JP2000065983A - Reactor water level instrumentation interlock device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a reactor scram avoiding device and improving the load factor of a reactor power plant by avoiding turbine trips in the case that water level rise is in transient caused by recirculation pump trip and the like but tripping turbine by using a reactor water level high signal in the case that the water level rise of the reactor is continuous. SOLUTION: To this device, a reactor water level high signal 30 and a recirculation pump trip signal 33 are input. A scram avoiding control circuit 35 is provided to immediately output a turbine trip signal 31 in the case only the reactor water level high signal 30 is input, but disturb the output of the turbine trip signal 31 for a specific time in the case both signals are valid.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an improved boiling water nuclear power plant, and to a reactor water level instrumentation interface for preventing a reactor water level from easily reaching a reactor scram when the water level rises due to a transient fluctuation of the reactor water level. Related to a lock device.

[0002]

2. Description of the Related Art In an improved boiling water nuclear power plant, as shown in the system configuration diagram of FIG. 11, steam generated in a reactor pressure vessel 2 forming an outer shell of a reactor 1 is supplied to a main steam pipe. 3 to the turbine 4,
After the work, the water is condensed by the condenser 5 and returns to water. The water is supplied to the reactor pressure vessel 2 through the water supply pipe 7 by the water supply pump 6 and returns to the reactor pressure vessel 2. The water supply pump 6 controls the water supply flow rate according to the water supply flow rate request signal 9 from the water supply control circuit 8. It is controlled so as to be fed into the reactor pressure vessel 2.

On the other hand, inside the reactor pressure vessel 2,
A core 10 that generates heat by fission in the water of the coolant, a steam-water separator 11 and a steam dryer 12 are provided, and around the core 10, in order to circulate the coolant through the core 10. A plurality of recirculation pumps 13 are installed, and the operation of the recirculation pump 13 is controlled by a recirculation flow control circuit 15 via a recirculation pump drive device 14.

[0004] The reactor water level of the coolant in the reactor pressure vessel 2 is always detected by a reactor water level gauge 16.
In a normal operation state, the reactor water level is near the middle position of the steam-water separator 11, and the reactor water level high preset value set in advance by design is at a position about 40 to 50 cm higher than the reactor water level.

Now, in the improved boiling water reactor, if the feedwater pump 6 continues to send an excessive feedwater flow rate to the reactor 1 due to the failure of the feedwater control circuit 8, the reactor water level monotonously increases. I do. On the other hand, when the recirculation pump 13 during operation trips, as shown in the characteristic curve of FIG. 12,
Reactor water level 18 is changed with recirculation pump
At the beginning of trip 13, the core flow increases due to an increase in voids in the coolant due to a decrease in the core flow 17.

However, the rise in the reactor water level is controlled by the water level control circuit 8 of the water supply control system via the reactor water level gauge 16.
The water supply flow rate is automatically reduced by the operation of the water supply control circuit 8, so that the reactor water level 18 immediately falls below the reactor water level high set value 19.

As shown in the block circuit diagram of FIG. 13, the water supply control circuit 8 includes a reactor water level signal 20, which is a difference between a reactor water level signal 20 from the reactor water level gauge 16 and a reactor water level setting signal 21. Deviation signal 22, main steam flow signal 23 and feedwater flow signal 24
And a mismatch flow rate signal 25 which is the difference between the two. As a result, the feedwater control circuit 8 outputs the feedwater flow rate request signal 9 during normal operation, and automatically controls the reactor water level 18 so that it is appropriately maintained.

On the other hand, as shown in the block diagram of FIG. 14, the reactor water level instrumentation interlock device 26 includes a reactor water level determination unit 27 for monitoring and protecting the reactor 1 and the turbine 4.
The reactor water level determination unit 27 includes a reactor water level signal 20 from the reactor water level gauge 16 and a preset reactor water level high set value 19 and a reactor water level high set value. 28
Is entered.

When the reactor water level signal 20 reaches the reactor water level high set value 19 or the reactor water level high set value 28, the reactor water level determination unit 27 Alternatively, the reactor water level signal 30 is output.

In addition, the reactor water level instrumentation interlock device 26 outputs a turbine stop signal 31 which is a trigger signal of a turbine trip interlock in response to the reactor water level signal 30 to trip the turbine 4. Together with the reactor scram to protect the turbine 4 and the reactor 1 safely. In addition, during the reactor scram, the feedwater pump 6 is caused to trip by issuing a trip signal from the reactor water level high signal 30 output from the feedwater control circuit 8.

