To protect the measurement electronics, the measuring device 43 is preferably 1.5 m away from the measuring head 50. In a preferred embodiment, the compiler link 59 is lockable, and the articulated arm 30 and the boom instrumented 40 are adapted to be able to transmit a repositioning force of a fuel assembly 2. In addition, the measuring head is equipped with gripping means, for example a grapple gripper, capable of grasping the head of the fuel assembly. It is then possible to exert a repositioning force on a fuel assembly 2 that is incorrectly positioned by using the displacement of the SCARA arm 30. In this operating mode, the remote adjustment of the buoyancy of the balloon located at the top of the instrumented pole 40 allows to compensate, or even cancel, the immersion weight of the fuel assembly, hooked to the gripper, to facilitate its repositioning.

The compilant link 59 is then lockable, the method comprises at least one step of resetting or repositioning the fuel assembly comprising:

the blocking of the compiler link 59, - gripping the head of the fuel assembly 2,

- The registration of the fuel assembly 2 by displacements of the articulated arm 30 SCARA type. When the instrumented pole 40 comprises a floating element 60 of variable size whose inflation and / or deflation is remotely controllable, said method comprises at least one step during which the piloting of the buoyancy element 60 compensates for the weight the fuel assembly 2 to facilitate its registration.

Finally, it determines (step S6) the absolute position of said fuel assembly 2 by the position of the articulated arm 30 and a displacement of the palpating members 51 induced by their cooperation with said fuel assembly 2. The system according to the invention thus comprises means mechanical mechanical recopy of the position of the fuel assembly 2, which, together with the knowledge of the position of the mechanical elements that carry them, that is to say the instrumented pole 40 and the articulated arm 30, can determine the absolute position of said fuel assembly 2 relative to the tank. The mechanical mechanical position feedback devices of the fuel assembly 2 here take the form of the amplifying rod 41.

Preferably, the articulated arm 30 is rotatably mounted on a positioning column 70 at the periphery of the reactor vessel 1 and said method further comprises a prior step (step SI) of initialization of absolute position in which two positions are located. reference for defining a polar frame in which said absolute position of the fuel assembly is determined.

Preferably, the absolute position of said fuel assembly 2 is determined with respect to a positioning mesh of fuel assemblies 2 in a reference associated with the vessel 1, in order to control the position of said fuel assembly in said mesh. In addition, the determination of the absolute position preferably takes into account the displacement in translation of the instrumented pole 40 relative to the articulated arm 30 on which said instrumented pole 40 is mounted in translation. The system according to the invention may also include, or be connected during its use, to a control member for controlling said system. Usually, this control system takes the form of a computer with system control software, associated with connections for sending commands and receiving measurement data.

A computing device, which may be the control device or a separate dedicated device, may be used to process the data representative of the positions of the various elements, as well as data from the palpation of the fuel assemblies, in order to determine the absolute position. of the fuel assembly. Preferably, said computing device comprises a memory containing a positioning mesh of fuel assemblies in a coordinate system associated with the tank, in order to control the position of said fuel assembly in said mesh by reporting the absolute position of the fuel assembly thus determined. as a location data of said assembly in said mesh.

An interesting embodiment consists in equipping the instrumented pole 40 with an automatic water-changing system of measurement head 50, for example at a section of the instrumented pole 40, with a watertight connector automatically connectable under water. A measuring head magazine 50, arranged on a fixed part such as the guide column 70, makes it possible to change the measuring head 50 at a distance without removing the system and without the intervention of operators on a footbridge at the right of the tank 1.

Preferably, the system according to the invention further comprises an extension mast attaching to the instrumented pole 40, said extension mast being provided with image sensors and manipulation and / or suction means. Figures 12 and 13 show the system according to the invention provided with an extension mast 80 in a low and high position respectively thereof. The extension mast is fixed on the pole 40 and follows the movements. This extension mast 80 comprises a pole 81 whose structure is substantially similar to that of the instrumented pole 40, to which it is fixed by clipping, mechanical clamping or any other attachment device 82. A support 88 placed at one end of extension pole 80 and is intended to rest towards the buoyancy element 60. The support 88 can cooperate with an end 61 of the instrumented pole 40 left free by the buoyancy element 60 to ensure a tight connection between respective cabling running in the instrumented pole 40 and in the extension pole 80.

