JPH0996693A - Control rod drive mechanism - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a control rod drive mechanism in which the reliability is enhanced, while facilitating the repair and replacement, by enhancing the rigidity thereby making it possible to inspect the driving state of control rod even during the operation of a plant. SOLUTION: The control rod drive mechanism comprises a magnet coupling including a first magnet disposed below a drive shaft while being split into a plurality of sections in order to transmit the rotary driving power of a motor to the drive shaft and a second driving side magnet 101 carried on the rotary shaft of motor while being split into a plurality of sections on the outside of the first magnet, and a tubular outer yoke 100 for fitting the second magnet 101 on the inner face side thereof. The surface 110 of outer yoke 100 for mounting the second magnet 101 is in flush, in the radial direction, with the inner face of outer yoke located above or it is set on the inside thereof.

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention relates to a control rod drive mechanism (hereinafter, referred to as CRD) used in a boiling water reactor (hereinafter, referred to as BWR) as a light water reactor.

[0002]

2. Description of the Related Art FIG. 10 is a schematic block diagram showing a general BWR. As shown in the figure, the reactor pressure vessel (hereinafter RP
It is called V. ) 1 contains a coolant 2 which also serves as a moderator, while a core 3 is arranged in the lower center of the RPV 1 and is surrounded by a core shroud 4. Core 3
A large number of fuel assemblies (not shown) are loaded in the fuel cell, and the control rods 5 are removably housed between a set of four fuel assemblies.

In this BWR, the coolant 2 flows upward in the core 3, while the heat generated by the nuclear fission chain reaction from the core 3 is transferred to the coolant 2 to heat and heat the coolant 2. The coolant 2 becomes a gas-liquid two-phase flow of water and steam, moves above the core 3, and is guided from the core 3 to the steam separator 6.

The gas-liquid two-phase coolant is separated into water and steam by a steam separator 6, and the steam is sent from a main steam pipe to a steam turbine system through a steam dryer (not shown) to be sent to a steam turbine. Drive. The steam that worked in the steam turbine system is condensed in the condenser and condensed.
It is returned to the RPV 1 as water supply through the water supply system.

On the other hand, the water separated by the steam separator 6 flows down the downcomer section 7 and is guided to the lower part of the core 3 in a state where it is mixed with the feedwater sent through the reactor condensate / feedwater system. , Is again guided to the core 3.

A control rod 5 is inserted into and removed from the core 3 of the RPV 1 by a CRD 8 for starting / stopping the reactor and adjusting the reactor output. This CRD8 is the bottom 1a of RPV1.
Is a one-piece structure housed in a CRD housing 9 extending downward from the lower flange 9 of the CRD housing 9.
It is fixed to a by bolting.

As shown in FIG. 11, the CRD 8 is an electric drive type CRD, and an electric motor 10 is attached to the lower part thereof. A rotary shaft 11 of the electric motor 10 is a drive shaft 13 of the CRD 8 via a gear coupling mechanism 12. Connected to. The drive shaft 13 is rotatably connected to a ball screw shaft 14, and a ball nut 15 is screwed onto the ball screw shaft 14.

The ball nut 15 has a pair of rollers 1
6 is attached so as to sandwich an axial mounting plate 18 formed on the inner peripheral surface of the guide tube 17. A hollow piston 19 is installed above the ball nut 15, and the hollow piston 19 is connected to the control rod 5 via a coupling 20 attached to the upper end.

An electromagnetic brake 21 is attached to the electric motor 10, and the electromagnetic brake 21 is operated to stop the electric motor 10. This electromagnetic brake 21
A synchro position detector 22 is provided at the lower end of the synchro position detector 22. The synchro position detector 22 detects the position of the control rod 5.

A motor bracket 23 is arranged around the gear coupling mechanism 12 in the upper part of the electric motor 10, and a spool piece 24 as a partition wall of the primary cooling water is fixed to the upper part of the motor bracket 23. ing. The drive shaft 13 penetrates the spool piece 24, and a gland packing 25 is used as a seal member for the drive shaft 13. In other stationary seal portions, rubber O-rings 26 and 27 are used.

Further, on the upper part of the guide tube 17,
A cylinder 29 is fixed via a stop piston 28 that prevents upward movement of the hollow piston 19 beyond a predetermined length,
A coil spring 30 is mounted between the cylinder 29 and the stop piston 28. The disc spring mechanism 3 for the buffer is provided between the cylinder 29 and the upper guide 31.
2 is installed.

In the CRD 8 thus constructed,
By rotating the electric motor 10, the ball screw shaft 14 rotates via the rotary shaft 11 and the drive shaft 13, and the rotation of the ball screw shaft 14 causes the ball nut 15 to move up and down.

At this time, the ball nut 15 moves up and down with the rotation of the mounting plate 18 being regulated by the roller 16 so that the control rod 5 moves up and down via the hollow piston 19 by the up and down movement of the ball nut 15. The vertical movement of the control rod 5 adjusts the amount of insertion and withdrawal into and from the core 3 to control the reactor output.