[0011]

The reasons for the rise in the reactor water level in a boiling water reactor are roughly classified into the case where an abnormality occurs in the water supply control system and excess water is supplied to the reactor 1, and the case where the coolant There are two cases where the recirculation pump 13 for circulating the oil is tripped. In the case of excess water supply, the reactor water level continues to increase monotonically because excess water is continuously supplied, and a positive reactivity is injected into the core 10 due to the low supply water temperature. Usually, the reactor power also increases at the same time.

On the other hand, when the recirculation pump 13 trips, the reactor water level rise is temporary, and even if the reactor water level rises or falls, the water supply control by the water supply control circuit 8 or the like is performed. Since the system is sound, the feedwater flow rate is automatically suppressed and the reactor water level returns to a normal state again.

Generally, when the reactor water level rises, the reactor 1
Since the moisture in the steam generated in the reactor increases, the efficiency and soundness of the turbine 4 may be unfavorable. Therefore, tripping the turbine 4 with the reactor water level high / low signal 30 is an interface necessary for safe operation. Lock. However, it is acceptable for the reactor water level 18 to be the reactor water level height setting value 28 for a limited short time.

Therefore, when the water level rises temporarily as in the case where the recirculation pump 13 trips, it can be expected that the reactor water level can be immediately lowered to a normal value by a sound water supply control system or the like. Rather, it is desirable to avoid the turbine shutdown and the reactor scram to continue the operation and to improve the operation rate of the nuclear power plant.

An object of the present invention is to stop the turbine by the reactor water level high signal when the water level of the reactor continues to rise, but the water level rise is caused by a transient of the recirculation pump due to a trip or the like. In a typical case, it is an object of the present invention to provide a reactor water level instrumentation interlock device that avoids a turbine stop and improves the operation rate of a nuclear power plant.

[0016]

According to a first aspect of the present invention, there is provided a reactor water level instrumentation interlock apparatus which receives a reactor water level high and low signal and a recirculation pump trip signal. A turbine stop signal is output immediately when only the reactor water level signal is high, but a scrum avoidance control circuit is provided for preventing the output of the turbine stop signal for a predetermined time when both signals are established. .

A turbine stop signal is output according to the reactor water level, and a reactor scram is generated by stopping the turbine. If the recirculation pump trips when the reactor water level is high, the reactor Since the cause of the water level is due to the trip of the recirculation pump, it is determined that the reactor water level rise is temporary. As a result, the output of the turbine stop signal is blocked for a predetermined time during which the reactor water level is temporarily rising, thereby avoiding unnecessary turbine stop and reactor scram.

According to a second aspect of the present invention, in the reactor water level instrumentation interlock device according to the first aspect, the scram avoidance control circuit includes a reactor water level elevation signal, a recirculation pump trip signal, and a reactor water level elevation. When a height signal is input and a turbine stop signal is output immediately when only the reactor water level signal and the reactor water level signal are used, the reactor water level signal and the recirculation pump trip signal are output. When both of the signals are satisfied, the output of the turbine stop signal is blocked for a predetermined time.

Even if the recirculation pump is stopped when the reactor water level is high, if the reactor water level becomes high, a turbine stop signal is immediately output, and the turbine stop and the reactor scram are performed. Protect turbines and reactors.

According to a third aspect of the present invention, in the reactor water level instrument interlock device according to the first or second aspect, the recirculation pump trip signal is set to a predetermined number or more of the individual recirculation pump trip signals. Is input from the number-of-trips detecting section which is output by the input of (1).

If the number of trips of the recirculation pump is equal to or greater than the set number, the cause of the reactor water level is caused by the trip of the recirculation pump, and it is determined that the rise of the reactor water level is temporary, and the turbine The output of the stop signal is blocked for a predetermined time to avoid unnecessary turbine stop and reactor scram. However, when the number of trips of the recirculation pump is equal to or less than the set number, the influence of the trip of the recirculation pump is small, and it is determined that the recirculation pump is not temporary. do.

