JPH0221554B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION (1) Technical Field of the Invention The present invention provides a holding mechanism in which an extension tube and a control rod can be attached and detached within a drive unit, and this holding mechanism is connected to a drive motor and a control rod through a screw shaft, a nut, etc. This is related to the mechanically driven control rod drive mechanism that moves up and down and stops at the required position using the brake. Especially when it is necessary to stop at a predetermined position such as when changing fuel, the extension beyond the holding mechanism may occur due to a failure of the brake, etc. The present invention relates to a control rod drive mechanism characterized by being provided with a device (lock mechanism) for preventing accidental falling (slipping) of the pipe portion and control rod.

(2) Prior art 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 tube sections (inner and outer extension tube partners or inner extension tube alone) (scram operation). When the electromagnet is demagnetized, the extension tube (inner extension tube alone or partner) and the control rod rapidly descend. On the other hand, the gripping operation of the control rods after the scram operation, as well as the startup and output operation of the reactor after gripping the control rods, are performed by the drive motor through the extension tube holding mechanism in the drive unit, screw shaft nut, etc. Then, at the required position, the motor is stopped, and at the same time, the brake in the drive unit locks the motor rotation shaft and stops the motor. When using a rotary plug as a fuel exchange method for a nuclear reactor, the extension tube section and control rod are separated when the rotary plug rotates, and then the extension tube section is pulled upward by the drive motor and brake via the above-mentioned holding mechanism, etc. , stop and hold the rotating plug in a position that does not interfere with its rotation.

The brakes of this type of control rod drive mechanism are normally of the de-energized type (the brake operates when the power is cut off, in case of a power loss accident, etc.). , it is opened by an electromagnet etc. built into the brake, but when the power is cut off, the electromagnet demagnetizes,
The brake shoe closes and locks the motor's rotating shaft. ), and is structured to be locked by the brake when the drive motor stops. Therefore, the brake has sufficient capacity to stop the inertial rotational force due to the weight of the holding mechanism, extension tube, etc., which is a movable weight less than that of the motor.

However, in the unlikely event that a failure occurs in the brake mechanism, etc., and sufficient locking action is no longer possible, the weight of the moving parts such as the holding mechanism and extension tube may
The screw shaft rotates, and the holding mechanism and extension pipe part fall under their own weight. (Slips down due to rotation of the screw shaft) In such a situation, if the reactor is operating, the control rod will be inserted into the core as the extension tube slides down, and will be buffered by the buffer installed in the guide tube and stopped. do. Therefore, damage to the equipment can be prevented, but if it is in output operation, it may cause an abnormal stop. On the other hand, during refueling, since the control rods and extension tubes are separated, there is a possibility that the falling extension tubes may collide with the control rods or nearby core components, causing damage. be. Similarly, if the brake fails in the adjustment test equipment in the air or gas atmosphere before operation and installation, there is a risk that the extension pipe may fall accidentally, causing damage to the equipment.

(3) Purpose of the Invention The purpose of the present invention has been made to address the above-mentioned problems, and is to provide a remote-type accidental drop prevention method that prevents the extension pipe from accidentally falling due to brake failure during fuel exchange, etc. A device is installed (manual operation is possible if necessary) to prevent damage to core components or test equipment due to accidental falling (slipping) of the extension tube.

(4) Structure of the Invention 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 a plurality of them are installed in the upper lid 3 of the reactor vessel. Of these, the drive unit 1 is
It has an elongated cylindrical housing 4 that stands upright, and a drive motor 5 is mounted at the top of the housing 4.
a and a brake 5b are housed. The output shaft 6 of the drive motor 5a is supported by a ball bearing 7, passes through a seal flange portion 8, and is connected to a lead screw 9. The lead screw 9 extends vertically downward, and its lower end is inserted into the magnetic case 10. It has been inserted. On the other hand, a screw nut 11 is screwed into the lead screw 9, and a load cell mounting plate 12, a load cell 13, a magnetic case 10, an electromagnet 14, etc. are integrally attached to the screw nut 11. The electromagnet 14 is integrated with the load cell mounting plate 12, etc., and is moved up and down by the rotation of the drive motor 5a.
The vertical movement of the screw nut 11 is guided by the guide protrusion of the screw nut 11 engaging with the guide mechanism on the inner circumferential wall of the housing 4 without rotation.

