Reactor vessel investigation device

Abstract

Disclosed is an investigation device comprising a support unit (12) and an investigation tool (14) mounted on the support unit (12), the investigation tool (14) having a movable part (16) and an investigation head (18), the movable part (16) being mounted on the support unit (12) for translation along a horizontal translation axis (C), and the investigation head (18) being configured to be inserted into a connecting pipe (8) and carrying one or more probes (38) for performing measurements on the connecting pipe (8), wherein translation of the movable part (16) allows the investigation head (18) to be inserted into the connecting pipe (8). The investigation head (18) is attached to the movable part (16) via a positioning tool (20) having at least two degrees of freedom, including translation along a vertical positioning direction (DZ) and rotation about a vertical positioning axis (Z).

Description

[Technical Field]

[0001] The present invention relates to the field of reactor vessel investigation, and in particular to a reactor vessel investigation device. [Background technology]

[0002] A light water nuclear reactor includes a reactor vessel containing a reactor core made up of a plurality of nuclear fuel assemblies arranged side by side within the reactor vessel.

[0003] The reactor vessel is closed by a lid and is provided with connecting pipes that open into the reactor vessel, through which the reactor vessel is connected to a loop of fluid circuits called the "primary circuit" that are designed for the circulation of water called "primary water".

[0004] Each loop in the primary circuit has a pump called a "primary pump" to ensure the circulation of primary water within the loop, and a steam generator to generate steam using the primary water circulating within the loop. The primary circuit also has at least one pressurizer to maintain a predetermined pressure of the primary water within the primary circuit and within the reactor vessel.

[0005] During operation, primary water circulates through the reactor vessel in a loop where it contacts the nuclear fuel assemblies, where it is heated, and then directed to the steam generator in the primary circuit loop.

[0006] The primary circuit is therefore a closed circuit that ensures the transfer of the heat released within the reactor core (where the fuel is located and the chain reaction takes place) to the steam generator, which converts this heat into steam.

[0007] It is necessary to carry out an inspection of the reactor vessel, and in particular of the connecting pipes provided therein, such inspections being carried out, for example, during maintenance work carried out during the shutdown phase of the reactor.

[0008] It is desirable to be able to perform reactor vessel inspections in a simple and efficient manner in order to limit the time required for maintenance operations. Summary of the Invention [Problem to be solved by the invention]

[0009] One of the aims of the present invention is to propose a reactor vessel investigation device that allows for simple and efficient investigation. [Means for solving the problem]

[0010] To achieve this object, the present invention proposes an apparatus for inspecting a reactor vessel having a connecting pipe opening into the reactor vessel, the inspection apparatus comprising a support unit configured to be attached to the reactor vessel and an inspection tool attached to the support unit, the inspection tool comprising a movable part and an inspection head carried by the movable part, the movable part being attached to the support unit so as to be able to translate along a horizontal translation axis, the inspection head being configured to be inserted into the connecting pipe and carrying one or more probes for performing measurements in the connecting pipe, the translation of the movable part allowing the inspection head to engage within the connecting pipe, the inspection head being attached to the movable part via a positioning tool having at least two degrees of freedom including translation along a vertical positioning direction and rotation about the vertical positioning axis.

[0011] A positioning tool having degrees of freedom for translation along the vertical direction and degrees of freedom for rotation around the vertical axis makes it possible to easily and properly position the investigation head inserted into the connecting pipe, particularly when the connecting pipe has a bend, and to perform highly accurate and precise measurements.

