JP2931700B2 - Internal pump speed detection system - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an internal pump for forcibly circulating a coolant in a nuclear reactor, and more particularly to an internal pump capable of measuring a change in the rotation speed of the internal pump when the pump is stopped. Related to a rotation speed detection system.

[0002]

2. Description of the Related Art A boiling water reactor as a light water reactor is shown in FIG.
As shown in (1), an internal pump 2 as a recirculation pump in the reactor is attached to the bottom of the reactor pressure vessel 1. A plurality of internal pumps 2 are installed along the circumferential direction around the bottom of the reactor pressure vessel 1, and the coolant (reactor water) above the core 3 is driven down by a pump as shown by an arrow a in FIG. It is sucked through the part 4, discharged to the lower part of the core, and guided to the core 3.

The internal pump 2 has a pump motor section 5
Is transmitted to the pump impeller 6 via the pump shaft, and the pump impeller 6 is rotationally driven, thereby forcibly circulating the reactor water in the reactor pressure vessel 1.

[0004] When the power supply is stopped and the vehicle runs free, the internal pump 2 gently reduces the pump speed in order to ensure the soundness of the fuel rods in the reactor.
It is necessary to reduce the reduction rate of the circulated reactor water. For this reason, it is designed so that the inertia amount of the pump rotation system in which the pump impeller 6 and the pump shaft are combined is large.

On the other hand, in order to ensure the soundness of the reactor core, it is necessary to confirm this amount of inertia. This inertia amount is defined as an inertia constant in the core safety analysis. The inertia constant is a time required for the pump speed before the internal pump is stopped to be reduced to half, and it is necessary to measure a time change of the pump speed after the internal pump is stopped. The time change depends on the state of the reactor before the internal pump 2 stops, that is, the fluid inertia of the coolant and the rotation speed before the pump stops. In particular, since the influence of fluid inertia cannot be simulated by a factory test or the like, it is necessary to measure the influence of the fluid inertia incorporated in an actual nuclear power plant.

[0006] The rotation speed of the pump shaft of the internal pump 2 incorporated in the nuclear power plant is measured by a tachometer that measures the rotation of the pump motor 5 that drives the pump impeller 6. The number of rotations of the internal pump 2 was detected by measuring the generation of one pulse per rotation of the pump motor 5.

However, in the detection of the pump rotation speed by the measurement of the tachometer, it is not possible to accurately detect a change in the rotation speed when the pump stops, in which the pump rotation speed attenuates in a short time. In order to detect a change in the number of rotations of the pump shaft when the pump is stopped, a rotation detector for detecting the number of rotations of the pump shaft is provided in the pump casing, and a through-hole for extracting an output from the rotation detector is provided in the pump. It must be drilled in the casing.

[0008]

However, if a through hole is formed in the pump casing, the sealing performance of the reactor pressure vessel 1 may be impaired, and the reliability of the reactor pressure vessel 1 may be reduced. .

The present invention has been made in view of the above circumstances, and can measure the pump rotation speed with high accuracy without providing a rotation detector for measuring the pump rotation speed. An object of the present invention is to provide a rotation speed detection system for an internal pump that can sufficiently secure the reliability of a container.

[0010]

In order to solve the above-mentioned problems, a system for detecting the rotational speed of an internal pump according to the present invention comprises a pump casing provided at the bottom of a reactor pressure vessel, and a pump casing provided inside the pump casing. And an internal pump for forcibly circulating reactor water in the reactor pressure vessel by driving the pump impeller, the power supply of the pump motor being provided. Magnetic field attenuation characteristic measuring means for previously measuring the attenuation characteristic of the magnetic field after interruption,
And a residual voltage measuring means for measuring the residual voltage after the power supply is cut off. The residual voltage measured by the residual voltage measuring means is corrected by the magnetic field attenuation characteristic to measure an induced electromotive voltage. The change is detected as a change in the pump rotational speed after the power is cut off.

