JPS6118709B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a control rod drive mechanism in which a holding mechanism for detachably supporting an extension rod and below is provided in a drive part, and in particular, an erroneous scram prevention device for preventing detachment of the holding mechanism. The invention relates to the control rod drive mechanism provided.

Conventionally, in this type of control rod drive mechanism, an electromagnet alone or a combination of an electromagnet and a link mechanism are used to connect and disconnect the extension rod, and when the electromagnet is demagnetized, the extension rod and the extension rod are connected. The control rod connected to the machine falls rapidly. When using a rotating plug as a fuel exchange method for a nuclear reactor, when the rotating plug rotates, it is necessary to separate the extension rod from the control rod and then pull up and hold only the extension rod. A window on the side of the drive unit was opened and a breakaway prevention jig was installed to prevent the extension rod from falling and damaging the core components even if the extension rod protection mechanism became detached due to a loss accident or vibration. With this conventional method, it is extremely difficult to work from the side of the drive units that are lined up in the upper part of the narrow furnace, and some of them cannot be installed in the center. Furthermore, opening the window destroys the pressure boundary, and it takes a lot of time to restore the pressure boundary, such as by replacing the gas inside the drive unit. In addition, with the conventional method, the fall prevention device can only be installed when the control rod is stopped at a specific position, and the scram shock absorber does not work during adjustment tests in the air or gas atmosphere before operation. Even when checking the operation in a combined state, there is a risk of erroneous scramming and damage to the equipment.

SUMMARY OF THE INVENTION An object of the present invention has been made in view of the above-mentioned points, and by providing the extension rod holding mechanism with a remote-controlled accidental scram prevention mechanism that prevents the extension rod from being separated, the extension rod holding mechanism can be removed during fuel exchange, etc. The purpose of this is to lock the extension rod and prevent it from falling and damaging core components.

Hereinafter, the present invention will be explained in detail with reference to the drawings of one embodiment.

The control rod drive mechanism includes a drive section 1 as shown in FIG.
and a lower mechanism 2, and several of them are implanted in the upper lid 3 of the reactor vessel. Of these, the drive unit 1 has an elongated cylindrical housing 4 that stands up on the upper lid 3, and a drive motor 5 is housed in the top of the housing 4. The output shaft of the drive motor 5 is supported by a ball bearing 6 and connected to a lead screw 7.
extends vertically downward, and its lower end is inserted into the finger support cylinder 8.

On the other hand, a screw nut 9 is screwed onto the lead screw 7.
An electromagnet 21 is integrally attached to the. The electromagnet 21 is moved up and down by the rotation of the drive motor 5, and the up and down movement of the electromagnet 21 is caused by the engagement of the guide protrusion of the screw nut 9 with the guide groove on the inner circumferential wall of the housing 4. Guided without rotation.

The armature 22 is placed on the upper end of the finger support cylinder 8, while the lower end of the finger support cylinder 8 grips the outer extension rod 12 and the inner extension rod 13 via a latch mechanism 10. There is. The electromagnet 21 has an electromagnet 2
A scram lock bolt 23 for screwing together the drive unit 1 and the armature 22 is attached, and is rotated by an operating rod 24 inserted from the upper end of the drive unit 1 and a handle 25.

Further, the lower mechanism 2 has a guide tube 11 that is inserted into the upper cover 3 of the reactor vessel and hangs down from the upper cover into the reactor vessel, and the upper end flange of the guide tube 11 is fitted into the housing 4. are doing. Said guide tube 11
incorporates an outer extension rod 12 and an inner extension rod 13 so as to be vertically slidable. A pair of clippers 14 is swingably supported at the lower end of the outer extension rod 12, and the clippers 14 fixedly support a control rod 15 inserted into the reactor core. Note that bellows 16 and 17 are interposed between the guide tube 11 and the outer extension rod 12 and between the extension rods 12 and 13, respectively, to prevent radioactive gas or steam from inside the housing 4. This prevents leakage.

2 and 3 are detailed views of the device for preventing erroneous scrams. When the scram lock bolt 23 is not screwed into the armature 22, the coil spring 26 that works to push up the scram lock bolt 23 is connected to the electromagnet 21. Scram lock bolt 2
Further, limit switches 27a and 27b are provided for determining whether or not the scram lock bolt 23 is screwed together.

Next, the operation of the control rod drive mechanism will be described.

During normal operation, the electromagnet 21 is energized with the scram lock bolt 23 unscrewed during a shim operation to adjust the reactivity of the reactor. As shown in FIG. 1, the rotational movement of the drive motor 5 is converted into the vertical movement of the electromagnet 21 by the lead screw 7, and furthermore, the vertical movement of the electromagnet 21 is converted into the vertical movement of the electromagnet 21 by the armature 22 and the finger support cylinder 8. , the latch mechanism 10, and the outer extension rod 12 to the control rod 15, causing the control rod 15 to move up and down. The shim operation is performed in this manner.

