JPH0341393A - Detecting device for coupling of control rod - Google Patents

Abstract

PURPOSE:To enable a highly accurate detection of a coupling condition of control rods by moving a control rod drive mechanism of a BWR, at a very little distance. CONSTITUTION:At an inside surface of a hollow piston 18 which moves up- and downwardly along a roller 16 provided at an inside surface of a guide tube 8, and at an inside surface of a nut 15, a screw axis 14 is provided. This screw axis 14 has a hollow part 35, into which a coil 36 is inserted and a cable 37 led out from the coil 36, is connected to a signal processing unit 38. In case that an incompletely uncoupled control rod drive mechanism is withdrawn, the piston 18 does not move and the screw axis 14 moves downwardly and therefore a relative movement occurs between the piston 18 and the screw axis 14. By the relative movement between a magnet 39 provided to the piston 18 and the coil 36 provided to the screw axis 14, an electromotive current flows through the coil 36 and the current is detected by the device 38. When the electromotive current flows, an incompletely uncoupled condition is displayed and when the electromotive current does not flow, a completely uncoupled condition is displayed.

Description

DETAILED DESCRIPTION OF THE INVENTION [Object of the Invention] (Industrial Application Field) The present invention relates to a control rod coupling detection device used in a boiling water nuclear reactor or the like.

(Prior Art) Generally, in a boiling water nuclear reactor, the output of the reactor is controlled by inserting and removing the control rods into and from the reactor core using a control rod drive mechanism provided at the lower part of the reactor pressure vessel.

That is, as shown in FIG. 2, a large number of control rod drive mechanisms 2 are provided at the bottom of the boiling water reactor pressure vessel 1, and the control rods 3 connected to the top of the control rod drive mechanisms 2 are guided into the reactor core 4. It was being inserted or withdrawn.

FIG. 3 shows a longitudinal section of this conventional control rod drive mechanism 2. As shown in FIG. Reactor pressure vessel 1 only partially shown in the figure
A long control rod drive mechanism housing 5 passes through and is fixed to the lower end of the rod.

The control rod drive mechanism 2 is fixed to the control rod drive mechanism housing 5 by a mounting port 6, and an outer tube 7 and a guide tube 8 are provided inside the housing 5.
are arranged concentrically and fixed in order. An electric motor 10 is attached to the lower end of the outer tube 7 via a spool piece 8a and a motor bracket 9. This electric motor 10 drives the control rod 3 to be inserted and removed, and the rotation of the rotation start shaft 11 is transmitted to the rotation transmission shaft 13 via the gear device I2. The upper end of this rotation transmission shaft 13 is coupled to a screw shaft 14 through a keyed groove. This screw shaft 14 is formed in a length that reaches from the lower end to the upper end of the control rod drive mechanism housing 5, and a nut 15 is screwed onto this screw shaft 14. This nut 15 is prevented from rotating by engaging a roller 16 attached to its outer periphery with a groove 17 cut into the inner surface of the guide tube 8, and is raised or machined by forward and reverse rotation of the screw shaft 14. On top of the nut 15, a long hollow piston □18, which is placed over the outside of the screw shaft 14, is placed so as to be able to approach and separate.

This hollow piston 18 has a coupling spud 1 at the upper end which connects the control rod 3 when the nut 15 is in its lowest position.
9 is formed to have a length that just protrudes into the reactor pressure vessel 1. The hollow piston 18 is prevented from rotating by engaging a roller 16 attached to its lower end with a groove 17, and is further engaged with a window (not shown) formed in the guide tube 8 to prevent the hollow piston 18 from falling. Latch 20 to prevent
is provided.

Inside the control rod drive mechanism housing 5 are its lower flange,
Water (purge water) is always filled through the inlet 21 provided in the outer tube 7 and guide tube 8 in this order, and this water passes through the gap between the hollow piston 18 and the labyrinth seal 22 and enters the reactor pressure vessel 1. is flowing inside.

Normal insertion and withdrawal of control rods by the control rod drive mechanism 2 formed in this manner is performed as follows.

That is, by rotating the electric motor 10 in the forward and reverse directions, the screw shaft 14 is rotated in the forward and reverse directions, and the nut 15 is raised or lowered. Then, the hollow piston 18 placed on the nut 15 by its own weight moves up and down together, and the control rod connected to the upper end of the hollow piston 18 via the coupling spud 19 is inserted into the reactor core 4. Being pulled out.

On the other hand, when rapid insertion of a control rod is required, high-pressure water is supplied from the inlet 21 to the lower part of the hollow piston 18 in the control rod drive mechanism housing 5, and the hollow piston 18, which is only resting on the nut 15 by its own weight, is The piston 18 separates from the nut 15 and moves rapidly upward, rapidly inserting the control rod into the reactor core 4. The lower end of the latch 20 then engages the lower edge of a window (not shown) to prevent the hollow piston 18 from lowering.