Next, a case where an emergency situation occurs in the BWR and the reactor is scrammed will be described. That is, at the time of reactor scram, the scram insertion pipe 33 connected to the lower flange 9a of the CRD housing 9 is used to feed the inlet 3
The high-pressure drive water is supplied to the lower surface side of the hollow piston 19 via 4. By supplying this high-pressure drive water, ball nut 1
The hollow piston 19 installed on the No. 5 is pushed up and the control rod 5 is inserted into the core 3 at high speed, so that the reactor is scrammed. Here, the scrum position of the hollow piston 19 is detected by a scrum position detector 36 having a reed switch 35.

In the above-mentioned conventional CRD, the drive shaft 1
3 penetrates the spool piece 24 as the partition wall of the primary cooling water, and the gland packing 25 is used as the seal member of the drive shaft 13. In the other static seal parts, the rubber seal part cannot completely seal the primary cooling water, and some leakage is allowed. Further, since the gland packing 25 and the rubber O-rings 26 and 27 are made of a non-metallic material, they deteriorate over time and need to be replaced regularly. As a result, there is a problem that the maintenance frequency becomes high.

In order to solve this problem, therefore, the rotational power of the electric motor is transmitted to the ball screw in a non-contact manner via the pressure partition wall by the magnetic force of the magnet, so that the penetrating portion of the pressure partition wall becomes unnecessary. Drive mechanism is Japanese Patent Application No. 7-325
It has been filed as No. 57.

The invention described in Japanese Patent Application No. 7-32557 will be described with reference to FIG. CRD50
Is an electric drive type control rod drive mechanism, which is fixed to the lower flange 9a of the CRD housing 9 arranged so as to extend downward from the bottom portion 1a of the RPV 1 by bolting.

An electric motor 51 such as a stepping motor is attached to the lower portion of the CRD 50, and the rotational driving force from the electric motor 51 is transmitted to the drive shaft 53 via the magnet coupling 52. Magnet coupling 52
Is an inner magnet 54 that is disposed below the drive shaft 53 and serves as a first magnet on the driven side.
And an outer magnet 55 as a second magnet on the drive side, which is provided on the shaft of the electric motor 51 with a spool piece 56 as a primary cooling water partition wall separated from the outside. Each of the inner magnet 54 and the outer magnet 55 has a structure in which an even number of cylindrical magnets are vertically divided and magnetized in the radial direction to alternately arrange magnetic poles.

The drive shaft 53 is connected to the ball screw shaft 14, and the rotational driving force of the drive shaft 53 is transmitted to the ball screw shaft 14. The rotation of the ball screw shaft 14 causes the ball nut 1 to rotate.
5, the hollow piston lifting mechanism is constituted by the ball screw shaft 14, the ball nut 15, and the roller 16 as in the conventional example shown in FIG.

A motor bracket 57 is arranged above the electric motor 51 and around the magnet coupling 52. And spool piece 56 and CRD
A metal O-ring 66 is used as a seal member between the lower flange 9a of the housing 9 and the metal O-ring 66 prevents primary cooling water from leaking.
Maintenance frequency is lower than that of rubber O-rings.

In the CRD 50 having such a structure,
The magnetic coupling 5 is driven by the rotation of the electric motor 51.
The drive shaft 53 is rotated via 2. That is, the outer magnet 55 on the drive side is rotated by the rotational driving of the electric motor 51, and the inner magnet 54 on the driven side is rotated with this rotation, thereby rotating the drive shaft 53. When the drive shaft 53 rotates, the ball screw shaft 14 is rotated to move the ball nut 15 up and down (up and down). As the ball nut 15 moves up and down, the control rod 5 moves up and down via the hollow piston 19 to adjust the furnace power.

The control rod 5 is held at the insertion position by restricting the rotation of the ball screw shaft 14 by the holding torque of the electric motor 51 itself. On the other hand, in the case of scramming the reactor, it is the same as the conventional example shown in FIG.

In the conventional example shown in FIG. 12, the CRD 50 is used.
Is disposed below the drive shaft 53 and is the inner magnet 5 on the driven side.
4 and the spool piece 5 on the outside of the inner magnet 54.
By arranging the magnet coupling 52 composed of the outer magnet 55 on the drive side provided on the shaft of the electric motor 51 with the space 6 therebetween, the seal portion of the drive shaft 53 is unnecessary. Therefore, since there is no part that penetrates the spool piece 56, a shaft seal member such as the conventional gland packing is not required.

Further, FIG. 13A shows the CRD 50 of FIG.
FIG. 13 (b) is a partial longitudinal sectional view showing a magnet coupling soundness diagnostic apparatus applicable to FIG. 13 (a).
FIG. 7 is a sectional view taken along the line D-D of FIG. Since only the lower portion of the spool piece 56 and its peripheral portion are different from the embodiment shown in FIG. 12, only that portion is shown in FIG. 13 (a). Hereinafter, the hollow cylindrical portion below the spool piece 56 is referred to as a pressure partition wall 58. And in FIG. 13 (a),
The pressure partition 58 is not shown in cross section. In this conventional technique, a linear or film-shaped conductor is arranged between the inner magnet 54 (first magnet) and the outer magnet 55 (second magnet). In FIG. 13A, a linear conducting wire 59 is attached to the outer peripheral surface of the pressure partition wall 58 so as to reciprocate in the vertical (axial) direction. Further, FIG. 13B shows a part of the magnetic field between the inner magnet 54 and the outer magnet 55.
5, the outer yoke 60, the inner yoke 61, and the gap between the inner magnet 54 and the outer magnet 55
A magnetic circuit is formed and a magnetic field as shown in the figure is generated. Inner magnet 54 and outer magnet 5 during driving
5 rotates in synchronism with the rotation of the magnetic field while keeping the distribution of the magnetic field almost the same as at rest.

