Device for extracting nuclear fuel rods or cluster rods and extraction method using such an extraction device

Abstract

A puller device (10) comprising an attachment portion (12) configured to be inserted through an end without a cap into a sleeve (4) of a rod (2), and a gripping portion (14), the attachment portion (12) comprising an elongate body (16) along a longitudinal axis (A) and at least one tooth (18) protruding from the body (16), the or each tooth (18) being configured to allow forced axial insertion of the attachment portion (12) into the sleeve (4) and to engage with an inner surface (4A) of the sleeve (4) to prevent extraction of the attachment portion (12) from the sleeve (4).

Description

Technical Field

[0001] The present invention relates to the field of maintenance of nuclear fuel assemblies, control clusters and / or fixed clusters. Background Art

[0002] The nuclear fuel assembly comprises a bundle of nuclear fuel rods held by a frame. Each rod comprises a tubular sleeve surrounding a fission column formed by a stack of nuclear fuel pellets and closed at both ends by end plugs welded to the sleeve.

[0003] In addition to the function of sealing the nuclear fuel rod, at least one of the two end plugs also has the function of allowing the nuclear fuel rod to be grasped, for example, to be removed from or inserted into the frame of its nuclear fuel assembly. For example, such removal or insertion is performed when the nuclear fuel rod is damaged in order to repair or replace the nuclear fuel rod.

[0004] The nuclear fuel rod may lose its end plug having a manipulation function, or may need to be removed when the end plug is damaged, for example. Therefore, it is difficult to extract the nuclear fuel rod that has lost its manipulation device from the nuclear fuel assembly.

[0005] A rod cluster consists of a support structure that carries a bundle of rods (hereinafter referred to as "cluster rods"), which are intended to be inserted into the guide tubes of a fuel assembly. Each cluster rod comprises a tubular sleeve that surrounds an absorber rod or another type of rod and is closed at both ends by end plugs welded to the sleeve. The absorber rod contains, for example, one or more neutron-absorbing materials. Another type of rod can be an alumina rod, a secondary source rod, or a primary source rod.

[0006] The cluster rods can be released from their upper end plugs and fall into corresponding guide tubes of the receiving rod cluster of the nuclear fuel assembly.

[0007] FR1225784 discloses a nuclear fuel rod removal device comprising a tool having three jaws each having a recess on a jaw face that contacts the outer face of the nuclear fuel rod, and a ball or roller housed in each recess that locks the jaws to the outside of the nuclear fuel rod sleeve when the tool is lifted.

[0008] EP0200988 discloses a device for extracting nuclear fuel rods, which includes a cylindrical receiving portion and a cylindrical thrust rod. The cylindrical receiving portion receives a tube made of elastomeric material, which will cover the top end of the fuel rod. The cylindrical thrust rod is movably installed in the receiving portion to deform the tube made of elastomeric material laterally so as to clamp the sleeve of the nuclear fuel rod on the outside.

[0009] US 4986955 discloses a device for extracting a peripheral nuclear fuel rod from a nuclear fuel assembly, the extraction device comprising a gripper for externally gripping the nuclear fuel rod.

[0010] KR101163118 discloses a nuclear fuel rod extraction device comprising a circular gripper for externally gripping the rod and a pin insertable into the rod to prevent the gripper from crushing the gripped sleeve. SUMMARY

[0011] It is one of the objects of the present invention to provide a device for extracting a nuclear fuel rod, which allows a reliable and easy extraction.

[0012] To this end, the invention proposes an extraction device for extracting a nuclear fuel rod or cluster rod, the extraction device comprising an attachment portion and a gripping portion, the attachment portion being configured to be inserted through an end portion without plug into a sleeve of the rod, the attachment portion comprising a body elongated along a longitudinal axis and at least one tooth protruding from the body, the tooth or each tooth being configured to allow the axial insertion of the attachment portion into the cladding by force and to engage with an inner surface of the sleeve to prevent the extraction of the attachment portion from the sleeve.