After that, when the hollow piston 18 is lowered again by the electric motor 10, the screw shaft 14 is rotated in the insertion direction, and the nut 15 and the hollow piston 18 are brought into contact with each other, thereby returning the latch 20 inward and securing it to the window. is loosened, and then the screw shaft 14 is rotated in the drawing direction to lower the hollow piston 18.

At the end of the rapid insertion of the control rod 3, the heated hollow piston 18 and the control rod 3 must be damped.

For this reason, the control rod drive mechanism 2 is provided with a disc spring 23 above as a buffer mechanism. The heated hollow piston 18 collides with the throttle 24, and the throttle 24 compresses the disc spring 23, resulting in deceleration.

Thereafter, the latch 20 of the hollow piston 18 as described above.
engages with the lower edge of the window (not shown) to prevent the hollow piston 18 from descending, but for the sake of reactor operation management, it monitors whether the hollow piston 18 and the control rods 3 are inserted into the reactor core. There is a need.

By the way, during periodic inspections, the control rod drive mechanism 2 having the above configuration is removed and reinstalled.

The control rod drive mechanism 2 first connects the electric motor 10 to the rotation transmission shaft 1.
3 and then the spool piece 8 with the disc 29 installed.
Remove a. Finally, the bayonet coupling between the four fingers 30 provided at the tip of the hollow piston 18 and the socket 31 provided on the control rod 3 shown in FIGS. 4 and 5 is connected by rotating the hollow piston 18 450 times. The control rod drive mechanism 2 is removed from the housing 5 in an uncoupled state.

The coupling spud 19 shown in FIGS. 4 and 5 is constructed as follows. That is, the hollow piston 1 is placed in the socket 31 provided at the bottom of the control rod 3.
The four fingers 30 provided at the tip of 8 are inserted and joined together. Four protrusions 32 are provided at equal intervals on the inner surface of the socket 31, and each protrusion 32 has a recess 34 into which a bulge 33 provided on the outer surface of the finger 30 is inserted. When the bulge 33 of the finger 30 is inserted into the recess 34 of the protrusion 32 in the socket 31, the joint is established, and the 45
When the bulging portion 33 is removed from the recess 34 by rotation, the coupling is released and an uncoupled state is established.

All of these operations are performed remotely by an operator operating push buttons on the control panel from a control room.

(Problems to be Solved by the Invention) When the control rod drive mechanism 2 is removed from the inside of the housing 5 during periodic inspection, when the control rod drive mechanism is moved from a coupled state to an uncoupled state,
If uncoupling becomes incomplete for some reason, the hollow piston 18 will be attached to the control rod 3, and the control rod drive mechanism 2 will not be able to be removed from the housing 5. Further, when the control rod drive mechanism 2 is pulled out while attached to the control rod 3, the hollow piston 18 and the nut 15 are separated, and when the control rod drive mechanism 2 is pulled out considerably, an uncoupled state occurs due to vibrations or the like. In this case, the hollow piston 18 will fall, and a large impact load will be applied to the nut 15 that supports the hollow piston 18, potentially damaging the nut 15.

Therefore, it is necessary to confirm that the hollow piston 18 and the control rod 3 are completely uncoupled.

When the conventional control rod drive mechanism 2 is removed, a load meter is attached to a handling device (not shown) and the uncoupled state is detected by monitoring whether the weight of the hollow piston decreases in the uncoupled state.

However, since the value of the load meter fluctuates greatly, there is a problem in that it is difficult to detect the weight of the hollow piston 18.

The present invention has been made in order to solve the above-mentioned problems, and is a control rod that can detect the uncoupled state of the piston and control rod by simply moving the control rod drive mechanism slightly. An object of the present invention is to provide a coupling detection device.

[Structure of the Invention] (Means for Solving the Problems) The present invention is characterized in that a screw shaft provided in a housing moves up and down by the rotation of an electric motor, and a hollow piston connecting a control rod is driven by the screw shaft. An outer tube, a guide tube, and the hollow piston are arranged concentrically within the housing, and a throttle and stop piston are inserted between the hollow piston and the outer tube, and the control rods are inserted into and removed from the reactor core to operate the reactor. It consists of a control rod drive mechanism configured to control output, a magnet is provided at the lower end of the hollow piston, a coil is provided in the screw shaft, and a signal processing device is provided to measure the electromotive current of the coil. It is characterized by becoming.

