JP2008020405A - Control rod driving mechanism - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To simplify the lower section of a reactor pressure vessel by installing a control rod driving mechanism above the reactor pressure vessel, and enhance its maintenance characteristics and reliability. <P>SOLUTION: A control rod driving mechanism for inserting a control rod into a core of the reactor pressure vessel downward from the upper side and pulling the control rod upward from the lower side comprises a motor 31 installed above an upper end plate 19 of the reactor pressure vessel, a drive shaft 21 externally threaded and having the bottom end connected with the control rod, a roller nut 35 screwed on the drive shaft 21, a motor side magnet coupling 32 provided on the motor side and an outer cylinder side magnet coupling 33 arranged concentrically with the motor side magnet coupling 32 for transmitting the rotation force to the roller nut 35. The motor 31 turns the roller nut 35 through the motor side magnet coupling 32 and the outer cylinder side magnet coupling 33 for vertically moving the control rod through the drive shaft 21. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a control rod drive mechanism in a nuclear reactor, and more particularly to a control rod drive mechanism of a type in which a control rod is inserted vertically downward from an upper part of a core.

  A boiling water reactor is generally configured as shown in FIG. That is, reference numeral 1 in the figure denotes a reactor pressure vessel, and a shroud 2 is provided in the reactor pressure vessel 1, and a core 3 is disposed in the shroud 2. The core 3 is configured by arranging a large number of fuel assemblies in a lattice pattern, and a control rod 4 having a cross-shaped cross section is inserted into the gap between the fuel assemblies from below to adjust the output of the core 3. It is configured as follows. That is, a housing 5 is vertically penetrating through the bottom 1a of the reactor pressure vessel 1, a control rod drive mechanism is provided in the housing 5, and the operating piston to which the control rod 4 is connected. The control rod 4 is inserted and pulled out by driving the.

  As described above, since the conventional control rod drive mechanism is provided in the housing that extends downward through the reactor pressure vessel 1, the installation height of the reactor pressure vessel is increased, and as a result, the reactor is retracted. There are problems such as an increase in the size of the vessel and an increase in manufacturing costs, and a problem that a large space is required below the reactor pressure vessel in order to remove the control rod drive mechanism. It is also necessary for safety reasons to make the reactor containment vessel that contains the coolant in the case of the loss of coolant accident, which is the design standard of the reactor, smaller.

In view of this, an apparatus has been proposed in which the control rod drive mechanism is housed in the reactor so that the lower part of the reactor pressure vessel can be simplified (see Patent Document 1).
JP 2002-55189 A

  However, the control rod drive mechanism described in Patent Document 1 is housed in a reactor pressure vessel, and an electric appliance for operating the control rod drive mechanism is required to be provided in the boundary. Electric power for operating the mechanism needs to be transmitted from outside the reactor, and the wires must be arranged through the reactor pressure vessel, making the mechanism complicated and maintainability of the control rod drive mechanism. In addition, there is a problem that reliability may be lowered.

  In view of such a point, the present invention can install a control rod drive mechanism above the reactor pressure vessel upper end plate, simplify the lower portion of the reactor pressure vessel, and improve its maintainability and reliability. An object of the present invention is to provide a control rod drive mechanism.

  The present invention relates to a reactor that is a pressure boundary in a control rod drive mechanism in which a control rod is inserted into a core in a reactor pressure vessel from the top to the bottom and a pulling operation is performed from the bottom to the top. A motor installed above the upper end plate of the pressure vessel, a control shaft connected to the lower end, a drive shaft threaded on the outer periphery, a roller nut screwed to the drive shaft, and provided on the motor side A motor-side magnet coupling, and an outer-body-side magnet coupling that is disposed concentrically with the motor-side magnet coupling and transmits a rotational force to the roller nut. The roller nut is rotated through an outer body side magnet coupling, and the control rod is moved up and down through the drive shaft. That.

  Since the present invention is configured as described above, the control rod drive mechanism does not protrude from the lower part of the reactor pressure vessel, the lower structure of the reactor pressure vessel is simplified, and the height of the reactor pressure vessel is reduced. As a result, the reactor pressure vessel becomes smaller, which is advantageous in terms of seismic design, and the manufacturing cost can be reduced. Moreover, since all the electric parts can be placed outside the reactor pressure vessel, there is an effect that an electric wire penetrating the reactor pressure vessel is not required.

