Apparatus for extracting nuclear fuel rods or cluster rods and extraction method using such an extraction apparatus - Patent Application 20070122997

Abstract

The extraction device (10) includes a mounting portion (12) and a gripping portion (14) configured to be inserted into the sleeve (4) of the rod (2) through the end without the end plug, the mounting portion (12) including an elongated body (16) along a longitudinal axis (A) and at least one tooth (18) protruding from the body (16), the or each tooth (18) configured to allow the mounting portion (12) to be forcibly inserted axially into the sleeve (4) and to engage an inner surface (4A) of the sleeve (4) to prevent the mounting portion (12) from being extracted 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 technology]

[0002] A nuclear fuel assembly comprises a bundle of nuclear fuel rods held by a framework, each rod containing a tubular sleeve containing a fissile column formed by a stack of nuclear fuel pellets and closed at both ends by end plugs welded to the sleeve.

[0003] At least one of the two end plugs, in addition to sealing the nuclear fuel rod, has the function of gripping the nuclear fuel rod and allowing it to be extracted from or inserted into the framework of the nuclear fuel assembly, for example, to repair or replace the nuclear fuel rod if it is damaged.

[0004] Nuclear fuel rods may lose their end plugs with handling capabilities or may need to be removed, for example if the end plugs are damaged, making it difficult to extract the nuclear fuel rods that have lost their handling capabilities from the nuclear fuel assembly.

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

[0006] The cluster rod becomes disengaged from its upper end plug and is allowed to fall into the corresponding guide tube of the nuclear fuel assembly that contained the bundle.

[0007] French Patent Application Publication No. 1225784 discloses a nuclear fuel rod removal device that includes a tool with three claws, each having a recess on the surface of the claw that contacts the outer surface of the nuclear fuel rod, and a ball or roller housed in each recess that provides a locking of the claw against the exterior of the sleeve of the nuclear fuel rod when the tool is lifted.

[0008] EP 0 200 988 A1 discloses a device for extracting nuclear fuel rods, which includes a cylindrical housing containing an elastomeric tube for capping the fuel rod, and a cylindrical thrust rod movably mounted within the housing for laterally deforming the elastomeric tube to externally clamp the sleeve of the nuclear fuel rod.

[0009] US Pat. No. 4,986,955 discloses an extraction device for extracting peripheral nuclear fuel rods from a nuclear fuel assembly, the extraction device including a clamp for clamping the nuclear fuel rods from the outside.

[0010] Korean Patent No. 101163118 discloses a nuclear fuel rod extraction device that includes a circular clamp for clamping the rod from the outside and a pin that can be inserted into the rod to prevent the clamped sleeve from being crushed. [Prior art documents] [Patent documents]

[0011] [Patent Document 1] French Patent Application Publication No. 1225784 [Patent Document 2] European Patent Application Publication No. 0200988 [Patent Document 3] U.S. Patent No. 4,986,955 [Patent Document 4] Korean Patent No. 101163118 Summary of the Invention [Problem to be solved by the invention]

[0012] One object of the present invention is to provide an apparatus for extracting nuclear fuel rods that allows reliable and easy extraction. [Means for solving the problem]

[0013] To this end, the invention proposes an extraction device for extracting nuclear fuel rods or cluster rods, comprising a mounting portion and a gripping portion configured to be inserted into the sleeve of the rod through its unplugged end, the mounting portion comprising a body extending along the longitudinal axis and at least one tooth projecting from said body, the or each tooth being configured to allow the mounting portion to forcibly insert the mounting portion axially into the cladding and to engage the inner surface of the sleeve to prevent extraction of the mounting portion from the sleeve.

