JPS633295A - Nuclear-reactor safety protection system - 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 Industrial Application] The present invention relates to a nuclear reactor safety protection system, and in particular, to further improvement of a nuclear reactor safety protection system in which a so-called weak current circuit and a strong current circuit including a power stage coexist. This is related to improving the reliability of

[Conventional technology]

In nuclear couplants, in order to ensure the safety of the reactor, when abnormal transient conditions may occur,
A safety protection system is provided to prevent this. For example, "Systems and Control", vol. 18.

No. 7, 1974, pages 14 to 20, the function and structure of the safety system are described. To simplify this configuration, as shown in Fig. 2, the output signals from the redundant sensors 1 to 3 are taken into the trial J devices 4 to 6, and the majority decision of the trip signals output from each measurement device is performed. They are assembled to drive the scram electromagnet 9. here,
7 is a majority circuit, and 8 is a control device. Among these, there are examples in which the circuit up to the majority circuit is configured with an IC circuit, and the control device 8 is configured with a relay or a contactor, or the majority circuit 7 and the control device 8 are configured with a relay or a contactor. In either case, the part that drives the scram electromagnet is a relay or contactor circuit.

As is well known, a relay or contactor has a configuration shown in FIG. 3, with a coil 11 on the primary side and contacts 12, 13, and 14 on the secondary side. 10 is a relay or contactor. The contact 12 is called a B contact and is in contact with the common contact 13 when the coil 11 is not energized.
The contact 14 is called an A contact and is not in contact with the common contact 13 when the coil 11 is not energized.By the way, the safety protection system needs to operate in any situation in the plant. For example, a scram must be possible even if the power supply connected to the contacts of the relay or contactor 10 of FIG. 3 is lost. For this reason, the above-mentioned relay or contactor uses A contacts, and normally the coil 11 is energized to bring the contacts 13 and 14 into contact, and the scram electromagnet is energized. When released, the scram electromagnet becomes de-energized and scrams. Therefore, the safety protection system is very safe because even if the power supply connected to the contacts is lost, the system will be scrammed.

The scram electromagnet is driven by an alternating voltage of about 100V and is generally called a power stage. On the other hand, the relay or contactor that drives the scram electromagnet is excited by a signal from an electronic circuit using an IC, LSI, or the like. Therefore, a relay or contactor has both a low current section and a high current section. For this reason, high insulation between the primary and secondary sides of a relay or contactor is required.

Generally, the physical distance between the primary and secondary sides of a relay or contactor is several meters to several (meters), providing sufficient insulation. However, the larger the atomic couplet, the more Reliability of the safety protection system is important, and it is desirable that the insulation between the primary and secondary sides of the relay or contactor described above be even higher.

In particular, it is necessary to eliminate as much as possible noise from the high-voltage section that mixes into the low-voltage section and causes malfunctions, which lowers the plant operating rate and system reliability.

[Problem that the invention seeks to solve]

In the conventional example described above, in order to increase the reliability of the reactor safety protection system, there are manufacturing constraints even if attempts are made to increase the physical distance between the primary and secondary sides of the relay or contactor to improve insulation. It is a process that obtains much higher insulation properties than conventional products.

The purpose of the present invention is to provide extremely high insulation between the scram electromagnet and the device that excites this electromagnet, and to always maintain majority logic even if the redundant devices that are separated into each system fail. An object of the present invention is to provide a nuclear reactor safety protection system that can be assembled to apply a scram signal to a scram electromagnet.

[Means for solving problems]

In a nuclear reactor safety protection system, the present invention provides a light emitting element in the output part of a signal processing device that independently processes output signals from redundant sensors and outputs a trip signal,
The circuit that drives the scram electromagnet is configured with an optical switch, and the above light emitting element and the optical switch are connected with an optical fiber cable, greatly improving the environmental resistance of the reactor safety protection system.In addition, one signal processing device Even if a signal processing device fails, by fixing the output signal of the failed signal processing device to logic 170 ++ or logic II I If, majority logic is formed using the output signals from the signal processing devices other than the failed signal processing device, and scram is performed. The optical switch is configured to be able to output a signal, and an optical thyristor is used as an optical switch to detect the AC voltage applied to the optical thyristor, and stop the optical signal applied to the optical thyristor only when this voltage is near the zero cross. The feature is that the operation of the scram electromagnet is monitored by detecting the current flowing through the scram electromagnet or the sound when the scram electromagnet operates, thereby making the safety protection system even more reliable. .