According to a fourth aspect of the present invention, in the reactor water level instrumentation interlock device according to any one of the first to third aspects, the reactor water level setting signal input to the water supply control circuit is the reactor water level elevation signal. The setting is changed by the following. When the recirculation pump trips at a high reactor water level, the output of the turbine stop signal is blocked for a predetermined time, and the setting of the reactor water level setting signal is changed to reduce the flow rate of water supplied to the reactor by the water supply control circuit. By doing
Reduce reactor water level to ensure turbine shutdown and avoid reactor scram.

A reactor water level instrumentation interlock device according to a fifth aspect of the present invention is characterized in that, in any of the first to fourth aspects, the feedwater pump is tripped by a turbine stop signal. When the reactor water level is high and the turbine stop signal output is blocked for a predetermined period of time to prevent turbine shutdown and reactor scram, a feedwater pump trip is not performed. Quantity and reactor water level can be maintained.

A reactor water level instrument interlock device according to a sixth aspect of the present invention is characterized in that a reactor water level signal detected by the reactor water level gauge is input via a primary delay circuit. The reactor water level signal from the reactor water level gauge becomes a delayed water level signal in the primary delay circuit. As a result, the maximum value of the temporary fluctuation of the reactor water level is reduced, so that it is difficult to reach the reactor water level. Therefore, it is possible to avoid turbine shutdown and reactor scram.

According to a seventh aspect of the present invention, in the reactor water level instrumentation interlock device, when a predetermined number of recirculation pumps are tripped, a healthy recirculation pump is raised to a maximum speed to perform core flow compensation. It is characterized by performing.
When a predetermined number of recirculation pumps have tripped, the speed of the healthy recirculation pump is increased to the maximum speed to compensate for the insufficient core flow rate due to the recirculation pump trip, and the recirculation pump is The turbine shutdown and the reactor scram are avoided by suppressing the rise in the reactor water level caused by the shutdown of the reactor.

[0026]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS One embodiment of the present invention will be described with reference to the drawings. Note that the same components as those of the above-described prior art are denoted by the same reference numerals, and detailed description thereof will be omitted.
The first embodiment relates to claim 1, and as shown in the block diagram of FIG.
The reactor water level signal 20 from the reactor water level gauge 16 and the preset reactor water level high set value 19 and the reactor water level high set value 28 are input, and the reactor water level high signal 30 is generated. A reactor water level determination unit 27 for outputting is provided.

Further, the reactor water level signal 30 and the recirculation pump trip signal 33 output from the recirculation flow control circuit 15 are input to the turbine 4 to output a turbine stop signal 31.
, And a scrum avoidance control circuit 35 including a logic circuit and the like.

As to the setting of the operation time in the timer 34, when the reactor water level continues to exceed the reactor water level, the moisture content of steam generated in the reactor 1 and sent to the turbine 4 increases. The humid steam impairs the soundness of the turbine 4. From this, it is determined in advance that the reactor water level exceeds the reactor water level height setting value 28 and steam with a high moisture content is not sent to the turbine 4.

Next, the operation of the above configuration will be described. In the reactor water level instrument interlock device 32, when the reactor water level rises and the reactor water level signal 20 detected by the reactor water level gauge 16 exceeds the reactor water level height set value 28, the The reactor water level signal 30 is output to the scram avoidance control circuit 35. At this time, the recirculation pump 13
If there is no trip of the recirculation flow control circuit 15
Is not output to the scrum avoidance control circuit 35.

Accordingly, the reactor water level instrumentation interlock device 32 immediately outputs the turbine stop signal 31 to the turbine 4, so that the turbine 4 is stopped and the reactor scram is performed. As a result, the reactor water level continues to exceed the reactor water level height set value 28, and a large amount of steam with increased moisture is sent to the turbine 4, thereby preventing the soundness of the turbine 4 from being impaired. The turbine 4 and the reactor 1 are safely protected.

When the reactor water level rises due to the trip of the recirculation pump 13, the scram avoidance control circuit 35 of the reactor water level instrumentation interlock device 32 sends the reactor water level determination unit 27 Reactor water level high and low signal 30
And the recirculation pump trip signal 33 from the recirculation flow control circuit 15 are input. Thus, the output of the turbine stop signal 31 for stopping the turbine 4 is blocked during the operation time of the timer 34.

However, if the output of the reactor water level high / low signal 30 from the reactor water level determination unit 27 continues even after the set time of the operation of the timer 34 has elapsed, the reactor water level rises. Is not caused by the trip of the recirculation pump 13, and outputs a turbine stop signal 31 to the turbine 4 to stop the turbine 4 and scram the reactor.