[0014] In particular embodiments, the extraction device comprises one or more of any of the following features, taken individually or in any technically feasible combination: - the or each tooth is configured to resist withdrawal of the attachment portion from the sleeve by holding the tooth in compression against the inner surface of the sleeve; - the attachment portion includes a plurality of teeth angularly distributed around the body; - the attachment part comprises teeth regularly distributed in angle, in particular teeth uniformly distributed in angle; - the mounting portion includes a plurality of teeth axially distributed along the body; - the attachment portion includes at least one blade having a plurality of arms each forming a respective tooth; - the mounting portion comprises a plurality of blades 22 spaced axially along the body according to a regular or irregular distribution; - The blades are angularly offset from each other; - the body includes a plurality of axial sections stacked axially in alternating order with the blades; - the axial section includes one or more intermediate sections placed between the two blades; - Axial sections and blades are stacked along the central shaft; - the body includes axial sections each having angularly offset interlocking orientation elements, such that two axially stacked sections are angularly offset due to the interlocking of their orientation elements; - the mounting part has a bearing part configured to press against an edge of the end of the sleeve due to insertion of the mounting part into the sleeve; - the mounting part has a bearing surface associated with each tooth, and each bearing surface is arranged in such a way that the tooth bears against the bearing surface when a force is applied to the extraction device in a direction to extract the mounting part from the sleeve; - each bearing surface is oriented axially and radially inward in the direction of withdrawal of the mounting part from the sleeve and is inclined relative to the longitudinal axis;

[0015] The invention also relates to an assembly comprising a nuclear fuel rod or cluster rod and an extraction device as defined above adapted for the insertion and locking of its attachment part inside the sleeve of the rod.

[0016] The present invention also relates to a method for extracting a nuclear fuel rod or cluster rod from a nuclear fuel assembly, wherein the sleeve of the rod does not have a closed end plug at one end, and the attachment portion of the extraction device as defined above is forcibly inserted into the open end of the sleeve, after which the gripping portion of the extraction device is pulled to extract the rod from the nuclear fuel assembly.

[0017] The invention and its advantages will be better understood from the following description, given by way of example only and made with reference to the accompanying drawings, in which: [Brief explanation of the drawings]

[0018] [Figure 1] FIG. 1 is an elevational view of an undamaged nuclear fuel rod having an upper end plug configured for handling the rod and a lower end plug not configured for handling the rod. [Figure 2] FIG. 2 is a schematic view of a damaged nuclear fuel rod without its upper end plug configured for handling and extraction equipment prior to insertion of the extraction equipment into the rod. [Figure 3] FIG. 2 is a schematic view of a damaged nuclear fuel rod without its upper end plug configured for handling and extraction equipment after insertion of the extraction equipment into the rod. [Figure 4] FIG. 4 is a top view of the blade of the extraction device of FIGS. 2 and 3; [Figure 5] FIG. 4 is a perspective view of a medial axial section of the extraction device of FIGS. 2 and 3; [Figure 6] 1 is an elevational view of an extraction device according to one particular embodiment. [Figure 7] FIG. 12 is an elevational view of an extraction device according to another particular embodiment. DETAILED DESCRIPTION OF THE INVENTION

[0019] 1, an intact nuclear fuel rod 2 includes a tubular sleeve 4 extending along a longitudinal axis A that is intended to house a fissile column formed of cylindrical nuclear fuel pellets (not shown) stacked axially within the sleeve 4. The rod 2 is intended to be integrated into a nuclear fuel assembly that includes a bundle of parallel rods held together by a nuclear fuel assembly skeleton that includes a lower nozzle and an upper nozzle.

[0020] During operation, within the reactor core or handling or storage pool, the nuclear fuel assemblies are supported by their lower nozzles and positioned vertically, with each rod extending vertically.

[0021] In the remainder of this specification, the terms "upper" and "lower" will be understood to refer to the normal vertical orientation of the rods within the nuclear fuel assembly that are located at the lower nozzle.

[0022] 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.

[0023] 1, the lower end plug 6 does not have a handling function, in other words, it is not configured to handle the rod 2. In contrast, the upper end plug 8 has a handling function, in other words, it is configured to handle the rod 2 by an associated handling tool (not shown).