Due to the rotating magnetic field generated by the rotation of the inner magnet 54 and the outer magnet 55, an induced voltage is generated in the axial direction of the conducting wire 59 in the vertically stretched portion of the conducting wire 59. If the rotational speed of the magnet is constant, this electromotive force causes a periodic voltage having a waveform as shown in FIG. In addition, in this figure, the waveform is trapezoidal, but generally the waveform is slightly different depending on the shape of the magnet,
When a wide magnet is used, the upper and lower flat portions tend to be long. The amplitude of this voltage is proportional to the magnetic flux density created by the inner magnet 54 and the outer magnet 55 in the gap between these magnets. Therefore, by measuring the amplitude of the voltage, the magnetic force of the magnet is determined, and the presence or absence of deterioration of the magnetic force is confirmed in the plant operating state without overhauling the control rod drive mechanism and the spool piece.

FIGS. 15A and 15B show the outer magnet 55.
It shows a detailed structure of the periphery. Upper bearing 6
2. The outer rotor 64 whose both ends are supported by the lower bearing 63 has an outer magnet 55 (second magnet) at a predetermined interval along the inner peripheral wall of the outer yoke 60.
Is arranged. The outer magnet 55 is fixed by a pin 103 via a magnet fixing member 102.

Generally, when a magnetized magnet is to be mounted in the radial direction close to the yoke, it is difficult to assemble due to the attraction force between the magnet and the yoke, and the magnet may be damaged by being strongly hit during mounting. In order to prevent this, it is a general method to mount the magnet in a regular position while bringing the magnet into contact with the magnet mounting surface 110 of the yoke and sliding the magnet.
In the invention described in Japanese Patent Application No. 7-32557, the upper yoke 62 has a shape in which the upper end portion of the outer yoke 60 is recessed inward for mounting the upper bearing 62. Therefore, the flange 65 and the outer yoke 60 have a split structure, and the outer magnet 55 is arranged from below. After attaching the flange 65 to the outer yoke 6
The structure is attached to 0.

[0028]

The conventional control rod drive mechanism as described above has the following problems. In the case of the divided structure of the flange 65 and the outer yoke 60 as shown in FIG. 15, since the motor power is input to the flange 65, a rotation stopping structure or a welding structure by fixing the key or the pin 113 to the joint portion with the outer yoke 60 is used. It is necessary to increase the rigidity of this part by adopting it and increasing the wall thickness.
Therefore, as compared with the case of the integrated structure, there is a problem that the structure is complicated, the manufacturing man-hours are increased, and the outer rotor 64 becomes heavy, so that a large motor power is required.

Further, as a problem common to the conventional control rod drive mechanism shown in FIG. 12 and the invention described in Japanese Patent Application No. 7-32558, a state where friction is increased due to contact between the core and the control rod, etc. If the electric motor 10 is used to insert the control rod, the control rod cannot be smoothly inserted, and an excessive load is applied to the ball screw shaft 14, the ball nut 15, and the like, which may cause damage. In addition, the fuel may be damaged. The inspection to determine the magnitude of this frictional force was carried out at the time of regular inspection.

As another object of the invention described in Japanese Patent Application No. 7-32558, in general, when a magnet is impacted,
It is known that the magnetic force may decrease slightly. There was a possibility that shock load and seismic load at the time of scrum could be applied to the magnet.

Further, regarding the magnet coupling soundness diagnostic device in the previous term, when the disconnection between the inner magnet and the outer magnet or the deterioration of the insulator (not shown) around the inner magnet and the outer magnet occurs, the motor and the spool piece are driven by the control rod. It was necessary to remove it from the mechanism for repair and replacement.

The present invention has been made in view of the above conventional circumstances, and an object thereof is to increase the rigidity of the structure and to improve the reliability by making it possible to inspect the control rod drive state even during plant operation. At the same time, it is to provide a control rod drive mechanism that is easy to repair and replace.

[0033]

In order to achieve the above object, in the control rod drive mechanism of the present invention, according to the invention of claim 1, a hollow piston having a control rod for controlling the output of the nuclear reactor at the upper end is used. The rotation of the electric motor is transmitted to the lifting device that raises and lowers the control rod through the drive shaft to insert and pull out the control rod into the core, while at the time of scram, high-pressure water is injected to push up the hollow piston to move the control rod into the core. In a control rod drive mechanism that is rapidly inserted into a drive shaft, a first magnet is provided in a plurality of parts below the drive shaft to transmit the rotational drive force of the electric motor to the drive shaft, and a first magnet is provided outside the first magnet. A magnet coupling having a second magnet on the driving side, which is arranged in a plurality of parts on the rotary shaft of the electric motor, and a cylindrical outer member for mounting the second magnet on the inner surface side. And a York, radial position of the mounting surface of the second magnet of the outer yoke and the second
It is formed at the same position as or inside the radial position of the inner surface of the outer yoke above the mounting surface of the magnet.