[0012] According to certain embodiments, the survey device includes one or more of the following optional features, selected individually or in any technically possible combination: - the positioning tool includes a sliding connection that allows translation along the vertical positioning direction; - the positioning tool includes a pivot connection that allows rotation about a vertical positioning axis; - The positioning tool has rotational freedom around a horizontal positioning axis, - the positioning tool includes a pivot connection that allows rotation about a horizontal positioning axis, the positioning tool includes a sliding connection that allows translation along a vertical positioning direction, a pivoting connection that allows rotation about a vertical positioning axis, and a pivoting connection that allows rotation about a horizontal positioning axis; the sliding connection, the pivotal connection of the vertical positioning axis and the pivotal connection of the horizontal positioning axis are kinematically arranged in series, preferably in this order, between the base of the mounting mechanism configured to be fixed to the movable part and the investigation head; - the positioning tool comprises an actuator for controlling the position of the investigation head relative to a base of the positioning tool fixed to the movable part, the support unit includes a mounting assembly configured to be installed in the reactor vessel, carrying a tooling support, the movable part being translatably mounted to the tooling support along a translation axis; the positioning tool is mounted via a rotation mechanism for rotational movement about a vertical axis of rotation relative to the mounting assembly; the mounting assembly includes a support assembly configured to rest on an upper edge of the reactor vessel and a mounting column extending vertically downward from the support assembly, the tooling support being attached to a lower end of the mounting column; the support assembly includes a central piece and legs extending radially from the central piece, each leg having a distal end opposite the central piece configured to rest on an upper edge of the reactor vessel, and a mounting column extending downwardly from the central piece; - each leg is a metal beam that extends substantially horizontally when the support unit is installed in the reactor vessel; - each leg is removably attached to the central part and / or the mounting column is removably fixed to the central part; the support assembly includes a respective foot disposed at a distal end of each leg to provide a scaffold for the legs to rest on an upper edge of the reactor vessel, the feet being configured to self-center the support unit relative to the reactor vessel under the effect of the weight of the support unit; - each foot is articulated to an associated leg about an articulation axis and has a vertical support portion arranged to rest vertically on the upper edge of the reactor vessel and a horizontal support portion arranged to rest horizontally on a side wall of the reactor vessel, so that when the support unit is installed on the reactor vessel, each foot rests vertically on the upper edge of the reactor vessel via its vertical support portion, whereby the foot rotates about its articulation axis and the horizontal support portion of the foot tends to move into contact with the side wall under the effect of the weight of the support unit; - each probe is selected from an eddy current probe or an ultrasonic probe; The survey head carries a number of probes arranged in a star shape, the probes being distributed around a central axis of the survey head and each probe being directed radially outwards.

[0013] The invention and its advantages will be better understood from reading the following description, given by way of non-limiting example only, and made with reference to the accompanying drawings, in which: [Brief explanation of the drawings]

[0014] [Figure 1] 1 is a cross-sectional view of a reactor vessel and an investigation device fixed to the vessel for investigating the reactor vessel connecting pipes. [Figure 2] FIG. [Figure 3] FIG. 1 is a perspective view of a positioning tool and an investigation head carried by the positioning tool. [Figure 4] FIG. 1 is a perspective view of the research device disassembled and packaged for transport. DETAILED DESCRIPTION OF THE INVENTION

[0015] As shown in FIG. 1, the reactor vessel 2 extends along a central vertical axis, hereinafter referred to as the vessel axis A.

[0016] The reactor vessel 2 comprises a cylindrical side wall 4 of circular cross section about the vessel axis A, the lower end of which is closed by a base (not shown), for example of hemispherical shape.

[0017] The reactor vessel 2 has, at the upper end of its side wall 4, an upper edge which defines an upper opening 6 intended to be closed by a lid (not shown).

[0018] In a known manner, the side wall 4 has at its upper end an annular fastening area, commonly called a flange, adapted to fasten the lid to the side wall 4 .

[0019] The fastening is generally carried out by means of bolts distributed around the periphery of the flange, the flange including fastening holes designed to receive the bolts.

[0020] The reactor vessel 2 is provided with connecting pipes 8 for connecting the reactor vessel 2 to the primary circuit of the nuclear power plant. Two diametrically opposed connecting pipes 8 are visible in Figure 1. In practice, the reactor vessel 2 may be provided with, for example, two, four, six or eight connecting pipes 8.