[Effect]

By configuring the safety protection system for the x-reactor as described above, the insulation between the signal processing section and the power stage can be extremely high, and
Even if one scram processing device fails, the remaining devices can always make a majority decision, and the operation of the scram electromagnet can be constantly monitored, so the reliability and environmental resistance of the safety protection system can be extremely high.

〔Example〕

Hereinafter, specific embodiments of the present invention will be described in detail using the drawings. Equally numbered parts in each drawing indicate equivalent parts.

FIG. 1 shows a basic embodiment of the present invention,
The signal processing devices 20, 21, 22, and 23 are devices that take in signals from the sensors 1 to 3,100, process them, and output a trip signal when the result exceeds a specified value. There may be a plurality of sensor signals input to each device 20 to 23.

In this embodiment, the Scrum function is divided into four systems. The scram signal of each system is output by combining the 2 out of 4 logic of the trip signal which is the output signal of the signal processing unit 20 to 23, but 1 out of 2 twice N
The present invention can be similarly applied to the case where a scram signal is output by assembling logic using other methods such as logic.

Further, the majority circuit 24 shown in FIG. 1 is configured to scram upon loss of the logic 140'', that is, a signal loss, from the viewpoint of safe operation.

The signal processing devices 20-23 and the majority circuits 24-27 are connected by optical fibers 56-59. Each optical fiber is directly connected to the gates of optical switches 44 to 55 forming majority logic. Here, the number of each optical fiber is a
= d. A majority circuit 24 constituted by an optical switch serves as a switch for determining whether or not to apply the alternating current voltage 28 to the excitation coil 36 of the scram electromagnet 40. The other scram electromagnets 41, 42, and 43 have similar circuit configurations. 37-39 are each 7463 stones for scrum 41
~43 excitation coils.

The optical fiber between the No. 421 processing device and the majority voting circuit is
- It can be configured as shown in FIG. Although the configuration of the optical fiber S6 between the signal processing device 20 and the majority circuit is shown here, the same applies to the optical fibers 57 to 59. Fourth
-The signal processing device 20 in FIG. 6 is shown with only its output section being shown in a simplified manner.

In FIG. 4, 61 is a light emitting element, 60 is a light emitting element driving circuit, 99 is an arithmetic processing unit, 98 is an output signal from a sensor, and 97 is a trip command signal. The current signal flowing through the light emitting element 61 becomes an optical signal of the optical fiber 56. The optical fiber 56 transmits the optical signal from the light emitting element 61 to each majority circuit 2.
Distribute between 4 and 27. Furthermore, one majority circuit is distributed to three optical fibers. This corresponds to the optical switch that constitutes the majority circuit.

Each optical switch performs switching according to the strength of the optical signal guided by the fiber.

Therefore, scram signals 32 to 35 are outputted in accordance with the optical signals from each signal processing device.

As described above, the signal processing devices 20 to 2 configured with electronic circuits
The 3 side and the optical switches 24 to 27, which are the electrical power stage, are electrically independent, and each system is also electrically independent, so the system has very high environmental resistance and reliability, and is superior to conventional systems. There are no such problems at all.

The configuration shown in FIG. 5 is an example in which the light emitting elements 61 shown in FIG. 4 are installed in correspondence with the number of optical switches, and is intended to distribute risks. For example, among the light emitting elements 63 to 68,
Even if the output light of light emitting element 63 becomes logic ``0'', the output light from other elements is logic 1'1'', and compared to Fig. 4, this part is dangerous, and the dangerous dispersion rate is 12 times higher. expensive.