According to a second aspect of the invention, in the first aspect of the invention, a ring for mounting a bearing is provided on the inner surface of the outer yoke above the mounting surface of the second magnet.

According to a third aspect of the invention, in the first aspect of the invention, a conductor for generating an induced voltage by a rotating magnetic field generated by the rotation of the first magnet and the second magnet is provided between the first magnet and the second magnet. It is arranged to detect a change in the waveform of the induced voltage caused by a change in the torque angle formed between the first magnet and the second magnet.

According to a fourth aspect of the invention, in the third aspect of the invention, there is provided means for estimating the torque angle by measuring the change in the waveform of the induced voltage. According to a fifth aspect of the present invention, in the fourth aspect of the invention, the left / right symmetry is used for the means for estimating the torque angle with respect to the time history waveform of a half cycle of the waveform of the induced voltage.

According to a sixth aspect of the invention, in the fifth aspect of the invention, the left-right symmetry of the half-cycle time history waveform of the induced voltage is a voltage for two regions with an intermediate time of the half-cycle as a boundary. The values are evaluated by comparing the time integral values.

The invention according to claim 7 is the invention according to claim 4, further comprising means for estimating a load amount applied to the lifting device of the hollow piston from the torque angle. According to the invention described in claim 8, in the invention described in claim 1,
The surface of at least one of the magnet and the second magnet is coated.

According to a ninth aspect of the invention, in the first aspect of the invention, at least one of the first magnet and the second magnet is adjacent to the magnet in the axial direction, the radial direction, and the circumferential direction. The elastic body is provided in at least one of the gaps with the member.

According to a tenth aspect of the invention, in the invention of the first aspect, an elastic body is provided in the gap between at least one of the divided magnets of the first magnet and the second magnet. is there.

According to an eleventh aspect of the invention, in the invention of the first aspect, an elastic body is provided in the gap between the outer yoke and the second magnet. According to a twelfth aspect of the invention, in the first aspect of the invention, a magnetic sensor for detecting a magnetic field generated from the first magnet and the second magnet is provided on an outer peripheral portion of a housing that houses the magnet coupling.

According to a thirteenth aspect of the present invention, in the first aspect of the present invention, a magnetic sensor for detecting a magnetic field generated from the first magnet and the second magnet is provided inside a housing for accommodating the magnet coupling. is there.

According to a fourteenth aspect of the invention, in the thirteenth aspect of the invention, the magnetic sensor is detachably provided from the outside of the housing that accommodates the magnet coupling.

According to a fifteenth aspect of the invention, in the invention of the first aspect, the first magnet and the second magnet are rotatably supported by a slide bearing. In the control rod drive mechanism having the above structure, according to the first aspect of the invention, the outer magnet (second magnet) can be mounted while sliding along the magnet mounting surface from above the outer yoke.

According to the second aspect of the present invention, the outer yoke and the portion for mounting the bearing on the upper portion of the outer yoke have a divided structure, so that the magnet is inserted from above the outer yoke regardless of the positional relationship between the bearing mounting surface and the magnet mounting surface. The outer magnet can be mounted on the outer yoke while sliding along the mounting surface.

According to the present invention, the torque angle of the first and second magnets of the magnet coupling changes according to the load torque, and the time history of the induced voltage changes due to the change of the torque angle. Utilizing that the waveform changes
By detecting the change in the waveform, the amount of load applied to the lifting device for the hollow piston can be measured.

According to the sixth aspect of the invention, the load amount can be measured by paying attention to the symmetry of the waveform among the time history changes of the waveform. According to the eighth aspect of the present invention, the cushioning effect is provided by disposing the elastic body between the structural members.

According to the twelfth to fourteenth aspects of the invention, the magnitude of the magnetic force of the magnet can be measured by measuring the magnitude of the leakage magnetic flux at the upper ends of the first and second magnets. Further, when the magnet coupling does not rotate synchronously and a slip occurs, the occurrence can be detected by a change in the output waveform of the magnetic sensor. Further, when the magnetic sensor fails or deteriorates, the magnetic sensor can be replaced or repaired without attaching or detaching the control rod drive mechanism or the electric motor.

According to the fifteenth aspect of the present invention, the use of the slide bearing can exert a cushioning effect against vibrations, and the dimension determination can be made more flexible than the rolling bearing.

[0050]

Embodiments of the present invention will be described below with reference to the drawings.

[0051]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS A first embodiment of the control rod drive mechanism according to the present invention will be described below with reference to FIG. 1A and 1B are enlarged views of a portion corresponding to the second magnet shown in FIG. Outer rotor 1 whose both ends are supported by an upper bearing 105 and a lower bearing 106
07 is an outer yoke 100 and an outer sleeve 10
4, outer magnet 101, spacer 108 and the like. A plurality of magnet fixing members 102 for fixing the outer magnet 101 (second magnet) are fixed by pins 103 along the inner peripheral wall of the outer yoke 100 at predetermined intervals.