  FIG. 1 is a view showing an example of a reactor internal structure to which a control rod drive mechanism of the present invention is applied. In a reactor pressure vessel 10, a fuel assembly installed in a bundle-in basket 11 is shown. A core 13 composed of 12 is disposed. The core 13 is supported by a core support plate 14 provided in the reactor pressure vessel 10, and a shroud 15 is provided on the outer periphery of the core 13. The upper part of the bundle-in basket 12 is supported by an upper lattice plate 16 supported by a shroud 15. A shroud head 17 is disposed above the shroud 15, and a control rod guide tube 18 extends upward from the shroud head 17. The control rod guide tube 18 is coupled to a lower portion of a control rod drive mechanism 20 installed above the reactor pressure vessel upper end plate 19.

  As shown in FIG. 2, a later-described drive shaft 21 driven by the control rod drive mechanism 20 is coupled to an extension shaft 23 by a gripper 22, and the extension shaft 23 is coupled to a control rod 25 by a gripper 24. The control shaft 25 is inserted into and extracted from the core 13 by moving the drive shaft 21 up and down by the rod drive mechanism 20. The control rod 25 is moved up and down smoothly by the control rod guide tube 18 guiding the extension shaft 23 and the drive shaft 21, and the control rod 25 is guided by the outer peripheral portion of the bundle-in basket 11 in the core. The drive shaft 21, the extension shaft 23, and the control rod 25 are disassembled and connected by inserting a jig into the drive shaft 21 and the extension shaft 23 in the control rod drive mechanism 20 from above the reactor pressure vessel upper end plate 19. Can be done.

  3 is a longitudinal sectional view of the control rod drive mechanism 20, and FIG. 4 is a cross-sectional view taken along the line AA of FIG. 3. A housing 26 of the control rod drive mechanism 20 is mounted through the reactor pressure vessel upper end plate 19. A housing upper lid 27 is mounted on the upper portion of the housing 26 penetrating the reactor pressure vessel upper end plate 19. In the housing 26 to which the housing upper lid 27 is mounted, an outer body 28 is provided concentrically with the housing 26 so as to be rotatable around an axis by bearings 29 and 30.

  A motor 31 is installed above the housing upper lid 27, and a motor-side magnet coupling 32 that rotates along the outer periphery of the upper portion of the housing upper lid 27 is provided on a rotating shaft (not shown) of the motor 31. Is provided. On the other hand, an outer cylinder side magnet coupling 33 is mounted on the outer periphery of the top end portion of the outer cylinder 28 so as to face the motor side magnet coupling 32 with the housing upper lid 27 interposed therebetween. Thus, when the motor-side magnet coupling 32 is rotated by the operation of the motor 31, the outer-body-side magnet coupling 33 is rotationally driven by the motor-side magnet-coupling 32, and the outer-body-side magnet coupling 33 is interposed. Thus, the outer body 28 is rotated around the axis.

  By the way, an inner cylinder 34 is disposed in the outer cylinder 28 concentrically with the outer cylinder 28. A key 28 a extending in the axial direction is provided on the inner surface of the outer cylinder 28. The key 28 a is engaged with a key groove on the outer surface of the inner cylinder 34, and the inner cylinder 34 is rotated by the rotation of the outer cylinder 28. In addition, the inner cylinder 34 is movable up and down with respect to the outer cylinder 28. A roller nut 35 is disposed on the inner cylinder 34 such that the roller nut 35 can only move up and down to some extent. The roller nut 35 is urged downward by a spring 36 provided between the roller nut 35 and the inner cylinder 34. Has been. The drive shaft 21 that can move only in the vertical direction is screwed onto the roller nut 35, and when the inner cylinder 34 rotates through the outer cylinder 28, the inner cylinder 34 rotates through the roller nut 35. Thus, the drive shaft 21 moves up and down. Thus, by changing the rotation direction of the motor 31, the rotation directions of the outer cylinder 28, the inner cylinder 34, and the roller nut 35 are also changed, and the vertical movement direction of the drive shaft 21 can be changed.