The configuration shown in FIG. 6 is an example in which the light emitting elements 63 to 68 in FIG. 63
If the electrical part of the optical switch malfunctions to cause the optical switch to go into the open mode, the other light emitting elements 64 to 68 will no longer receive current and will no longer output light to the optical fiber. On the other hand, in FIG. 6, the light emitting elements 63 to 68 are driven in parallel, so even if the electrical part of one light emitting element fails in the open mode, the other light emitting elements 64 to 68 68 is not affected by this in any way. In addition, 62.69 is 60
Similarly, it is a light emitting element drive circuit.

With the above configuration, the reliability of the safety protection system is further improved.

The configuration shown in FIG. 7 is another embodiment of the present invention.

In this system, the majority logic is not constructed using an optical switch as shown in FIG. 1, but the majority logic is constructed using the optical fiber itself, and the alternating current voltage applied to the scram electromagnet is controlled by one optical switch. Note that the example shown in FIG.
Although only the parts related to driving the scram electromagnet 40 in the figure are shown in correspondence, other swirler 11 electromagnets 41 to
The same applies to the driving portion 43.

In this embodiment, the optical switch 71 focuses on switching depending on the amount of light applied to the gate, and is configured to combine optical signals output from each of the signal processing devices 20 to 23 within the optical fiber 70. This optical fiber 70
At 701, optical fibers connected to each signal processing device are fused. For example, when realizing the 2 out of 4 logic shown in the majority circuit in FIG. 1, three or more of the optical signals output from each signal processing device are
11u (with optical signal), the optical switch 71 is in the switch ○N state, and two or more of each optical signal are in the logic "O" state.
With one or more configurations, it is only necessary to predetermine the output light from each signal processing device so that the optical switch 71 is in the OFF state when there is no optical signal (no optical signal).
While increasing the reliability and environmental resistance of the system, only one optical switch is required, making the optical switch part of the power stage significantly smaller.

Furthermore, it is easy to understand that the fused portion 701 of the optical fiber 70 can be realized by optical addition.

The configuration shown in FIG. 8 is the signal processing bag 5ff2 shown in FIG.
Although it corresponds to the output section of 0, this circuit is intended to further improve the reliability of the system. The concept is as follows.

As shown in Figure 1, the logic of the majority circuit is 2 outof
4, and one system of signal processing equipment has failed. In this state, if the other signal processing devices are healthy, there will be no chance of erroneous scramming, but if one of the remaining signal processing devices fails, there is a possibility of erroneous scramming.

Although scram is a safe event for plant operation, it reduces plant availability. Therefore, even if one system of signal processing devices fails, majority logic is applied to the output signals of the remaining devices to further improve system reliability.

Specifically, this is accomplished as follows.

Now, the signal output from each signal processing device is A.

Let them be B, C, and D. 2 out of 4 logical X is given by the following equation.

X=(A+B)・(A+C)・(A+D)・(B+
C)・(B+D)・(C+D) When the above equation is transformed, it becomes as follows.

X=ABC+BCD+CDA ten DAB...■
However, the formula (2) is a logic that gives priority to the logic uOn.

In equation (2), for example, if D=“1”, then X is expressed by the following equation.

X=AB+AC+BC...■ By the way, the formula ■ is 2 out of 3 for signals A, B, and C.
Builds logic.

That is, by forcibly setting the output signal of the failed signal processing device to logic ii 1 u, 2 outof
It is possible to construct 2 out of 3 logics from 4 logics.

A circuit that realizes this is shown in FIG. Light emitting element 61
is controlled by a drive circuit 72. The diagnostic circuit 73 diagnoses whether or not this drive circuit is normal.0 When the diagnostic circuit 73 determines that the drive circuit 72 is malfunctioning,
A command signal is output to the changeover switch 76 to change the contact point of the switch from the contact point 77 to the contact point 78. As a result, a voltage M< is applied to the light emitting element 61, and no optical signal is output.

Therefore, the majority decision circuit constituted by the optical switches 44 to 55 is configured in such a way that 2 out of 3 logics are set up for automatic switching, so that the majority logic of the power stage can always be set up, and the reliability of the system is improved. I'm even more excited.