[0013] In particular embodiments, the extraction device comprises one or more of the following optional features taken separately or according to any technically feasible combination:

[0014] - the tooth or each tooth is configured to hinder the extraction of the attachment portion from the sleeve by keeping the tooth pressed against the inner surface of the sleeve;

[0015] - the attachment portion comprises a plurality of teeth angularly distributed around the body;

[0016] - the attachment portion comprises teeth regularly angularly distributed, in particular uniformly angularly distributed;

[0017] - the attachment portion comprises a plurality of teeth axially distributed along the body;

[0018] - the attachment portion comprises at least one blade having a plurality of arms each forming a corresponding tooth;

[0019] - the attachment portion comprises a plurality of blades 22 axially spaced along the body according to a regular or irregular distribution;

[0020] - the blades are angularly offset from each other;

[0021] - the body comprises a plurality of axial segments axially alternately stacked with the blades;

[0022] - the axial segments comprise one or more intermediate segments interposed between two blades;

[0023] - axial segments and blades are stacked along the central axis;

[0024] - the body comprises axial segments each having angularly offset interlocking orientation elements, such that two segments stacked axially are angularly offset due to the interlocking of their orientation elements;

[0025] The attachment portion has a bearing portion configured to be pressed against an edge of the end portion of the sleeve as a result of the attachment portion being inserted into the sleeve.

[0026] - the attachment part has a bearing surface associated with each tooth, each bearing surface being arranged so that when a force is exerted on the extraction means in the direction of extraction of the attachment part from the sleeve, the tooth presses against the bearing surface;

[0027] Each bearing surface is inclined relative to the longitudinal axis, oriented axially in the direction of extraction of the attachment portion from the sleeve and radially inwards.

[0028] The invention also relates to an assembly comprising a nuclear fuel rod or clustered rod and an extraction device as defined above, adapted to insert and lock its attachment portion in the sleeve of the rod.

[0029] The invention also relates to a method for extracting a nuclear fuel rod or a cluster of rods from a nuclear fuel assembly, the sleeve of which has no closing end plug at one end, wherein an attachment part of an extraction device, such as defined above, is forcibly inserted into the open end of the sleeve and then the gripping part of the extraction device is pulled to extract the rod from its nuclear fuel assembly. BRIEF DESCRIPTION OF THE DRAWINGS

[0030] The invention and its advantages will be better understood from the following description given by way of example only and with reference to the accompanying drawings, in which:

[0031] Figure 1 is a front elevational view of an undamaged nuclear fuel rod having an upper end plug configured for use with a manipulation rod and a bottom end plug not used for manipulation rod;

[0032] Figure 2 and Figure 3 Before inserting the extraction device into the rod ( Figure 2 ) and after ( Figure 3 ), wherein the damaged nuclear fuel rod is not configured as an upper end plug for manipulation;

[0033] Figure 4 yes Figure 2 and Figure 3 A top view of the blades of the extraction device;

[0034] Figure 5yes Figure 2 and Figure 3 A perspective view of an intermediate axial segment of an extraction device;

[0035] Figure 6 is a front view of an extraction device according to a specific embodiment;

[0036] Figure 7 is a front view of an extraction device according to another specific embodiment. DETAILED DESCRIPTION

[0037] exist Figure 1 In the embodiment, an intact nuclear fuel rod 2 comprises a tubular sleeve 4 extending along a longitudinal axis A, which sleeve is intended to receive a fissile column formed by cylindrical nuclear fuel pellets (not shown) stacked axially inside the sleeve 4 .

[0038] The rods 2 are intended to be integrated into a nuclear fuel assembly comprising a bundle of parallel rods held together by a nuclear fuel assembly frame comprising a lower nozzle and an upper nozzle.

[0039] In operation, in the core of a nuclear reactor or in a handling or storage pool, the nuclear fuel assembly is placed so as to be supported vertically on its lower nozzle, with each rod extending vertically.

[0040] In the remainder of this description, the terms "upper" and "lower" are understood to refer to the generally vertical orientation of the rods in a nuclear fuel assembly placed on its lower nozzle.

