JPS6029693A - Drive for control rod - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Application of the Invention] The present invention relates to a control rod drive device for a nuclear reactor, and particularly to a control rod drive device driven by an electric motor.

[Background of the invention]

Approximately 200 control rods are used in large nuclear power reactors. Inserting all control rods into the reactor core and shutting down the reactor in an emergency is also important for safe operation of the reactor.

In a boiling water reactor, a control rod drive device with a full stroke of about 4 meters and a minimum drive unit of about several meters is used. FIG. 1 shows the control drive system.

In FIG. 1, a control rod 9 is inserted into or withdrawn from a nuclear reactor core (not shown), and this operation is performed by an electric motor 1 rotating a screw 4 and moving a nut 5 up and down.

That is, the threaded part of the screw 4 is tightly fitted into the nut 5, and there is a connecting rod 7 above the nut 5 that moves together with the control rod 9, and the control rod moves according to the vertical movement of the nut. be.

The position of the control rod is determined by a position detector 2 connected to the shaft of the motor 1.
This can be determined by detecting the number of rotations and angle of the screw 4.

In addition, 8 is a part of a pressure vessel, and 6 is a housing which accommodates a control rod drive part.

FIG. 2 is a diagram illustrating a conventional control rod drive system. One motor drive circuit 40 is provided for each motor so that all control rods can be driven simultaneously in the event of a nuclear reactor emergency.
In other words, there are as many control rods as there are control rods. The button and flow line drive circuit 40 is a circuit composed of semiconductors that controls the forward rotation, reverse rotation, and rotation speed of the electric fertilizer iso 1.
A diagram illustrating the inside is shown in FIG. The current from the source 80 is rectified by the rectifier 43, and the impark circuit 41 generates a variable frequency alternating current power necessary for driving the electric IRS 1, and supplies it to the motor 1. The inverter circuit 41 is controlled by a control circuit 42, and FIG. 4 shows an explanatory diagram of control of the rotational speed of the electric motor.

In order to accurately and minutely drive the control rod, the electric motor 1 needs to rotate through the inverter output power supply of the motor drive circuit 40. A situation in which the electric motor does not rotate when the inverter output power is connected, a state in which it cannot be controlled at any time, is called a step-out, and is a state that is unsuitable for micro-drive control of control rods. In order to control the motor to prevent it from stepping out, when driving the control rod, it is necessary to start at a low speed that allows the motor to start rotating, and then gradually accelerate it to the rated speed (l). period to-t1). Conversely, when stopping, 1 speed V
o'! You need to slow down and then stop.

Referring to FIG. 2, the method of operating the control rod will be explained.

Normal control rod operation is performed by the motor control circuit 31 receiving an operation signal 101 generated by the control rod operating device 20 in accordance with a command from a plant operator, and selecting the motor to be driven and the direction of rotation. , and a movement distance control command to the electric drive circuit 40.

Normally, control rods are operated one at a time or several at the same time.

In the event of a nuclear reactor emergency, the motor control circuit 31 takes in the scram signals 103 to 106 output from the reactor emergency shutdown (safety cooling) device 50 via the logic circuit 32, and all electric motors ζ11 to 11 are simultaneously operated at the maximum speed. 1 drive, and the control rod 9 is inserted into the reactor core.

The reactor emergency shutdown system W50 includes four identical and independently separated emergency shutdown circuits A1. A2. B1. , 'B2 has been constructed'. The logic circuit 32 outputs the emergency insertion signal 10 if both A1 and A2 and/or both B1 and B2 output the scram signal at the same time.
7 is output.

Note that, for the sake of simplicity, the control rod position indicating circuit is not shown in FIG.

