JP2001027684A - Control system for control rod - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a control rod control system which can restrict an unnecessary rod withdrawal block signal generated due to a control rod position deviation possibly brought about from a normal characteristic of an induction motor, and can detect an irregularity of the induction motor itself by monitoring the control rod position deviation. SOLUTION: The control rod control system compares a gang deviation large set value 108 which is a slightly larger value than a control rod positioned deviation possibly brought about from a normal characteristic of an induction motor empirically obtained beforehand in accordance with a control rod maximum drive distance, and a gang deviation 106 with each other by a comparator 114, and outputs a control rod withdrawal block signal 107 when the gang deviation 106 is larger than the gang deviation large set value 108.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a control rod control system for a boiling water nuclear power plant, and more particularly to a control rod for controlling a control rod using a detected control rod position to adjust a reactor power. Related to control system.

[0002]

2. Description of the Related Art In an advanced nuclear power plant (ABWR),
The operation of the control rod is performed by electric drive. The power control of the reactor
The operation is performed by the operation of the control rod.

The operation of the control rod is performed based on a control rod operation procedure in accordance with an operation command from a control rod operation monitoring panel in the central control room. The operation of the control rod is performed by a step motor,
This is performed according to a pulse signal from the speed control circuit. Speed control of the step motor is performed by changing the frequency of the pulse signal.

In order to control the power of the reactor by pulling / inserting the control rod into / from the core, it is necessary to detect the position of the control rod in the core.
Therefore, two synchro transmitters are connected to the motor shaft so that the current position of the control rod can be known.

[0005] As a technique related to the control rod operation by the step motor, there are techniques described in Japanese Patent Application Laid-Open Nos. 55-143604 and 57-208880.

[0006]

When a stepping motor is used as a control rod drive motor and a fine drive is possible, a large number of power supply panels for the drive motor and laid cables are generated. For this reason, adoption of an induction motor (induction motor) as a control rod drive motor is under study.

[0007] The induction motor includes a primary-side stator (stator) and a secondary-side rotor (rotor).
The secondary winding receives electric energy from the primary side by an electromagnetic induction effect, converts the electric energy into mechanical energy through an air gap, rotates the rotor, and generates mechanical power.

In this induction motor, the number of revolutions cannot be controlled by current control on the stator side. In addition, in the induction motor, the motor slip differs for each control rod due to the variation in the load torque, and as a result, the respective driving speeds also differ. Further, it is conceivable that the driving speed varies depending on fluctuations in the voltage and frequency of the power supply that is the driving source of each control rod. For this reason, when the control rod is pulled out by a gang, there is a possibility that a control rod pull-out prevention signal caused by “large control rod position deviation” is generated due to a position deviation that can occur due to the characteristics of the normal induction motor as described above. There is a need to prevent it.

On the other hand, in order to detect abnormal behavior due to a failure of the induction motor itself during gang drive, it is necessary to monitor control rod position deviation among a plurality of gang driven control rods. It is important to monitor the control rod position deviation in order to diagnose the abnormality of the motor itself.

SUMMARY OF THE INVENTION It is an object of the present invention to suppress an unnecessary control rod withdrawal prevention signal generated by a control rod position deviation that can occur due to the characteristics of a normal induction motor, and to detect a control rod position deviation by detecting abnormality of the induction motor itself. It is to provide a control rod control system that can be performed by monitoring.

[0011]

The above object is achieved by monitoring the distance or time of a gang-driven control rod during gang pull-out, thereby variably setting a set value of a gang deviation. .

[0012] According to the above, it is possible to prevent unnecessary pulling out of the control rod due to a large positional deviation caused by the principle characteristics of the induction motor and other factors, so that the output control of the nuclear power plant becomes possible as before. Thus, the operability of the reactor is ensured.

[0013]

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

The present invention is applied to a case where a control rod is gang-pulled in a nuclear power plant.

FIG. 1 shows the overall configuration of a control rod control system in a nuclear power plant when an induction motor according to the present invention that does not control the speed of a motor is used.