The lower portion of the outer sleeve 104 is fixed to the inner peripheral side of the lower portion of the outer yoke 100 by welding or the like. After inserting the outer magnet 101 from above into the space formed by the outer yoke 100, the plurality of magnet fixing members 102, and the outer sleeve 104, the spacer 108 is inserted into the upper portion of the outer magnet 101, and the spacer 108 and the outer yoke are inserted. The outer portion is assembled by fixing 100 and the spacer 108 and the outer sleeve 104 by means such as welding or pinning. The outer magnet 101 is in contact with the outer yoke 100 on the magnet mounting surface 110. The spacer 10
It is also possible for 8 to have a structure integral with the outer sleeve 104.

Generally, when a magnetized magnet is to be mounted in the radial direction close to the yoke, it is difficult to assemble due to the attractive force between the magnet and the yoke, and the magnet may be damaged by being urged with force during mounting. . In order to prevent this, it is a general method to bring the magnet into contact with the magnet mounting surface of the yoke and slide it on the surface to mount it at a regular position. To make this possible, position the inner surface of the outer yoke above the upper end of the magnet outside the magnet mounting surface and mount the outer magnet from above, or place the inner surface of the outer yoke below the lower end of the magnet outside the magnet mounting surface. It is conceivable that the magnet is attached from below after it is positioned. However, in the latter case, the outer yoke 100 has a flange portion at the lower part for coupling with the motor shaft, and this flange portion and the outer yoke need to have a divided structure. It is advantageous in securing the rigidity of the flange portion to which the motor power is applied.

2A and 2B are sectional views showing a second embodiment of the control rod drive mechanism according to the present invention. A ring 109 for mounting a rolling bearing is fitted on the upper portion of the outer yoke 100. By providing a cage on the ring 109 and the outer yoke 100, these cores can be aligned. In this example, the upper bearing 105, which is a rolling bearing, is used for rotating the inner ring and fixing the outer ring. The outer yoke 100 is assembled by inserting the outer magnet 101 from above into the space formed by the outer yoke 100, the plurality of magnet fixing members 102 and the outer sleeve 104, and then fitting the ring 109 to the upper portion of the outer magnet 101. The ring 109 and the outer yoke 100 and the ring 109 and the outer sleeve 104 are fixed by welding or the like. In this embodiment, the bearing mounting surface 111 is inside the magnet mounting surface 110. However, by mounting the outer magnet 101 before mounting the ring 109 to the outer yoke 100, the magnet is brought into contact with the magnet mounting surface 1110 to slide. It is possible to install it in the regular position while doing it. Therefore, it is possible to flexibly select the size of the bearing. The fixing of the ring 109 and the outer yoke 100 is not limited to welding, but a fixing method such as pinning or a tight spring can be used. Further, if a magnetic material is used as the ring 109, it can be fixed by the attraction force with the outer magnet 101. Further, the ring 109 and the outer sleeve 104 may be integrally formed.

In the first and second embodiments, rolling bearings are used as bearings, but the present invention is not limited to this, and sliding bearings using white metal, lubricating oil impregnated material, resin, etc. can also be used. is there. Generally, impregnated bearings and the like are made of a porous material and have a Young's modulus smaller than that of a general metal. Further, the sliding bearing has a thicker oil film than the rolling bearing in which the surface pressure between the rolling element and the ball race is high and the oil film is thin. These act to increase the buffering effect against vibrations, and can be expected to have the effect of maintaining the soundness of the magnet against the impact load when the control rod drive mechanism drives the scrum and the vibration when the earthquake occurs. Further, it is possible to more flexibly determine the dimension than the rolling bearing whose dimension is defined by the standard.

Also, in the first and second embodiments, the outer yoke 100 and the magnet fixing member 102 are separate bodies and they are fixed by pins, but the present invention is not limited to this, and the outer yoke 100 and the magnet fixing member 102 are not limited to this. The and may be manufactured as an integral structure by forging or the like. As a result, the manufacturing process can be shortened and the manufacturing cost can be reduced.

A third embodiment of the control rod drive mechanism according to the present invention will be described below with reference to FIGS. FIG. 3 shows FIG.
5 is an example of an output voltage waveform when the first and second magnets are synchronously rotating in the magnet coupling soundness diagnostic device shown in FIG. Although this example shows a case of an eight-pole configuration, there are four combinations of N-pole and S-pole of the magnet, so that when the first and second magnets make one rotation, a voltage waveform of four cycles appears. One cycle of this is shown in Fig. 3.
It is shown in FIG. Now, the description will focus on the half cycle in which the output of the left half is positive, but the same applies to the right half. Axis 112 is located at the temporal center of this half cycle portion. The waveform indicated by symbol A is an example of a voltage waveform in a state where no load is applied to the magnet coupling, and is substantially symmetrical with respect to the axis 112. However, the symmetry is broken in the waveform indicated by the symbol B when the load torque is applied.

