JPH09101394A - Reactor water level controller - Google Patents

Abstract

(57) [Summary] (Modified) [PROBLEMS] Stabilizing the reactor water level by controlling the recirculation pump or the selective control rod when the drain pump stops and a partial loss of the feed water flow rate and its temperature occurs. And a reactor water level control device for avoiding unnecessary reactor scrum. A control rod (11) in a core (9), a plurality of recirculation pumps (10) for circulating a coolant in the core, and a feed water heater (14) inserted in a feed / condensation system that supplies the coolant to a nuclear reactor (8). In a boiling water nuclear power plant equipped with a drain pump 19 for collecting drain, the rotation of the recirculation pump 10 is specified when the drain pump is stopped by detecting the operating state of the drain pump and the spare drain pump is not started. A water level control device (20) that suppresses fluctuations in the reactor water level by installing the selective control rod (11) after a predetermined time and reducing the speed to a value is provided.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a reactor water level control device for suppressing fluctuations in the reactor water level in a boiling water nuclear power plant when the drainage pump of the feed / condensation system is stopped.

[0002]

2. Description of the Related Art In a boiling water nuclear power plant, a feed water heater is inserted in a feed / condensate system for supplying a coolant to a nuclear reactor, and steam is used as a heat source to heat feed water passing through the feed water heater. However, the drain water of the steam after heating the feed water in the feed water heater is primarily stored in the drain tank, and there is a case in which the drain water at this high temperature is boosted by the drain pump and sent to the feed / condensate system. .

As a result, the residual heat of the steam that has heated the feed water by the feed water heater is recovered into the feed / condensate water through the drain water, thereby improving the thermal efficiency of the plant.
Generally, in a boiling water nuclear power plant, three drain pumps are installed, usually two are operated, and the other one is a standby machine.

In the conventional water level control device, when the water level in the drain tank drops excessively for some reason, this drain pump automatically stops the two units in operation in order to avoid a situation in which the flow rate of the drain pump cannot be secured. At the same time, automatic startup of one spare drain pump is also blocked.

However, in this case, the total flow rate of the drain water injected into the water supply / condensation system is lost, so that the suction pressure of the water supply / condensation pump having this injection flow rate on the suction side is reduced. descend. In addition, although two water supply / condensation pumps are operating under normal rated conditions, if suction pressure drops excessively, the soundness of the pump may be impaired due to cavitation, etc. 1 out of the water pump
Automatically stop the platform.

Further, in order to secure a sufficient suction pressure, the automatic start of the spare feed / condensate water pump is prevented. Therefore, if the water level in the drain tank is excessively lowered, the state finally shifts to the feed / condensation operation by one feed / condensation pump, and the coolant supply capacity to the reactor is reduced.

If one of the drain pumps is abnormally stopped for some reason, the backup drain pump is normally automatically started regardless of the drop in the drain tank water level. However, if the backup pump of this drain pump fails to start, the flow rate of the drain water injected into the water supply / condensation system will be reduced by the amount of one stopped unit. Stop.

Here, when the capacity of one backup / condensation pump is smaller than the capacity of one normal / condensation pump in normal operation, the supply / condensation water is lost when the flow rate of one drain pump is lost. One pump standby machine may automatically start. Even in such a case, the coolant supply capacity to the nuclear reactor is reduced.

As described above, when one or two drain pumps are stopped and the backup drain pump is not started, one condensing / condensing pump is automatically stopped.
The transient change in this case is shown in the characteristic curve diagram of FIG. Here, (a) shows the characteristic curve of the reactor power 1, the core flow rate 2, (b) the feed water flow rate 3, the reactor steam flow rate 4, and (c) the reactor water level 5.

By stopping the drain pump and the feed / condensate water pump, the feed water flow rate 3 suddenly decreases and reaches the maximum flow rate when one feed / condensate pump is operating. During this period, the reactor water level 5 drops,
Since the water supply flow rate 3 is at the maximum level of the water supply capacity, the flow rate cannot be increased in order to suppress the water level drop.

After this, the recirculation pump starts decelerating upon determining the stop of the water supply / condensation pump, the inactivation of the standby machine, and the drop in the water level that deviates from the normal operating range. Along with this, the core flow rate 2 is reduced to the flow rate corresponding to the minimum rotation speed. When the core flow rate 2 decreases, the balance with the reactor output 1 changes and the coolant overheat state occurs, so that the void ratio of the reactor increases, and the negative void reactivity injection by this causes the reactor output 1 Also decreases rapidly.

The void fraction increased here means that the reactor power is 1
And the core flow rate 2 are balanced, the level gradually returns to the same level as the initial value. Therefore, in this returning process, since the void rate gradually decreases, the reactor output 1 also gradually increases due to the positive void reactivity effect and goes toward the settling state.