In such a system, the frost, motive control device, 3
0 and the motor drive circuit 40 are used not only during normal operation but also during emergencies, and therefore need to have high reliability equivalent to that of a nuclear reactor emergency shutdown system (safety protection system). However, these are originally circuits made up of multiple semiconductors to accurately drive control rods by small amounts each time during normal operation, and the number of component parts is small, making it difficult to improve reliability as a single item. There is. Therefore, if a failure were to occur, all or one control rod would not be able to be driven. It is not preferable to add a redundant circuit to these circuits as a countermeasure against this heat '1, since the switching circuit will be complicated and the size, quantity and cost will increase significantly.

[Purpose of the invention]

The present invention has been made in view of the above points, and its purpose is to control a control rod drive mechanism that increases the reliability of the device so that control rods can be inserted into the reactor core in the event of an emergency in a nuclear reactor. The goal is to provide equipment.

[Summary of the invention]

The present invention is characterized in that the control rod drive mechanism is provided with a motor exclusively for emergency insertion, in addition to the motor for normal operation, and the control circuit for the motor for emergency insertion is separate and independent from the circuit for normal operation. shall be.

[Embodiments of the invention]

Examples of the present invention will be described in detail below.

An embodiment of the control rod drive mechanism and its control system of the present invention is shown in FIGS. 5 to 8. That's a shame, like-numbered parts in each drawing indicate corresponding parts.

In FIG. 5, the control rod drive mechanism portion shown above the electric motor 1 is the same as in FIG. 1. A position detector 2 is connected to the shaft of the electric motor 1 on the opposite side to the screw 4 (that is, on the lower side), and the shaft is configured to pass through the inside of the position detector. Details of this point are shown in FIG. A position transmitter 16 is connected to the motor shaft 12 via gears 14 and 15.
The position detector 2 is configured so that it can be attached. An emergency insertion electric motor 10 is coupled to this electric motor shaft 12 via a transmission mechanism 11. Any type of electric motor may be used as the emergency insertion electric motor 10, but in the present invention, a three-phase visiting electric motor is used as an embodiment. Induction motors have a large starting torque and can be started even under somewhat heavy loads. In addition, it has the advantage of being structurally simple and less likely to break down, so it is suitable for emergency insertion of control rods. However, since the induction motor is a high-speed rotating machine, it is necessary to reduce the rotation speed to the rotation speed of the screw 4 in accordance with the insertion speed of the control rod, and in the present invention, the transmission mechanism 11 fulfills this function. The transmission mechanism 11 also has a veri clutch function to prevent the screw 4 from being damaged due to excessive torque.

In the present invention, the electric motor 1 is an electric motor that rotates at a low rotational speed so that it can be directly connected to the screw 4, and a permanent magnet is used on the rotor side. The rod 9 can be brought to a stop without the need for additional brakes. In other words, since the drive mechanism of the present invention does not have an electromagnetic brake or a mechanical brake that operates depending on the power supply, the starting torque of the emergency insertion motor is the sum of the holding torque of the motor 1 and the load torque in terms of the shaft of the motor 1. Rather, it is sufficient if the structure is large enough to allow insertion of a control rod.

FIG. 7 shows an embodiment of the control system of the present invention. Normal control rod insertion'' and withdrawal operations are performed using the control rod operating device 20.
, the motor control circuit 31, and the motor drive circuit 40 provided for each control rod to rotate the motor 1 forward or reverse.

In an emergency, the scram signals 103 to 106 from the reactor emergency shutdown device 50 are sent to the emergency insertion motor power supply switching circuit 70.
Power from the power source 80 is supplied to the emergency insertion electric motor 10 via the power source 80, and the control rod 9 is inserted into the reactor core.

FIG. 8 shows an embodiment of the electric control circuit 70 for emergency insertion. Emergency shutdown circuit A1 of the reactor emergency shutdown (safety maintenance) device 50. A2. B1. Scram signal 103 from B2
106, electromagnetic switches 71 to 74 corresponding to each operate. The contacts of the electromagnetic switches 71 to 74 are connected to the power source 80, which causes a closed circuit if both or one of the scram signals A1 and A2 and both or one of the scram signals B1 and B2 occur simultaneously. It is configured to supply power to the emergency insertion electric motor 10. Note that the transformer 75 receives η5. This is provided to create a 1L voltage insulated power source for the magnetic switch, and even if the source for the electromagnetic switch is created using a different method than the example shown in this figure, it will not defeat the purpose of the present invention. It does not change.