The extension mast 80 is in fact provided with image sensors and handling and / or suction means. The image sensors of the extension mast are preferably located on a plurality of sides thereof to enable control operations not only of the lower core plate, but also of the vessel walls and the bottom of the mast. tank. The manipulation / suction means may take the form of a suction pump and are mainly intended for the removal of possible migrating bodies in the context of cleaning operations.

The system according to the invention and the method that it allows to implement bring many advantages. The accuracy of the measurement is due to a chain of mechanical dimensions and not to an averaged calculation from a video measurement of the games between fuel assemblies.

The system provides the possibility of controlling the position of each fuel assembly head 2, in the horizontal plane but also vertically, thus making it possible to detect an abnormal height.

The system provides the ability to control the position of each fuel assembly during refueling operations of the fuel assemblies. Since the device is independent of the loading machine, it can perform its measurements on a fuel assembly that has just been put down, in masked time, while the loading machine is fetching the next fuel assembly.

Knowing the absolute position of the fuel assemblies makes it possible to map the reactor core, and checking each fuel assembly number makes it possible to incorporate these numbers in the cartography.

Claims

claims

1. System for controlling the position of a fuel assembly (2) in the tank (1) of a nuclear reactor, characterized in that it comprises palpating members for implementing a mechanical probe of the head of a fuel assembly (2) to determine an absolute position of said fuel assembly (2).

2. System according to the preceding claim, characterized in that it comprises mechanical devices for copying the position of the fuel assembly (2).

3. System according to one of the preceding claims, wherein the palpating members are determining pins (51) adapted to cooperate with holes (S) for centering the head of the fuel assembly (2).

4. System according to one of the preceding claims, characterized in that it comprises an articulated arm (30) of SCARA type and an instrumented pole (40) mounted in translation on said articulated arm (30), a measuring head ( 50) being disposed on the instrumented pole (40).

5. System according to the preceding claim, wherein the measuring head (50) is arranged on the instrument pole (40) by means of a compilant link (59), and in that inside said pole, an amplifying rod (41) connecting the measuring head (50) to a measurement system is pivotally mounted on said rod (41) along a transverse axis perpendicular to the longitudinal axis of said rod (41).

6. System according to the preceding claim, wherein the compilant link (59) is lockable, the measuring head (50) is equipped with a gripping means of the head of the fuel assembly (2), and the articulated arm. (30) and the instrumented pole (40) are adapted to be able to transmit a repositioning force of a fuel assembly (2).

7. System according to any one of claims 4 to 6, characterized in that it further comprises an extension mast (80) attaching to the instrumented pole (40), said mast (80) extension being equipped with image sensors (55) and handling and / or suction means.

8. System according to any one of claims 4 to 7, wherein the instrumented pole (40) further comprises a flotation element.

9. System according to any one of claims 4 to 8, wherein the measuring head (50) comprises image sensors (55).

10. System according to the preceding claim, wherein the image sensors (55) are load-fed circuit hardened cameras or hardened tube cameras.

11. System according to any one of claims 9 or 10, wherein image sensors (55) and palpating members are alternately arranged on the measuring head (50) at the vertices of a square.

12. System according to any one of claims 9 to 11, characterized in that it comprises drive members for rotating the instrumented pole (40) by an angle Θ.

13. System according to the preceding claim, wherein the angle between on the one hand a first straight line passing through at least one image sensor (55) and a center of rotation of the measuring head (50) and other a second straight line passing through a palpating member 51 and the center of rotation of the measuring head (50) is equal to Θ.

14. System according to claim 8, wherein the buoyancy element (60) is a buoy whose buoyancy is sufficient to ensure the floatation of the instrumented pole (40) in the heat transfer fluid of the vessel (1).

15. System according to claim 8, wherein the flotation element (60) is a balloon whose inflation and / or deflation is remotely controllable in order to control the buoyancy of the rod in the heat transfer fluid of the tank (1). ).

16. System according to any one of claims 4 to 15, wherein the instrumented pole (40) consists of a honeycomb tube.

17. System according to any one of claims 4 to 15, wherein the instrumented pole (40) has a diameter less than or equal to the center distance of the fuel assemblies.

18. System according to any one of claims 4 to 17, wherein the measuring system is located in the instrumented pole (40) at a distance greater than 1 m from the measuring head (50).