When the reactor output 1 decreases, the reactor steam flow rate 4 also decreases, and eventually falls below the feed water flow rate 3. During this period, the reactor water level 5 is greatly lowered due to the mismatch between the feed water flow rate 3 and the reactor steam flow rate 4. Immediately after the reactor steam flow rate 4 falls below the feedwater flow rate 3, the reactor water level 5 continues to drop slightly due to the gradual decrease behavior of the reactor void fraction. Eventually, the water level lowering effect due to the gradual decrease of the void ratio is overcome by the water level recovery effect due to the positive mismatch exceeding the reactor steam flow rate 4 of the feed water flow rate 3 and the reactor water level 5 gradually returns to the initial water level 6.

In this way, the reactor water level drop during the transition is suppressed, so that the reactor scrum is avoided. In Fig. 4, the reactor scrum value 7 of the scrum setting value due to the decrease of the reactor water level 5 is set to -60 cm.

[0015]

As described above, when one or two drain pumps stop and the standby machine does not start, eventually one of the feed / condensate pumps automatically stops and the Insufficient supply of coolant to the furnace. Therefore, the reactor output 1, that is, the reactor steam flow rate 4 is reduced due to the deceleration of the recirculation pump, so that the reduction of the reactor water level due to the mismatch between the feed water flow rate 3 and the reactor steam flow rate 4 is suppressed.

In this case, the transient change in the reactor water level 5 is caused by the feed water flow rate 3 that decreases with the stop of the drain pump and the feed / condensate pump and the reactor steam flow rate 4 that decreases with the subsequent recirculation pump deceleration. The negative mismatch flow rate up to the point below will greatly affect the reactor water level 5.

Therefore, even if the reactor steam flow rate 4 finally falls below the feedwater flow rate 3 due to the recirculation pump deceleration, if the time to reach such a state is not reached quickly, the decrease in the reactor water level will be large, and the reactor water level will decrease. Can cause scrum,
As a result, there is a problem that the operating rate of the nuclear power plant is lowered.

Further, the conventional speed-reducing function of the recirculation pump when the water supply capacity is lowered is originally intended to reduce the reactor steam flow rate 4 to a flow rate level commensurate with the water supply capacity. However, when the drain water flow rate is lost due to the stop of the drain pump, since the drain water is high temperature water, a part of the flow rate of the recovered water recovered by the high temperature water is lost and It will also cause a drop in temperature of the flow rate itself, ie a partial loss of feedwater heating.

The decrease of the feed water temperature due to the partial loss of the feed water heating gradually decreases the temperature of the recirculation flow rate mixed with the feed water flow rate in the reactor downcomer region, and accordingly, the coolant at the reactor inlet. The temperature also gradually decreases and a positive reactivity is added to the reactor fuel.

Therefore, even if the reactor output 1 is decreased by the speed reduction of the recirculation pump and the fluctuation of the reactor water level 5 due to the mismatch between the reactor steam flow rate 4 and the feed water flow rate 3 is suppressed, the coolant is Since the temperature gradually decreases, the reactor output 1 and the reactor steam flow rate 4 continue to gradually increase even after the water level fluctuation settling. When this exceeds the water supply capacity, there is a problem that the reactor water level 5 decreases again and eventually reaches the reactor scrum value of 7 and becomes the reactor scrum.

The loss of heating of the feed water due to the loss of the drain water flow rate due to the stop of the drain pump leads to a larger decrease in the coolant temperature in a plant having a higher heat recovery rate by the drain pump. As described above, the reactor scram may be generated unnecessarily depending on the stop of the drain pump, and further, not only the operation rate of the nuclear power plant is lowered, but also the obstacle to the stable supply of electric power is impaired. Also becomes.

The object of the present invention is to stabilize the reactor water level by controlling the recirculation pump or the selective control rod when the drain pump stops and a partial loss of the feed water flow rate and its temperature occurs. Another object of the present invention is to provide a reactor water level control device that avoids unnecessary reactor scrum.

[0023]

In order to achieve the above object, a reactor water level control apparatus according to the invention of claim 1 is a plurality of recirculation pumps for circulating a selective control rod in a core and a coolant in a core. And in a boiling water nuclear power plant equipped with a drain pump for collecting the drain of the feed water heater inserted in the feed / condensation system for supplying the coolant to the reactor to the feed / condensation system, the operating state of the drain pump is detected. When the drain pump stops and the backup drain pump does not start, the rotation speed of the recirculation pump is reduced to a predetermined value, and
A water level control device for suppressing fluctuations in the reactor water level by inserting the selection control rod after a predetermined time is provided.

When the drain pump stops and the standby drain pump does not start, the flow rate of the feed water supplied to the reactor decreases and the output decreases, and the feed water heating function by the drain water is lost and the water is restored. The output gradually increases due to the decrease in the temperature of the reactor, and this influence lowers the reactor water level.