[0021] Each connecting pipe 8 opens along a substantially horizontal pipe axis B into the interior of the reactor vessel 2, in particular into the side wall 4.

[0022] The tube axis B of each connecting tube 8 is preferably radial with respect to the vessel axis A of the reactor vessel 2 .

[0023] Each connecting pipe 8 may have a bend located along the connecting pipe 8 at a distance from the junction of the connecting pipe 8 with the side wall 4. An investigation device 10 is attached to the reactor vessel 2.

[0024] The investigation device 10 is installed on the upper edge of the side wall 4 , in particular on the flange of the side wall 4 .

[0025] In the following description, directional terms such as “horizontal” and “vertical”, “top” and “bottom” are expanded with reference to the survey device 10 attached to the reactor vessel 2 .

[0026] As shown in FIGS. 1 and 2, the investigation apparatus 10 includes a support unit 12 configured to be mounted to the reactor vessel 2 and an investigation tool 14 attached to the support unit 12 .

[0027] The inspection tool 14 includes a movable part 16 carried by the support unit 12 so as to be movable along a horizontal translation axis C relative to the support unit 12, and an inspection head 18 configured to be inserted into the connecting pipe 8 to perform an inspection of the connecting pipe 8, in particular to perform measurements inside the connecting pipe 8, the inspection head 18 being attached to the movable part 16 via a positioning tool 20.

[0028] As shown in Figure 1, the support unit 12 is configured so that the movable part 16 is positioned with its horizontal translation axis C parallel to, and preferably coincident with, the pipe axis B of the connecting pipe 8 under investigation.

[0029] As shown in FIG. 3, the positioning tool 20 has at least two degrees of freedom, including translation along a vertical positioning direction DZ and rotation about a vertical positioning axis Z.

[0030] The positioning tool 20 therefore enables the investigation head 18 to translate along a vertical positioning direction DZ relative to the movable part 16 and to move rotationally about a vertical positioning axis Z.

[0031] The positioning tool 20 includes, for example, a sliding connection 24 that allows translation along the vertical positioning direction DZ. The sliding connection 24 has translation along the vertical positioning direction DZ as its only degree of freedom.

[0032] The positioning tool 20 includes, for example, a pivotal connection 26 that allows rotation about a vertical positioning axis Z. The pivotal connection 26 has rotation about the vertical positioning axis Z as its only degree of freedom.

[0033] Preferably, the sliding connection 24 and the pivotal connection 26 are kinematically arranged in series between the movable part 16 and the investigation head 18, preferably in that order.

[0034] The positioning tool 20 includes, for example, a base 28 configured to be firmly fixed to the movable part 16, and an intermediate part 30 attached to the base 28 via one of the sliding connection 24 and the pivot connection 26, and the investigation head 18 attached to the intermediate part 30 via the other of the sliding connection 24 and the pivot connection 26.

[0035] Preferably, the intermediate piece 30 is attached to the base 28 via a sliding connection 24 and the survey head 18 is attached to the intermediate piece 30 via a pivot connection 26 .

[0036] Advantageously, the positioning tool 20 has a degree of freedom of rotation about a horizontal positioning axis R. The investigation head 18 is carried by the movable part 16 and is rotatable about the horizontal positioning axis R.

[0037] The positioning tool 20 includes, for example, a pivotal connection 32 that allows rotation about a horizontal positioning axis R. The pivotal connection 32 has rotation about the horizontal positioning axis R as its only degree of freedom.

[0038] In one embodiment with an intermediate piece 30 , the survey head 18 is attached to the intermediate piece 30 via a pivot connection 32 .

[0039] Advantageously, the positioning tool 20 has exactly three degrees of freedom: translation along the vertical positioning direction DZ, rotation about the vertical positioning axis Z, and rotation about the horizontal positioning axis R.

[0040] Advantageously, the positioning tool 20 comprises actuators configured to move the investigation head 18 relative to the movable part 16 according to each degree of freedom of the positioning tool 20 .