Note that the resistor 74 in FIG. DC power supply 75. The portion consisting of contact 78 is for outputting logic 171 I+ from switch 76. This means that the system has logical rl
1 Used when giving priority to +j. Further, the contact 79 is for outputting a logic "0" from the switch 76. The 2 out of 4 logical Y at this time is given by the formula 0.

Y = AB + AC + AD + BC + BD + CD... ■Here, for example, if D = "0", Y is 0 formula % formula % In other words, in this case as well, 2 out of 4 to 2 o
ut of 3 logic can be constructed. In such a case, it is possible to switch the selector switch 76 to the contact 79 and make a majority decision using one less piece of information.

FIG. 9 shows the embodiment shown in FIG. 7 with the same functions as those described above. For the failed drive circuit 72, in order to set the output logic IJO11 of the signal processing device,
The changeover switch 76 is connected to a contact 79. As for other signal processing devices, the amount of light that has been available up until now is insufficient.
Since ut of 3 logic cannot be constructed, 2 with 3 signals
Switch 76 is switched to contact 78 to obtain a current corresponding to the amount of light that can be set out of 3.

By configuring each signal processing device as described above, the reliability of the safety protection system can be further improved.

By the way, in the 0 expression or the 0 expression, if one signal is set to logic "0", the logical product of two other remaining signals is obtained, and the logical sum is obtained at "1". In this way, the ideas described above can be applied to various redundant configurations.

The embodiment shown in FIG. 10 is an example in which the reliability of the system is further improved by diagnosing the power stage.

In this embodiment, an optical thyristor is applied to the optical switch, and the optical thyristor is momentarily turned off to test the power stage. In FIG. 11, if the optical thyristor is deenergized before time t1, it will be in the OFF state after time t1, so if it is re-energized at time tz after crossing zero potential, it will be in the ON state from this time. Use this fact to test the power stage.

The test device 89 takes in the signal detected by the phase detection circuit 86 of the AC voltage 28 via an optical fiber, and
At the time of "tt", a signal is output to the switch 80 and the logic "0" is output.
'' is output from the light emitting element.

The output of 89 is simultaneously output to other devices 21-23.

As a result, the majority circuit 24 is turned off after time t1, and the scram electromagnet attempts to operate. Then, the test device 89 outputs a command signal to the changeover switch 80 so that the changeover switch 80 returns to its original state at time t2.

As a result, the absolute value of the excitation current of the scram electromagnet becomes low during the period from t1 to t2. This is detected by resistor 81,
An absolute value circuit 82 converts the signal into an absolute value signal, and a comparator 84 compares the signal with a preset base voltage 83. This result is converted into an optical signal by an electrical/optical conversion circuit 85 and is connected to an optical fiber 87.
to the test equipment via. The test device 89 is from t1 to
It is determined whether the power stage is normal or not based on the value of the signal sent from the conversion circuit 85 during the period t2.

The phase detection circuit 86 detects the zero cross period to=tz of the AC voltage.
and transmits the detection result (logic “0” or par 1″’) to the test device 89, and the test device 89 detects the period to=tx
It is easy to understand that even if the optical thyristor is de-energized, the health of the power stage can be checked in the same way as described above.

In any of these examples, using the phase near the zero cross is better than using the near peak value, for example, because even if a problem occurs in the failure diagnosis device itself, the scram will be canceled as a result. This is because the habituation that occurs can be reduced.

By doing so, the reliability can be made even higher than that of the safety protection system. In addition, if the DC voltage of each circuit installed on the power stage side is converted from AC voltage 28 to DC, a new ff
This has the effect of not requiring an i source.

Further, in the above example, the current flowing through the excitation coil 36 of the scram electromagnet 40 is detected, but the same process can be performed by detecting the sound when the scram electromagnet is about to operate instead.

Even by combining the embodiments described so far, it is possible to further improve the reliability of the system.

Further, the configuration of the optical switch inside the majority circuit 24 etc. is as follows.
The present invention is not limited to the example shown in FIG. 1, and may be configured as shown in FIG. 12, for example. In addition, various other circuits are possible.