Further, during scram, the electromagnet 21 is demagnetized. By demagnetizing the electromagnet 21, the armature 22 is separated from the electromagnet 21, and the finger support cylinder 8 and both extension rods 1 are thereby separated.
2, 13 and the control rod 15 are dropped together,
A scrum operation is performed.

If there is a risk of equipment damage due to scram operation, such as when replacing fuel, operate the accidental scram prevention device using the following procedure. In other words, the drive motor 5
is rotated to lower the movable parts such as the extension rod 12 and control rod 15 to the full insertion position (lower limit). Although the erroneous scram prevention device can be operated at any position in the vertical drive, it is operated at the full insertion position to ensure greater safety in consideration of the possibility of the device falling due to operation of the erroneous scram prevention device at an intermediate position. Next, the operating rod 24 is lowered and its tip is inserted into the square hole in the head of the scram lock bolt 23. Furthermore, by attaching a special handle 25 to the upper end of the operating rod 24 and rotating it, the scram lock bolt 23 is screwed into the armature 22 via the operating rod 24, and the electromagnet 21 and the armature 22 are mechanically connected. The operation of the false scram prevention device ends. Further, whether or not the scram lock bolt 23 is completely screwed in is determined by the operation of the limit switch 27 for scram lock detection. After the operation is completed, the operating rod 24 is pulled up and placed so that it does not interfere with the operation of the electromagnet 21 and below. The erroneous scram prevention device is released by the reverse procedure to the above, and the determination is made by the operation of the scram unlock detection limit switch 27b.

The above is one example to explain the present invention,
It is possible to modify the embodiments described above without departing from the spirit of the invention. Instead of the threaded part of the scram lock bolt 23, the tip of the scram lock bolt 23 is made T-shaped as shown in FIG. 4, and is inserted into the U-shaped groove of the armature 22, so that the armature 22 and below can fall during a scram. When locking to prevent accidental scrams, use the scram locking rod 31.
The T-shaped upper surface of the armature 22 is pushed in with the operation rod 24 until it reaches the lower surface of the armature 22, and then rotated 90 degrees. By pulling up the operating rod 24 in this state, the scram lock rod 31 is pushed upward by the spring 26, and the groove on the lower surface of the armature 22 engages with the T-shaped portion of the scram lock rod 31, so that the rotation of the scram lock rod 31 is fixed and the electromagnet 21
Then, the armature 22 becomes mechanically locked, and a similar effect can be obtained. Further, in FIG. 5, the scram lock rod 31 is operated by rotating it by a dedicated small motor 35 through the sprockets 32, 33 and the chain 34, which results in remote automatic operation. In this case, the operating rod 24 is attached so that even if the small motor 35 breaks down, it can be restored by manual operation.

As explained above, according to the present invention, the control rod drive mechanism is remotely controlled by the operating rod attached to the top of the control rod drive mechanism, so there is no need to lift or disassemble many control rod drive mechanisms, and sufficient work space can be secured. Significant effects can be achieved such as shortening work time, reducing radiation exposure for workers, and improving plant operation rates. Since the operation method is performed manually, there is no risk of failure and it is reliable compared to using a motor or the like. In addition, since the scram lock state occurs at any position in the drive stroke, it is useful not only for driving during refueling, but also when the scram buffer does not work, such as during adjustment tests in the atmosphere or Ar gas before operation, and during maintenance. It can be driven without fear of erroneous scram even during work. Furthermore, the structure is simple, and the height and outer diameter of the control rod drive mechanism can be made compact.

[Brief explanation of the drawing]

FIG. 1 is a longitudinal sectional view showing an embodiment of the control rod drive mechanism of the present invention, FIG. 2 a is a longitudinal sectional view showing the erroneous scram prevention device of FIG. FIG. 3 is a vertical cross-sectional view showing when the lock mechanism in FIG. 2 is released, and FIG. 4 is an explanatory view showing another embodiment of the lock mechanism in FIG. b is a bottom view of a, c is a longitudinal sectional view showing the state after the lock mechanism is activated, and FIG. 5 is a longitudinal sectional view showing another embodiment of FIG. 5... Drive motor, 12... Outer extension rod, 13... Inner extension rod, 22... Armature, 23... Scram lock bolt, 26... Spring, 27a, 27
b...Limit switch, 31...Scrum lock rod, 32, 33...Sprocket, 34...Chain.

Claims (1)

[Claims] 1. A motor fixed to the upper part of the cylindrical housing, a lead screw connected to the lower part of the motor, a screw nut screwed to the lead screw, and a screw nut fixed to the lower part of the screw nut. A control rod drive consisting of an electromagnet, an armature installed at the bottom of the electromagnet so that it can be connected by attraction by the magnetic force of the electromagnet, and a control rod detachably attached to the bottom of the armature via an extension rod. The control rod drive mechanism includes a scram lock bolt that mechanically connects the electromagnet and the armature, the head of the scram lock bolt being rotatable from directly above by an operating rod.