[0041] The undamaged rod 2 has end plugs that close the ends of the sleeve 4. In particular, the rod 2 has a lower end plug 6 that closes the lower end of the sleeve 4 and an upper end plug 8 that closes the upper end of the sleeve 4.

[0042] like Figure 1 As shown, the lower end plug 6 has no operating function, in other words, it is not designed for operating the rod 2. In contrast, the upper end plug 8 has an operating function, in other words, it is designed for operating the rod 2 by means of an associated operating tool (not shown).

[0043] More specifically, upper end plug 8 is configured to allow rod 2 to be extracted from its nuclear fuel assembly by pulling rod 2 upwardly out of the nuclear fuel assembly using an extraction tool adapted to grip upper end plug 8 .

[0044] If the rod 2 is damaged, the upper end plug 8 with the operating function may be lost from the rod 2 and the sleeve 4 with its upper end open will no longer have an operating function, making it impossible to extract the rod 2 by means of the upper end plug 8.

[0045] exist Figure 2 and Figure 3In the embodiment shown, the rod 2 has no upper end plug 8 and the sleeve 4 is open at its upper end.

[0046] The extraction device 10 is configured to allow the rod 2 to be pulled out by the end (in particular the upper end) which has lost the end plug.

[0047] The extraction device 10 comprises an attachment portion 12 which is configured to be inserted axially into the interior of the sleeve 4 through the open upper end of the sleeve 4 and to be locked therein, and a clamping portion 14 which is configured to be clamped by a manipulation tool, preferably by the same manipulation tool provided for extracting the undamaged rod 2, in other words, the same manipulation tool as is provided for clamping the missing end plug, here the upper end plug 8.

[0048] The attachment portion 12 forms a harpoon with one or more retaining teeth, in particular with several rows of retaining teeth.

[0049] The attachment portion 12 extends along a longitudinal axis A.

[0050] The attachment portion 12 is configured to be inserted in the insertion direction F1 ( Figure 2 ) is axially inserted into the sleeve 4, and the attachment portion 12 is only matched with the inner surface 4A of the sleeve 4 to resist the attachment portion 12 in the withdrawal direction F2 ( Figure 3 ) is mechanically locked inside the sleeve 4 by the displacement relative to the sleeve 4.

[0051] The attachment portion 12 may be inserted into the sleeve 4 with force.

[0052] For example, the attachment portion 12 is configured such that the insertion force required to push the attachment portion 12 axially into the sleeve 4 in the insertion direction F1 is strictly smaller than the axial resistance force that must be overcome to extract the attachment portion 12 from the sleeve 4 in the extraction direction F2.

[0053] Therefore, it is easier to insert the attachment portion 12 into the sleeve 4 than to extract the attachment portion 12 from the sleeve 4 .

[0054] For example, the insertion force is less than 50 daN (deca Newtons), preferably less than 40 daN, more preferably less than 30 daN.

[0055] The attachment portion 12 is constructed so that the locking force is strictly greater than the extraction force to be exerted on the rod 2 to extract the rod 2 from its assembly, increasing the safety margin.

[0056] The locking force can be adjusted according to a predetermined extraction force. Thus, if the extraction force from the fuel assembly is 30 daN, the locking force is, for example, greater than 50 daN.

[0057] The attachment portion 12 comprises a body 16 extending along a longitudinal axis A and carrying one or more blades 22. Each blade 22 has one or more teeth 18, each tooth 18 projecting radially outwardly relative to the longitudinal axis A from the body 16.

[0058] Each tooth 18 is configured to interfere with an inner surface 4A of the sleeve 4 to allow insertion of the attachment portion 12 into the sleeve 4 in an insertion direction F1 and to resist extraction of the attachment portion 12 from the sleeve 4 in an extraction direction F2 .

[0059] Each tooth 18 has a free end 18A arranged for contact with the inner surface 4A of the sleeve 4 .

[0060] Each tooth 18 is configured so that its free end 18A rubs against the inner surface 4A of the sleeve 4 by generating a first axial force on the displacement of the attachment part 12 in the insertion direction F1 in the sleeve 4, which is greater than a second axial force in the extraction direction F2 of the attachment part 12 from the sleeve 4.

