Device and installation for extracting at least one migrating body present within a fuel assembly of a nuclear reactor

Abstract

The invention relates in particular to a device (4) for suctioning at least one migrating body (MB) present within a fuel assembly (1) of a nuclear reactor, characterized in that it comprises: - a movable suction support (40), provided with a fitting (41) shaped to be connected to a suction source; - said support (40) comprising at least two angularly offset, conduit-shaped branches (42, 43), the free end (420, 430) of these branches (42, 43) being shaped to receive a suction nozzle (6A-6E); - said support (40) and said branches (42, 43) being in fluidic connection with said suction source via said fitting (41). Figure for the abstract: Figure 5

Description

Title of the invention: Device and installation for the aspiration of at least one migrating body present within a fuel assembly of a nuclear reactor

[0001] GENERAL TECHNICAL DOMAIN

[0002] The field of the present invention is that of the maintenance of nuclear fuel assemblies used in nuclear reactors, and more particularly that relating to the preparation of assemblies before introduction into reactor or storage in pool.

[0003] The term “preparation” will be understood here as any operation intended to restore the external cleanliness of the fuel assembly to as close as possible to that in which it was originally before its introduction into the core of the nuclear reactor, during its first loading, or before its storage in a pool.

[0004] It relates more particularly to a device and installation for the aspiration of at least one migrating body present within a fuel assembly of a nuclear reactor. STATE OF THE ART

[0005] With reference to the attached [Fig.1], a fuel assembly 1 is shown among the plurality of assemblies constituting the core of a nuclear reactor.

[0006] It comprises two upper end caps 10 and lower end caps 11 between which are the structure of the assembly (guide tubes 12 and grids 13), as well as fuel rods 14.

[0007] The fuel assembly 1 rests at the bottom of the reactor core 2 by the lower end 11.

[0008] When setting up such assemblies in the core, it is necessary that their positioning in their respective dedicated location gives them a stable hold, in a vertical position with reference to the X-X' axis of the largest dimension of the assembly 1.

[0009] The fuel assembly rests at the bottom of the core 2 on four support points 15, which constitute feet 15a and 15b visible in the attached [Fig.2].

[0010] The two feet 15b are perfectly flat, while the other two have a bore allowing for proper positioning of the tip 11 when installing the core assembly 1. The lower plate of the core is perforated with holes to allow the cooling water to circulate vertically from bottom to top. This cooling water, as it circulates in the primary circuit, may pick up debris, which is called "migrating bodies" (MB).

[0011] To prevent this debris from damaging the pencils, the lower assembly tip is equipped with a "debris-removal grid" 16, which filters it. This grid can therefore become filled with CM debris during a cycle.

[0012] In the context of the present invention, the term "migrating body" means any object made of any endogenous or exogenous material that may have various origins and is commonly found in any industrial setting. Without limitation, this may include debris from welding or machining operations.

[0013] This can also include small components such as, for example, screws, bolts, washers, springs, metal chips, etc.

[0014] During a shutdown with unloading, the assemblies are extracted to be inspected underwater, from all angles, using cameras, in search of various defects, then returned to the core for the next cycle or are placed in a cooling pool in the fuel building in order to remove any detected migrating bodies.

[0015] A migrating body present on the grid can have several impacts if the assembly is reloaded as is:

[0016] • By blocking part of the filter formed by the debris screen, it modifies the circulation of cooling water can induce vibrations / turbulence and lead to "fretting" (friction of the rods on the skeleton of the assembly leading to a potential rupture of the rod cladding which surrounds the Uranium pellets and which constitutes the first safety barrier);

[0017] • If a migrating body is still present on the debris screen during reloading, During reloading, it could potentially pass through the debris screen and end up between the pencils. If it is a metallic object, there is a risk of the sheath being punctured, resulting in a leaky core;

[0018] • During recharging, and in particular upon arrival of the lower nozzle of assembly on the lower core plate, a still-present migrating body can apply deformation to the assembly.

[0019] • A 1mm thickness increase under an assembly foot represents a 20mm difference during its handling with the tool, this can cause the assembly to catch on the pins of the upper internal elements when the vessel is opened (which constitutes a major event). This can lead to a rupture of the cladding which constitutes the first of the three safety barriers which prevent the dispersion of radioactive products contained in the fuel.