(Function) If uncoupling is incomplete and the control rod drive mechanism is pulled out, the hollow piston does not move and the screw shaft moves downward, causing relative movement between the hollow piston and the screw shaft. An electromotive current flows through the coil due to the relative movement between the magnet provided on the hollow piston and the coil provided on the screw shaft.

This electromotive current is detected by a signal processing device. When an electromotive current flows, an incomplete reciprocal coupling state is displayed, and when no electromotive current flows, a complete uncoupling state is displayed.

(Embodiment) An embodiment of the control rod latch mechanism detection device according to the present invention will be described with reference to FIG.

Note that FIG. 1 shows only the main parts of the present invention, and the same parts as in FIG. 3 are designated by the same reference numerals, and the explanation of the overlapping parts will be omitted.

In the first drawing, a hollow piston 18 that moves up and down along a roller 16 provided on the inner surface of a guide tube 8 and a screw shaft 14 are provided on the inner surface of a nut 15. This screw shaft 14 has a hollow portion 35, into which a coil 36 is inserted. A cable 37 led out from this coil 36 is connected to a signal processing device 380. Further, a magnet 39 is provided within the lower end portion of the hollow piston 18 . A cable 37 is provided inside the wrench device 40 provided at the lower end of the guide tube 8.
A fixing member 41 is provided to support the. Screw shaft 14
A connecting member 42 is connected to the lower end of.

Here, when pulling out the control rod drive device, remove the electric motor 10 and spool piece 8a shown in FIG. Insert into the hollow part 35 of the screw shaft 14.

When pulling out the control rod drive device, if the coupling spud 19 and control rod are incompletely uncoupled, the wrench device 40. Guide tube8. A screw shaft 14 fixed to the connecting member 42. Natsu 15. A fixing member 41 attached to the wrench device 40. The col 36 attached to the fixed member 41 is pulled out downward, but only the hollow piston 18 remains without being pulled out. In this case, a relative movement occurs between the coil 36 and the hollow piston 18, and the hollow piston 1
A current is generated in the coil 36 by the relative movement of the coil 36 and the magnet 391 embedded in the coil 36. This current is measured by the signal processing device 38, the uncoupling state is displayed, and an alarm is generated.

Therefore, the uncoupling state can be detected by only moving the control rod drive mechanism 2 by a small amount, thereby improving the reliability of the operation and eliminating problems such as damage to the nut 15.

[Effects of the Invention] According to the present invention, it is possible to detect the control rod and the coupling state with high precision, and it is possible to immediately take countermeasures against the uncoupling state, thereby improving work efficiency and improving the reliability of handling work. This contributes to improving performance and preventing equipment damage.

[Brief explanation of drawings]

FIG. 1 is a vertical cross-sectional view partially showing essential parts of an embodiment of the control rod coupling detection device according to the present invention, FIG. 2 is a partial cross-sectional view of a conventional boiling water reactor, and FIG. The figure is a schematic sectional view of a conventional control rod drive mechanism, Figure 4 is a longitudinal sectional view showing the control rod coupling in Figure 3, and Figure 5 is a cross-sectional view taken along A in Figure 4. It is a front view. A line 1...Reactor pressure vessel 2...Control rod drive mechanism 3...Control rod 4...Reactor core 5...Control rod drive housing 6...Mounting bolt 7...Outer tube 8...Guide tube 8a...Spool piece 9...Motor bracket 0...Electric motor 1...Rotation starting shaft 2...Gear device 3...Rotation transmission shaft 4...Screw shaft 5 ... Nut 6 ... Roller 3 17 ... Groove 18 ... Hollow piston 19 ... Coupling spud 20 ... Latch 21 ... Inlet 22 ... Labyrinth seal 23 ... Disc Spring 24... Throttle z5... Stop piston 26... Control rod guide tube base 27... Outer tube upper guide 28... Coil spring 29... Disc 30... Finger 31... Socket 32...Protrusion 33...Multiple portion 34...Indentation 35...Hollow portion 36...Coil 4 37...Cable 38...Signal processing device 39...Magnet 40... Wrench device 41...Fixing member 42...Connecting member (8733) Agent: Patent attorney Yoshiaki Inomata (and others)
1 person) 5

Claims (1)

[Claims] The rotation of the electric motor causes a screw shaft provided in the housing to move up and down, and this screw shaft drives a hollow piston that connects the control rod, so that an outer tube, a guide tube, and the hollow piston are arranged concentrically within the housing. a control rod drive mechanism configured to have a throttle and a stop piston inserted between the hollow piston and the outer tube, and to control the output of the reactor by inserting and removing the control rod into the reactor core; A coupling detection device for a control rod, characterized in that a magnet is provided at the lower end of the hollow piston, a coil is provided in the screw shaft, and a signal processing device is provided to measure the electromotive current of the coil.