[0061] Each tooth 18 is flexible so as to bend rearwardly when the attachment portion 12 is inserted into the sleeve 4 in a forward direction.

[0062] Each tooth 18 is for example formed by a flexible tab of a corresponding blade 22, projecting radially relative to the body 16. Each blade 22 has a thickness measured along the longitudinal axis A that may vary according to the required axial force.

[0063] Each blade 22 is made of metal, for example, and has good bending properties. Each blade 22 is made of steel with high elastic properties, such as spring steel.

[0064] Each blade 22 is constructed so that each tooth 18 of the blade 22 bends backward due to the insertion of the attachment portion 12 into the sleeve 4 in the insertion direction F1, and once the attachment portion 12 has been inserted into the sleeve 4, it is pressed against the inner surface 4A of the sleeve 4 without returning to resist the attachment portion 12 from being pulled out of the sleeve 4 in the extraction direction F2.

[0065] like Figure 4 As shown, each blade 22 has, for example, a plurality of teeth 18. The number of teeth 18 is chosen according to the required insertion and locking forces and is here equal to four.

[0066] The body 16 of the attachment portion 12 includes a bearing surface 20 associated with each tooth 18 .

[0067] Each bearing surface 20 is inclined relative to the longitudinal axis A, oriented axially towards the extraction direction F2 and radially inwards. Each bearing surface 20 forms a non-zero angle α with a radial plane relative to the longitudinal axis A.

[0068] The presence of the inclined bearing surface 20 increases the force with which the tooth 18 may flip during extraction, thereby increasing the extraction locking force generated by the tooth 18 .

[0069] The body 16 is here formed with a plurality of axial segments 28 aligned along the longitudinal axis A of the body 16 , and a plurality of blades 22 with teeth 18 interposed between the axial segments of the body 16 .

[0070] The body 16 has a lower segment 24 and an upper segment 26 , and an intermediate segment 28 disposed axially between the lower segment 24 and the upper segment 26 .

[0071] The blades 22 are interposed between the axial segments, and each blade 22 is received between two axial segments. Figure 2 and Figure 3 As shown, each blade 22 is for example interposed between two intermediate segments 28. Each intermediate segment 28 is arranged axially between two blades 22 and forms an axial spacer of the blades 22.

[0072] Each intermediate segment 28 has an axial bore 30 . Each blade 22 has a central bore 54 .

[0073] The attachment portion 12 includes a central rod 32 along which the blades 22 and the intermediate segments 28 are alternately assembled. The central rod 32 extends through the central hole 54 of each blade 22 and the axial hole 30 of each intermediate segment 28.

[0074] A central rod 32 extends between the lower section 24 and the upper section 26 , to which the central rod 32 is secured.

[0075] The center rod 32 has one end that is, for example, welded to the lower segment 24 and a threaded end that is screwed into a threaded hole in the upper segment 26 .

[0076] The lower section 24 has a conical shape that converges in the insertion direction F1 . This facilitates the insertion of the attachment portion into the sleeve 4 .

[0077] The clamping part 14 comprises a cylindrical portion 34 , which is topped by a clamping tip 36 allowing the clamping part 14 to be grasped by means of an associated extraction tool.

[0078] The attachment portion 12 has a support portion 35, which is constructed to be pressed against the edge of the open upper end of the sleeve 4 due to the insertion of the attachment portion 12 into the sleeve 4, so as to ensure the sealing of the open upper end of the sleeve 4, thereby limiting the contamination of the contents of the sleeve 4 toward the outside.

[0079] The support portion 35 is located between the main body 16 and the clamping portion 14, is frustoconical and widens from the main body 16 towards the clamping portion 14, its outer diameter adjacent to the end of the clamping portion 14 being greater than the inner diameter of the sleeve 4 and its outer diameter adjacent to the end of the main body 16 being less than the inner diameter of the sleeve 4.