[0011]

The power of the pump motor for driving the internal pump is cut off, and the magnetic field attenuation characteristic measuring means measures the attenuation characteristic of the magnetic field of the pump motor in advance.
The residual voltage after power-off of the pump motor is measured by the residual voltage measuring means, and the residual voltage measured by the residual voltage measuring means is corrected by the magnetic field attenuation characteristic measured by the magnetic field attenuation characteristic measuring means. Measuring the induced electromotive voltage after the power supply of the pump motor is turned off, and detecting the pump rotational speed after the power supply of the pump motor is turned off by detecting a change in the induced electromotive voltage. It is not necessary to make a hole, the hermeticity is maintained, and the rotational speed of the internal pump can be accurately measured only by measuring the residual voltage of the pump motor.

[0012]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below with reference to FIGS.

FIG. 1 is a system diagram schematically showing an embodiment of an internal pump rotation speed detecting system according to an embodiment of the present invention, and FIG. 2 is a diagram showing the internal configuration of the internal pump shown in FIG. FIG. 3 is a longitudinal sectional view, and FIG. 3 is an explanatory view showing magnetic field attenuation characteristic measuring means for measuring the attenuation characteristic of the magnetic field of the internal pump in advance.

In a boiling water reactor as a light water reactor, a reactor core 11 is accommodated in a reactor pressure vessel 10, and a core shroud 12 defining the reactor core 11 and an inner peripheral wall of the reactor pressure vessel 10 are provided between the reactor shroud 12 and the inner peripheral wall of the reactor pressure vessel 10. An annular downcomer 13 is formed. A plurality of internal pumps 15 are arranged below the downcomer section 13 at intervals in the circumferential direction as recirculation pumps in the reactor.

As shown in FIG. 2, the internal pump 15 is a pump unit 1 disposed inside the reactor pressure vessel 10.
6 and a pump motor unit 17 disposed outside thereof, and a reverse rotation preventing device 18 provided at a lower end of the pump motor unit 17. The pump motor section 17 is housed in a pump casing 20 which is vertically provided in a liquid-tight manner at a pump nozzle section 19 at the bottom of the reactor pressure vessel 10.

The pump casing 20 contains a motor casing 22 containing a stator 21 therein, and a rotor 23 provided in the stator 21 is attached to a motor shaft 24. The motor shaft 24 is fitted to the lower part of the pump shaft 25 and integrally connected to the pump shaft 25, while the motor shaft 24 is supported by an upper radial bearing 26 and a lower radial bearing 27. An auxiliary impeller 28 is provided at the lower end of the motor shaft 24.
The upper and lower portions 8 are also supported by the upper thrust bearing 29 and the lower thrust bearing 30. A lower cover 31 is attached to a lower end of the pump casing 20 to seal the inside of the pump casing 20.

The pump shaft 25 is connected to the pump casing 2
0, and extends into the reactor pressure vessel 10 through the pump nozzle 19, and the pump 1
6 is mounted. The pump impeller 33 is connected to the pump nozzle 19 by the downcomer 13.
It is housed in a diffuser 34 seated on top.

A purge water device 36 is provided above the pump motor unit 17. The purge motor supplied by the supply pipe 37 of the purge water device 36 causes the pump motor unit 17 to move inside the reactor pressure vessel 10. The purge water completely separated from the reactor water and supplied from the supply pipe 37 is drained by the drain pipe 38.

The pump motor unit 17 is provided with a heat exchanger 40 for cooling the pump motor unit 17. The cooling water cooled by the heat exchanger 40 is supplied to the pump motor unit 1.
7 effectively cools the coil of the pump motor section 17 to prevent a temperature rise.