If the rise in the reactor water level is caused by a trip of the recirculation pump 13 and is temporary due to a transient phenomenon from the generation of a void in the reactor 1, the timer 34 Within the set time of operation,
The feedwater flow rate is automatically reduced by the feedwater control of the feedwater control circuit 8. Accordingly, when the reactor water level immediately drops and becomes equal to or lower than the reactor water level height set value 28, the reactor water level height signal output from the reactor water level determination unit 27 to the scram avoidance control circuit 35. 30 stops.

As a result, the turbine stop signal 31 is not output to the turbine 4 from the reactor water level instrumentation interlock device 32 continuously after the set time of the timer 34, so that the stop of the turbine 4 and the reactor scram Is avoided, and the turbine 4 is continuously operated, so that the normal operation of the nuclear reactor 1 is maintained. Therefore, the operation rate of the nuclear power plant is improved by the stable operation of the nuclear reactor 1.

Since the second embodiment is a modification of the first embodiment, the description of the same components as those of the first embodiment will be omitted, and only the differences will be described. explain.

As shown in the block diagram of FIG. 2, the reactor water level instrumentation interlock device 36 includes a reactor water level signal 20 from the reactor water level gauge 16 and a preset reactor water level high set value. 19 and the reactor water level height setting value 28, and further the reactor water level height setting value 37 are inputted, and the reactor water level which outputs the reactor water level height signal 30 and the reactor water level height signal 38 A determination unit 39 is provided.

It is to be noted that, if the reactor water level rises above this value in advance, the moisture content of the steam sent to the turbine 4 abnormally increases. Water level that needs to be stopped. Further, a reactor water level height signal 30 and a reactor water level height signal 38 from the reactor water level determination unit 39, and a recirculation pump trip signal output from the recirculation flow control circuit 15
33, a timer 34 for outputting a turbine stop signal 31 to the turbine 4 and a scrum avoidance control circuit 40 having a logic circuit and the like.

Next, the operation of the above configuration will be described. As described above, when the reactor water level rises due to an abnormality in the water supply control system or a trip of the recirculation pump 13 and exceeds the reactor water level height set value 28, the reactor water level meter In the interlock device 36, the first
In the same manner as in the embodiment, the operation of the turbine 4 is continued or stopped, and the turbine 4 and the reactor 1 are appropriately operated and protected.

However, if the rise of the reactor water level further exceeds the reactor water level height setting value 37, the reactor water level determination unit
When the reactor water level height signal 38 is output from 39,
It is necessary to prevent the soundness of the turbine 4 from being impaired due to the abnormal increase in the moisture contained in the steam from the significant rise in the reactor water level.

Accordingly, the turbine stop signal 31 is immediately transmitted to the turbine 4 regardless of whether the recirculation pump trip signal 33 is input from the recirculation flow control circuit 15 while the timer 34 in the scram avoidance control circuit 40 is operating. Output,
The reactor 4 is stopped and protected, and a reactor scram is performed.

Since the third embodiment is a modification of the first embodiment according to the third aspect, the description of the same components as those of the first embodiment will be omitted, and different portions will be described. explain. As shown in the block diagram of FIG. 3, the reactor water level instrumentation interlock device 32 includes a reactor water level determination unit 27 and a scram avoidance control circuit 35.

The scrum avoidance control circuit 35 includes:
By inputting an individual recirculation pump trip signal 41 from each recirculation pump driving device 14 for notifying the stop of each of the plurality of recirculation pumps 13 installed in the reactor 1, recirculation is performed for a predetermined number or more. According to the pump trip, the recirculation pump trip signal 42 is input from a recirculation flow control circuit 44 including a trip number detection unit 43 that outputs a recirculation pump trip signal 42.

Next, the operation of the above configuration will be described. In the scram avoidance control circuit 35 of the reactor water level instrumentation interlock device 32, as described above, the reactor water level rises due to an abnormality in the water supply control system, and exceeds the reactor water level height set value 28. In this case, the turbine 4 is stopped in the same manner as in the first embodiment, and the turbine 4 and the reactor 1 are protected by the reactor scram.