[0080] It can be seen in Figure 3 that, as a result of the insertion of the attachment portion 12 into the sleeve 4 along the insertion direction F1, the support portion 35 presses against the edge of the open upper end of the sleeve 4 and ensures a seal, thereby limiting the contamination of the contents of the sleeve 4 towards the outside.

[0081] The clamping tip 36 has a conical base 38 converging in the extraction direction F2, which extends by a cylindrical intermediate rod 40 of the same diameter as the upper end of the conical base 38, the intermediate rod 40 carrying a conical head 42 having a base adjacent to the intermediate rod 40 and a diameter greater than that of the intermediate rod 40, so that a radial shoulder 44 is defined between the intermediate rod 40 and the head 42.

[0082] The clamping tip 36 is preferably identical to the clamping tip of the original end of the rod 2, thereby allowing the extraction device 10 to be gripped by the extraction tool associated with the rod 2.

[0083] As Figure 4 illustrated, each blade 22 has a plurality of arms distributed around a central axis of the blade 22, this central axis of the blade 22 coinciding with the longitudinal axis A of the device. Each arm forms a respective tooth 18.

[0084] Preferably, the teeth 18 are regularly distributed around the longitudinal axis A, in particular uniformly distributed around the longitudinal axis A, with a constant angular spacing between the teeth 18.

[0085] Here, each blade 22 has four arms defining four teeth 18 distributed at an angular spacing of 90° around the axis of the blade 22.

[0086] The free end 18A of each tooth 18 has two sharp corners 46 formed respectively by the intersection of two side edges 48 of the tooth 18 with an end edge 50 of the tooth 18. This allows the locking force of the free end 18A on the inner surface 4A of the sleeve 4 to be increased.

[0087] The end edge 50 of each tooth 18 defines a respective sharp corner 46 with each side edge 48 of the tooth 18. For example, each side edge 48 is concave.

[0088] Each blade 22 is provided with a central hole 54 compatible in size with the central rod 32, in other words this allows the central rod 32 to be inserted into the central hole 54.

[0089] The tooth 18 has a free end 18A of dimensions and sufficient flexibility suitable for allowing insertion while generating a high locking force with the inner surface 4A of the sleeve 4 and having a good return resistance.

[0090] Figure 5 is a perspective view of the intermediate segment 28 according to certain embodiments.

[0091] The intermediate section 28 is cylindrical and extends along a longitudinal axis A.

[0092] The intermediate segment 28 has an axial upper end 56 and an axial lower end 72. The upper end 56 is provided with a housing 58 for receiving the blade 22, the housing 58 being delimited by a discontinuous peripheral edge 60 formed by segments 62 separated by openings 64. The housing 58 is arranged to receive a central portion of the blade 22, each tooth 18 exiting the housing 58 through a respective opening 64.

[0093] Due to the reception of the teeth 18 in the openings 64 , the blades 22 received in the receptacles 58 are angularly indexed relative to the intermediate segment 28 about the longitudinal axis A. Thus, each tooth 18 is angularly indexed about the longitudinal axis A relative to the body 16 .

[0094] A bearing surface 20 is formed on the intermediate section 28. In particular, the bearing surface 20 is formed at the bottom of the opening 64 and is inclined relative to a plane perpendicular to the longitudinal axis A to support the tooth 18 during compression.

[0095] Each intermediate segment 28 is provided with an directional element capable of interlocking with the directional elements of other intermediate segments 28 stacked axially therewith, so that the stacked intermediate segments 28 are angularly offset around the longitudinal axis A, preferably with regular angular spacing from one intermediate segment 28 to the next intermediate segment 28.

[0096] Here, each intermediate segment 28 comprises a lug 68 projecting from the upper end 56 and a cavity 70 formed in its axial lower end 72. The cavity 70 is complementary to the lug 68 and is intended to receive a lug of another identical intermediate segment 28.

[0097] The lugs 68 and the cavities 70 are angularly offset by an angular spacing β about the longitudinal axis A to achieve an angular offset of the stacked intermediate segments 28. The angular spacing β is, for example, 5°.

[0098] Figure 6 The front view shows the use of Figure 5 The extraction device 10 is manufactured with the middle part 28 .