A plurality of fuel rods 3 are provided at intervals in a reactor 1 to be controlled by the present system while being immersed in cooling water 2. In the space between the fuel rods 3, a plurality of control rods 4 which can be inserted / removed are arranged.

Each of the control rods 4 is raised and lowered by an induction motor 5 via a control rod drive mechanism 16, and is inserted / removed into a space between the fuel rods 3. Further, a control rod position detector 6 for detecting the displacement of the control rod 4 and a braking brake 7 and a holding brake 8 for stopping the induction motor 5 are arranged.

The control system used in the present embodiment includes a device for operating the control rod 4, a control rod operation monitoring panel 12 provided in a central control room, and an operation of the induction motor 5. A control rod drive auxiliary panel 9 having a device for controlling the control rod is compared with the control rod operation command content from the central control room and the current state of the control rods. A control rod position transmission auxiliary panel 10 for outputting an operation command to the drive auxiliary panel 9 and a control rod brake control device auxiliary panel 11 having a device for controlling a brake operation.
And

The control rod operation monitoring panel 12 has an input / output device (not shown) for an operator to operate and monitor, and a procedure for pulling and inserting control rods in a nuclear power plant, and an operation amount. Storage of the control rod operation procedure and comparison between the input command 14 and the control rod operation procedure. If there is no problem with the input command 14, control rod drive control / position for transmitting a pull-out / insertion command to the control rod position transmission auxiliary panel 10. It has a pointing device 13.

The input / output devices include a display device for displaying the coordinates of control rods, a coordinate selection button, and an instruction input device for operating instruction buttons for control rod operation mode, insertion, and withdrawal. The operator commands the operation of the control rod using these devices. The signal is sent to the control rod drive control / position pointing device 13.
Sent to However, if the wrong control rod is selected and the control rod is withdrawn, the thermal margin of the reactor may be deviated and a dangerous situation may occur. Therefore, the control rod drive control / position indicating device 13 stores a control rod operation procedure in which a control rod withdrawal / insertion procedure and an operation amount are determined in advance. Therefore, when operating the control rod, it is always monitored whether the selected control rod is the control rod of the coordinate to be operated and whether the operation amount does not exceed the specified value. Next, the operation of this embodiment will be described with reference to FIGS. The control rod position signal 100 in FIG.
The control rod position is transmitted to the control rod operation monitoring panel 12 via the control rod position transmission auxiliary panel 10 and is controlled by the control rod drive control / position indicating device 13.
It is taken in.

In the control rod drive control / position indicating device 13 shown in FIG. 2, the control rod position signals 100a to 100n of the control rods selected when the control rods are pulled out are transmitted to the maximum value selection circuit 101 and the minimum value selection circuit 101. The maximum value 103 and the minimum value 104 input to the circuits 102 and selected by the respective circuits.
Are input to a subtractor 105 to output a gang deviation 106
Is output. When the gang deviation 106 exceeds the gang deviation large set value 108, the control rod withdrawal prevention signal 107
Is output.

On the other hand, the large gang deviation set value 108 is set by the following method. The control rod withdrawal command signal 115 is input to the gang control rod position selection circuit 109, and the gang control rod position selection circuit 109 outputs the position signal 100 when the control rod withdrawal command signal 115 is input.
a to 100n are recognized as the position signals 100a to 100n immediately before the gang drive of the gang-selected control rod, and the position signal of the control rod at the highest position among the position signals 100a to 100n is the control rod position signal before the gang drive. 1
Output as 10. The average value of the position signals 100a to 100n may be output as the control rod position signal 110 before the gang drive. Control rod position signal 11 before gang drive
0 and the maximum value 103 of the control rod position are input to the subtractor 111, and the control rod maximum drive distance 112 during gang drive is output.