As shown in FIG. 1, the pump motor section 17 is connected to a motor drive power supply 44 by an electric wire (power supply cable) 45.
The internal pump 15 is driven by a drive voltage supplied from the motor drive power supply 44. When power is supplied to the pump motor unit 17 of the internal pump 15, the pump motor unit 17 is driven, and the pump shaft 35 is driven to rotate. The rotation of the pump shaft 25 causes the pump impeller 33 of the pump section 16 to rotate. Due to the rotation of the impeller 33, the reactor water in the reactor pressure vessel 10 is sucked from the upper portion through the downcomer portion 13 from the suction port 16a,
It is discharged from the lower discharge port 16b below the core 11. The discharged reactor water is subsequently guided to the reactor core 11 and forcedly circulated in the reactor pressure vessel 10.

In the system for detecting the rotation speed of the internal pump 15, a pump rotation speed detection device 46 is provided on an electric wire (power cable) 45 extending from the motor drive power supply 44 to the internal pump 15. The rotation speed detecting device 46 includes a measuring wire 47 branched from the middle of the wire 45, and the other end of the measuring wire 47 is connected to an attenuator 48. The attenuator 48 reduces the high voltage to a voltage that can be input to the recorder 49.

The attenuator 48 is connected via a signal line 50 to a recorder 49 for recording a voltage waveform.
9, a time change of a voltage value (voltage waveform) is recorded. The attenuator 48 and the recorder 49 constitute a residual voltage measuring unit 51. The residual voltage measuring unit 51 measures the residual voltage of the pump motor unit 17 after the power to the internal pump 15 is shut off. .

If the motor drive power supply 44 of the pump motor section 17 is suddenly shut off during the operation of the internal pump 15, the motor shaft 25 gradually rotates because the motor rotation system has a large inertial force. It drops and eventually stops.

A magnetic field is generated in the pump motor unit 17 by a current remaining on the rotor (rotor) 23 that rotates integrally with the motor shaft 25 during a period from when the power of the motor shaft 25 is turned off to when the motor shaft 25 is completely stopped. This magnetic field acts on the stator (stator) 21 to generate power. At this time, the pump motor unit 17 of the internal pump 15 functions as a generator. Therefore, a voltage is generated in the electric wire 45 connected to the motor drive power supply 44. The electromotive voltage generated after the power is cut off is proportional to the strength of the magnetic field and the rotation speed of the motor shaft 25 and the rotor 23.

However, if the residual magnetic field of the rotor 23 is constant, the peak voltage after the power supply is cut off matches the rotation speed of the rotor 23 (see FIG. 6), but the inside of the rotor 23 that rotates due to the inertia of the pump rotation system. The magnetic field decays in a short time. For this reason, the attenuation of the magnetic field affects the attenuation of the voltage value generated after the power is turned off. Therefore, after the power is cut off, the pump motor unit 17 corrects the residual voltage value of the pump motor unit 17 in consideration of the magnetic field attenuation characteristics, and changes the induced electromotive voltage of the pump motor unit 17 to match the rotation speed of the rotor 23. Is obtained, a precise change in the number of rotations of the rotor 23, that is, the motor shaft 24 and the pump shaft 25 can be obtained.

The damping characteristic of the magnetic field depends on the pump motor unit 1
7, the magnetic field attenuation characteristic of the pump motor unit 17 can be determined in advance by a unit test.

Magnetic field attenuation characteristic measuring means 5 for measuring the magnetic field attenuation characteristic of the pump motor section 17 of the internal pump 15
2 is configured as shown in FIG.

The motor characteristics of the pump motor section 17 of the internal pump 15 are checked by a unit test.
The motor may have the same electrical characteristics as the pump motor unit 17 before it is attached to the pump motor unit 17.

The pump motor section 17 is provided with a motor drive power supply 54 (this power supply 54 is a motor drive power supply 44 shown in FIG. 1).
It may be. ), While the power supply 5
5 is detachably connected to an external motor 56 connected to the motor 5. Then, the pump motor unit 1 is
An electric voltage measuring device 58 for measuring a change in the electromotive voltage after the power of the pump motor unit 17 is cut off is connected to the electric wire 57 connected to the electric motor 57.
Is connected.