[0024] More specifically, the upper end plug 8 is configured so that the rod 2 can be extracted from the nuclear fuel assembly by pulling the rod 2 upwardly and out of the nuclear fuel assembly using an extraction tool suitable for grasping the upper end plug 8.

[0025] If the rod 2 is damaged, the upper end plug 8 with its handling function may be missing from the rod 2 and the sleeve 4 that opens at its upper end may no longer have a handling function, so that it may not be possible to extract the rod 2 using the upper end plug 8.

[0026] In Figures 2 and 3, the rod 2 is without its upper end plug 8 and the sleeve 4 is open at its upper end.

[0027] The extraction device 10 is configured so that the rod 2 can be extracted through the end not provided with an end plug, in particular the upper end.

[0028] The extraction device 10 comprises a mounting portion 12 configured to be inserted axially into the interior of the sleeve 4 through its open upper end and to be locked inside the sleeve 4, and a gripping portion 14 configured to be gripped by a handling tool, preferably the same handling tool provided for extracting the undamaged rod 2, in other words the same handling tool provided for gripping the missing end plug, here the upper end plug 8.

[0029] The attachment portion 12 forms a harpoon-shaped portion with one or more retaining teeth, in particular with several rows of retaining teeth.

[0030] The mounting portion 12 extends along a longitudinal axis A.

[0031] The mounting portion 12 is configured to be inserted axially into the sleeve 4 in an insertion direction F1 (Figure 2) and to be mechanically locked within the sleeve 4, resisting movement of the mounting portion 12 relative to the sleeve 4 in a withdrawal direction F2 (Figure 3) opposite to the insertion direction F1, solely by cooperation of the mounting portion 12 with the inner surface 4A of the sleeve 4.

[0032] The mounting portion 12 is forcibly insertable inside the sleeve 4 .

[0033] The mounting portion 12 is, for example, axially inserted into the sleeve 4 in an insertion direction F1 by the mounting portion 1 2 is configured so that the insertion force required to force the mounting portion 12 out of the sleeve 4 in the withdrawal direction F2 is entirely less than the axial blocking force that must be overcome to withdraw the mounting portion 12 out of the sleeve 4.

[0034] Therefore, it is easier to insert the attachment portion 12 inside the sleeve 4 than to pull the attachment portion 12 out of the sleeve 4 .

[0035] The insertion force is, for example, less than 50 daN (decaNewtons), preferably less than 40 daN, and more preferably less than 30 daN.

[0036] The attachment portion 12 is configured so that the locking force is entirely greater than the pull-out force that must be exerted on the rod 2 to pull it out of the assembly, plus a safety margin.

[0037] The locking force is adjustable as a function of a predetermined extraction force, so that for example, if the extraction force from the fuel assembly is 30 daN, the locking force is greater than 50 daN.

[0038] The mounting portion 12 includes a body 16 that extends along a longitudinal axis A and carries one or more blades 22. Each blade 22 has one or more teeth 18, each tooth 18 projecting radially outward from the body 16 relative to the longitudinal axis A.

[0039] Each tooth 18 is configured to interfere with the inner surface 4A of the sleeve 4 to allow insertion of the mounting portion 12 into the sleeve 4 in an insertion direction F1 and to resist withdrawal of the mounting portion 12 from the sleeve 4 in a withdrawal direction F2.

[0040] Each tooth 18 has a free end 18 A provided for contacting the inner surface 4 A of the sleeve 4 .

[0041] Each tooth 18 is configured to rub its free end 18A against the inner surface 4A of the sleeve 4 by generating a first axial force that opposes movement of the mounting portion 12 inside the sleeve 4 in an insertion direction F1 that is greater than a second axial force in a withdrawal direction F2 of the mounting portion 12 out of the sleeve 4.

[0042] Each tooth 18 is flexible in such a way that it flexes rearward upon insertion of the mounting portion 12 into the sleeve 4 in the forward direction.