[0020] Furthermore, the possible deformation of the assembly due to a migrating body during reloading may make future extraction of this assembly from the core difficult.

[0021] If migrant bodies are detected inside a combustible assembly, they must be removed without fail.

[0022] The extraction of migrating bodies is, moreover, a task made difficult by hostile environmental conditions (irradiation, contamination, heat, etc.) specific to work in ionizing environments.

[0023] Suitable and robust tools must be used to make these operations possible, tools which must also be remotely controlled.

[0024] A device has already been proposed which allows the aspiration of migrating bodies CM present at the level of the feet of combustible assemblies.

[0025] Figures 3 and 4 show such a device 3.

[0026] It includes a supporting structure 30 which is compatible with a descender not shown, i.e. a vertically mobile device, which is a common piece of equipment present in combustible buildings, the main use of which is to lower the combustible assemblies into the pool of the combustible building.

[0027] The principle of this device is based on a two-nozzle system, namely a lateral nozzle 31 shown in [Fig.3] and a vertical nozzle 32 shown in [Fig.4].

[0028] It also includes a suction pump 33 and a filter 34.

[0029] The nozzle change is carried out when the device is out of water.

[0030] The pump assembly 33 and supporting structure 30 is inserted onto the descender, while the filter 34 is installed at a later stage.

[0031] The nozzle is brought into contact and moved via the control of the descent mechanism. Since no remote adjustment of the nozzles is possible, the nozzle positioning is adjusted during equipment preparation.

[0032] The aspiration system is activated by activating the pump 33 via a switch, accessible from a push-button box.

[0033] This solution has significant limitations because:

[0034] 1) There is no pilot control system, so the operation of this device is minimal intuitive and delicate;

[0035] 2) Only two nozzle designs are available, a vertical nozzle and a nozzle lateral. In addition, the suction operations must be carried out in two distinct phases, one with the vertical suction nozzle, the other with the lateral suction nozzle. Handling the entire assembly is time-consuming (approximately one hour to perform the changeover) and therefore requires additional dosimetry for the operators;

[0036] 3) No adjustment of the nozzle position is possible remotely, which implies the presence of operators to adjust them and therefore a dosimetric impact for the workers;

[0037] 4) There is no dedicated lifting system: the installation must be carried out via a auxiliary system via slings;

[0038] 5) There is no tooling mounting support: the tooling assembly requires auxiliary supports;

[0039] 6) The tooling does not include a camera, so additional equipment is to plan for monitoring operations;

[0040] 7) There is no control over the suction power, just a simple switch ensuring the pump starts or stops.

[0041] The present invention aims to provide a simple and practical solution to at least some of these problems. PRESENTATION OF THE INVENTION

[0042] Thus, the invention relates to a device for suctioning at least one migrating body present within a fuel assembly of a nuclear reactor, characterized in that it comprises:

[0043] - a mobile suction support, provided with a fitting shaped to be connected to a source of suction;

[0044] - said support comprising at least two angularly offset branches, in the shape of conduits, the free end of these branches being shaped to receive a suction nozzle.

[0045] - said support and said branches being in fluidic connection with said source suction via said fitting;

[0046] Thanks to these characteristics, it is possible to carry out aspiration operations of migrating bodies, even when these are lodged between fuel rods of the fuel assembly, in regions close to the core of the rod bundle, under particularly satisfactory access conditions.

[0047] According to other advantageous and non-limiting features of this device, taken alone or in any technically compatible combination of at least two of them:

[0048] - said support is mobile in rotation relative to a frame.

[0049] Thanks to this feature, the device can be easily oriented relative to the position of the migrating body CM.

[0050] - said frame includes a motor shaped to allow rotation of said support.

[0051] Thanks to this feature, the rotational movement is facilitated.

[0052] - at least one conduit-shaped branch incorporates damping equipment longitudinal.

[0053] Thanks to this feature, the pressure of the nozzle against the combustible assembly is dampened.

[0054] - said damping equipment consists of a spring integrated into a sheath, which constitutes a part of said conduit.

[0055] Thanks to this feature, the damping device does not take up any space other than that of the sheath.

[0056] - said free end of said branches is shaped to receive a nozzle removable and interchangeable suction cup.

[0057] Thanks to this feature, the nozzle can be chosen according to the configuration.

[0058] - at least one of the duct-shaped branches can be oriented as required.