Next, the control rod maximum driving distance 112 is input to a function generator 113. In the function generator 113, the gang deviation large set value 10 corresponding to the control rod maximum drive distance 112 is set.
8 is stored, and when the control rod maximum drive distance 112 is input, the corresponding large gang deviation set value 108 is output. In addition, as this gang deviation large set value 108,
A slightly larger value (for example, 5% larger) than the control rod position deviation that may occur from the characteristics of the normal induction motor, which is obtained in advance by experiment according to the maximum drive distance of the control rod.
Is set. Since the control rod position deviation that can occur due to the characteristics of a normal induction motor increases as the control rod maximum drive distance increases, as shown by the function generator 113 in FIG. It is set to increase as the distance 112 increases.

The gang deviation large set value 108 variably set by the above method and the gang deviation 106 are compared with the comparator 1
14, when the gang deviation 106 exceeds the large gang deviation set value 108, the control rod withdrawal prevention signal 10
By outputting 7, the driving of the control rod 4 is stopped.

In the present embodiment described above, a value slightly larger than the control rod position deviation that can be caused by the characteristics of the normal induction motor obtained in advance through experiments is set as the large gang deviation setting value 108. A control rod withdrawal prevention signal is not generated for a control rod position deviation that can occur due to the characteristics of the induction motor described above, whereas a control rod withdrawal prevention signal is generated for a control rod position deviation that occurs due to an abnormality in the induction motor itself. This is based on the fact that the control rod position deviation caused by the abnormality of the induction motor itself is sufficiently larger than the control rod position deviation that can occur due to the characteristics of the normal induction motor.

According to this embodiment, an unnecessary pull-out prevention signal generated by a control rod position deviation that may occur due to the characteristics of a normal induction motor is suppressed, and the abnormality detection of the induction motor itself is performed by the control rod position. This can be done by monitoring the deviation.

[0027]

As described above, according to the present invention,
Unnecessary withdrawal prevention signals generated by control rod position deviations that can occur due to the characteristics of ordinary induction motors can be suppressed, and abnormality detection of the induction motor itself can be performed by monitoring the control rod position deviations.
Therefore, the operation efficiency of the reactor can be improved, and the safety of the reactor can be ensured.

[Brief description of the drawings]

FIG. 1 is a configuration diagram of a control rod control system according to a preferred embodiment of the present invention.

FIG. 2 is a configuration diagram of a control rod drive control / position indicating device 13 of FIG.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Reactor, 2 ... Cooling water, 3 ... Fuel rod, 4 ... Control rod, 5
... Induction motor, 6 ... Control rod position detector, 7 ...
Braking brake, 8: Holding brake, 9: Control rod drive auxiliary panel, 10: Control rod position transmission auxiliary panel, 11: Control rod brake controller auxiliary panel, 12: Control rod operation monitoring panel, 13
... Control rod drive control / position indicating device, 16 ... Control rod drive mechanism, 101 ... Maximum value selection circuit, 102 ... Minimum value selection circuit, 105, 111 ... Subtractor, 109 ... Gang control rod position selection circuit, 113 ... Function Generator, 114 ... Comparator.

 ──────────────────────────────────────────────────続 き Continuing from the front page (72) Yoshifumi Nagata, Inventor 3-1-1, Sachimachi, Hitachi-City, Ibaraki Pref. Hitachi, Ltd. Hitachi Plant (72) Inventor Katsumasa Narikawa 3-Chome, Sachimachi, Hitachi, Ibaraki No. 1-1 F-term in Hitachi, Ltd. Hitachi Plant (reference) 2G075 AA04 BA04 CA39 DA02 DA18 EA08 FA20 FB07 FC07 GA30

Claims (2)

[Claims] In a control rod control system for pulling / inserting a control rod electrically driven by an induction motor into a reactor, a plurality of control rods of a reactor having a large number of control rods are simultaneously scanned. A control rod control system characterized by variably setting a set value of a control rod position deviation large withdrawal prevention signal between control rods. 2. The control rod control system according to claim 1, wherein the variable set value according to claim 1 is set by a drive distance, a drive time, or both the drive time and a drive distance of each control rod to be gang driven.