[0099] The intermediate segments 28 are angularly offset, with each intermediate segment 28 being offset from the next intermediate segment 28 along an angular spacing β by interlocking the lugs 68 in the cavities 70 .

[0100] Here, the upper segment 26 is provided with a cavity for receiving the lug 68 of the first intermediate segment 28 .

[0101] Due to the angular offset of the intermediate segments 28, the blades 22 are angularly offset relative to each other according to the angular spacing β. Thus, the teeth 18 are distributed angularly around the body 16 and axially along the body 16. This facilitates effective locking of the attachment portion 12 in the sleeve 4 using different generatrixes.

[0102] The teeth 18 are distributed in groups of teeth arranged at the same axial position, the teeth 18 in a single group of teeth are distributed angularly around the body 16 , and a plurality of groups of teeth are distributed axially along the body 16 .

[0103] The tooth sets are also angularly offset relative to each other. The teeth 18 in each tooth set are angularly offset relative to the teeth 18 in the subsequent tooth set along the body 16.

[0104] Here, the teeth 18 of each blade 22 form a tooth set arranged at the same axial position.

[0105] Figure 2 and Figure 3 The extraction device 10 has a modular construction, which allows varying the number of teeth 18 . In particular, the number of teeth 18 is adjusted by varying the number of blades 22 and intermediate segments 28 of the body 16 .

[0106] exist Figure 7 In the illustrated embodiment, the extraction device 10 includes a single blade 22 interposed between an upper segment 26 and a lower segment 24. The extraction device 10 lacks an intermediate segment 28.

[0107] Return to Figure 2 and Figure 3 In operation, with the rod 2 lacking the upper end plug 8 and the sleeve 4 open at its upper end, the user forcibly inserts the attachment portion 12 of the extraction device 10 into the open upper end of the sleeve 4. Insertion is accomplished using an insertion force in the insertion direction F1. Once the attachment portion 12 is inserted into the sleeve 4, it is locked within the sleeve 4 due to its teeth 18, which grip only the inner surface 4A of the sleeve 4. Then, using a suitable tool, the operator grasps the gripping portion 14 and pulls it upward to extract the rod 2 from its nuclear fuel assembly. The gripping force is greater than the force required to extract the rod 2 from its nuclear fuel assembly, so that lifting the extraction device 10 allows the rod 2 to be lifted from the nuclear fuel assembly.

[0108] The extraction device 10 is simple and reliable to use. The extraction device 10 is fixed to the sleeve 4 simply by forcing the fixing portion 12 into the sleeve 4. The extraction device 10 is only released from the sleeve 4 by a force greater than the locking force, which is greater than the force used to extract the rod 2 from the nuclear fuel assembly frame.

[0109] The attachment portion 12 and the clamping portion 14 of the extraction device 10 form a replacement end plug that replaces the original end plug of the rod 2. When inserted into the sleeve 4, the extraction device 10 closes the sleeve and prevents the expulsion of the nuclear fuel pellets received therein.

[0110] The number, geometry and arrangement of teeth 18 allow variation of the insertion force of extraction device 10 in sleeve 4 and the locking force generated by teeth 18 of extraction device 10 inserted into sleeve 4. A person skilled in the art will know how to adapt the number, geometry and arrangement of teeth 18 to a specific application.

[0111] like Figure 4 The blades 22 shown allow forming the teeth 18 to limit the insertion force, thereby generating a sufficient locking force with a limited risk of return.

[0112] Other tooth geometries are also possible.

[0113] In an alternative, each blade 22 is circular and continuous and extends around the body 16. Each blade 22 is in the form of a washer, for example, having a continuous circular peripheral edge forming a single circular tooth.