The 1 ff 1 l rod inserted at the full pail position will be stopped by the slip clutch, but if the electric motor 10 continues to rotate as it is, the life of the Vesi clutch will be shortened, so it is necessary to stop the electric motor 10 to maintain the life of the Vesi clutch. is desirable. For this reason, the timer 76 in FIG. 8 opens its time limit contact 77 after a predetermined time after the control rod starts insertion.
The electric motor 10 is stopped by turning off the operation of the electromagnetic switch. The set value of the timer 76, that is, the time during which the electric motor is driven, may be set so that the control rod at the fully withdrawn position can be inserted to the fully inserted position.

The time required for a control rod to move a full stroke varies depending on the speed of the control rod, but if it is several 10 gates per minute, it will take several 1 minutes.
The value ranges from 0 seconds to several minutes. Note that even if the power to the emergency insertion electric motor 10 is turned off, the control rod can continue to be stopped at that position without falling due to the holding torque of the electric motor 1 as described above.

FIG. 9 shows another embodiment of the present invention. In normal control rod operation, the control rods are only driven one at a time or several at the same time, so we installed as many motor drive circuits as the number of control rods that are to be driven at the same time, and drive the control rods in proportion. It can be configured to: The same applies to the case where several control rods are moved at the same time, so to simplify the explanation, FIG. 9 shows an example when the control rods are moved one by one. There is only one electric motor and drive circuit 40, and the selection switching circuit 60 obtains information about the control rod to be driven from the control signal 102, and selects the electric motor (,
Connect Xjl11 to the motor drive circuit 40. Otherwise, the control rods are energized during normal operation in the same manner as described above. The circuit for inserting all control rods in an emergency is the same as in FIGS. 7 to 8 described above, and the operation is also the same. By constructing the motor in this manner, the number of motor drive circuits is reduced, the occurrence of failures as a whole is reduced, reliability is further improved, and the entire apparatus is constructed compactly.

FIG. 10 shows another embodiment of the present invention. In order to reliably stop the nuclear reactor, an emergency insertion motor power supply switching circuit 70 is installed.
Four circuits are provided, and each control rod is configured to belong to one of the circuits. With this configuration, even if one circuit fails, the remaining circuits can insert as many control rods as necessary to stop the reactor, improving reliability. can be done. However, by providing four power supplies 80 and making them correspond to each motor power supply switching circuit 70, the separation and independence of the four circuits can be further strengthened, and reliability can be further improved. In the above description, an example has been described in which the motor power supply switching circuit and the like are divided into four circuits, but it is clear that the number does not need to be limited to four. In addition, in FIG. 10, for simplicity of explanation, only the circuit of the emergency insertion motor is shown, and the circuit for operating the normal control rod 1 can be constructed in the same way as in FIG. 7 or 9. Okay, so it's not shown.

In the above embodiment, that is, in FIG. 5, the position detector 2 is provided below the electric motor 1, but it may also be provided above the electric motor 1, that is, on the screw 4 side.

In the above embodiment, the electric motor 1 is used to stop the control rod.
Although it depends on the holding torque, an electromagnetic brake may be provided separately to provide redundant stopping functions and to increase stopping maintenance torque. If a motor without holding torque is used as the motor 1, a device is required to stop and hold the control rod, but this device may be an electromagnetic brake or other device. It's okay.

In the above embodiment, the logic of the reactor emergency shutdown device 50 and the emergency insertion logic circuit 32 is a logic circuit called 1 Out of 2 duplication, but it is not limited to this.
, 2 out of 3, or other logic does not change the gist of the present invention.

Further, in FIG. 8, the emergency insertion motor power supply switching circuit 70 has been described as being constituted by an electromagnetic switch, but it may be constituted by a semiconductor such as a Zyristor or a transistor.