The measurement of the magnetic field attenuation characteristic of the pump motor unit 17 by the magnetic field attenuation characteristic measuring means 52 is performed as follows.

First, the pump motor section 17 and the external motor 56 are connected (coupling), and both motors 17 and 56 are connected.
Are driven by the power sources 54 and 55, respectively, to rotate the pump motor unit 17 and the external motor 56 at the same rotation speed.

Next, the power supply 54 of the pump motor unit 17 is cut off, and the external motor 56 is rotated at the rotation speed before the power supply of the pump motor unit 17 is cut off. Pump motor unit 1 at this time
7 is measured by the electromotive voltage measuring device 58, and the change in the electromotive voltage of the pump motor unit 17 is measured. That is, the change in the electromotive voltage of the pump motor unit 17 after the power is cut off is measured by the electromotive voltage measuring device 58 while the rotation speed of the pump motor unit 17 after the power cut is kept constant.

The change in the electromotive voltage at this time is as follows. Since the rotation speed of the pump motor unit 17 is constant, the pump motor unit 1 after the power is turned off without considering the change in the rotation speed of the pump motor unit 17.
7 changes in the electromotive voltage in accordance with the attenuation of the magnetic field generated.
Therefore, the electromotive voltage measuring device 58 can measure only the change in the electromotive voltage according to the attenuation characteristic of the magnetic field, excluding the change in the number of revolutions of the pump motor unit 17. The magnetic field attenuation characteristics of the unit 17 can be obtained.

Next, the operation of the rotation speed detection system for the internal pump will be described.

The internal pump 15 mounted on the reactor pressure vessel 10 performs a single test of the pump motor unit 17 of the internal pump 15 before the operation of the internal pump 15 as shown in FIG. The magnetic field attenuation characteristics of the unit 17 are obtained in advance. At the time of this unit test, the external motor 56 is connected to the pump motor unit 17 and the pump motor unit 17 and the external motor 56 are rotated at the same rotation speed. Thereafter, the power supply to the pump motor unit 17 is stopped, and a change in the electromotive voltage of the pump motor unit 17 is measured by the electromotive voltage measuring device 58 as the magnetic field attenuation characteristic means 52. The characteristics are determined in advance.

Next, an internal pump 15 is attached to the reactor pressure vessel 10 to perform a required operation, and forcibly recirculate the reactor water in the reactor pressure vessel 10.

When the pump drive power supply 44 of the pump motor unit 17 of the internal pump 15 attached to the reactor pressure vessel 10 is cut off for some reason, the residual voltage remaining in the pump motor unit 17 is reduced by the attenuator 48. Is measured and recorded by the recorder 49 via the.
FIG. 4 shows the peak voltage P of the pump motor unit 17 at this time.
And a residual voltage V _{1 represented} by an approximate curve of the peak voltage P
Is shown. The attenuation of the residual voltage in the pump motor unit 17 is determined by a combination of the attenuation of the pump rotation speed and the attenuation of the magnetic field.

Therefore, after the power of the pump motor unit 17 is cut off, the pump motor unit 17 measured by the recorder 49 is turned off.
Is divided by a previously determined magnetic field attenuation characteristic of the pump motor unit 17, a change in the induced electromotive voltage due to only the attenuation of the pump rotation speed can be obtained. From the change in the induced electromotive voltage, the pump motor unit 17 can be obtained. Change in the number of rotations can be obtained.

FIG. 5 shows the residual voltage V ₁ of the pump motor section 17.
Is the magnetic field attenuation characteristic of the pump motor unit 17 (magnetic field attenuation M)
Is a graph showing the induced electromotive voltage V ₂ of the pump motor unit 17 corrected in the above, and the induced electromotive voltage V ₂ is proportional to the pump rotation speed. For example, one rotation of the rotor 23 of the pump motor unit 17 corresponds to four peak voltages P Equivalent to a minute.