The magnetic case 10 has a load cell mounting plate 12 and a load cell 13 mounted on its upper end, while an inner extension tube 17 is gripped at the inner lower end of the magnetic case 10 via an armature 15 and a ring mechanism 16. Further, at the outer lower end of the magnetic case 10, there is a latch mechanism 18, and a finger support cylinder 19 for opening and closing the latch mechanism.
The outer extension tube 20 is gripped through the outer extension tube 20. The dimensions between the link mechanism 16 that grips the inner extension tube 17 and the latch mechanism that grips the outer extension tube 20 are regulated so that a predetermined dimension can be maintained.
When the link mechanism 16 is closed and the latch mechanism 18 is closed, the gripper 22 for the control rod 21, which will be described later, is sized so that it can grip the control rod, that is, maintain the control rod latched state. Next, when the link mechanism 16 is open and the latch mechanism 18 is closed, the inner extension tube 17 is coaxial with the outer extension tube 20 due to its own weight with respect to the outer extension tube 20 held by the latch mechanism 18. It descends several tens of mm inside the tube and is gripped by the outer extension tube 20 and stopped. In this state, the gripper 22 is in a state where it releases the control rod 21, that is, the control rod is in a delatched state. Note that the link mechanism 16 is opened by demagnetizing the electromagnet 14.

Further, the lower mechanism 2 has a guide tube 23 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 23 is fitted into the housing 4. are doing. Said guide tube 23
The outer extension tube 20 and the inner extension tube 17 are assembled so as to be slidable in the vertical direction. The above outer extension tube 20
A pair of grippers 22 are swingably supported at the lower end of the reactor, and the grippers 22 fixedly support a control rod 21 inserted into the reactor core. Note that there are bellows 24 between the guide tube 23 and the outer extension tube 20, and between both the extension tubes 17 and 20.
25 are interposed, respectively, to prevent radioactive gas or steam from leaking into the housing 4.

FIG. 2 is a detailed view of an extension tube accidental fall prevention device which is an embodiment of the present invention. The device consists of a load cell mounting plate 12 with an elongated hole 26, a T-shaped lockshaft 27, and a lock motor 28 for rotating the lockshaft. There is. The lower end of the T-type lockshaft 27 is T
It is shaped like a mold and has an integrated structure. Also the same T
A chain sprocket 29a is integrally installed in the middle of the mold lockshaft, and is connected via a chain 30 to a sprocket 29b installed integrally on the lock motor 28 side. The chain 30 also has a plurality of idlers 31, one of which has a limit switch operating rod 32 integrally attached to the idler 31 so as to be able to rotate as the chain 30 moves, and within the turning radius of the limit switch operating rod 32. A lock detection limit switch 33a and an unlock detection limit switch 33b are installed.

(5) Effect of the invention During normal operation, during shim operation (up and down movement of control rods) to adjust the reactivity of the reactor, the electromagnet 14 is energized with the extension tube accidental fall prevention device unlocked. I'll keep it. (The state in which the link mechanism 16 is closed and the latch mechanism 18 is closed) As shown in FIG. Further, the vertical movement of the electromagnet 14 etc. is transmitted to the control rod 21 via the armature 15, the link mechanism 16, the latch mechanism 18, and the inner and outer extension tubes 17 and 20. move up and down. The shim operation is performed in this manner. Further, during scram, the electromagnet 14 is demagnetized. Due to the demagnetization of the electromagnet 14, the armature 15 is separated from the electromagnet 14, and the link mechanism 16 is thereby also opened, so that the inner extension tube 17 is lowered relative to the outer extension tube 20, so that the lower end of the extension tube The claws of the gripper 22 are closed to release the control rod 21 and a scram operation is performed.

If the extension tubes 17, 20 accidentally fall during fuel exchange, etc., and there is a risk of damaging equipment, etc., operate the extension tube accidental fall prevention device of the present invention according to the following procedure. The control rod 21 and extension tubes 17, 20 are inserted to the lower end position by the drive motor 5a, and the electromagnet 1
Demagnetize 4. When the electromagnet 14 is demagnetized, the link mechanism 16 opens, and the inner extension tube 17 becomes the outer extension tube 1.
8, the claws of the gripper 22 close, and the connection with the control rod 21 is released.
(Delatched) After this, the drive motor 5a is turned on again.
The extension tubes 17 and 20 are pulled up to the upper end position, and the drive motor 5a is stopped. Drive motor 5
At the same time as the motor shaft a is stopped, the motor shaft is locked by the brake 5b, and the extension tube sections 17 and 20 are stopped at the upper end positions.As a backup of this stop lock, the extension tube accidental fall prevention device is activated.

The latch mechanism 1 holds and suspends the extension pipe parts 17 and 20 when the extension pipe parts 17 and 20 are at the upper end position.
8, Magnetic case 10, Load cell mounting plate 1
The entire second and other holding mechanisms have also moved together to the upper end position.

In this position, the T-shaped lock shaft 27 attached to the seal flange portion 8 is attached to the load cell mounting plate 1.
It is in a state where it is inserted into an elongated hole 26 pre-drilled in 2. Of course T-type lockshaft 2
The orientation of the T-shaped protrusion at the lower end of 7 and the orientation of the elongated hole 26 match. When the locking motor 28 is rotated from this state, the sprocket 29b, which has been decelerated as the motor 28 rotates, gradually begins to rotate. The increased turning angle is transferred to the T-type lockshaft 2 via a chain 30 attached to the sprocket 29b.
7. Limit switch operating rod 32 of idler 31
The limit switch operating rod 32 is transmitted to
contacts the lock detection limit switch 33a. Due to the contact, the locking motor 28 is stopped, and the operation for preventing the extension tube from falling accidentally is completed.