In addition, in order to ensure the life of the clutch clutch, the emergency insertion electric motor 10 is activated only for a predetermined period of time depending on the timer 76.
0 may be stopped. For example, the signal from the position transmitter 16 of the position detector 2 is processed by the control rod position signal processing device, so a signal from this device indicating that each control rod is at the full insertion position is waited for.
This signal can stop the emergency insertion electric motor 10. Further, the position detector 2 may be provided with a separate switch for detecting that it is at the full insertion position.

Alternatively, the slip clutch itself may be provided with a switch that detects its operation, and the emergency insertion electric motor 10 may be stopped when the switch is operated.

〔Effect of the invention〕

As described above, according to the present invention, the device for normal control rod operation and the device for inserting control rods in an emergency are configured separately, so the former device is more compact. In addition, the latter device can be constructed with a simple circuit and can be separated and independent from the former device, which is a general system, so it has higher reliability and safety. Therefore, the effect is great for atomic couplers.

[Brief explanation of the drawing]

Figure 1 is a diagram showing a conventional control rod drive mechanism, Figure 2 is a diagram explaining a conventional control rod drive system, Figure 3 is a diagram explaining the inside of a motor drive circuit, and Figure 4 is a diagram explaining the motor drive circuit. Fig. fi-S5 is a diagram illustrating an embodiment of the control rod drive mechanism of the present invention, and Fig. 6 is a diagram illustrating an embodiment of the position detector portion of the control rod drive mechanism of the present invention. The explanatory diagram, Fig. 7, is of the present invention? 8 is a diagram illustrating an embodiment of the 1fll iql system, FIG. 8 is a diagram illustrating an embodiment of the control circuit for the emergency insertion motor of the control system of the present invention, and FIG.
The figures are diagrams illustrating other embodiments of the control system of the present invention,
FIG. 10 is a diagram illustrating another embodiment of the control circuit for the rapid insertion viewing machine of the control system of the present invention. DESCRIPTION OF SYMBOLS 1...Electric motor, 2...Position detector, 4...Screw, 5...Nut, 6...Housing that accommodates the control rod drive section, 7...Connection 4'! 'l'-18... Part of pressure vessel, 9... Control rod, 10... Electric motor for emergency insertion, 11... Transmission mechanism, 12... Motor shaft, 1
4... Gear, 15... Gear, 16... Position transmitter, 20... Control rod operation console, 30... Control rod control device, 31... Motor control circuit, 32... Fire emergency insertion logic circuit, 33...AND circuit, 34...AND circuit, 35...OR circuit, 40...motor 1 drive circuit,
41... Inverter circuit, 42... Control circuit, 43
...Rectifier, 50...Reactor emergency shutdown device, 51.
...Emergency stop circuit AI, 52...Emergency stop circuit A, 2
) 53...Emergency stop circuit Bl, 54...Emergency stop circuit B2.60...Selection switching circuit, 70...Emergency insertion motor power supply opening/closing circuit, 71...Electromagnetic switch A, 1.
72...Electromagnetic switch A2.73...Electromagnetic switch B1
．． 74...Electromagnetic switch B2.75...Transformer, 7G
...Timer, 77...Time-limited contact of timer 76, 80
... Electromagnetic, 101 ... Operation signal, 102 ... Control signal, 103 ... Scram signal AI, 104 ... Scram signal A2. 105 ... Scram signal Bl, 10
6...Scrum signal J32, Mei 30 74 diagram 5g

Claims (1)

[Claims] 1. A control characterized by comprising a first electric motor for minute positioning that inserts or withdraws a control rod, and a second electric motor for high-speed drive that inserts or withdraws a control frame. Rod drive. 2° A first electric motor for micro-positioning that inserts or withdraws the control rod, and a second electric motor for high-speed drive that inserts or withdraws the control rod, and the first and second electric motors are mutually connected. A control rod drive device characterized in that an independent control circuit is provided in the control rod drive device.