At this time, the water level control device detects that the drain pump is stopped and the standby drain pump is not activated, and first reduces the rotational speed of the recirculation pump to a predetermined value to reduce the core flow rate. , After a predetermined time, the selection control rod is inserted to reduce the reactor power. As a result, it is possible to suppress fluctuations in the reactor water level and prevent unnecessary reactor scrum by suppressing the decrease in the reactor water level and promptly recovering the initial water level.

According to a second aspect of the present invention, there is provided a reactor water level control device, which comprises a selective control rod in the core, a plurality of recirculation pumps for circulating the coolant in the core, and a feed / condensation system for supplying the coolant to the reactor. In a boiling water nuclear power plant equipped with a drain pump that collects the drain of the feed water heater inserted in the water supply / condensation system, the drain pump is stopped by detecting the operating state of the drain pump and the reactor water level, and a preliminary drain When the pump does not start, it is detected that the reactor water level has dropped after a predetermined time, and at least one of the recirculation pumps is tripped to suppress fluctuations in the reactor water level. To do.

When the drain pump stops and the standby drain pump does not start, the flow rate of the feed water supplied to the reactor decreases and the output decreases, and the feed water heating function due to the drain water is lost and the feed water is restored. The output gradually increases due to the decrease in the temperature of the reactor, and this influence lowers the reactor water level.

At this time, the water level control device detects that the drain pump is stopped and the standby drain pump is not started, and that the reactor water level has dropped after a predetermined time, and at least one recirculation pump is provided. By tripping the above, the reactor flow rate is reduced by reducing the core flow rate. As a result, it is possible to suppress fluctuations in the reactor water level and prevent unnecessary reactor scrum by suppressing the decrease in the reactor water level and promptly recovering the initial water level.

A reactor water level control apparatus according to a third aspect of the present invention is a supply / condensation system for supplying a coolant to a selective control rod in the core, a plurality of recirculation pumps for circulating the coolant in the core, and a reactor. In a boiling water nuclear plant equipped with a drain pump that collects the drain of the feed water heater inserted into the water supply / condensation system, the drain pump is stopped by detecting the operating state of the drain pump and the reactor steam flow rate and feed water flow rate. If the standby drain pump does not start, it is detected that the reactor steam flow rate exceeds the feed water flow rate after a predetermined time, and at least one of the recirculation pumps is tripped and the reactor water level is tripped. Is suppressed.

When the drain pump stops and the backup drain pump does not start, the flow rate of the feed water supplied to the reactor decreases and the output decreases, and the feed water heating function due to the drain water is lost and the feed water is restored. The output gradually increases due to the decrease in the temperature of the reactor, and this influence lowers the reactor water level.

At this time, the water level control device detects that the drain pump is stopped and the standby drain pump is not activated, and that the reactor steam flow rate exceeds the feed water flow rate after a predetermined time, so that the number of recirculation pumps decreases. Even if one or more units are tripped, the reactor flow is reduced by reducing the core flow rate. As a result, it is possible to suppress fluctuations in the reactor water level and prevent unnecessary reactor scrum by suppressing the decrease in the reactor water level and promptly recovering the initial water level.

According to a fourth aspect of the present invention, there is provided a reactor water level control system comprising: a selective control rod in the core, a plurality of recirculation pumps for circulating the coolant in the core, and a feed / condensation system for supplying the coolant to the reactor. In a boiling water nuclear power plant equipped with a drain pump that collects the drain of the feed water heater inserted in the water supply / condensation system, the drain pump is stopped by detecting the operating state of the drain pump and the feed water temperature, and a spare drain When the pump does not start, it is possible to detect that the feed water temperature has fallen below the set value after a predetermined time and to trip at least one of the recirculation pumps to suppress fluctuations in the reactor water level. Characterize.

When the drain pump is stopped and the backup drain pump is not started, the flow rate of the feed water supplied to the reactor is reduced and the output is decreased, and the feed water heating function by the drain water is lost to restore the supply. As the water temperature decreases, the output gradually increases, and this effect lowers the reactor water level.

At this time, the water level control device detects that the drain pump is stopped and the standby drain pump is not started, and that the feed water temperature is below the set value after a predetermined time, and at least the number of recirculation pumps is reduced. The reactor power is reduced by tripping one or more units to reduce the core flow rate. As a result, it is possible to suppress fluctuations in the reactor water level and prevent unnecessary reactor scrum by promptly suppressing the decrease in the reactor water level and restoring the initial water level.

According to a fifth aspect of the present invention, there is provided a reactor water level control device, wherein a selective control rod in the core, a plurality of recirculation pumps for circulating the coolant in the core, and a feed / condensation system for supplying the coolant to the reactor. In a boiling water nuclear plant equipped with a drain pump that collects the drain of the feed water heater inserted in the feed / condensate system, the recirculation pump when the operating state of the drain pump is detected and the drain pump is stopped. Is provided with a water level control device that reduces the fluctuation of the reactor water level by lowering the temperature to a predetermined rotation speed.