[0041] Each actuator of the positioning tool 20 is, for example, an electric actuator, in particular an electric motor, a pneumatic actuator, or a hydraulic actuator.

[0042] The positioning tool 20 includes, for example, a translation actuator 34 for ensuring translation along a vertical positioning direction DZ, a vertical rotation actuator 36 for ensuring rotation about a vertical positioning axis Z, and / or a horizontal rotation actuator 37 for ensuring rotation about a horizontal positioning axis R.

[0043] The survey head 18 carries one or more probes 38, each configured to perform measurements on the connecting pipe 8 into which the survey head 18 is inserted.

[0044] Each probe 38 is selected from, for example, an eddy current probe and an ultrasonic probe, and such a probe allows non-destructive testing of the metal parts and / or welds of the connecting pipe 8.

[0045] Each probe 38 is oriented radially relative to a central axis D of the investigation head 18 which coincides with the pipe axis B when the investigation head 18 is inserted into the connecting pipe 8, for example.

[0046] When, as in the example shown, the survey head 18 rotates relative to the movable part 16 about a horizontal positioning axis R, this horizontal positioning axis R preferably coincides with the central axis D of the survey head 18 .

[0047] The inspection head 18 includes, for example, a plurality of probes 38 arranged in a star shape around the central axis D of the inspection head 18, with each probe 38 pointing radially outward relative to the central axis D of the inspection head 18.

[0048] As can be seen in FIG. 2 , the support unit 12 includes a mounting assembly 40 carrying a tooling support 42 configured to be installed on the reactor vessel 2, with the movable portion 16 of the inspection tool 14 translationally mounted to the tooling support 42 along a translation axis C.

[0049] Preferably, tooling support 42 is mounted for rotational movement about a vertical orientation axis E relative to mounting assembly 40 via a rotation mechanism 44. Rotation mechanism 44 includes, for example, a rotating ring.

[0050] The rotation mechanism 44 preferably includes an actuator 46 for ensuring rotation of the tooling support 42 about the orientation axis E relative to the mounting assembly 40. The actuator 46 is, for example, an electric actuator, such as an electric motor, a pneumatic actuator, or a hydraulic actuator.

[0051] The mounting assembly 40 is configured to be installed on the reactor vessel 2 , particularly on the upper edge of the reactor vessel 2 , with the orientation axis E of the tooling support 42 coinciding with the central axis A of the reactor vessel 2 .

[0052] The mounting assembly 40 includes, for example, a support assembly 48 configured to be placed on the upper edge of the reactor vessel 2 and a mounting column 50 extending vertically downward from the support assembly 48, and the tooling support 42 is mounted to the lower end of the mounting column 50, preferably via a rotation mechanism 44 disposed at the lower end of the mounting column 50.

[0053] As shown in FIG. 1 , when the mounting assembly 40 is installed in the reactor vessel 2 , the mounting column 50 extends vertically downward into the interior of the reactor vessel 2 and the tooling support 42 is located inside the reactor vessel 2 .

[0054] The support assembly 48 may, for example, be star-shaped and may have a central part 52 and a plurality of legs 54, in particular three legs 54, extending radially from the central part 52, each leg 54 having a proximal end connected to the central part 52 and a distal end opposite the central part 52 that is configured to rest on the upper edge of the reactor vessel 2.

[0055] The support unit 12 is preferably removable to facilitate its transport. The survey device 10 can in fact be transported from one reactor to another to perform surveys of various reactors.

[0056] Preferably, each leg 54 of the support assembly 48 is removably attached to the central part 52 of the support assembly 48, thereby allowing the support assembly 48 to be disassembled.

[0057] Preferably, the mounting column 50 is removably attached to the support assembly 48, in particular to the central part 52 of the support assembly 48. It is possible to have a number of mounting columns 50 of different lengths and to select the appropriate mounting column 50 depending on the height at which the connecting pipe 8 of the reactor vessel 2 to be investigated is located.