The rise in the reactor water level is caused by the recirculation pump 13
If the trip is caused by the trip, the scram avoidance control circuit 35 of the reactor water level instrumentation interlock device 32, the trip number detection unit 43 of the recirculation flow control circuit 44, When the pump 13 trips, a recirculation pump trip signal 42 is output.

Accordingly, in the scram avoidance control circuit 35, when the reactor water level rises due to the trip of the recirculation pump 13 and exceeds the reactor water level height set value 28, the trip of the recirculation pump 13 If the number is less than the preset number, the recirculation pump trip signal 42 is not input. Thereby, it is determined that the rise in the reactor water level is less affected by the trip of the recirculation pump 13,
Immediately, the turbine stop signal 31 is output to stop the turbine 4 and perform the reactor scram.

However, if the number of trips of the recirculation pump 13 is equal to or greater than the set number, the recirculation pump trip signal is sent from the number-of-trips detector 43 of the recirculation flow control circuit 44.
Since 42 is input, it is determined that the rise in the reactor water level is significantly affected by the trip of the recirculation pump 13.

For this reason, in the scrum avoidance control circuit 35, the turbine stop signal is output during the operation time of the timer 34.
Although the output of 31 is blocked, after the operation of the timer 34 has elapsed the set time, if the output of the reactor water level high / low signal 30 from the reactor water level determination unit 27 is still continued, A turbine stop signal 31 is output to the turbine 4 and the turbine 4
Shutdown and reactor scram.

The rise of the reactor water level is caused by the recirculation pump 13
Is caused by a trip that is equal to or greater than the set number, and is temporary due to a transient phenomenon, the reactor water level falls during the operation of the timer 34, and becomes less than or equal to the reactor water level height set value 28. Therefore, the output of the reactor water level high / low signal 30 from the reactor water level determination unit 27 stops.

Accordingly, the turbine stop signal 31 is not output from the reactor water level instrumentation interlock device 32, so that the stop of the turbine 4 and the reactor scram are avoided,
The normal operation of the nuclear reactor 1 is maintained by the continuous operation of the turbine 4, and the operation rate of the nuclear power plant is improved.

The fourth embodiment relates to claim 4 and is a modification of the first embodiment. Therefore, the description of the same components as those in the first embodiment will be omitted, and the differences will be described. explain. As shown in the block circuit diagram of FIG. 4, the reactor water level deviation signal input to the feed water control circuit 8
On the upstream side of the reactor water level setting signal 21, a signal for lowering the reactor water level setting signal 21 by the water level setting width preset by the input of the reactor water level high / low signal 30 is added by the water level setting change circuit 45. It has a configuration.

Next, the operation of the above configuration will be described. In the water supply control circuit 8, the reactor water level setting signal
A reactor water level deviation signal 22 between the reactor water level signal 21 and the reactor water level signal 20 and a mismatch flow rate signal 25 based on a main steam flow rate signal 23 and a feed water flow rate signal 24 are inputted. Water supply control for the furnace 1 is performed. At this time,
In the reactor water level setting signal 21, when the reactor water level is in a normal state, a difference from the reactor water level signal 20 is directly input to the water supply control circuit 8 as a reactor water level deviation signal 22.

However, when the rise in the reactor water level exceeds the reactor water level high set value 28 for some reason, the reactor water level high signal 30 is input to the water level setting change circuit 45, thereby the water level setting change circuit A step 45 lowers the reactor water level setting signal 21 by a predetermined water level setting width. Therefore, the reactor water level deviation signal 22 decreases and is input to the water supply control circuit 8, so that the water supply flow rate request signal 9 output from the water supply control circuit 8 to the water supply pump 6 decreases, and the water supply pump 6
The flow rate of the water supply supplied to the containment vessel 2 is narrowed down.

As a result, the reactor water level in the reactor 1 is lowered. For example, apart from the scram avoidance function of the scram avoidance control circuit 35 in the first embodiment, the water level setting change circuit 45 and the water supply control circuit By controlling the feedwater flow rate by 8 and avoiding the shutdown of the turbine 4 and the reactor scram, soundness can be ensured more reliably.

The fifth embodiment relates to claim 5 and relates to the first to fourth embodiments, and the first embodiment will be described as an example. As shown in the block diagram of FIG. 5, the reactor water level instrumentation interlock device
The turbine stop signal 31 output from the
And the water supply control circuit 46 supplies a water supply pump trip signal to the water supply pump 6 according to the turbine stop signal 31.
47 is output to trip the water supply pump 6.