[0043] Each tooth 18 is formed, for example, by a flexible tab of a corresponding blade 22, which tab projects radially relative to the body 16. Each blade 22 has a thickness, measured along the longitudinal axis A, that can vary according to the desired axial force.

[0044] Each blade 22 is made of, for example, a metal with excellent bending properties, or a steel with high elastic properties, such as spring steel.

[0045] Each blade 22 is configured such that each tooth 18 of the blade 22 bends rearward due to insertion of the mounting portion 12 inside the sleeve 4 in the insertion direction F1, and once the mounting portion 12 is inserted into the sleeve 4, presses against the inner surface 4A of the sleeve 4 without reversing, against withdrawal of the mounting portion 12 from the sleeve 4 in the withdrawal direction F2.

[0046] 4, each blade 22 has, for example, a plurality of teeth 18. The number of teeth 18, here four, is selected depending on the desired insertion and locking forces.

[0047] The body 16 of the mounting portion 12 includes a bearing surface 20 associated with each tooth 18 .

[0048] Each bearing surface 20 is oriented axially and radially inwardly toward the withdrawal direction F2 and is inclined relative to the longitudinal axis A. Each bearing surface 20 forms a non-zero angle α with the radial plane relative to the longitudinal axis A.

[0049] The presence of the inclined bearing surface 20 increases the force with which the tooth 18 can reverse during extraction, thereby improving the extraction locking force generated by the tooth 18 .

[0050] The body 16 is here formed with a plurality of axial sections 28 aligned along the longitudinal axis A of the body 16 and a plurality of blades 22 carrying teeth 18 positioned between the axial sections of the body 16.

[0051] Body 16 has a lower section 24 and an upper section 26 , as well as an intermediate section 28 axially disposed between lower section 24 and upper section 26 .

[0052] The blades 22 are positioned between the axial sections, with each blade 22 housed between two axial sections. As illustrated in Figures 2 and 3, for example, each blade 22 is positioned between two intermediate sections 28. Each intermediate section 28 is axially disposed between two blades 22 and forms an axial spacer for the blades 22.

[0053] Each intermediate section 28 has an axial orifice 30. Each blade 22 has a central orifice 54.

[0054] The mounting portion 12 includes a central rod 32 along which the alternating blades 22 and intermediate sections 28 are mounted. The central rod 32 extends through a central orifice 54 of each blade 22 and an axial orifice 30 of each intermediate section 28.

[0055] The central rod 32 extends between the upper and lower sections 26, 24 to which it is fixed.

[0056] The center rod 32 has, for example, an end welded to the lower section 24 and a threaded end that threads into a threaded hole in the upper section 26 .

[0057] The subsection 24 has a conical shape that converges in the insertion direction F1, which facilitates the insertion of the attachment part inside the sleeve 4.

[0058] The gripping portion 14 includes a cylindrical portion 34 with an uppermost gripping tip 36 that allows the gripping portion 14 to be grasped with an associated extraction tool.

[0059] The mounting portion 12 has a bearing portion 35 configured to press against the edge of the open upper end of the sleeve 4 upon insertion of the mounting portion 12 inside the sleeve 4, ensuring a seal of this open upper end of the sleeve 4 and thus limiting contamination of the contents of the sleeve 4 toward the outside.

[0060] The bearing portion 35 is positioned between the body 16 and the gripping portion 14, the bearing portion 35 being frustoconical and widening from the body 16 toward the gripping portion 14, the end thereof adjacent to the gripping portion 14 having an outer diameter larger than the inner diameter of the sleeve 4, and the end thereof adjacent to the body 16 having an outer diameter smaller than the inner diameter of the sleeve 4.

[0061] As can be seen in FIG. 3, upon insertion of the mounting portion 12 inside the sleeve 4 along the insertion direction F1, the bearing portion 35 presses against the edge of the open upper end of the sleeve 4, ensuring an airtight seal and limiting contamination of the contents of the sleeve 4 towards the outside.