19. System according to any one of claims 4 to 18, wherein the instrumented pole (40) is mounted in translation on the articulated arm (30) by means of an oversized rack driven by a motor equipped with a gear reducer. negative game.

20. System according to any one of claims 4 to 19, wherein the articulated arm (30) comprises two length members (31, 32) connected by a hinge (33) on tapered roller bearings motor-biased by a servomotor equipped with a gearbox with negative clearance.

21. System according to any one of claims 4 to 20, wherein the two length elements (31, 32) of the articulated arm (30) each comprise at their end an articulation on tapered roller bearings mounted in prestress motorized by a servomotor equipped a negative gear reducer.

22. System according to any one of the preceding claims, characterized in that it comprises securing means by pneumatic clamping to a column (70) for guiding placed on the periphery of the reactor vessel (1).

23. System according to the preceding claim, further comprising indexing means on the edge of the tank (1) or on threads adjacent to the guide column (70), said indexing means ensuring the angular positioning of the system. pneumatic clamping on said column (70).

24. System according to claim 3, comprising at least one determination pin (51) comprising at least one centering spring intended to cooperate with walls of holes (S) for centering fuel assembly (2).

25. A method for controlling the position of a fuel assembly (2) in the vessel (1) of a nuclear reactor, characterized in that an absolute position of the fuel assembly (2) is determined by mechanical palpation of the fuel cell (2). fuel assembly (2) by means of palpating members of a system for controlling the position of a fuel assembly (2) in the tank (1) of a nuclear reactor.

26. Method according to the preceding claim, characterized in that it comprises the steps according to which:

positioning (S0) an instrumented pole (40) mounted on an articulated arm (30) of SCARA type facing a theoretical position of a fuel assembly (2),

descending (S1, S4) said instrumented pole (40) until palpating members arranged on a measuring head (50) of said instrument pole (40) cooperate (S5) with said fuel assembly (2), determining (S6) the absolute position of said fuel assembly (2) by the position of the articulated arm (30) and a displacement of the palpation members induced by their cooperation with said fuel assembly (2).

27. Method according to the preceding claim, wherein the articulated arm (30) is rotatably mounted on a positioning column at the periphery of the reactor vessel (1), said method further comprising a step (SI) of initialization of absolute position in which there are two reference positions to define a polar frame in which said absolute position of the fuel assembly (2) is determined.

28. Method according to one of claims 26 to 27, wherein the absolute position of said fuel assembly (2) is determined with respect to a fuel assembly positioning mesh (2) in a reference associated with the tank (1). , in order to control the position of said fuel assembly in said mesh.

29. Method according to one of claims 26 to 28, wherein the determination (S6) of the absolute position takes into account the displacement in translation of the instrumented pole (40) relative to the articulated arm (30) on which said pole instrumented (40) is mounted in translation.

30. Method according to one of claims 26 to 29, wherein the measuring head (50) comprises image sensors (55), said method further comprising at least one step according to which, by means of sensors of images (55), there is a fuel assembly identifier disposed thereon.

The method according to any one of claims 26 to 30, wherein the measuring head (50) comprises image sensors (55) and,

during a first part of the descent of the instrumented pole (40), the image sensors (55) are opposite the centering holes (S) of the fuel assembly (2), then

the instrumented pole (40) is pivoted so that the palpating members are facing the holes (S) for centering the fuel assembly (2) during a second part of the descent.

32. Method according to the preceding claim, wherein during the first part of the descent, we verify:

the cleanliness and integrity of the holes (S) for centering the fuel assemblies,

- The alignment of the measuring head (50) with the fuel assembly (2).

33. Method according to any one of claims 26 to 32, wherein a compilant link (59) is lockable, the measuring head (50) comprises a gripping means of the fuel assembly head (2) and said method comprises at least one step comprising:

blocking the compiler link (59),

- gripping the head of the fuel assembly (2),

- The registration of the fuel assembly (2) by displacements of the articulated arm (30) SCARA type.

34. Method according to the preceding claim, wherein the instrumented pole (40) comprises a floating element (60) of variable size whose inflation and / or deflation are remotely controllable, said method comprising at least one step during which the piloting the buoyancy element (60) makes it possible to compensate for the weight of the fuel assembly (2) in order to facilitate its registration.