Next, the operation of the above configuration will be described. In the scram avoidance control circuit 27 of the reactor water level instrumentation interlock device 32, when the reactor water level rises and the reactor water level signal 20 exceeds the reactor water level height set value 28, the reactor water level height signal 30 To the scrum avoidance control circuit 35,
The turbine 4 is stopped by the turbine stop signal 31.

At this time, if the recirculation pump 13 has tripped, it is assumed that the reactor water level has exceeded the reactor water level high / low set value 28 and that the timer 34 , The output of the turbine stop signal 31 is blocked for the set time, thereby preventing the turbine 4 from stopping immediately and becoming a reactor scram.

Here, in the conventional water supply control circuit 8, since the reactor water level elevation signal 30 is outputted to the water supply pump 6, the trip signal is outputted.
Even when the reactor water level temporarily exceeds the reactor water level setting value 28, the water supply pump 6 will rip, which hinders the continuous operation of the turbine 4 and avoidance of the reactor scram. .

However, in the water supply control circuit 46, a turbine stop signal 31 for stopping the turbine 4 is provided.
, The feedwater pump trip signal 47 is output, so that the feedwater pump 6 does not trip if the reactor water level rises above the reactor water level setting value 28 due to the temporary rise in the reactor water level.

As a result, when the reactor scram avoidance control circuit 35 of the reactor water level instrumentation interlock device 32 avoids the reactor scram, the feedwater pump 6 does not trip.
By supplying an appropriate supply water flow rate, an appropriate reactor water level is maintained, and the continuous operation of the turbine 4 and the operation of the nuclear power plant are performed.

The sixth embodiment relates to claim 6, which is to avoid a turbine stop due to a transient fluctuation of the reactor water level due to a delay of the water level signal. The sixth embodiment will be described as an example.

As shown in the block diagram of FIG. 6, a scram avoidance control circuit 48 that determines an abnormal rise in the reactor water level from the reactor water level signal 20 and outputs a turbine stop signal 31 includes:
A primary delay circuit 49 in which an appropriate delay time constant has been set in advance, and a reactor that determines an abnormal rise in the reactor water level based on the delayed water level signal 50 from the primary delay circuit 49 and outputs a reactor water level high / low signal 30 The water level determination circuit 27 is used.

Next, the operation of the above configuration will be described. In the reactor water level instrumentation interlock device 48,
When the reactor water level signal 20 output from the reactor water level gauge 16 is input, a primary delay circuit 49 gives the reactor water level signal 20 a delay corresponding to the delay time constant, and a reactor water level determination circuit.
Output to 27 as delay water level signal 50.

In the reactor water level determination circuit 27, if the delayed water level signal 50 exceeds the reactor water level height set value 28 due to the rise of the reactor water level for some reason, it is determined that the reactor water level is abnormally high. A reactor water level signal 30 is issued. As a result, the reactor water level instrumentation interlock device 48
Is to output a turbine stop signal 31 to the turbine 4 to stop the turbine 4 and scram the reactor.

At this time, in the reactor water level instrumentation interlock device 48, as shown in FIG. 7A, the reactor water level signal 20 increases as the reactor water level rises.
But the time t ₁ the highest value reactor water level High High setpoint near
In the case of conditions beyond 28, delay level signal 50 outputted from the primary delay circuit 49, as shown in FIG. 7 (b), the maximum value is lower with time t ₂ appears near the reactor The water level is lower than the set value of 28.

Therefore, when the reactor water level rises temporarily due to transient fluctuations, this maximum value is suppressed and does not exceed the reactor water level height set value 28, so that the reactor water level determination circuit 27 The reactor water level signal 30 is not output, so that the shutdown of the turbine 4 and the reactor scram are avoided.

[0066] Incidentally, the case where increase in the reactor water level continues, as the reactor water level signal 20 is shown in (a) of the characteristic diagram of FIG. 8, the reactor at time t ₁ increases monotonously In the case where the water level exceeds the water level high set value 28, the delay water level signal 50 output from the primary delay circuit 49 is
(B), the at slightly later time t ₂ from the time t _1, it will exceed the reactor water level High High setpoint 28.