FIG. 4 is a cross-sectional view showing the phase relationship between the first and second magnets in the unloaded state, where the centers of the widths of the outer magnet 101 and the inner magnet 113 are almost the same due to the attractive force and repulsive force of the magnets. The matched phase relationship is stable.

On the other hand, as shown in FIG. 5, when there is a load, it is most preferable that the first and second magnets rotate by a certain angle relative to the phase relationship shown in FIG. 4 until the load and the magnetic force are balanced. It is stable. This relative angle determined according to the load is called the torque angle. Therefore, the circumferential distribution of the magnetic field in the gap between the outer magnet 101 and the inner magnet 113 changes depending on the load, and the change in waveform as shown in FIG. 3 is observed.

Therefore, the load torque applied to the magnet coupling, that is, the load torque applied to the ball screw of the lifting device can be estimated by detecting the change in the waveform, particularly the change in the symmetry of the waveform. To evaluate symmetry,
For example, a method is conceivable in which time integration is performed on each of the left and right voltage waveforms with the axis 112 of FIG. 3 as a boundary, and the area between the voltage waveform and the axis of 0 is calculated and compared. At this time, by appropriately weighting the voltage value and integrating it, the load torque detection sensitivity can be increased even when the asymmetry is slight.

This load torque is related to the rotational friction due to wear of the ball screw, the friction between the control rod and the fuel, etc. By evaluating this, the lifting device of the control rod drive mechanism,
It is possible to diagnose whether there is any abnormality in the distortion of the fuel or control rods or the installed state without stopping the reactor.

Next, a fourth embodiment of the control rod drive mechanism according to the present invention will be described with reference to FIG. The magnet 114 in FIG. 6 is an inner magnet or an outer magnet. This surface is coated with resin or plating. This allows the magnet to have a buffering effect against shock. Generally, when a shock is applied to the magnet, the magnetic force may be slightly decreased. However, according to this embodiment, the effect of maintaining the soundness of the magnet against the shock load and the seismic load when the scram of the control rod drive mechanism is driven is obtained. Can be expected. In addition, the inner magnet is always in water and in a corrosive environment, but this coating isolates it from water and prevents corrosion.

A fifth embodiment of the control rod drive mechanism according to the present invention will be described with reference to FIG. FIG. 7 shows the outer rotor 107. Leaf springs 120, 121, 122 are arranged between the outer magnet 101 and the outer yoke 100, the outer sleeve 104, and the magnet fixing member 102. As a result, the same shock buffering effect as the coating of the fourth embodiment can be provided, and the effect of maintaining the soundness of the magnet against the shock load and seismic load when driving the scrum can be expected. Axial direction of outer yoke 100,
Three types of leaf springs 120, 121, 122 are arranged to absorb the impact in the circumferential direction and the radial direction. The present embodiment can be similarly applied to the first magnet (inner magnet).

A spring structure such as a disc spring can be used instead of the leaf spring. Further, a thin member having a shock absorbing effect, such as a rubber or resin sheet, has the same effect.

A sixth embodiment of the control rod drive mechanism according to the present invention will be described with reference to FIG. FIG. 8 shows a sectional view of a portion corresponding to the spool piece 56 of FIG. The magnetic sensor 116 is mounted on the outer peripheral portion of the motor bracket 123, and its signal line 118 is connected to the signal processor 117. The magnetic sensor 116 may be an eddy current displacement meter, a Hall element, or the like, and as a simple one, a conductor wire, a film, a plate, a coil, or the like that generates an induced voltage due to a change in a magnetic field can be considered.

Generally, the magnetic coupling is the first
Since it forms a closed magnetic circuit consisting of the magnet, the second magnet, the yoke, and the air gap between the magnets,
There is almost no leakage flux to the outside, but there is a relatively large leakage flux near the end of the magnet. The magnitude of the leakage magnetic flux increases as the magnetic force of the magnet, that is, the residual magnetic flux density increases. In this embodiment, the magnetic sensor 116 is arranged near the end portion where the leakage magnetic flux is relatively large, and the magnetic force of the magnet is measured. This measurement can be easily done while the reactor is in operation, and without disassembling and checking the magnetic coupling,
The degree of magnetic force deterioration can be determined.

Further, as the magnet coupling rotates, the magnetic field produced by the leakage magnetic flux changes with time. Generally, when the magnet coupling slips, the first and second magnets rotate irregularly relative to each other, so that the time change of the magnetic field is different from that during the synchronous rotation. Therefore, if the output waveform of the magnetic sensor 116 is processed by using a signal processing device that separates components of the output waveform having different frequencies, for example, a frequency filter, a frequency analyzer, or the like, it is possible to detect the occurrence of slippage.

Further, during synchronous rotation, the torque angles of the first and second magnets change according to the magnitude of the load torque, so the circumferential distribution of the magnetic field near the magnet ends also changes. Therefore, the load torque applied to the ball screw of the lifting device can be estimated by detecting the change in the waveform of the magnetic sensor 116. The same method as in the third embodiment can be used to detect the change in the waveform. In addition, this magnetic sensor 1
Since 16 is attached to the outside of the motor bracket 123, this attachment / detachment can be performed without attaching or detaching the motor (not shown) or the motor bracket 123. Therefore, even if the magnetic sensor 116 fails or deteriorates, it is easy to replace it.

