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WO-2026093120-A1 - MAINTENANCE TOOL FOR SCREWING A NUT AROUND A STUD

WO2026093120A1WO 2026093120 A1WO2026093120 A1WO 2026093120A1WO-2026093120-A1

Abstract

This maintenance tool (1) for screwing a nut (3) around a stud (5) protruding from a flange (7) comprises a carrying ring (9) comprising a chamber (11) with an opening (13) on one side, and a gear socket (15) positioned in the chamber (13), the gear socket (15) being intended to fit the shape of the nut (3) carried in the chamber (11) and being mobile along a rotational movement on itself and a translation toward the opening (13).

Inventors

  • Declerck, Didier

Assignees

  • AKTIEBOLAGET SKF

Dates

Publication Date
20260507
Application Date
20251023
Priority Date
20241030

Claims (10)

  1. 1. Maintenance tool (1) for screwing a nut (3) around a stud (5) protruding from a flange (7), the maintenance tool (1) comprising a carrying ring (9) comprising a chamber (11) with an opening (13) on one side, and a gear socket (15) positioned in the chamber (13), the gear socket (15) being intended to fit the shape of the nut (3) carried in the chamber (11) and being mobile along a rotational movement on itself and a translation toward the opening (13), the rotational movement and the translation being destined to be decorrelated in order to reset the stroke of the gear socket (15) according to the direction of its translation.
  2. 2. Maintenance tool (1) according to claim 1, wherein the gear socket (15) comprises an external thread (17), the maintenance tool (1) comprising a motor (20) and a drive sprocket (19) engaged with the external thread (17) of the gear socket (15), the motor (20) driving the drive sprocket (19) so that the gear socket (15) rotates on itself.
  3. 3. Maintenance tool (1) according to claim 2, wherein the motor (20) is an electric motor.
  4. 4. Maintenance tool (1) according to any of the claims 2 and 3, comprising an abutment ring (21) forming the opening (13) of the chamber (11) and preventing the gear socket (15) to disengage with the drive sprocket (19) and to drop when there is no nut (3) in the carrying ring (9).
  5. 5. Maintenance tool (1) according to any of the preceding claims, comprising a spring (23) positioned in the chamber (11), the spring (23) exerting a force on the gear socket (15) and/or the nut (3) aiming to push said nut (3) out of the chamber (11) toward the opening (13).
  6. 6. Maintenance tool (1) according to any of the preceding claims, comprising a support cylinder (25) protruding from the carrying ring (9) toward the flange (7) and destined to fix a distance between said carrying ring (9) and the flange (7).
  7. 7. Maintenance tool (1) according to any of the preceding claims, wherein the stroke of the gear socket (15) is inferior to half of the length of the nut (3). 2024P00081DE
  8. 8. Maintenance tool (1) according to any of the preceding claims, comprising a lever (27) being mobile between an opened position and a closed position of the chamber (11), the lever (27) being destined to support the nut (3) when being in the closed position.
  9. 9. Maintenance tool (1) according to, wherein the carrying ring (9) comprises at least two chambers (11) and gear sockets (15), preferably 10 chambers (11) and gear sockets (15).
  10. 10. Method to use the maintenance tool (1) according to any of the preceding claims, comprising the following steps: Approaching (step El) the maintenance tool (1) carrying a nut (3) fitted in the gear socket (15) from the flange (7) and the stud (5) in order for the nut (3) and the stud (5) to touch each other; Setting in motion (step E2) the gear socket (15) with a helical movement toward the opening in order to screw the nut (3) around the stud (5); - Replacing (step E3) the nut (3) entirely in the chamber (11) without unscrewing said nut (3) from the stud (5) by approaching the carrying ring (9) from the flange (7); - Repeating the last two steps (E2; E3) of setting in motion the gear socket (15) and replacing the nut (3) in the chamber (11) until the nut (3) abuts (step E4) against the flange (7).

Description

2024P00081 DE Maintenance tool for screwing a nut around a stud The present disclosure relates to nuclear reactor maintenance equipment, specifically tools for tensioning and detensioning control rod drive mechanism (CRDM) assemblies within an evolutionary power reactor. More specifically, the present disclosure relates to the screwing of nuts on the adapter nozzle of the control rod drive mechanism in order to ensure a correct sealing of said adapter nozzle. Maintenance activities within nuclear reactors are complex, often requiring the shutdown of the facility and intricate maneuvers to access and service the internal components. These activities are further complicated by the need to minimize radiation exposure for personnel and the spatial constraints of the reactor's interior. Traditional methods for servicing these components involve intricate procedures that are not only time-consuming but also pose a risk of exposure to hazardous conditions. Conventional approaches to servicing internal components often rely on a series of manual manipulations and the use of specialized tools to secure and adjust various fasteners. These tools operate effectively within the confined spaces of the reactor and ensure that no parts are misplaced or dropped, as such incidents could lead to significant operational disruptions and potential safety hazards. The industry has recognized the need for improved tools that enhance safety, efficiency, and precision during these maintenance operations. Maintenance of control rod drive mechanisms (CRDMs) in power reactors presents a significant challenge due to the close proximity of CRDM assemblies within the reactor's closure head. The CRDM facilitates the movement of control rods, which regulate the nuclear reaction. During maintenance, the tightening and loosening of nuts and studs that secure the CRDMs are tasks that require preci se execution. Traditional methods for performing these tasks involve manual operations that are time-consuming and expose maintenance personnel to radiation for extended periods. Furthermore, the risk of 2024P00081 DE dropping components such as nuts within the reactor poses a significant contamination threat. Existing solutions for CRDM maintenance involve the use of tools that require manual handling of nuts and studs, which can be cumbersome and inefficient. These tools often necessitate the removal of surrounding CRDM assemblies to access the target assembly, leading to increased downtime and radiation exposure. It should be noted that a reactor comprises for example between 10 and 200 CRDM. Additionally, the manual retention mechanisms used to hold the nuts in place are prone to failure, increasing the risk of losing nuts within the reactor. The complexity of these tools and the precision required for their operation also contribute to the overall challenge of maintaining CRDMs efficiently and safely. The present maintenance tool addresses these challenges by providing an automated solution for the screwing of nuts around studs useful for the tensioning and detensioning of said studs on CRDM assemblies. An advantage of the present invention is to offer a great stroke for screwing a nut around a stud with a particularly compact design. The invention relates to a maintenance tool, for example of a control rod drive mechanism of a power reactor, for screwing a nut around a stud protruding from a flange, the maintenance tool comprising a carrying ring comprising a chamber with an opening on one side, and a gear socket positioned in the chamber, the gear socket being intended to fit the shape of the nut carried in the chamber and being mobile along a rotational movement on itself and a translation toward the opening, the rotational movement and the translation being destined to be decorrelated in order to reset the stroke of the gear socket according to the direction of its translation. It is understood that the rotational movement and the translation being destined to be decorrelated does not mean that those movements can’t be correlated, for example during a screwing, but said movements have the possibility to be decorrelated. The maintenance tool thus permits to screw nuts on studs of a CRDM, the maintenance tool being reusable for all the CRDM of a reactor. 2024P00081 DE The translation and the rotational movement are not linked into a fixed helical movement. Thus, a helical movement for screwing can be obtained, as well as only a pure translation in order to reset the stroke of the gear socket and increase the total stroke on which a nut can be screwed, with a great compacity of the maintenance tool . This effect constitutes the center of the invention. According to one embodiment, the gear socket comprises an external thread, the maintenance tool comprising a motor and a drive sprocket engaged with the external thread of the gear socket, the motor driving the drive sprocket so that the gear socket rotates on itself. Advantageously, the mo