However, the rising rate of the water level is delayed in the rise as compared with the reactor water level signal 20, but thereafter changes substantially in the same manner. Therefore, this lag level signal
The reactor water level determination circuit 27 to which 50 has been input issues a reactor water level height signal 30 when the reactor water level height set value 28 is exceeded, and stops the turbine 4 and shuts down the reactor 4 by the turbine stop signal 31. Do the scrum.

Thus, when the reactor water level continuously rises, the turbine 4 is stopped, and when the reactor water level recovers normally in a short time due to transient fluctuations, the turbine 4 is stopped and the reactor scram is avoided. Thus, the soundness of the turbine 4 can be ensured and the operation rate of the nuclear power plant can be improved.

The seventh embodiment relates to claim 7, which compensates for the insufficient flow rate of the stopped recirculation pump.
An embodiment will be described as an example. As shown in the block diagram of FIG. 9, as the reactor water level instrumentation interlock device, the output from the recirculation pump driving device 14 is provided between the recirculation pump driving devices 14 that operate the respective recirculation pumps 13. When the individual recirculation pump trip signal 41 reaches a preset number, the number of trips detector 52 outputs a speed-up signal 51.
It has.

The recirculation flow rate control unit 54 includes a speed-up control unit 54 that outputs a speed-up request signal 53 for raising the maximum speed to each of the sound recirculation pumps 13 based on the speed-up signal 51. The circuit 55 is provided.

Next, the operation of the above configuration will be described. In the improved boiling water reactor, ten recirculation pumps 13 are usually installed in one reactor 1, although it depends on the power scale. Therefore, here, the description will be made assuming that ten recirculation pumps 13 are installed.

When the recirculation pump 13 stops, the core flow decreases accordingly. Here, for example, when four of the ten recirculation pumps 13 stop, as shown in the characteristic curve diagram of FIG. 10, the core flow rate 17b decreases, and the reactor water level 18b is temporarily reduced due to the void effect. When the reactor water level reaches a high level, the turbine stops and a reactor scram occurs.

However, in the recirculation flow control circuit 55, the number of trips detector 52 is set in advance so as to output the recirculation pump trip signal 51 in response to the input of the four individual recirculation pump trip signals 41. It should be noted that this set number can be appropriately set as needed.

If the four recirculation pumps 13 trip during operation due to a failure or the like, a shortage occurs in the core flow rate and the recirculation flow rate for securing the core flow rate.
52 outputs a recirculation pump trip signal 51. At this time, the speed-up control unit 54 that has received the recirculation pump trip signal 51 outputs a speed-up request signal 53 to the recirculation pump driving devices 14 of the remaining six healthy recirculation pumps 13.

The above-mentioned sound 6
The recirculation pump 13 increases its operating speed to the maximum speed, so that the insufficient core flow is compensated by the rapid increase of the recirculation flow, and the core flow is reduced as shown in FIG.
17a can be reduced. As a result, the occurrence of voids is suppressed, so that the reactor water level 18a is suppressed from rising rapidly and fluctuating, and it is possible to prevent the reactor water level from reaching the reactor water level, stopping the turbine 4 and causing reactor scram. be able to.

[0076]

As described above, according to the present invention, in a nuclear power plant of an improved boiling water reactor, a reactor water level instrumentation interlock device is provided for temporarily setting a reactor water level by a plurality of recirculation pump trips or the like. Detects fluctuations to avoid turbine shutdown and reactor scram caused by this, and when the reactor water level rises due to other factors, turbine shutdown and reactor scram are immediately generated when the reactor water level reaches a high level. Let it. Therefore, the number of unnecessary reactor shutdowns is reduced, the operation rate and reliability of the nuclear power plant are improved, and there is an effect on the stable supply of electric power.

[Brief description of the drawings]

FIG. 1 is a block diagram showing a reactor water level instrument interlock device according to a first embodiment of the present invention.

FIG. 2 is a block diagram of a reactor water level instrument interlock device according to a second embodiment of the present invention.

FIG. 3 is a block diagram of a reactor water level instrument interlock device according to a third embodiment of the present invention.

FIG. 4 is a block diagram of a water supply control circuit according to a fourth embodiment of the present invention.

FIG. 5 is a block diagram showing a reactor water level instrument interlock device according to a fifth embodiment of the present invention.

FIG. 6 is a block diagram of a reactor water level instrument interlock device according to a sixth embodiment of the present invention.