When the drain pump is stopped and the backup drain pump is not started, the flow rate of the feed water supplied to the reactor is reduced and the output is decreased, and the feed water heating function by the drain water is lost to restore the supply. As the water temperature decreases, the output gradually increases, and this effect lowers the reactor water level.

At this time, the water level control device detects the stop of the drain pump, reduces the rotational speed of the recirculation pump to a predetermined value, and reduces the core flow rate to reduce the reactor output. As a result, it is possible to suppress fluctuations in the reactor water level and prevent unnecessary reactor scrum by promptly suppressing the decrease in the reactor water level and restoring the initial water level.

According to a sixth aspect of the present invention, there is provided a reactor water level control apparatus, which comprises a selective control rod in the core, a plurality of recirculation pumps for circulating the coolant in the core, and a feed / condensation system for supplying the coolant to the reactor. In a boiling water nuclear power plant equipped with a drain pump that collects the drain water of the feed water heater inserted in the water supply / condensation system, when the water level in the drain tank is detected and the water level in the drain tank falls below the set value. A water level control device for suppressing fluctuations in the reactor water level is provided by lowering the recirculation pump to a predetermined rotation speed.

When the drain pump is stopped and the backup drain pump is not started, the flow rate of the feed water supplied to the reactor is reduced and the output is lowered, and the feed water heating function by the drain water is lost to restore the supply. As the water temperature decreases, the output gradually increases, and this effect lowers the reactor water level.

At this time, the water level control device detects that the drain pump is stopped and the backup drain pump is not activated by lowering the water level in the drain tank, and reduces the rotation speed of the recirculation pump to a predetermined value. Reactor power is reduced by reducing the core flow rate. As a result, it is possible to suppress fluctuations in the reactor water level and prevent unnecessary reactor scrum by promptly suppressing the decrease in the reactor water level and restoring the initial water level.

[0041]

BEST MODE FOR CARRYING OUT THE INVENTION An embodiment of the present invention will be described with reference to the drawings. Note that the same components as those of the above-described related art are denoted by the same reference numerals, and detailed description thereof is omitted. First
The embodiment corresponds to claim 1, and as shown in the block diagram of FIG. 1, a core 9 is provided inside the reactor 8, a plurality of recirculation pumps 10 around the core 9, or a reactor provided outside the reactor 8. A plurality of jet pumps connected to the recirculation pump are arranged, and the reactor output is controlled by the circulating flow rate of the coolant in the core 9.

A control rod 11 is installed in the core 9 by a control rod drive mechanism 12 at the lower part of the reactor so that the control rod 11 can be freely inserted and extracted. The degree of insertion of the control rod 11 controls the reactor output. Be seen.

A plurality of operating feed / condensate pumps 13 as a feed / condensate system are connected to the nuclear reactor 8 via a feed water heater 14 to feed the feed / condensate 15 to the reactor 8. Further, the feed water heater 14 heats the feed water 16 passing through the inside by using extraction steam of a turbine system (not shown) as a heat source.

It should be noted that the feed water heater 14 has 17
A drain tank 18 for temporarily collecting
A drain pump 19 is connected between the drain tank 18 and the suction side of the feed / condensate pump 13, and the drain pump 19 feeds the drain water 17 together with the feed water 16 to the feed / condensate pump.
Sent to 13.

Further, the water level control device 20 of the present invention comprises a drain pump operating state monitoring device 21, a water level fluctuation suppression determination device 22 and a timer 23, and monitors the drain pump 19 and a recirculation pump rotation speed control device. Control rod via control rod drive mechanism 12 along with control of recirculation pump 10 via 24
It is configured to perform 11 controls.

Next, the operation of the above configuration will be described. Supply / condensate water 15 is sent to the reactor 8 from a supply / condensation pump 13 that operates a plurality of units. The feed / condensate water 15 is heated to a sufficiently high temperature by the feed water heater 14 and then mixed with the recirculation flow rate in the reactor 8. The feed water heater 14 uses the extracted steam of a turbine system (not shown) as a heat source, and the extracted steam is condensed by heat exchange with the feed water 16 to become high-temperature drain water 17, which is temporarily stored in a drain tank 18.

The drain water 17 is pressurized by the drain pump 19 and merges with the water supply 16 on the suction side of the water supply / condensation pump 13. At this time, since the drain water 17 is high in temperature, the water supply 16
By joining with, it becomes a part of the heat source of the condensate water 15 and contributes to the improvement of the thermal efficiency of the nuclear power plant.