[0062] The gripping tip 36 has a conical base 38 converging in the withdrawal direction F2 extended 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, thus defining a radial shoulder 44 between the intermediate rod 40 and the head 42.

[0063] The gripping tip 36 is preferably identical to the tip of the original end of the rod 2 and allows the extraction device 10 to be gripped by an extraction tool attached to the rod 2.

[0064] 4, each blade 22 has a plurality of arms distributed about a central axis of the blade 22 which coincides with the longitudinal axis A of the device. Each arm defines a respective tooth 18.

[0065] 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 pitch between the teeth 18 .

[0066] Each blade 22 here has four arms defining four teeth 18 distributed at an angular pitch of 90° around the axis of the blade 22 .

[0067] The free end 18A of each tooth 18 has two ridges 46 formed by the intersection of the end edge 50 of the tooth 18 and two side edges 48 of the tooth 18. This makes it possible to increase the locking force of the free end 18A on the inner surface 4A of the sleeve 4.

[0068] The end edge 50 of each tooth 18 defines a respective angle 46 with each side edge 48 of that tooth 18. Each side edge 48 may be, for example, concave.

[0069] Each blade 22 is provided with a central orifice 54 that corresponds to the size of the central rod 32, in other words, allows the central rod 32 to be inserted into the central orifice 54.

[0070] The teeth 18 have dimensions and sufficient flexibility at the free ends 18A suitable to create a high locking force with the inner surface 4A of the sleeve 4 and to allow insertion while exhibiting good resistance to inversion.

[0071] FIG. 5 is a perspective view of the middle section 28 according to certain embodiments.

[0072] The intermediate section 28 is cylindrical and extends along a longitudinal axis A.

[0073] The intermediate section 28 has an axially upper end 56 and an axially lower end 72. The upper end 56 is provided with a housing 58 for receiving the blades 22, bounded by a discontinuous peripheral rim 60 formed by segments 62 separated by openings 64. The housing 58 is provided to receive a central portion of the blades 22, with each tooth 18 extending from the housing 58 through a respective opening 64.

[0074] The blades 22 contained within the housing 58 are angularly indexed about the longitudinal axis A relative to the intermediate section 28 due to the reception of the teeth 18 within the openings 64. Thus, each tooth 18 is angularly indexed about the longitudinal axis A relative to the body 16.

[0075] A bearing surface 20 is formed on the intermediate section 28. Specifically, the bearing surface 20 is formed on 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.

[0076] Each intermediate section 28 is provided with an orientation element that can be interlocked with that of another intermediate section 28 axially stacked with that intermediate section 28, such that the stacked intermediate sections 28 are angularly offset about the longitudinal axis A, preferably with a regular angular pitch from one intermediate section 28 to the next.

[0077] Here, each intermediate section 28 includes a projection 68 projecting from its upper end 56 and a cavity 70 formed within its axially lower end 72. The cavity 70 is complementary to the projection 68 for accommodating the projection of another identical intermediate section 28.

[0078] The protrusions 68 and cavities 70 are angularly offset by an angular pitch β about the longitudinal axis A to achieve the angular offset of the stacked intermediate sections 28. The angular pitch β is, for example, 5°.

[0079] FIG. 6 shows in elevation the extraction device 10 made with the intermediate section 28 according to FIG.

[0080] The intermediate sections 28 are angularly offset, with each intermediate section 28 being offset from the next intermediate section 28 along an angular pitch β by the interlocking of the projections 68 within the cavities 70 .

[0081] Here, the upper section 26 is provided with a cavity for receiving the protrusion 68 of the first intermediate section 28 .

[0082] Due to the angular offset of the intermediate sections 28, the blades 22 are angularly offset relative to one another according to an angular pitch β. The teeth 18 are therefore angularly distributed axially around and along the body 16, which promotes effective locking of the attachment portion 12 in the sleeve 4 with the different generatrix lines of the sleeve.