[0059] Thanks to this feature, one can position oneself in the best possible way with respect to the body migrant to aspire to.

[0060] - it includes a sliding leakage flow management system, adjustable under water or out of water.

[0061] Thanks to this feature, it is possible to adapt the flow rate according to the nozzle in place.

[0062] The present invention also relates to an installation for the aspiration of at least one migrating body present within a fuel assembly of a nuclear reactor, characterized in that it comprises a device according to one of the preceding characteristics, as well as a human-machine interface which includes at least one of the following equipment: emergency stop module of said device, remote control lever of said device and its mobile tools, module for limiting the forces on the motors which equip said mobile tools, control with display screen.

[0063] Thanks to these features, the operator has a direct view of the operations in progress and can intervene if necessary. DESCRIPTION OF THE FIGURES

[0064] Other features and advantages of the invention will become apparent from the description which will now be given, with reference to the attached drawings, which represent, by way of example but not limitation, at least one possible embodiment.

[0065] On these drawings:

[0066] Fig. 1 is a simplified perspective view of a combustible assembly in accordance with the prior art and discussed above;

[0067] Fig. 2 is a simplified perspective and low-angle view of the lower face of the lower end of the assembly of Fig. 1;

[0068] The [Fig.3] is a perspective diagram of a tool for suctioning migrating bodies in accordance with the prior art and discussed above;

[0069] The [Fig.4] is another perspective diagram of a tool for suctioning migrating bodies in accordance with the prior art and discussed above;

[0070] Fig. 5 is a perspective view of a possible embodiment of the device according to the invention;

[0071] Fig. 6 is a side view of the device of Fig. 5, shown without nozzles;

[0072] The [Fig.7] and a top view of the device of the [Fig.6];

[0073] The [Fig.8A] is a diagram of a first nozzle that can be used with the device of the [Fig.5];

[0074] Fig. 8B is a diagram of a second nozzle that can be used with the device in Fig. 5;

[0075] The [Fig.8C] is a diagram of a third nozzle that can be used with the device of the [Fig.5];

[0076] The [Fig.8D] is a diagram of a fourth nozzle that can be used with the device of the [Fig.5];

[0077] The [Fig.8E] is a diagram of a fifth nozzle that can be used with the device of the [Fig.5];

[0078] Fig. 9 is a perspective diagram of the device in Fig. 5, more specifically intended to illustrate the damping systems of the device;

[0079] Fig. 10 is a perspective diagram of the device of Fig. 5, the first nozzle of which is arranged horizontally;

[0080] Fig. 11 is a scheme analogous to that of Fig. 10, the first nozzle being arranged vertically;

[0081] Fig. 12 is a perspective diagram of the device of Fig. 5, the second nozzle of which is arranged horizontally;

[0082] Fig. 13 is a scheme analogous to that of Fig. 12, the second nozzle being arranged vertically. DETAILED DESCRIPTION OF THE INVENTION

[0083] The present invention relates firstly to a device for aspirating at least one migrating body CM, present within a fuel assembly 1 of a nuclear reactor, such as that represented in [Fig.1] discussed above.

[0084] In what follows and unless explicitly stated, the motorization means which enable the movement of movable elements have not been shown in the figures, in order not to make them unnecessarily heavy.

[0085] A non-limiting example of such a device is shown in the attached figures 5 to 7 and 9 to 13.

[0086] This device 4 comprises, firstly, a mobile suction support 40, provided with a fitting 41 shaped to be connected to a suction source not shown. This fitting 41 extends essentially along a longitudinal axis x.

[0087] In the embodiment shown, this support 40 is provided to be mobile in rotation relative to a frame 5 which, seen from above (see [Fig.7]), has the general shape of a stirrup.

[0088] The support 40 has at its base a transverse axis, (i.e. parallel to the z-axis) passing through and not shown, the ends of which are mounted for rotation in parallel flanges 50 of the frame 5.

[0089] Thus, the support 40 can take different orientations on demand, as shown in figures 10 to 13.

[0090] In [Fig.7], it can be seen that the fitting 41 is connected to the support 40 via one of the flanges 50.

[0091] The support 40 has, seen from the side, the general shape of the letter "V", namely that it has two angularly offset branches 42 and 43, in the shape of conduits.

