JPH0625923B2 - Bypass management circuit for reactor safety protection system - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to improvement of a bypass management circuit of a multiplexed reactor safety protection system.

<Prior Art> An example of a conventional management circuit will be described with reference to FIG. T
₁ , T ₂ , T ₃ measure physical quantities of the same measurement object 3
In the transmitter of the channel, PV ₁ , PV ₂ , PV ₃ are the measured values. S ₁ , S ₂ , S ₃ are test switch means, and on the steady (N) side, measured values PV ₁ , PV ₂ , PV
₃ to the signal processing means C ₁ , C ₂ , C ₃ , and at the test (T) side, test jacks TJ ₁ , TJ ₂ , TJ ₃
The test signal applied to the signal processing means C ₁ , C ₂ , C
Lead to ₃ .

In the steady state, these signal processing means perform signal processing such as predetermined calculation bias setting on each measured value, and process signals PV ₁ ′, PV ₂ ′ and PV ₃ ′ are processed into bistable circuits B ₁ , B ₂ , sending to B _3.

The bistable circuit compares the output level of each processing means with a normal level set value, and in the case of an abnormal state in which this set value is exceeded, a normal state of "1" logic and the output level of the processing means is less than or equal to the set value In case of, the comparison output A of “0” logic
Sends L ₁ , AL ₂ and AL ₃ .

BS ₁ , BS ₂ and BS ₃ are vice-table switch means that are manually operated, and have comparative outputs AL ₁ and AL.
₂ and AL ₃ are led to a common trip determination circuit TR on the steady (N) side, and a comparative output AL on the trip (T) side.
It leads to the comparative output display lamps L ₁ , L ₂ and L ₃ which are lit when ₁ , AL ₂ and AL ₃ are “1” logic.

TR is a trip determination circuit, which monitors the logical state of the comparison output input via the bistable switch means, and trips the trip signal Q for shutting down the reactor when two of the three inputs are "1" logic. To send. Even if the bistable switch is operated to the T side in the test state,
The input is treated as "1" logic.

The reactor safety protection system is required to have high reliability and safety in order to stop the reactor safely and surely when necessary.

It is also stipulated as a guideline for multiplicity (guideline 29), testability (guideline 33), single failure criterion (guideline 29), etc. in the Safety Committee Review Guidelines for Light Water Reactor Facilities for Nuclear Power Plants There is.

Conventionally, the third method is a rational method that satisfies these guidelines.
The triplicate system shown in the figure was used. In this system, even if one of the three channels fails on the unsafe side (a state in which a signal to shut down the furnace cannot be transmitted), the remaining two channels are protected as long as they are normal.

<Problems to be Solved by the Invention> However, since the above guideline must be satisfied even during the test and calibration of one channel, the bistable switch means of the channel is tripped (T) during the test and calibration. It is necessary to switch to the side. In this state, the 20UT OF3 circuit operates substantially as a 1OUT OF2 circuit, so that if any one of the remaining two channels malfunctions to generate a trip signal, the furnace is stopped, which is inconvenient.

Problem 1 That is, the conventional triplicate system has a high possibility of shutting down the furnace unnecessarily due to the failure of other channels during the test and calibration.

From the same viewpoint, when _one of the transmitters T _{1 to} T ₃ fails, the bistable switch of the channel is tilted to the trip (T) side. It may be possible to recover the faulty transmitter by replacing it in a short period of time, but in some cases it may be necessary to leave it until the next plant shutdown due to the effects of radiation.

Problem 2 Such a leaving period becomes longer than the time required for the above test and calibration, and there is a high possibility that the furnace will be unnecessarily stopped due to a failure of another channel during this period.

It is an object of the present invention to provide a bypass management circuit that solves such problems with simple additional elements.

<Means for Solving the Problems> The structural features of the present invention are that the signal processing means processes the transmitter output through the test switch means, and the output level of the signal processing means is the normal level set value. A bistable means for comparing and generating an alarm output, a "0" logic signal generating means for outputting a "0" logic indicating that the output level of the signal processing means is in a normal state, and an alarm for the bistable means First bypass switch means for switching the output and the "0" logic of the "0" logic signal generating means, and the "0" in cooperation with the first bypass switch means.
Second bypass switch means for switching between "0" logic of the logic signal generating means and a bypass terminal representing a bypass connection, and bistable switch means for switching between the output from the first bus path switch means and a test terminal for test operation. 4 measurement channels are provided, and the output of the first bypass switch means via the bistable switch means of each measurement channel is monitored to detect that 2 out of 4 inputs are abnormal state outputs. A trip determination circuit that outputs a trip signal that instructs the reactor to stop at a certain time and the output of the second bypass switch means of each measurement channel are monitored, and an alarm is issued when 2 out of 4 inputs are in a bypass state. A bypass alarm judgment circuit that outputs a signal is installed, and 1 measurement channel out of 4 measurement channels is installed. Tunnel test lies in executing the trip judgment based on the output of the other three measuring channels during calibration or failure.

<Operation> In the quadruple system, each channel is tested, calibrated by the first bypass switch means, or a "0" logic signal is supplied to the trip judging circuit via the bus table switch means at the time of transmitter failure. It is possible to operate the circuit substantially as a 20UT OF3 circuit.

The status of bypass is "0" supplied through the second bypass switch means which is interlocked with the first bypass switch means.
It is monitored by a bypass alarm decision circuit that receives a logic signal.

<Embodiment> The characteristic part of the present invention will be described for the first channel out of the four channels with reference to FIG. The same components as those in FIG. 3 are designated by the same reference numerals and the description thereof will be omitted.