FIG. 9 shows a seventh control rod drive mechanism according to the present invention.
The following shows an example. This is the case where the magnetic sensor 116 is installed inside the motor bracket 123. According to the present embodiment, it is possible to measure a portion closer to the magnet coupling, so that it is possible to improve the sensitivity. Since the magnetic sensor 116 is detachably fixed from the outside of the motor bracket 123, the magnetic sensor 116 can be easily replaced even if the magnetic sensor 116 fails or deteriorates.

[0070]

As described above, in the control rod drive mechanism of the present invention, according to the first aspect of the invention, the outer magnet is slid from above the outer yoke along the inner surface of the outer yoke while sliding the outer magnet. Since the magnet can be attached to the outer yoke, the magnet can be easily assembled to the yoke, and the manufacturing process can be shortened and the manufacturing cost can be reduced. Further, unlike the case where the outer yoke is assembled from below, the outer yoke and its lower flange can be integrally formed, the rigidity of the outer yoke can be increased, and the structure is simple and the manufacturing cost can be reduced.

According to the second aspect of the invention, the dimensions of the bearing can be flexibly determined while maintaining the features of the first aspect of the invention. According to the invention as set forth in claims 3, 4, 5, and 7, by determining the load amount of the lifting device of the control rod drive mechanism, it is possible to determine the wear deterioration state of the inside of the lifting device, the distortion of the fuel and the control rod, and the installation state. It is possible to diagnose whether there is any abnormality without stopping the nuclear reactor, and it is possible to improve the soundness and operability of the nuclear power plant.

In the invention according to claim 6, the diagnosis can be easily performed. In the inventions according to claims 8 to 11, the soundness of the magnet can be maintained against an impact load and an earthquake load when the control rod drive mechanism is driven by a scrum.

According to the twelfth to fourteenth aspects of the present invention, the soundness of the magnet coupling and the control rod drive mechanism is diagnosed by determining the degree of deterioration of the magnetic force of the magnet and detecting the occurrence of slippage of the magnet coupling. Can be easily done in the state. Further, since the magnetic sensor can be easily attached and detached, it can be easily replaced or repaired in the event of deterioration or failure.

According to the fifteenth aspect of the present invention, by using the slide bearing, the effect of maintaining the soundness of the magnet against shock load and seismic load when the control rod drive mechanism is driven by the scrum can be expected, and the dimension is determined by the rolling bearing. Can be done flexibly.

[Brief description of drawings]

1A is a vertical cross-sectional view showing a first embodiment of a control rod drive mechanism according to the present invention, and FIG. 1B is an A- in FIG.
A line arrow sectional view.

2A is a longitudinal sectional view showing a second embodiment of the control rod drive mechanism according to the present invention, and FIG. 2B is a B- in FIG. 2A.
FIG.

FIG. 3 is an output waveform diagram of the magnet coupling soundness diagnostic device in the third embodiment of the control rod drive mechanism according to the present invention.

FIG. 4 is a first and second unloaded state in the third embodiment.
Cross-sectional view showing the phase relationship of the magnet

FIG. 5 is a transverse cross-sectional view showing the phase relationship between the first and second magnets in the third embodiment under a load.

FIG. 6 is a structural diagram showing a fourth embodiment of the control rod drive mechanism according to the present invention.

7 (a) is a vertical cross-sectional view showing a fifth embodiment of the control rod drive mechanism according to the present invention, and FIG. 7 (b) is a C- line in FIG. 7 (a).
A sectional view taken along the line C.

FIG. 8 is a vertical sectional view showing a sixth embodiment of the control rod drive mechanism according to the present invention.

FIG. 9 is a longitudinal sectional view showing a seventh embodiment of the control rod drive mechanism according to the present invention.

FIG. 10 is a vertical cross-sectional view of a reactor pressure vessel for explaining an installation state of a control rod drive mechanism.

FIG. 11 is a vertical cross-sectional view showing a conventional example of a control rod drive mechanism.

FIG. 12 is a vertical cross-sectional view showing a conventional example of a control rod drive mechanism.

13A is an enlarged vertical sectional view showing a portion of a magnet coupling sounding device in a conventional example of a control rod drive mechanism, and FIG. 13B is a sectional view taken along the line DD in FIG. 13A.

FIG. 14 is an output waveform diagram of a magnet coupling sounding device in a conventional example of a control rod drive mechanism.