[0058] Advantageously, each leg 54 is a metal beam that extends substantially horizontally when the support assembly 48 is installed on the upper edge of the reactor vessel 2 .

[0059] A support assembly 48 with such legs 54 has a reduced vertical dimension, which facilitates deployment of the survey device 10 given the limited space available within a nuclear power plant.

[0060] Advantageously, the support assembly 48 includes a foot 56 at the distal end of each leg 54, and during installation of the support unit 12 on the reactor vessel 2, the legs 54 are placed on the reactor vessel 2, in particular on the upper edge of the reactor vessel 2, via the foot.

[0061] The feet 56 are configured to self-center the support unit 12 relative to the reactor vessel 2, and the self-centering occurs under the effect of the weight of the support unit 12 during installation of the support unit 12 on the upper edge of the reactor vessel 2.

[0062] In one embodiment, each foot 56 is articulated to the associated leg 54 about an articulation axis F that is horizontal and preferably orthogonal radial with respect to the central axis A of the reactor vessel 2, and has a vertical support portion 58 arranged to rest vertically on the upper edge of the reactor vessel 2, and a horizontal support portion 60 arranged to rest horizontally on the side wall 4 of the reactor vessel 2, preferably via a horizontal support pad 62.

[0063] The feet 56 are configured such that when the support unit 12 is installed on the reactor vessel 2, each foot 56 rests vertically on the reactor vessel 2 by virtue of its vertical support portion 58, whereby the foot 56 rotates about its articulation axis F and the horizontal support portion 60 of the foot 56 tends to move into contact with the side wall 4 under the effect of the weight of the support unit 12.

[0064] This substantially simultaneous support of the horizontal support portion 60 of the foot 56 against the side wall 4 of the reactor vessel 2 during installation of the support unit 12 causes the support unit 12 to self-center under the effect of the weight of the support unit 12 .

[0065] As shown in FIG. 4, the removable support unit 12 can be easily transported, for example, on a transport cradle 64 having supports 66 for securing the various separable elements of the support unit 12.

[0066] In the example shown, the tooling support 42 equipped with the rotation mechanism 44 is mounted on a dedicated support 66. The central part 52 and the mounting column 50, which remain assembled, are fixed to a transport cradle 64. The legs 54 have been disassembled from the central part 52 and fixed to the dedicated support 66. Only two of the legs 54 are visible in Figure 4.

[0067] In operation, the support unit 12 is assembled as needed, for example, by securing the legs 54 to the central piece 52, thus forming the support assembly 48, and securing the assembly formed by the tooling support 42 and the rotation mechanism 44 to the lower end of the mounting column 50.

[0068] The inspection tool 14 is mounted on a tooling support 42. More particularly, the movable part 16 is mounted on the tooling support 42, and the inspection head 18 is carried by the movable part 16 via the positioning tool 20.

[0069] The mounting assembly 40 is installed so that it rests on the upper edge of the reactor vessel 2. The tooling support 42 is then located inside the reactor vessel 2, and the inspection tool 14 is positioned at an appropriate height to insert the inspection head 18 into the connecting pipe 8 to be inspected.

[0070] The tooling support 42 rotates about an orientation axis E to point the inspection tool 14 towards the connecting pipe 8 and, in particular, aligns the horizontal translation axis C with the pipe axis B of this connecting pipe 8 .

[0071] The movable part 16 translates and inserts the investigation head 18 into the connecting pipe 8. Measurements are carried out using one or more probes 38 by moving the investigation head along the pipe axis B and, if possible, by moving the investigation head 18 in rotation about a horizontal positioning axis R.

[0072] The positioning tool 20 has a degree of freedom of vertical translation along the vertical positioning direction DZ and a degree of freedom of rotation about the vertical positioning axis Z, allowing the positioning of the investigation head 18 within the connecting pipe 8 to be precise.

[0073] This allows for high precision positioning of the probes 38 which may be affected by changes in the distance between each probe 38 and the inner surface of the connecting tube 8 .