FIGS. 7A and 7B are characteristic curve diagrams when a recirculation pump according to a sixth embodiment of the present invention is stopped, in which FIG. 7A shows the related art and FIG.

FIGS. 8A and 8B are characteristic curve diagrams of a sixth embodiment according to the present invention during operation of a recirculation pump, wherein FIG. 8A shows the related art and FIG. 8B shows the present invention.

FIG. 9 is a block diagram of a recirculation flow control circuit according to a seventh embodiment of the present invention.

FIG. 10 is a characteristic curve diagram when a recirculation pump is stopped according to a seventh embodiment of the present invention.

FIG. 11 is a system configuration diagram of a conventional improved boiling water nuclear power plant.

FIG. 12 is a characteristic curve diagram of a core flow rate and a reactor water level at the time of a recirculation pump trip.

FIG. 13 is a block diagram of a conventional water supply control circuit.

FIG. 14 is a block diagram of a conventional reactor water level instrumentation block.

[Explanation of symbols]

1 ... Reactor, 2 ... Reactor pressure vessel, 3 ... Main steam pipe, 4 ...
Turbine, 5 ... condenser, 6: water supply pump, 7: water supply pipe,
8, 46, 53: Water supply control circuit, 9: Water supply flow rate request signal, 10
... core, 11 ... water separator, 12 ... steam dryer, 13 ... recirculation pump, 14 ... recirculation pump drive, 15,44,55 ... recirculation flow control circuit, 16 ... reactor water level gauge, 17 , 17a, 17b ...
Core flow rate, 18, 18a, 18b: Reactor water level, 19: Reactor water level high setting value, 20: Reactor water level signal, 21: Reactor water level setting signal, 22: Reactor water level deviation signal, 23: Main steam flow rate signal,
24: Feed water flow signal, 25: Mismatch flow signal, 26, 32,
36,48… Reactor water level instrumentation interlock device, 27,39…
Reactor water level judgment unit, 28: Reactor water level high / low set value, 29: Reactor water level high signal, 30: Reactor water level high / low signal, 31: Turbine stop signal, 33, 42, 51 ... Recirculation pump trip signal ,
34… Timer, 35, 40… Scrum avoidance control circuit, 37… Reactor water level high and low set value, 38… Reactor water level high and low signal, 41…
Individual recirculation pump trip signal, 43, 52: number of trip detectors, 45: water level setting change circuit, 47: feed water pump trip signal, 49: primary delay circuit, 50: delayed water level signal, 51: speed-up signal, 53 ... speed-up request signal, 54 ... speed-up control unit.

Claims (7)

[Claims] In a reactor water level instrumentation interlock device of a boiling water reactor, a reactor water level elevation signal and a recirculation pump trip signal are input, and when only the reactor water level elevation signal is detected, the turbine is immediately turned on. A reactor water level instrumentation interlock device, comprising: a scram avoidance control circuit that outputs a stop signal, but blocks output of the turbine stop signal for a predetermined time when both signals are satisfied. 2. The scram avoidance control circuit inputs a reactor water level elevation signal, a recirculation pump trip signal, and a reactor water level elevation signal, and receives the reactor water level elevation signal atoms and the reactor water level. When only the height signal is output, the turbine stop signal is immediately output.However, when both the reactor water level height signal and the recirculation pump trip signal are established, the output of the turbine stop signal is prevented for a predetermined time. The reactor water level instrumentation interlock device according to claim 1, wherein: 3. The reactor water level instrumentation interlock device, wherein the recirculation pump trip signal is input from a trip number detection unit that outputs by inputting a predetermined number or more of individual recirculation pump trip signals. The reactor water level instrumentation interlock device according to claim 1 or 2, wherein: 4. The reactor water level instrument interlock device according to claim 1, wherein a setting of a reactor water level setting signal input to a water supply control circuit is changed by the reactor water level elevation signal. The reactor water level instrumentation interlock device according to claim 3. 5. The reactor scram avoidance device according to claim 1, wherein the feedwater pump is tripped by the turbine stop signal in the reactor water level instrumentation interlock device. 6. A reactor water level instrument interlock device, wherein a reactor water level signal detected by the reactor water level meter is input via a primary delay circuit. 7. A reactor water level instrument interlock device, wherein when a predetermined number of recirculation pumps trip, a healthy recirculation pump is raised to a maximum speed to perform core flow compensation. Reactor water level instrumentation interlock device.