[0083] The teeth 18 are distributed in sets of teeth disposed at the same axial position, with the teeth 18 of each set of teeth being angularly distributed around the body 16 and the sets of teeth being axially distributed along the body 16.

[0084] The tooth sets are also angularly offset relative to one another, with the teeth 18 of each tooth set being angularly offset relative to the teeth 18 of the succeeding tooth set along the body 16.

[0085] The teeth 18 of each blade 22 here form a set of teeth arranged at the same axial position.

[0086] 2 and 3 is of modular construction, which allows for the number of teeth 18 to be varied. In particular, the number of teeth 18 is accommodated by varying the number of blades 22 and intermediate sections 28 of the body 16.

[0087] 7, the extractor 10 includes a single blade 22 positioned between the upper section 26 and the lower section 24. The extractor 10 does not have a middle section 28.

[0088] 2 and 3 , in operation, with the rod 2 missing the upper end plug 8 and the sleeve 4 open at its upper end, a user forcibly inserts the attachment portion 12 of the extraction device 10 into the open upper end of the sleeve 4. This insertion is performed using an insertion force in an insertion direction F1. Once the attachment portion 12 is inserted into the sleeve 4, the attachment portion 12 becomes locked inside the sleeve 4 because its teeth 18 exclusively grip the inner surface 4A of the sleeve 4. Then, using a suitable tool, an operator grasps the gripping portion 14 and pulls it upward to extract the rod 2 from the nuclear fuel assembly. The clamping force is greater than the force extracting the rod 2 from the nuclear fuel assembly, so that the rod 2 can be lifted from the nuclear fuel assembly by lifting the extraction device 10.

[0089] The extraction device 10 is simple to use and reliable. It is fixed to the sleeve 4 by simply forcibly inserting the fixing part 12 inside the sleeve 4. The extraction device 10 can only be disengaged from the sleeve 4 under a force exceeding the locking force, which is greater than the force required to extract the rod 2 out of the frame of the nuclear fuel assembly.

[0090] The attachment portion 12 and gripping portion 14 of the extractor 10 form a replacement end plug that replaces the original end plug of the rod 2. Once inserted into the sleeve 4, the extractor 10 closes the sleeve and prevents the escape of the nuclear fuel pellets contained within the sleeve 4.

[0091] The number, geometry and arrangement of the teeth 18 can vary the insertion force of the extractor 10 into the sleeve 4 and the locking force generated by the teeth 18 of the extractor 10 inserted into the sleeve 4. A person skilled in the art will know how to adapt the number, geometry and arrangement of the teeth 18 to a particular application.

[0092] The blade 22 shown in Figure 4 allows for limiting the insertion force and generating sufficient locking force while limiting the risk of inversion.

[0093] Other tooth geometries are possible.

[0094] In one variation, each blade 22 is circular and continuous, extending around the body 16. Each blade 22 has the shape of a washer, for example, with a continuous circular periphery that forms a single circular tooth.

[0095] Furthermore, the extraction apparatus 10 has been described in connection with nuclear fuel assembly rods. However, such an extraction apparatus can be adapted or used to handle damaged cluster rods, whether they are control or fixed cluster rods. Fixed cluster rods are damaged by the loss of their upper end plugs, which function as interlocks with the support structure that ensures the collective handling of all rods comprising the cluster. Such cluster rods include tubular sleeves, the upper end of which is interlocked and closed by plugs. The sleeves of control cluster rods are filled with material that serves the rod's function, to a greater or lesser extent. A damaged rod lacking an upper end plug has no handling function at all. The extraction apparatus 10 utilized for such damaged rods thus improves this situation by allowing the rods to be handled in the same manner as when used to handle damaged fuel assembly rods. [Explanation of symbols]