Here, the drain pump 19 and the drain tank 18
If the drain pump 19 itself stops due to a drop in the water level, the drain pump 19 itself fails, etc. Bring However, this drain pump
The operating state of 19 is constantly monitored by the drain pump operating state monitoring device 21 of the water level control device 20 by the drain pump operating state signal S ₁ .

The drain pump operating state signal S ₁
Contains various information regarding the operating state of the drain pump 19, such as pump speed, pump flow rate, pump differential pressure, pump motor voltage, and the like. This drain pump operating condition monitoring device
21 determines whether the drain pump 19 is stopped or the standby machine is not started. The drain pump operating condition monitoring device 21 is a drain pump.
When the stop of 19 and the start-up of the drain pump standby unit are detected, the drain pump abnormality signal S
Transmit ₂ .

In the water level fluctuation suppression determination device 22, the drain pump abnormality signal S ₂ is input, and it is determined whether or not the water level fluctuation suppression operation is necessary in light of the plant operating conditions such as reactor output and core flow rate at that time. If it is determined that it is necessary, the recirculation pump speed reduction request signal S ₃ is transmitted to the recirculation pump rotation speed control device 24. Further, the reactor output reduction request signal S ₄ is output to the timer 23, and the timer 23
After the elapse of a predetermined set time, the selection control rod insertion request signal S _{5 is} issued to the selection control rod previously selected from the control rods 11.
Is output to the control rod drive mechanism 12.

The recirculation pump rotation speed control device 24 inputs the recirculation pump lowering speed request signal S ₃ to change all the rotation speeds of the plurality of recirculation pumps 10 to the rotation speed speed control signal S.
Control by ₆ to lower to the minimum value. As a result, the core flow rate is reduced, and the reactor output, and further the reactor steam flow rate are reduced. Further, when the control rod driving mechanism 12 receives the selection control rod insertion request signal S ₅ , the control rod driving mechanism 12 inserts a selection control rod selected in advance among the control rods 11 to reduce the reactor output and the reactor steam flow rate.

Next, the water level control of the reactor in the above operation will be described. Here, it is assumed that during the rated output operation of the reactor 8, for example, the drain tank 18 is lowered in water level so that the two drain pumps 19 are automatically stopped and the start-up of the standby machine is prevented. At this time, one of the two units of the supply / condensation pump 13 in operation is automatically stopped, and the suction pressure of one unit of the supply / condensation pump 13 that continues to operate is ensured. The flow rate and temperature of 15 will decrease.

When the drain pump 19 is stopped and the start-up of the standby machine is blocked, this state is set.
21 detects based on the drain pump operating state signal S ₁ and immediately thereafter outputs a drain pump abnormality signal S ₂ to the water level fluctuation suppression determination device 22. The water level fluctuation suppression determination device 22,
As shown in the flow chart of the logic circuit of FIG. 2, the recirculation pump speed reduction request signal S ₃ is sent to the recirculation pump rotation speed control device 24 based on the drain pump abnormality signal S _2, and the recirculation is performed by the rotation speed control signal S ₆ . The rotation speed of the pump 10 is reduced to the minimum speed.

Furthermore, the reactor output reduction request signal S ₄ sent from the water level fluctuation suppression determination device 22 is the selected control rod insertion request signal S ₄ which reaches the control rod drive mechanism 12 after a predetermined time via the timer 23. Therefore, the insertion of the selective control rod, which is a part of the control rod 11, into the core 9 is started.

The comparative characteristic curve diagram of FIG. 3 shows the transient changes in the present invention and the conventional water level control in comparison. In each curve, the present invention shows the solid line reactor output 25,
The core flow rate 26, feed water flow rate 27, reactor steam flow rate 28, reactor water level 29, and the conventional example (same as in FIG. 4) are the reactor output 1, the core flow rate 2, the feed water flow rate 3, and the reactor steam flow rate in the broken line. 4, indicated by the reactor water level 5.

According to the water level control device 20 of the present invention, since the speed reduction start of the recirculation pump 10 is based on the operating state of the drain pump 19, compared with the case of being based on the operating state of the conventional feed / condensate pump 13. Get faster For this reason, the decrease of the core flow rate 26 and the reactor power 25 is reduced by the conventional core flow rate 2 and the reactor power 1
Therefore, the arrival time of the mismatch in which the reactor steam flow rate 28 is lower than the feed water flow rate 27 is also faster than the mismatch arrival time of the conventional reactor steam flow rate 4 and the feed water flow rate 3.

As a result, the reactor water level 29, which is suppressed by the operation of the water level control function, is significantly eased as compared with the amount of decrease in the conventional reactor water level 5. Thereafter, when the selective control rod insertion is started 30, the reactor power 25 and the reactor steam flow rate 28 are further reduced. For this reason, the mismatch with the feed water flow rate 27 becomes large, and therefore, the reactor water level 29 is further promptly recovered to the initial water level 6.