Furthermore, in the above embodiment, the case where the scram is performed by de-energizing the coil of one electromagnet was described, but when the scram is performed by de-energizing the coil of two electromagnets as shown in FIG. 13, the majority vote shown in FIG. It will be easily understood that this can be achieved by increasing the number of circuits 24 to 27 in accordance with the number of electromagnet coils.

If it is possible to manufacture an optical thyristor that can directly drive the scram electromagnet with an optical signal, applying this optical thyristor to the present invention can provide a highly reliable safety protection system.

〔Effect of the invention〕

As described above, according to the present invention, the signal processing section and the power stage of each redundant system are connected by optical fibers, and an optical switch is used in the power stage, so that the safety of the reactor safety protection system is maintained. Environmental friendliness and reliability can be greatly improved. Furthermore, the output signal of the failed signal processing device is set to logic +4.
It is possible to fix it to 011 or 1" and create majority logic using the output signals from the remaining healthy devices, further improving the reliability of the system. Furthermore, by using an optical thyristor in the power stage, the zero cross of the thyristor Since diagnosis is performed by turning off the optical thyristor in the vicinity, the reliability of the system is further improved.

Therefore, the present invention is particularly effective when applied to safety protection systems that require high reliability.

[Brief explanation of drawings]

Fig. 1 is a diagram showing the basic configuration of an embodiment of a nuclear reactor safety protection system according to the present invention, Fig. 2 is a diagram showing an example of a conventional safety protection system, and Fig. 3 is a diagram showing the configuration of a relay or contactor. , Fig. 4 shows an embodiment in which an optical signal from one light emitting element is distributed to each majority circuit by an optical fiber, and Fig. 5 shows an embodiment in which light emitting elements are connected in cascade and a corresponding number of optical fibers are used. 6 is a diagram showing an example in which a plurality of light emitting elements are driven in parallel and a corresponding number of optical fibers are used, and FIG.
FIG. 8 is a diagram showing an embodiment including a failure diagnosis device for constructing majority logic using the output signals of the remaining devices even if one system of signal processing devices fails, FIG. 9 is a diagram showing an embodiment equipped with a fault diagnosis device to which the embodiment of FIG. 7 is applied, FIG. 10 is a diagram showing an embodiment equipped with a power stage fault diagnosis device, and FIG. FIG. 12 is a diagram showing the detection timing of the phase detection circuit, FIG. 12 is a diagram showing another embodiment of the majority voting circuit, and FIG. 13 is a diagram showing the detection timing of the two i! ! It is a figure which shows the structure which scrams by de-excitation of the coil of a magnet. 1 to 3,100...-sensor, 4 to 6... measuring device,
7...Majority circuit, 8...Control device, 9...Scrum electromagnet, 10...Relay or contactor,
11... Coil, 12-14... Contact, 20-23
... Signal processing device, 24-27 ... Majority circuit, 2
8-31... AC voltage, 32-35... Scram signal, 36-39... Excitation coil, 40-43... Scram electromagnet, 44-55... Optical switch, 56-
59... Optical fiber, 60, 62.69... Light emitting element drive circuit, 61.63-68... Light emitting element, 70,
701... Optical fiber, 71... Optical switch, 72
...Drive circuit, 73...Diagnostic circuit, 74...Resistor, 75...DC power supply, 76...Switch, 77-7
9... Contact, 80... Switch, 81... Resistor,
82... Absolute value circuit, 83... Base $ power supply, 84...
- Comparator, 85... Electrical/optical conversion circuit, 86... Phase detection circuit, 87.88... Optical fiber, 89...
Test device, 97...Trip command signal, 98...
Sensor output signal, 99... Arithmetic processing unit.