[0096] 2 nuclear fuel rods 4 sleeves 6 Lower end plug 8 Upper end plug 10 Extraction device 12 Mounting part 14 Gripping part 16 Main Unit 18 teeth 20 Bearing surface 22 blades 24 Subdivision 26 Upper category 28 Intermediate division 30 Axial Orifice 32 Center Rod 34 Cylindrical section 36 Grip tip 38 Conical Base 40 Intermediate rod 42 Conical Head 44 Radial shoulder A longitudinal axis F1 Insertion direction F2 Pulling direction

Claims

1. 1. An apparatus (10) for extracting a nuclear fuel rod (2) or cluster rod, the extraction device (10) including a mounting portion (12) and a gripping portion (14) configured to be inserted into a sleeve (4) of the rod (2) through an end not provided with an end plug, the mounting portion (12) including an elongated body (16) along a longitudinal axis (A) and at least one tooth (18) protruding from the body (16), the tooth or each tooth (18) configured to allow the mounting portion (12) to be forcibly inserted axially into the sleeve (4) and to engage an inner surface (4A) of the sleeve (4) to prevent extraction of the mounting portion (12) from the sleeve (4), the mounting portion (12) including at least one blade (22) having a plurality of arms each forming a respective tooth (18).

2. 2. An 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 pressing the tooth (18) firmly against the inner surface (4A) of the sleeve (4).

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

4. 4. Extraction device (10) according to any one of claims 1 to 3, wherein the attachment portion (12) comprises teeth that are regularly and / or uniformly distributed in angle.

5. 5. Extraction device (10) according to any one of claims 1 to 4, wherein the mounting portion (12) comprises a plurality of teeth (18) distributed axially along the body (16).

6. 6. Extraction device (10) according to any one of claims 1 to 5, comprising a plurality of blades (22) spaced axially along the body (16) according to a regular or irregular distribution.

7. 7. The extraction device (10) of claim 6, wherein the blades (22) are angularly offset from one another.

8. 8. The extraction device (10) of any one of claims 1 to 7, wherein the body (16) comprises a plurality of axial sections (24, 26, 28) axially stacked in alternating order with the blades (22).

9. 9. The extraction device (10) of claim 8, wherein the axial section includes one or more intermediate sections (28) located between the two blades (22).

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

11. 11. The extraction device (10) of any one of claims 8 to 10, wherein the body (16) includes axial sections (28) each having angularly offset interlocking orientation elements, such that two axially stacked sections are angularly offset due to the interlocking of their orientation elements.

12. 12. The extraction device (10) according to any one of claims 1 to 11, wherein the mounting portion (12) has an abutment portion (35) configured to press against the edge of the end of the sleeve (4) upon insertion of the mounting portion (12) inside the sleeve (4) in order to provide a seal.

13. 13. An extraction device (10) according to any one of claims 1 to 12, wherein the mounting portion (12) has a bearing surface (20) associated with each tooth (18), and each bearing surface (20) is arranged in such a way that when a force is applied to the extraction device (10) in the direction (F2) of extraction of the mounting portion (12) from the sleeve (4), the tooth (18) presses against the bearing surface (20).

14. 14. The extraction device (10) according to claim 13, wherein each bearing surface (20) is oriented axially and radially inward in the extraction direction (F2) of the mounting portion (12) from the sleeve (4), while being inclined relative to the longitudinal axis (A).

15. 15. An assembly comprising a nuclear fuel rod or cluster rod and an extraction device (10) according to any one of claims 1 to 14, adapted for the insertion and locking of its attachment part (12) inside the sleeve (4) of the rod (2).

16. 15. A method for extracting a nuclear fuel rod or cluster rod from a nuclear fuel assembly, wherein the sleeve (4) of the rod (2) does not have an end plug at one end, and wherein the attachment portion (12) of the extraction device (10) according to any one of claims 1 to 14 is forcibly inserted into the open end of the sleeve (4), after which the gripping portion (14) of the extraction device (10) is pulled to extract the rod (2) from the nuclear fuel assembly.

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