The comparison output AL ₁ of the bistable means B ₁ is directly applied to the output display lamp L ₁ and connected to the steady side (N) terminal of the first bypass switch means BSP11. BP
S12 is a second bypass switch means that works in conjunction with the BPS 11.

G ₁ is a “0” logic signal generating means, the output of which is given to the bypass (BP) side of the first bypass switch and the steady (N) side of the second bypass switch means.

The output of the first bypass switch means BPS11 is guided to the trip determination circuit TR via the stationary contact of the bistable switch means BS1 and is output to the second bypass switch means BP.
The output of S12 is guided to the bypass alarm determination circuit BR.

The bypass alarm determination circuit BR has a 20UT OF4 circuit configuration similar to the trip determination circuit TR, and issues an alarm signal R when two channels of four channels are in a bypass state, that is, "1" logic input.

FIG. 2 shows another configuration similar to that of the first channel in FIG.
FIG. 3 is an overall configuration diagram including a channel configuration.

The operation of such a configuration will be described for the first channel in FIG.

1. Normal test and calibration (related to problem 1) (1) Interlocking bypass switch means BPS11, BP
Tilt S12 to the bypass (BP) side.

(2) Confirm that the bypass alarm judgment circuit BR does not output the alarm R of "2 channel abnormal bypass" and that the partial trip signal (trip signal of channel 1) is not output.

(3) addition of simulated input from the test jack TJ1 switches the test switch S1 to the test (T) side test while watching the output indicator lamp L1 of the bistable B _1, executes the calibration.

(4) After completing the test and calibration, restore the original procedure in the reverse order.

(5) According to the procedure described above, the "0" logic signal for channel 1 is supplied to the trip judgment circuit even during the test and calibration. Therefore, this judgment circuit should be operated substantially as a 20UT OF3 circuit. Therefore, it is possible to reduce the possibility of unnecessary furnace shutdown during the test and calibration as compared with the conventional system.

2. Long-term bypass due to transmitter failure (related to problem 2) (1) Bypass the first and second bypass switches (BP)
Defeat it to the side.

(2) Confirm that the bypass alarm judgment circuit BR does not output the alarm R of "bypass for two or more channels" and that the partial trip signal (trip signal of channel 1) is not output.

(3) The above procedure is the same as that in 1, but even in this state, it is equivalent to the 20 UT OF3 circuit of the conventional system at the normal time, and the possibility of unnecessary furnace shutdown can be reduced.

3. Test and calibration while another channel is bypassed (1) Tilt the bus table switch BS1 to the trip (T) side.

(2) Confirm that the partial trip signal (trip signal of the channel being bypassed) is output.

(3) addition of simulated input from the test jack TJ1 switches the test switch S1 to the test (T) side test while watching the output indicator lamp L1 of the bistable B _1, executes the calibration.

(4) After completing the test and calibration, restore the original procedure in the reverse order.

(5) By the above procedure, it is possible to execute the test and calibration under the condition equivalent to the test and calibration of the conventional system even when one channel is bypassed.

<Effects of the Invention> The concept of mutual monitoring of the bypass state is to automatically know whether the bypass states of the other three channels are known and perform a logical judgment when a bypass request is made for the channels to automatically perform “bypass” or “trip”. It can be considered as a state.

However, electrical coupling is essentially unfavorable because each channel of the security system is required to be independent and separate from each other. However, in the case of coupling, independence and separation must be taken into consideration by using an optical coupling element or an optical fiber, but such a method has technical difficulties, complexity, and economical problems, and further, originally, There is also a problem that the reliability of protection of the system is reduced.

According to the present invention, it is possible to realize a bypass management circuit that satisfies such requirements with the simplest circuit calibration and that solves the problems of the triplex system.

[Brief description of drawings]

FIG. 1 is a block diagram showing an embodiment of the present invention for one channel, FIG. 2 is an overall block diagram, and FIG. 3 is a block diagram showing an example of a conventional technique. _{T 1, T 2, T 3} ...... _{transmitter, S 1, S 2, S} 3 ...... test switch _{means, C 1, C 2, C} 3 ...... signal processing _{unit, B 1, B 2, B} 3 ... … Vice-stable means, G ₁ ,
G ₂ , G ₃ ... "0" logic signal generating means, BPS 11,
21, 31, 41 ... First bypass switch means, BP
S12, 22, 32, 42 ... Second bypass switch means, BS1, 2, 3, 4, ... Vise table switch means, TR ... Trip determination circuit, BR ... Bypass alarm determination circuit

Claims (1)

[Claims] 1. A signal processing means for processing a transmitter output as a signal through a test switch means, a bistable means for comparing an output level of the signal processing means with a normal level set value to generate an alarm output, and "0" logic signal generating means for outputting "0" logic indicating that the output level of the signal processing means is in a normal state, alarm output of the bistable means and "0" of the "0" logic signal generating means. First bypass switch means for switching between logic and second bypass switch means for switching between the "0" logic of the "0" logic signal generating means and a bypass terminal representing a bypass connection in cooperation with the first bypass switch means, A measurement switch comprising bistable switch means for switching the output from the first bypass switch means and a test terminal for test operation. 4 channels are provided, and the output of the first bypass switch means via the bistable switch means of each measurement channel is monitored to shut down the reactor when 2 out of 4 inputs are abnormal output. And a trip warning circuit for outputting a trip signal for instructing, and a bypass alarm for outputting an alarm signal when two of the four inputs are in a bypass state by monitoring the output of the second bypass switch means of each measurement channel. A decision circuit is installed so that one of the four measurement channels can be tested, calibrated or otherwise
A bypass management circuit for a reactor safety protection system, which makes a trip decision based on the output of a measurement channel.