[0074] In particular, vertical translation along the vertical positioning direction DZ allows for highly accurate vertical positioning even without vertical mobility of the tooling support 42, or rather, allows for more accurate positioning than with vertical movement of the tooling support 42, since only the inspection head 18 moves vertically, which can be done more accurately.

[0075] Furthermore, the connecting pipe 8 may have a bend, particularly a bend that bends in a horizontal plane.

[0076] The rotational freedom about the vertical positioning axis Z makes it possible to inspect such bends in the connecting pipe 8 by rotating the inspection head 18 and advancing the inspection head into the bend while keeping it aligned with the local central axis of the connecting pipe 8.

[0077] Using the survey device 10, it is possible to perform a reliable and efficient survey, with satisfactory survey accuracy, which allows to reduce the survey time, which ultimately limits the downtime of the reactor.

[0078] The survey device 10 is also easy to deploy and transport, particularly due to its support unit 12 having reduced dimensions due to the elimination of the need to specifically provide a mounting column 50 to allow vertical translation of the tooling support 42, and the ability to disassemble the support unit 12.

[0079] The removable support unit 12 is advantageously independent of the positioning tool 20 .

[0080] Therefore, according to another aspect, the present invention relates to an investigation device 10 for a reactor vessel 2 having a connecting pipe 8 opening into the reactor vessel 2, the investigation device 10 comprising a support unit 12 configured to be attached to the reactor vessel 2 and an investigation tool 18 attached to the support unit 12, the support unit 12 comprising a mounting assembly 40 configured to be placed on the upper edge of the reactor vessel 2 and carrying a tooling support 42 that carries the investigation tool 18, the mounting assembly 40 comprising a central part 52 and a plurality of legs 54, in particular three legs 54, extending radially from the central part 52, each leg 54 having a proximal end connected to the central part 52 and a distal end opposite the central part 52 that is configured to be placed on the upper edge of the reactor vessel 2, and each leg 54 being removably attached to the central part 52.

[0081] According to certain embodiments, the survey device includes one or more of the following optional features: each leg 54 is a metal beam that extends substantially horizontally when the mounting assembly 40 is installed in the reactor vessel 2; The mounting assembly 40 includes a mounting column 50 extending vertically downward from a central part 52; - the mounting column 50 is removably attached to the central part 52; the tooling support 42 is mounted so as to be rotatable about a vertical orientation axis E relative to the central part 52; and The tooling support 42 is attached to the lower end of the mounting column 50 . [Explanation of symbols]

[0082] 2 Reactor vessel 8 Connecting pipe 10. Research equipment 12 Support unit 14 Research Tools 16 Moving parts 18 Research Head 20 Positioning Tools

Claims

1. In an apparatus for inspecting a reactor vessel (2) having a connecting pipe (8) opening into the reactor vessel (2), the inspection apparatus includes a support unit (12) configured to be attached to the reactor vessel (2) and an inspection tool (14) attached to the support unit (12), the inspection tool (14) including a movable part (16) and an inspection head (18) carried by the movable part (16), the movable part (16) being attached to the support unit (12) so as to be able to translate along a horizontal translation axis (C), and the inspection head The device includes a movable part (16) having an inspection head (18) configured to be inserted into the connecting pipe (8) and carrying one or more probes (38) for performing measurements on the connecting pipe (8), and translation of the movable part (16) allows the inspection head (18) to engage within the connecting pipe (8), wherein the inspection head (18) is attached to the movable part (16) via a positioning tool (20) having at least two degrees of freedom, including translation along a vertical positioning direction (DZ) and rotation about a vertical positioning axis (Z).

2. 2. The survey device of claim 1, wherein the positioning tool (20) includes a sliding connection (24) that allows translation along a vertical positioning direction (DZ).

3. 3. Apparatus according to claim 1 or 2, wherein the positioning tool (20) comprises a pivotal connection (26) allowing rotation about a vertical positioning axis (Z).