As shown in FIG. 3 (c), the reactor water level 29 reaches the initial water level 6 shortly thereafter and causes some overshoot, but the control response of the feed water flow rate 27 stabilizes the initial water level early. Recovers to water level 6.

At the time of this event settling, the drain pump 19 is stopped because the output operation state (reactor output 25 and reactor steam flow rate 28) has a sufficient margin with respect to the maximum water supply capacity of the water supply / condensation system. Even if the output gradually increases due to the decrease in the feed water temperature due to the above, the reactor steam flow rate 28 does not exceed the maximum feed water capacity, and the control of the reactor water level 29 can be continued stably.

As described above, according to the first embodiment, it is possible to control the water level with a sufficient margin for the transient fluctuation of the reactor water level with respect to the set water level of the reactor scrum, and avoid unnecessary reactor scrum. be able to. Further, it is possible to maintain a sufficient water supply capacity even with respect to the output gradual increase phenomenon due to the decrease in the water supply temperature.

The present invention is not limited to the above-mentioned first embodiment, but can be modified in various ways as follows. It should be noted that the components having substantially the same functions as those in the first embodiment are designated by the same names and the same components are designated by the same reference numerals, and detailed description thereof will be omitted.

The second embodiment corresponds to claim 1, and most of the configuration is almost the same as the first embodiment, but the water level control device is a drain pump operating state monitoring device, a water level fluctuation suppression determination device, and It is equipped with a timer. As a function of this configuration, a water level control device (not shown) inputs the drain pump operating state signal S ₁ from the drain pump 19.

The drain pump operating state monitoring device according to the drain pump operating state signal S ₁ causes the drain pump operating state monitor S ₁ to stop when the drain pump 19 stops and the spare drain pump 19 does not start.
The drain pump abnormality signal S ₂ is output to the water level fluctuation suppression determination device.

The water level fluctuation suppression determination device which receives the drain pump abnormality signal S ₂ is the recirculation pump rotation speed control device 24.
On the other hand, first, the recirculation pump speed reduction request signal S ₃ is output to reduce the rotation speed of the recirculation pump 10 to a predetermined value. Further, a predetermined trip request signal of the recirculation pump is output after a predetermined time from the start of deceleration, and at least one or more recirculation pumps are tripped.

By decreasing the speed of the recirculation pump 10 and subsequently stopping at least one recirculation pump 10, the coolant flow rate in the reactor 8 is reduced at an appropriate speed, and Reduce the output. This allows the control rod
By reducing the reactor power without operating 11, reducing the reactor water level and quickly restoring it to the initial water level, the fluctuation of the reactor water level is suppressed and unnecessary reactor scrum is avoided. be able to.

The third embodiment corresponds to claim 1, and most of the configuration is almost the same as the first embodiment, but the water level control device (not shown) is a drain pump operating condition monitoring device and a water level fluctuation suppression determination device. It has a configuration with. As a function of this configuration, a water level control device (not shown) inputs the drain pump operating state signal S ₁ from the drain pump 19.

The drain pump operating state monitoring device according to the drain pump operating state signal S ₁ indicates that when the drain pump 19 is stopped and the spare drain pump 19 is not activated.
The drain pump abnormality signal S ₂ is output to the water level fluctuation suppression determination device. The water level fluctuation suppression determination device that receives the drain pump abnormality signal S ₂ outputs the recirculation pump lowering speed request signal S ₃ to the recirculation pump rotation speed control device 24 to determine the rotation speed of the recirculation pump 10. Decelerate to a specified value.

By decreasing the speed of the recirculation pump 10, the coolant flow rate in the nuclear reactor 8 is reduced at an appropriate speed to reduce the nuclear reactor output. This reduces the reactor power without operating the control rod 11, suppresses the decrease in the reactor water level, and quickly restores the initial water level, thereby suppressing fluctuations in the reactor water level and reducing unnecessary atoms. The furnace scrum can be avoided.

The fourth embodiment corresponds to claim 1, and most of the configuration is almost the same as the first embodiment, but a water level control device (not shown) is a drain pump operating state monitoring device and a water level fluctuation suppression determining device. It has a configuration with. As a function of this configuration, the water level control device receives the drain pump operating state signal S ₁ from the drain pump 19.

The drain pump operating state monitoring device responsive to the drain pump operating state signal S ₁ causes the drain pump operating state signal S ₁ to stop when the drain pump 19 stops and the spare drain pump 19 does not start.
The drain pump abnormality signal S ₂ is output to the water level fluctuation suppression determination device. The water level fluctuation suppression determination device that receives the drain pump abnormality signal S ₂ outputs the selection control rod insertion request signal S ₅ to the control rod drive mechanism 12, and selects the control rod 11 that has been selected in advance. Insert the control rod into the core 9.