  An outer cylinder side magnet 37 is provided on the upper part of the outer cylinder 28, an inner cylinder side magnet 38 is provided on the upper part of the inner cylinder 34, and a coil 39 is mounted on the outer periphery of the housing upper lid 27. When the coil 39 is energized, the inner trunk side magnet 38 is attracted to the outer trunk side magnet 37, and when the coil 39 is deenergized, the inner trunk side magnet 38 is attracted to the outer trunk side magnet 37. The inner cylinder 34 falls together with the drive shaft 21 and the control rod 25 so that a scram operation can be performed.

By the way, the drive shaft 21 is provided with a contact plate 40. During the scram operation, the contact plate 40 collides with a damper 41 provided at the lower portion of the housing 26 to absorb the load at the time of the scrum. be able to. Further, the load applied to the roller nut 35 is absorbed by the spring 36 provided between the inner cylinder 34 and the roller nut 35 during scram.
3 is a position detector that is inserted into the drive shaft 21 and the extension shaft 23 to detect the position of the control rod 25.

  Therefore, in order to raise and lower (pull out and insert) the control rod 25 to adjust the reactivity during normal operation, the coil 39 is energized while the outer trunk side magnet 37 and the inner trunk side magnet 38 are in contact with each other. The motor 31 is rotated in a state where the inner trunk side magnet 38 is attracted to the outer trunk side magnet 37. The rotation of the motor 31 is transmitted to the outer cylinder 28 via the housing upper lid 27 by the motor side magnet coupling 32 and the outer cylinder side magnet coupling 33, and the rotation of the outer cylinder 28 is transmitted to the inner cylinder 34 via the key 28a. The inner cylinder 34 rotates in the same phase as the outer cylinder 28. The roller nut 35 is also rotated by the rotation of the inner cylinder 34, the drive shaft 21 screwed into the roller nut 35 is raised or lowered, and the control rod 25 is pulled out and inserted.

  When the control rod 25 is scrammed, if the coil 39 is de-energized, the outer cylinder side magnet 37 and the inner cylinder side magnet 38 are not attracted to each other, and the inner cylinder 34 extends along the key 28 a of the outer cylinder 28. Fall. Since the roller nut 35 provided on the inner cylinder 34 is engaged with the drive shaft 21 via the threaded portion, the inner cylinder 34, the drive shaft 21, the extension shaft 23, and the control rod 25 are integrally free to move downward in the vertical direction. Fall. The free-falling control rod 25 falls between the bundle-in baskets 11 to complete the scrum.

  At the time of the above scram, impact is absorbed by the contact plate 40 attached to the drive shaft 21 colliding with the damper 41, and the impact load at the time of dropping is supported by the reactor pressure vessel upper end plate 19 through the housing 26. The

  After the scram of the control rod 25, the motor 31 is rotated in a direction in which the drive shaft 21, the extension shaft 23, and the control rod 25 move downward. At this time, the drive shaft 21, the extension shaft 23, and the control rod 25 are supported on the core support plate 14 after scramming and are restricted from moving vertically downward. The inner cylinder 34 is raised along the key 28a relative to the control rod 25. After the inner cylinder 34 is raised until the inner cylinder side magnet 38 attached to the inner cylinder 34 contacts the outer cylinder side magnet 37 in this way, the coil 39 is energized, whereby the outer cylinder side magnet 37 is energized. The inner cylinder side magnet 38 is attracted and the inner cylinder 34 is held against the outer cylinder 28. Thereafter, by rotating the motor 31 in the direction in which the drive shaft 21, the extension shaft 23 and the control rod 25 are raised, the control rod 25, the extension shaft 23 and the drive shaft 21 are raised, and the control rod 25 is moved with respect to the core 13. Withdrawn, normal operation is possible.

  The position of the control rod 25 is detected by a position detector 42 installed in the drive shaft 21. That is, since the movement of the control rod 25 is transmitted to the drive shaft 21 through the extension shaft 23, the position of the control rod 25 can be confirmed by detecting the position of the drive shaft 21 by the position detector 42.