4. 4. Apparatus according to any one of claims 1 to 3, wherein the positioning tool (20) has a degree of freedom of rotation about a horizontal positioning axis (R).

5. 5. The investigation device of claim 4, wherein the positioning tool (20) comprises a pivotal connection (32) allowing rotation about a horizontal positioning axis (R).

6. 2. The investigation device of claim 1, wherein the positioning tool (20) includes a sliding connection (24) that allows translation along a vertical positioning direction (DZ), a pivotal connection (26) that allows rotation about a vertical positioning axis (Z), and a pivotal connection (32) that allows rotation about a horizontal positioning axis (R).

7. 7. The investigation device according to claim 6, wherein the sliding connection (24), the pivot connection (26) of the vertical positioning axis (Z), and the pivot connection (32) of the horizontal positioning axis (R) are kinematically arranged in series between the base (28) of the mounting mechanism (20) configured to be fixed to the movable part (16) and the investigation head (18), preferably in this order.

8. 8. An investigation device according to any one of claims 1 to 7, wherein the positioning tool (20) comprises an actuator for controlling the position of the investigation head (18) relative to a base (28) of the positioning tool (20) fixed to the movable part (16).

9. 9. The investigation device according to claim 1, wherein the support unit (12) includes a mounting assembly (40) configured to be installed on the reactor vessel (2) and carries a tooling support (42), and the movable part (16) is mounted on the tooling support (42) for translation along a translation axis (B).

10. 10. The survey device of claim 9, wherein the tooling support (42) is mounted for rotational movement about a vertical axis of rotation (E) relative to the mounting assembly (40) via a rotation mechanism (44).

11. 11. The survey apparatus of claim 9 or 10, wherein the mounting assembly (40) includes a support assembly (48) configured to rest on an upper edge of the reactor vessel (2) and a mounting column (50) extending vertically downward from the support assembly (48), and the tooling support (42) is attached to a lower end of the mounting column (50).

12. 12. The survey device of claim 11, wherein the support assembly (48) includes a central piece (52) and legs (54) extending radially from the central piece (52), each leg (54) having a distal end opposite the central piece (52) configured to rest on an upper edge of the reactor vessel (2), and the mounting column (50) extending downwardly from the central piece (52).

13. 13. The survey device of claim 12, wherein each leg (54) is a metal beam that extends substantially horizontally when the support unit (12) is installed on the reactor vessel (2).

14. 13. Survey device according to claim 11 or 12, wherein each leg (54) is removably attached to the central part (52) and / or the mounting column (50) is removably fixed to the central part (52).

15. 15. The survey device of any one of claims 12 to 14, wherein the support assembly (48) includes a foot (56) disposed at a distal end of each leg (54) to provide a foothold for the legs (54) to rest on an upper edge of the reactor vessel (2), the feet (56) being configured to self-center the support unit (12) relative to the reactor vessel (2) under the effect of the weight of the support unit (12).

16. 16. The survey device according to claim 15, wherein each foot (56) is articulated to an associated leg (54) about an articulation axis (F) and has a vertical support portion (58) arranged to rest vertically on an upper edge of the reactor vessel (2) and a horizontal support portion (60) arranged to rest horizontally on a side wall (4) of the reactor vessel (2), and when the support unit (12) is installed on the reactor vessel (2), each foot (56) rests vertically on the upper edge of the reactor vessel (2) via its vertical support portion (58), whereby the foot (56) rotates about its articulation axis (F) and the horizontal support portion (60) of the foot (56) tends to move into contact with the side wall (4) under the effect of the weight of the support unit (12).

17. 17. An investigation device according to any one of the preceding claims, wherein each probe (38) is selected from an eddy current probe or an ultrasonic probe.

18. 18. An investigation device according to any one of claims 1 to 17, wherein the investigation head (18) carries a plurality of probes (38) arranged in a star shape, the probes (38) being distributed around a central axis (D) of the investigation head (18), each probe (38) being directed radially outward.

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