To release the extension pipe accidental fall prevention, follow the procedure in reverse to the above, and the determination is made using the unlock detection limit switch 33 installed at a position approximately 90 degrees back from the lock detection limit switch 33a attachment point.
This is done by operating b. Furthermore, if remote control becomes impossible due to a failure of the locking motor 28, etc., the housing 4
Manual operation is also possible by inserting a manual handle 34 from the top and connecting it to the T-shaped lockshaft 27.

(6) Effects of the Invention As explained above, the present invention has a locking mechanism that maintains a constant distance between the drive motor and the holding mechanism and does not restrict the extension pipe section having the control rod at the lower end. Therefore, even if the brake of the drive motor fails, the holding mechanism and the extension pipe section are prevented from falling.

In addition, the locking mechanism of the present application does not restrain the extension pipe section that has the control rod at the lower end, so if any abnormality occurs in an operating nuclear power plant, the control rod can be removed by demagnetizing the electromagnet at the bottom of the holding mechanism. can be dropped into the reactor core to shut down the reactor.

Furthermore, when a T-shaped lockshaft is used as in the embodiment shown in FIG. , significant effects such as shortening work time, reducing radiation exposure of workers, and improving plant operation rates can be achieved. Of course, it is effective in preventing accidental drops not only during brake backup when changing fuel, but also during adjustment tests and maintenance work in the atmosphere or gas. Furthermore, the structure is simple and has the advantage of being compact without changing the outer diameter, height, etc. of the conventional control rod drive mechanism.

(7) Other Embodiments of the Invention As shown in FIG. 3, there is also a method of locking the output shaft of the drive motor instead of using the T-type lockshaft.

In the configuration shown in FIG. 3, ball screws 34a, 34
Two b and multiple idlers 31 are installed, and none of them can rotate. A lock plate 35 with a polygonal hole in the center is located between the two ball screws 34a, 34b.
It is installed so that it can move up and down according to the rotation of the On the other hand, a polygonal surface 36 having a size slightly larger than the round shaft diameter is formed at the center of the output shaft 6 of the drive motor 5a. By moving the lock plate 35 from the round bar part of the output shaft 6 to the polygonal surface 36 by the rotation of the locking motor 28, the polygonal surface 36 on the lock plate 35 side and the polygonal surface on the output shaft 6 side are engaged, and remote control is performed. This makes it possible to prevent the output shaft 6 and the screw shaft 9 integrally connected from rotating.

Furthermore, in the case of manual operation, a locking plate 37 equivalent to a spanner is fitted into the polygonal output shaft 6 as shown in FIG. 38, it becomes possible to prevent the output shaft 6 and the screw shaft 9 from rotating.
Of course, like the other embodiments, the output shaft 6 is located above the seal flange 8 that constitutes the gas pounder of the control rod drive mechanism drive section, so the pounder will not be damaged during the work.

Furthermore, if the compactness of the drive unit comes at some cost, a reduction mechanism that can be rotated only from the drive motor side between the drive motor and the output shaft 6 (for example, a worm gear, a general gear, a multi-stage gear combination, etc.) By providing this, it is possible to prevent erroneous rotation due to the lower movable weight of the screw shaft 9, separately from the lock mechanism.

[Brief explanation of drawings]

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 extension tube accidental fall prevention device of FIG. Fig. 3a is a longitudinal sectional view showing another embodiment of Fig. 2a, Fig. 3b is a transverse sectional view thereof; FIG. 4 is a longitudinal sectional view showing another embodiment of FIG. 2a. 5a... Drive motor, 9... Screw shaft, 17... Inner extension tube, 20... Outer extension tube, 27... T-type lockshaft, 35... Lock plate.

Claims (1)

[Claims] 1. A drive motor installed outside the reactor vessel, a screw shaft rotated by the drive motor, a nut screwed into the screw shaft, and an electromagnet fixed to the nut at the bottom. A control rod comprising a holding mechanism, an extension tube section provided at the bottom of the holding mechanism and connected and separated by energization and de-energization of an electromagnet, and a control rod detachably provided at the lower end of the extension tube section. A control rod drive mechanism characterized in that the rod drive mechanism is provided with a locking mechanism that maintains a constant distance between the drive motor and the holding mechanism and does not restrict the extension pipe portion. 2. The control rod drive mechanism according to claim 1, wherein the locking mechanism is a T-type lockshaft mechanism that locks the vertical movement of the holding mechanism. 3. The control rod drive mechanism according to claim 1, wherein the lock mechanism is a lock plate mechanism that prevents rotation of the screw shaft.