[0092] In the example shown, there are two branches, but this number could be greater. Furthermore, in the figures, the angular separation between the two branches 42 and 43 is approximately 45°. However, it could be different, i.e., less than or greater than 45°, without, of course, taking the values ​​of 0° and 90°.

[0093] The value of 45° is preferable insofar as, when one of the two branches is connected to the source of inspiration, the other branch does not interfere in any way with this aspiration operation.

[0094] As previously stated, branches 42 and 43 are duct-shaped and are connected to fluidic connection 40 and the suction fitting 4L

[0095] The free end 420, respectively 430 of these branches is shaped to receive a suction nozzle, examples of which are shown in figures 8A to 8E.

[0096] Thus, in [Fig.8A] is shown a first example of nozzle 6A which has overall the shape of a vacuum cleaner nozzle and which is described as an "anti-debris device nozzle", because it can be used in particular to vacuum up a migrating body when it is placed on the anti-debris grid 16 and / or in the inter-pencil space 14.

[0097] Figure 8B shows a second example of nozzle 6B which has a design which follows the shape of the fuel rods at its free end and which is called an "inter-beam nozzle", because it can be used in particular to suck up a migrating body CM between fuel rod bundles 14.

[0098] Figure 8C shows a third example of a nozzle 6C which is provided with a long tube and which is described as a "foot assembly nozzle", because it can be used in particular to suck up a migrating body CM at the foot of a combustible assembly 1.

[0099] Figure 8D shows a fourth example of a 6D nozzle which is equipped with a fine tube and is described as a "capillary nozzle" because it can be used in particular to aspirate a very small migrating body CM lodged in a hard-to-reach place.

[0100] Figure 8E shows a fifth example of a 6E nozzle which is provided with a rotating scraper head at its free end and which is described as a "scraper nozzle", because it can be used in particular to detach / suck up a migrating body CM on the foot of the fuel assembly.

[0101] These are of course only non-limiting examples, so other nozzle shapes can be envisaged.

[0102] According to an advantageous embodiment, the free end 420, respectively 430 of the branches 42 and 43 is shaped to receive a removable and interchangeable suction nozzle.

[0103] As can be seen in [Fig.5], the device 4 can advantageously be provided with a sliding leakage flow management system 46, adjustable underwater or out of water.

[0104] It allows for flow management of the suction pump according to the nozzle in place and thus optimizes flow rates according to need.

[0105] This one works by sliding a flap covering an oblong hole.

[0106] Conversely, if no leakage flow is created, the suction will not be able to work with the smallest nozzle, such as the nozzle shown in [Fig.8D].

[0107] In an advantageous embodiment, at least one of the conduit-shaped branches 42 and 43 incorporates longitudinal damping equipment.

[0108] By the qualifier "longitudinal", it is understood that this damping equipment acts in parallel with the general direction of the branch it equips.

[0109] In the embodiment presented here, the equipment 421, respectively 431, consists of a helical spring which is integrated into a sheath, which forms part of the conduit of branches 42 and 43.

[0110] Such a sheath can be straight in shape, or have a variable inclination as required.

[0111] Because it is motorized, the support 40 allows the rotation of each nozzle (independently) in manual or automatic mode.

[0112] Advantageously and as illustrated in figures 5 and 9 to 13, the support 40 can accommodate a CA camera which is shown here at the end of an arm 44 equipped with three double ball joint articulation mechanisms 440 to 442, which allows, via a remote control, for it to be given any possible orientation.

[0113] The device 4 is also advantageously equipped with a manual joint 45 allowing the assembly to be raised to the edge of the pool, for the replacement of the nozzles.

[0114] A second aspect of the invention relates to an installation for the aspiration of at least one migrating body present within a fuel assembly 1 of a nuclear reactor, which is equipped with a device 4 such as that described above.

[0115] Advantageously, such an installation includes a programmable logic controller which is configured to control all the mobile and motorized equipment of the device 4.

[0116] According to the invention, this installation also includes a human-machine interface (not shown) which includes at least one of the following equipment (and preferably all of them): emergency stop module for said device, remote control lever for said device and its mobile tools, module for limiting the effort of the motors that equip said mobile tools, control unit with display screen, for example to view alarms, as well as feedback information on the operation of device 4 (motor intensity, pump flow rate, encoders, etc.).

[0117] Such tooling is designed to be positioned at the base and / or on one or the other of the four faces of a combustible assembly, to carry out the cleaning over the entire height of this assembly.