15A is an enlarged vertical sectional view showing a portion of a magnet coupling sounding device in a conventional example of a control rod drive mechanism, and FIG. 15B is a sectional view taken along the line EE in FIG. 15A.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Reactor pressure vessel 1a ... Bottom part 2 ... Coolant 3 ... Core 4 ... Core shroud 5 ... Control rod 6 ... Steam separator 7 ... Downcomer part 8 ... Control rod drive mechanism 9 ... CRD housing 9a ... Lower flange 10 ... Electric motor 11 ... Rotary shaft 12 ... Gear coupling mechanism 13 ... Drive shaft 14 ... Ball screw shaft 15 ... Ball nut 16 ... Roller 17 ... Guide tube 18 ... Mounting plate 19 ... Hollow piston 20 ... Coupling 21 ... Electromagnetic brake 22 ... Synchronization Position detector 23 ... Motor bracket 24 ... Spool piece 25 ... Gland packing 26 ... O ring 27 ... O ring 28 ... Stop piston 29 ... Cylinder 30 ... Coil spring 31 ... Top guide 32 ... Disc spring mechanism 33 ... Scrum insertion pipe 34 ... Note Inlet 35 ... Reed switch 36 ... Scrum position detector 50 ... Rod driving mechanism 51 ... Electric motor 52 ... Magnet coupling 53 ... Drive shaft 54 ... Inner magnet 55 ... Outer magnet 55 ... Spool piece 57 ... Motor bracket 58 ... Pressure partition wall 59 ... Conductor wire 60 ... Outer yoke 61 ... Inner yoke 62 ... Upper part Bearing 63 ... Lower bearing 64 ... Outer rotor 65 ... Flange 66 ... Metal O-ring 100 ... Outer yoke 101 ... Outer magnet 102 ... Magnet fixing member 103 ... Pin 104 ... Outer sleeve 105 ... Upper bearing 106 ... Lower bearing 107 ... Outer rotor 108 ... Spacer 109 ... Ring 110 ... Magnet mounting surface 111 ... Bearing mounting surface 112 ... Shaft 113 ... Inner magnet 114 ... Magnet 115 ... Spool piece 116 ... Magnetic sensor 117 ... Signal processor 1 8 ... the signal lines 120 ... leaf spring (a) 121 ... leaf spring (b) 122 ... leaf spring (c) 123 ... motor bracket

Claims (15)

[Claims] Claim: What is claimed is: 1. A rotation of an electric motor is transmitted via a drive shaft to an elevating device for ascending and descending a hollow piston having a control rod for controlling the output of a nuclear reactor at its upper end, and the control rod is inserted into or extracted from the core In a control rod drive mechanism for injecting high-pressure water at the time of scram and pushing up the hollow piston to rapidly insert the control rod into the core, in order to transmit the rotational drive force of the electric motor to the drive shaft, A magnet coupling having a first magnet provided in a plurality of lower parts and a second magnet on the driving side provided outside the first magnet and being provided in a plurality of parts on the rotating shaft of the electric motor. And a cylindrical outer yoke for mounting the second magnet on the inner surface side, and the radial position of the mounting surface of the second magnet of the outer yoke is the mounting position of the second magnet. A control rod drive mechanism, which is formed at the same position as or inside the radial position of the inner surface of the outer yoke above the surface. 2. The control rod drive mechanism according to claim 1, wherein a ring for mounting a bearing is provided on the inner surface of the outer yoke above the mounting surface of the second magnet. 3. A conductor for generating an induced voltage by a rotating magnetic field generated by the rotation of the first magnet and the second magnet is arranged between the first magnet and the second magnet, and the conductor is formed between the first magnet and the second magnet. 2. The control rod drive mechanism according to claim 1, wherein a change in the waveform of the induced voltage caused by a change in the torque angle formed between them is detected. 4. The control rod drive mechanism according to claim 3, further comprising means for measuring the change in the waveform of the induced voltage and estimating the torque angle. 5. The control rod drive mechanism according to claim 4, wherein the means for estimating the torque angle uses the left-right symmetry of a half-cycle time history waveform of the waveform of the induced voltage. 6. The left-right symmetry of the time history waveform for a half cycle of the induced voltage is 2 when the middle time of the half cycle is a boundary.
The control rod drive mechanism according to claim 5, wherein the time-integrated values of the voltage values are compared and evaluated for the regions. 7. The control rod drive mechanism according to claim 4, further comprising means for estimating a load amount applied to the lifting device of the hollow piston from the torque angle. 8. The control rod drive mechanism according to claim 1, wherein a surface of at least one of the first magnet and the second magnet is coated. 9. At least one of the gaps between at least one of the first magnet and the second magnet and the respective members adjacent to the magnet in the axial direction, the radial direction, and the circumferential direction. The control rod drive mechanism according to claim 1, further comprising an elastic body. 10. The control rod drive mechanism according to claim 1, wherein an elastic body is provided in a gap between at least one of the divided magnets of the plurality of divided first and second magnets. 11. The control rod drive mechanism according to claim 1, wherein an elastic body is provided in a gap between the outer yoke and the second magnet. 12. The control rod drive mechanism according to claim 1, wherein a magnetic sensor for detecting a magnetic field generated from the first magnet and the second magnet is provided on an outer peripheral portion of a housing that houses the magnet coupling. .. 13. The control rod drive mechanism according to claim 1, wherein a magnetic sensor that detects a magnetic field generated from the first magnet and the second magnet is provided inside a housing that houses the magnet coupling. 14. The control rod drive mechanism according to claim 13, wherein the magnetic sensor is provided detachably from the outside of a housing that houses the magnet coupling. 15. The control rod drive mechanism according to claim 1, wherein the first magnet and the second magnet are rotatably supported by a slide bearing.