  Moreover, when removing the control-rod drive mechanism 20, it carries out in the following procedures. That is, after the position detector 42 installed at the center of the drive shaft 21 is removed, a jig is inserted into the center hole of the drive shaft 21 to separate the gripper 22 between the drive shaft 21 and the extension shaft 23. Therefore, the jig is pulled up, and the driving shaft 21 and the inner cylinder 34 are pulled up to the uppermost part to fix the jig. Thereafter, the housing upper lid 27 is removed, and the housing 26 is taken out of the reactor pressure vessel 10 together with the outer cylinder 28 and the inner cylinder 34.

  By the way, although the thing which installed the damper 41 in the housing 26 was shown in the said embodiment, a damper can also be installed in the core support plate 14 and the load at the time of a scram can also be absorbed. In addition, by making the key 28a machined on the inner surface of the outer body 28 into a spiral shape, the dropping speed of the control rod 25 during scram can be adjusted.

The figure which shows an example of the reactor internal structure used as the application object of the control-rod drive mechanism of this invention. The whole figure for demonstrating the control-rod drive mechanism of this invention. The longitudinal cross-sectional view of a control-rod drive mechanism. AA sectional drawing of FIG. 1 is a schematic configuration diagram of a conventional boiling water reactor.

Explanation of symbols

10 reactor pressure vessel 11 bundle-in basket 12 fuel assembly 13 core 14 core support plate 15 shroud 16 upper lattice plate 17 shroud head 18 control rod guide tube 19 reactor pressure vessel upper end plate 20 control rod drive mechanism 21 drive shaft 22, 24 Gripper 23 Extension shaft 25 Control rod 26 Housing 27 Housing upper cover 28 Outer cylinder 29, 30 Bearing 31 Motor 32 Motor side magnet coupling 33 Outer cylinder side magnet coupling 34 Inner cylinder 35 Roller nut 36 Spring 37 Outer cylinder magnet 38 Inside Body side magnet 39 Coil 40 Bump plate 41 Damper 42 Position detector

Claims (7)

  In the control rod drive mechanism in which the control rod is inserted into the core in the reactor pressure vessel from the top to the bottom and the pulling operation is performed from the bottom to the top, the reactor pressure vessel upper end plate which is the pressure boundary , A drive shaft having a control rod connected to the lower end and threaded on the outer periphery, a roller nut screwed to the drive shaft, and a motor-side magnet cup provided on the motor side A ring, and an outer trunk side magnet coupling that is arranged concentrically with the motor side magnet coupling and transmits a rotational force to the roller nut. The motor side magnet coupling and the outer trunk side magnet are provided by the motor. A control rod characterized in that the roller nut is rotated via a coupling and the control rod is moved up and down via the drive shaft. Dynamic mechanism.   An outer cylinder provided with the outer cylinder side magnet coupling is rotatably provided in a housing disposed so as to penetrate the reactor pressure vessel upper end plate, and is rotated by the outer cylinder in the outer cylinder. The control rod drive mechanism according to claim 1, wherein an inner cylinder movable in the vertical direction with respect to the outer cylinder is disposed, and the roller nut is mounted on the inner cylinder.   An outer cylinder side magnet is provided at the upper part of the outer cylinder, an inner cylinder side magnet is provided at the upper part of the inner cylinder, and the coil disposed on the outer periphery of the outer cylinder is energized, thereby Attach to the outer cylinder side magnet and turn off the power to the coil to eliminate the attractive force of the inner cylinder side magnet to the outer cylinder side magnet so that the inner cylinder falls with the drive shaft and control rod. The control rod drive mechanism according to claim 2, wherein:   4. The control rod drive mechanism according to claim 3, wherein the coil is mounted on the outer periphery of a housing upper lid that covers the upper outer periphery of the outer body.   A damper is installed at a lower end portion in the housing, and a contact plate is attached to the drive shaft, so that the contact plate collides with the damper during a scram operation, and the impact is absorbed. The control rod drive mechanism according to any one of claims 2 to 4.   6. The control rod according to claim 1, wherein an extension shaft is connected to the drive shaft via a gripper, and a control rod is further connected to the extension shaft via a gripper. Drive mechanism.   The spring according to claim 1, wherein a spring for biasing the roller nut downward and absorbing a load applied to the roller nut during scram is interposed between the roller nut and the inner cylinder. The control rod drive mechanism according to any one of the above.

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