By inserting the selection control rod, the nuclear fission in the core 9 is reduced and the reactor power is reduced. As a result, the reactor output is reduced without controlling the core flow rate by the recirculation pump 10, and the decrease in the reactor water level is suppressed and the initial water level is quickly restored, thereby suppressing fluctuations in the reactor water level. It is possible to avoid unnecessary reactor scrum.

The fifth embodiment corresponds to claim 2, and most of the configuration is almost the same as that of the first embodiment, but a reactor water level gauge (not shown) is installed in the reactor 8 and the same is not shown. The water level control device is configured to include a drain pump operating state monitoring device, a water level fluctuation suppression determination device, a timer, and a reactor water level detector.

As a function of this configuration, the water level control device inputs the drain pump operating state signal S ₁ from the drain pump 19 and also inputs the reactor water level signal from the reactor water level gauge installed in the reactor 8. . The drain pump operating state monitoring device according to the drain pump operating state signal S ₁ causes the drain pump 19 to stop and the spare drain pump to operate.
When 19 does not start, the drain pump abnormality signal S ₂ is output to the water level fluctuation suppression determination device.

Separately, the reactor water level detector constantly monitors the reactor water level. However, when the drain pump abnormality signal S ₂ is output, when the reactor water level drops after a predetermined time, , And outputs a water level drop signal to the water level fluctuation suppression determination device. This water level drop signal and drain pump abnormality signal S ₂
The water level fluctuation suppression determination device that has input is output a selective trip request signal of the recirculation pump 10 to the recirculation pump rotation speed control device 24 to trip at least one recirculation pump.

By stopping at least one of the recirculation pumps 10, the coolant flow rate in the reactor 8 is appropriately reduced and the reactor output is reduced. This reduces the reactor power without operating the control rod 11, suppresses the decrease in the reactor water level, and quickly restores the initial water level, thereby suppressing fluctuations in the reactor water level and reducing unnecessary atoms. The furnace scrum can be avoided.

The sixth embodiment corresponds to claim 2, and most of the configuration is substantially the same as that of the fifth embodiment. As a function of this configuration, the water level control device is the drain pump.
The drain pump operating state signal S ₁ from 19 is input, and the reactor water level signal is input from the reactor water level gauge installed in the reactor 8.

The drain pump operating state monitoring device responsive to the drain pump operating state signal S ₁ determines that the drain pump 19 is stopped and the spare drain pump 19 is not activated.
The drain pump abnormality signal S ₂ is output to the water level fluctuation suppression determination device. Separately, the reactor water level detector constantly monitors the reactor water level. However, when the reactor water level decreases after a predetermined time when the drain pump abnormality signal S ₂ is output, the water level is lowered. The signal is output to the water level fluctuation suppression determination device.

The water level fluctuation suppression determining device, to which the water level lowering signal and the drain pump abnormality signal S ₂ are input, outputs the selection control rod insertion request signal S ₅ to the control rod driving mechanism 12 to output the control rod 11 control signal. The selection control rod selected in advance is inserted into the core 9. By inserting the selection control rod, the core 9
Nuclear fission in the reactor reduces and reduces reactor power.

As a result, the reactor output is reduced without controlling the core flow rate by the recirculation pump 10, the reactor water level is suppressed from being lowered, and the initial reactor water level is promptly restored. It is possible to suppress fluctuations and avoid unnecessary reactor scrum.

The seventh embodiment corresponds to claim 3, and most of the configuration is almost the same as that of the first embodiment, but a reactor steam flow meter and a feed / condensate pipe are provided in a main steam pipe (not shown). In addition to installing a reactor feed water flow meter in the above, a water level control device (not shown) also includes a drain pump operating state monitoring device, a water level fluctuation suppression determination device and a timer, a reactor steam flow rate detector and a reactor feed water flow rate detector. It is configured.

As a function of this configuration, the water level control device inputs the drain pump operating state signal S ₁ from the drain pump 19, receives the reactor steam flow rate signal from the reactor steam flow meter, and the reactor feed water flow rate. Input the reactor feedwater flow rate signal from the meter. The drain pump operating state signal S
_{By 1} , the drain pump operating state monitoring device outputs the drain pump abnormality signal S ₂ to the water level fluctuation suppression determination device when the drain pump 19 is stopped and the backup drain pump 19 is not activated.

Separately, the reactor vapor flow rate detector constantly monitors the reactor vapor flow rate, and the reactor feed water flow rate detector constantly monitors the reactor feed water flow rate. Is input to the water level fluctuation suppression determination device.
In the water level fluctuation suppression determination device, when it is detected that the reactor steam flow rate exceeds the reactor feed water flow rate after a predetermined time when the drain pump abnormality signal S ₂ is output, the recirculation pump rotation speed control device It outputs a selective trip request signal of the recirculation pump 10 to 24, and trips at least one or more recirculation pumps.