Therefore, if the attenuation ratio of the magnetic field of the pump motor unit 17 is R _P and the change in the pump speed is R, the following relational expression is established.

[0041]

(Equation 1)

[0042]

(Equation 2)

As described above, when the power of the pump motor unit 17 of the internal pump 15 is cut off, the residual voltage of the pump motor unit 17 is measured by the recorder 49 of the residual voltage measuring unit 51, and the measured residual voltage is measured. The voltage is corrected by the magnetic field attenuation characteristic measured in advance by the magnetic field attenuation characteristic measuring means 52,
The induced electromotive voltage of the pump motor unit 17 is measured. A change in the number of revolutions of the pump shaft 25 of the internal pump 15 can be detected from the measured induced electromotive voltage.

According to this embodiment, the internal pump 1
5 and the motor drive power supply 44 connected to the pump motor unit 17, the attenuator 4
By simply providing the recorder 49 for measuring the residual voltage of the pump motor unit 17 via the power supply 8, the number of rotations of the pump shaft 25 of the internal pump 15 after the power is shut off can be easily and accurately detected.

[0045]

As described above, the present invention provides a magnetic field attenuation characteristic measuring means for previously measuring the magnetic field attenuation characteristic after the power supply of the pump motor is cut off, and a residual magnetic field for measuring the residual voltage after the power supply of the pump motor is cut off. Voltage measuring means, and the residual voltage measured by the residual voltage measuring means is corrected by the magnetic field attenuation characteristic to measure an induced electromotive voltage after the power of the pump motor is cut off. Since the rotational speed of the internal pump is detected after the power is shut off, the rotational speed of the internal pump after the power is shut down can be measured with high accuracy without deteriorating the reliability of the reactor pressure vessel.

[Brief description of the drawings]

FIG. 1 is a system diagram schematically illustrating a part of a rotation speed detection system of an internal pump according to an embodiment of the present invention.

FIG. 2 is a longitudinal sectional view showing the internal configuration of the internal pump of FIG.

FIG. 3 is an explanatory diagram showing a magnetic field attenuation characteristic measuring unit that measures a magnetic field attenuation characteristic of an internal pump in advance.

FIG. 4 is a graph showing a residual voltage after the power of the motor unit of the internal pump is cut off.

FIG. 5 is a graph showing an induced electromotive force obtained by correcting the residual voltage shown in FIG. 4 with a magnetic field attenuation characteristic.

FIG. 6 is a diagram illustrating a relationship between a pump rotation speed and an induced electromotive voltage.

FIG. 7 is a partially cutaway perspective view showing a conventional reactor pressure vessel.

FIG. 8 is a longitudinal sectional view showing a conventional reactor pressure vessel.

[Explanation of symbols]

 Reference Signs List 10 reactor pressure vessel 11 core 12 core shroud 13 downcomer section 15 internal pump 16 pump section 17 pump motor section 20 pump casing 21 stator 23 rotor 25 pump shaft 44, 54 motor drive power supply 45 electric wire 46 pump rotation detector 47 measurement Electric wire 48 Attenuator 49 Recorder 50 Signal line 51 Residual voltage measuring means 52 Magnetic field attenuation characteristic measuring means 55 Power supply 56 External motor 58 Electromotive voltage measuring device

Claims (1)

(57) [Claims] 1. A pump casing provided at a bottom of a reactor pressure vessel, a pump motor housed in the pump casing, and a pump impeller rotationally driven by the pump motor. In the internal pump for forcibly circulating the reactor water in the reactor pressure vessel, the magnetic field attenuation characteristic measuring means for previously measuring the magnetic field attenuation characteristic after the power supply of the pump motor is turned off, and the residual voltage after the power supply is cut off And measuring the induced electromotive voltage by correcting the residual voltage measured by the residual voltage measuring means with the magnetic field attenuation characteristic. A system for detecting the rotation speed of an internal pump, wherein the system detects a change in rotation speed.