[0114] Furthermore, the extraction device 10 has been described in conjunction with nuclear fuel assembly rods. However, such an extraction device can also be applied to or used for handling damaged cluster rods, whether they are control cluster rods or fixed cluster rods. These latter are damaged by the loss of their upper end plugs, which function as a connection to the support structure that ensures grouped handling of all rods comprising the cluster. Such cluster rods consist of a tubular sleeve whose ends are closed by plugs, with the upper plugs serving as a connection. The sleeves of control cluster rods are more or less filled with material that serves as the rod's functional target. A damaged rod without its upper end plug has no handling function. The extraction device 10 employed on such a damaged rod remedies this situation by allowing it to be handled in the same manner as when handling damaged fuel assembly rods.

Claims

1. An extraction device (10) for extracting a nuclear fuel rod (2) or a cluster rod, the extraction device (10) comprising an attachment portion (12) and a gripping portion (14), the attachment portion (12) being configured to be inserted into a sleeve (4) of the rod (2) through an end portion which has lost an end plug, the attachment portion (12) comprising an elongated body (16) along a longitudinal axis (A) and at least one tooth (18) projecting from the body (16), the tooth (18) being configured to allow the attachment portion (12) to be inserted axially into the sleeve (4) by force and to engage with an inner surface (4A) of the sleeve (4) to prevent the attachment portion (12) from being extracted from the sleeve (4). in, The attachment portion (12) further comprises a plurality of blades (22) axially spaced along the body (16) according to a regular or irregular distribution, each blade having a plurality of arms each forming a corresponding tooth (18).

2. The extraction device (10) according to claim 1, wherein The or each tooth (18) is configured to resist extraction of the attachment portion (12) from the sleeve (4) by forcing the tooth (18) against the inner surface (4A) of the sleeve (4).

3. The extraction device (10) according to claim 1 or 2, wherein: The attachment portion (12) includes a plurality of teeth (18) angularly distributed around the body (16).

4. The extraction device (10) according to claim 1, wherein The attachment portion (12) comprises regularly angularly distributed teeth, and / or uniformly angularly distributed teeth.

5. The extraction device (10) according to claim 1, wherein The attachment portion (12) includes a plurality of teeth (18) distributed axially along the body (16).

6. The extraction device (10) according to claim 1, wherein The blades (22) are angularly offset from each other.

7. The extraction device (10) according to claim 1, wherein The body (16) includes a plurality of axial segments (24, 26, 28) stacked axially alternately with blades (22).

8. Extraction device (10) according to claim 7, wherein The axial segments include one or more intermediate segments (28) interposed between two blades (22).

9. Extraction device (10) according to claim 7 or 8, wherein: The axial segments (24, 26, 28) and the blades (22) are stacked along a central axis (32).

10. The extraction device (10) according to claim 7, wherein: The body (16) includes axial segments (28) each having angularly offset interlocking orientation elements such that two segments stacked axially are angularly offset due to the interlocking of their orientation elements.

11. The extraction device (10) according to claim 1, wherein The attachment portion (12) has an abutment portion (35) configured to press against the edge of the end of the sleeve (4) as the attachment portion (12) is inserted into the sleeve (4) to provide a seal.

12. The extraction device (10) according to claim 1, wherein The attachment portion (12) has a bearing surface (20) associated with each tooth (18), each bearing surface (20) being arranged such that the tooth (18) presses against the bearing surface (20) when a force is applied to the extraction device (10) in a direction (F2) of extracting the attachment portion (12) from the sleeve (4).

13. Extraction device (10) according to claim 12, wherein Each bearing surface (20) is inclined relative to the longitudinal axis (A) while being oriented axially in the direction (F2) of extracting the attachment portion (12) from the sleeve (4) and radially inwardly.

14. An assembly comprising a nuclear fuel rod or clustered rod and an extraction device (10) according to claim 1, the extraction device (10) being adapted to insert and lock its attachment portion (12) into the sleeve (4) of the rod (2).

15. A method for extracting a nuclear fuel rod or clustered rod from a nuclear fuel assembly, wherein the sleeve (4) of the rod (2) has lost its end plug at one end, wherein: The attachment portion (12) of the extraction device (10) according to claim 1 is forcibly inserted into the open end of the sleeve (4), and then the clamping portion (14) of the extraction device (10) is pulled to extract the rod (2) from its nuclear fuel assembly.

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