Claims (1)

[Claims] 1. Redundant sensors, a signal processing device that independently captures the output signals of these sensors and outputs a trip signal when each signal exceeds a specified value, and a trip signal transmission line and a trip signal transmission line. In a nuclear reactor safety protection system that includes a circuit that outputs a scram signal to a scram electromagnet in accordance with a majority decision result of a trip signal, the signal processing device includes a light emitting element that outputs a trip signal as an optical signal and a light emitting element drive circuit. A nuclear reactor safety protection system, characterized in that the transmission line is made of an optical fiber, and the scram signal output circuit is made of an optical switch operated by an optical signal transmitted by the optical fiber. 2. In claim 1, each signal processing device has one light emitting element, and the optical fiber transmits an optical trip signal from each light emitting element to a corresponding optical switch of each scram signal output circuit. What is claimed is: 1. A nuclear reactor safety protection system characterized in that the optical switch is a plurality of optical switches forming a majority circuit in each scram signal output circuit. 3. In claim 1, the light emitting elements in each signal processing device are a plurality of cascade-connected light emitting elements, and the optical fibers are a plurality of optical fibers corresponding to the number of the light emitting elements. . A nuclear reactor safety protection system, wherein the optical switch is a plurality of optical switches forming a majority circuit in each scram signal output circuit. 4. In claim 1, the light emitting elements in each signal processing device are a plurality of light emitting elements connected in parallel to each other, and the optical fibers are a plurality of optical fibers corresponding to the number of light emitting elements, A nuclear reactor safety protection system characterized in that the optical switch is a plurality of optical switches forming a majority circuit within each scram signal output circuit. 5. Claim 1, wherein the optical fiber includes an adder that adds optical signals from each signal processing device,
A nuclear reactor safety protection system, wherein each of the scram signal output circuits comprises one optical switch. 6. Claim 1, characterized in that the optical fiber itself has a structure for adding optical signals from each signal processing device, and each scram signal output circuit consists of one optical switch. Reactor safety protection system. 7. In any one of claims 1 to 4, the light-emitting cord drive circuit includes a circuit for diagnosing its own failure, and a circuit for diagnosing its own failure, and a circuit for diagnosing its own failure, and in the event of an abnormality, a signal processing device that 1. A nuclear reactor safety protection system comprising: a switching circuit that fixes an output signal of the signal processing device to logic "0" or logic "1" so that majority logic can be established using a trip signal of the signal processing device. 8. In claim 5 or 6, the light emitting element drive circuit has a circuit for diagnosing its own failure and a majority logic based on a trip signal from the remaining healthy signal processing circuit in the event of an abnormality. A nuclear reactor safety system characterized in that it is equipped with a switching circuit that cuts off the output signal of the signal processing device and increases the light intensity of the optical output signal of the remaining healthy signal processing device to a predetermined value so that the signal processing device can be assembled. Protective system. 9. Redundant sensors, a signal processing device that independently captures the output signals of these sensors and outputs a trip signal when each signal exceeds a specified value, a trip signal transmission line, and a majority decision of the transmitted trip signals. In a nuclear reactor safety protection system that includes a circuit that outputs a scram signal to a scram electromagnet in response to a signal processing device, the signal processing device outputs a trip signal as an optical signal, a light emitting element, a light emitting element drive circuit, and a light emitting element drive circuit. a changeover switch that connects and disconnects the drive signal to the light emitting element, the optical transmission line is made of an optical fiber, the scram signal output circuit is made of an optical switch that is activated by the optical signal transmitted by the optical fiber, and the optical a phase detection circuit that detects an alternating current voltage applied to the switch; a circuit that detects a change that occurs in the scram electromagnet when the drive signal to the light emitting element is intermittent; and an alternating current applied to the optical switch based on the phase detection signal. The changeover switch turns off the optical signal from the signal processing device before the voltage reaches zero potential, and when the AC voltage applied to the optical switch exceeds zero potential and a predetermined time has elapsed, the signal processing device turns off the optical signal again. A nuclear reactor safety protection system comprising a power stage diagnostic device that controls the output of a signal and determines the health of the power stage based on the output of the scram electromagnet change detection circuit. 10. The nuclear reactor safety protection system according to claim 9, wherein the scram electromagnet change detection circuit is means for detecting a current flowing through the electromagnet. 11. A nuclear reactor safety protection system according to claim 9, wherein the scram electromagnet change detection circuit is a means for detecting a sound generated during electromagnet operation. 12. The nuclear reactor safety system according to any one of claims 9 to 11, characterized in that the phase detection circuit is a phase detection circuit that detects a phase near zero crossing of the alternating current voltage. Protective system.