[0118] The device 4 is preferably positioned inside a descender which is usually fitted to a combustible assembly. The latter allows the tooling to be positioned facing the area concerned by the extraction of migrating bodies CM.

[0119] Progression along the fuel assembly is also achieved by movement of the descender, while the motors integrated into the device 4 ensure that it is brought into contact with the fuel assembly.

[0120] Unlike the prior art solution, the installation according to the invention integrates a human-machine interface and advantageously a control unit and a control joystick, in order to make operation easier and more flexible.

[0121] When an emergency stop device is integrated into the control system, it allows the operator to remotely stop the action of the tool.

[0122] When a load limiter is present on the motors (in case of overcurrent), this helps to protect the tooling and the environment (combustible assembly)

[0123] The installation allows for programming movements, with the possibility of automatic rotation movements.

[0124] Preferably, the joystick is intuitive and compatible with other tools

[0125] Thus, the operation of device 4 is made easy and intuitive, and the monitoring system allows for tracking the suction efficiency. Furthermore, the camera also allows for visual verification of the correct positioning of the selected nozzle and the behavior of the tooling.

[0126] Unlike the prior art solution, the device according to the invention allows the use of multiple nozzles.

[0127] Furthermore, it allows remote control of the tilting and rotation movements of the nozzles in order to optimize the positioning and efficiency of the suction process. Tilting is the movement along the z-axis of the nozzles of the two branches 42 and 43, made possible by the use of three motors, namely two motors allowing the nozzles to rotate on their own axis, and a motor allowing the support 40 to tilt up and down (similar to the movement of an arm). This tilting motion ensures the simultaneous tilting of the nozzles, and a rotational movement is associated with each nozzle (nozzle 1 and nozzle 2). These movements allow scraping and suction to be performed without risk of damaging the fuel assembly.

[0128] The device may have its own lifting equipment, with a proven system of quick-locking ball pins and "FME" (Foreign Material Exclusion), ensuring the lifting operation is safe. The "FME" design of this tooling takes into account the non-removability of the components that make up the tooling, in order to avoid any risk of losing an element in the building's pool.

[0129] Furthermore, the damping equipment 421, respectively 431 participates in managing the force when a nozzle presses against the fuel assembly.

[0130] Of course, the device according to the invention can be used with any type of suction source, via the adoption of a connector specific to the model used (modification of the "camlock", i.e. the cam coupler).

Claims

Demands

1. Device (4) for the aspiration of at least one migrating body (MB) present within a fuel assembly (1) of a nuclear reactor, characterized in that it comprises: - a movable aspiration support (40), provided with a fitting (41) shaped to be connected to a aspiration source; said support (40) comprising at least two angularly offset, conduit-shaped branches (42,43), the free end (420,430) of these branches (42,43) being shaped to receive a aspiration nozzle (6A-6E); - said support (40) and said branches (42,43) being in fluidic connection with said aspiration source via said fitting (41).

2. Device (4) according to claim 1, characterized in that said support (40) is mobile in rotation relative to a frame (5).

3. Device (4) according to claim 2, wherein said frame (5) includes a motor shaped to permit rotation of said support (40).

4. Device (4) according to any one of claims 1 to 3, characterized in that at least one conduit-shaped branch (42,43) incorporates a longitudinal damping device (421,431).

5. Device (4) according to claim 4, characterized in that said damping equipment (421,431) consists of a spring integrated in a sheath, which constitutes a part of said conduit.

6. Device (4) according to claims 4 or 5, characterized in that said free end (420,430) of said branches (420,430) is shaped to receive a removable and interchangeable suction nozzle (6A-6E).

7. Device (4) according to any one of claims 4 to 6, characterized in that at least one of the conduit-shaped branches (42,43) is orientable on demand.

8. 8. Device (4) according to any one of the preceding claims, characterized in that it comprises a sliding leakage flow management system (46), adjustable underwater or out of water.

9. Installation for the extraction of at least one migrating body (MB) present within a fuel assembly (1) of a nuclear reactor, characterized in that it comprises a device (4) according to one claims 1 to 8, as well as a human-machine interface which includes at least one of the following equipment: emergency stop module for said device, remote control lever for said device and its mobile tools, module for limiting the forces on the motors which equip said mobile tools, control unit with display screen.