By stopping at least one of the recirculation pumps 10, the coolant flow rate in the reactor 8 is appropriately reduced and the reactor output is reduced. This reduces the reactor power without operating the control rod 11, suppresses the decrease in the reactor water level, and quickly restores the initial water level, thereby suppressing fluctuations in the reactor water level and reducing unnecessary atoms. The furnace scrum can be avoided.

The eighth embodiment corresponds to claim 3, and most of the construction is substantially the same as that of the seventh embodiment. As a function of this configuration, the water level control device is the drain pump.
The drain pump operation state signal S ₁ from 19 is input, the reactor steam flow signal is input from the reactor steam flow meter, and the reactor feed water flow signal is input from the reactor feed water flow meter.

When the drain pump 19 is stopped and the spare drain pump 19 is not activated, the drain pump operating state monitoring device receives the drain pump operating state signal S _{1 from the} drain pump operating state signal S ₁ .
The drain pump abnormality signal S ₂ is output to the water level fluctuation suppression determination device. Separately, the reactor steam flow rate detector constantly monitors the reactor steam flow rate, and the reactor feed water flow rate detector constantly monitors the reactor feed water flow rate, but these signals are input to the water level fluctuation suppression determination device.

In the water level fluctuation suppression determination device, when it is detected that the reactor steam flow rate exceeds the reactor feed water flow rate after a predetermined time when the drain pump abnormality signal S ₂ is output, the control rod drive mechanism A selection control rod insertion request signal S ₅ is output to 12 and the selection control rods selected in advance from the control rods 11 are inserted into the core 9.

By inserting the selective control rod, nuclear fission in the core 9 is reduced and the reactor power is reduced. As a result, the reactor output is reduced without controlling the core flow rate by the recirculation pump 10, and the decrease in the reactor water level is suppressed and the initial water level is quickly restored, thereby suppressing fluctuations in the reactor water level. It is possible to avoid unnecessary reactor scrum.

The ninth embodiment corresponds to claim 4, and most of the construction is almost the same as that of the first embodiment, but a water supply thermometer is installed in a water supply / condensation pipe (not shown) and the same is not shown. The water level control device includes a drain pump operating state monitoring device, a water level fluctuation suppression determination device and a timer, and a reactor feed water temperature detector.

As a function of this configuration, the water level control device inputs the drain pump operating state signal S ₁ from the drain pump 19 and the reactor feed water temperature signal from the reactor feed water thermometer. The drain pump operating state monitoring device outputs the drain pump abnormality signal S ₂ to the water level fluctuation suppression determining device when the drain pump 19 is stopped and the backup drain pump 19 is not activated by the drain pump operating state signal S _1. To do.

Separately, the reactor feed water temperature detector constantly monitors the reactor feed water temperature, and when it is detected that the reactor feed water temperature falls below the set value after a predetermined time, the feed water temperature drop signal is sent to the water level. Output to the fluctuation suppression determination device. In the water level fluctuation suppression determination device, when the drain pump abnormality signal S ₂ and the feed water temperature decrease signal are input, a selective trip request signal of the recirculation pump 10 is output to the recirculation pump rotation speed control device 24, Trip at least one recirculation pump.

By stopping at least one of the recirculation pumps 10, the coolant flow rate in the reactor 8 is appropriately reduced and the reactor output is reduced. This reduces the reactor power without operating the control rod 11, suppresses the decrease in the reactor water level, and quickly restores the initial water level, thereby suppressing fluctuations in the reactor water level and reducing unnecessary atoms. The furnace scrum can be avoided.

The tenth embodiment corresponds to claim 4, and most of the construction is substantially the same as that of the ninth embodiment. As a function of this configuration, the water level control device is the drain pump.
The drain pump operating state signal S ₁ from 19 is input, and the reactor feedwater temperature signal is input from the reactor feedwater thermometer.

When the drain pump 19 is stopped and the spare drain pump 19 is not activated, the drain pump operating state monitoring device receives the drain pump operating state signal S _{1 from the} drain pump operating state signal S ₁ .
The drain pump abnormality signal S ₂ is output to the water level fluctuation suppression determination device. Separately, the reactor feedwater temperature detector constantly monitors the reactor feedwater temperature, and when it detects that the reactor feedwater temperature falls below the set value after a predetermined time, it judges the feedwater temperature drop signal as water level fluctuation suppression judgment. Output to the device.

In the water level fluctuation suppression determination device, when the drain pump abnormality signal S ₂ and the feed water temperature decrease signal are input,
Select control rod insertion request signal S ₅ to the control rod drive mechanism 12
Is output, and a selected control rod selected in advance from the control rods 11 is inserted into the core 9.

By inserting the selective control rod, the nuclear fission in the core 9 is reduced and the reactor power is reduced. As a result, the reactor output is reduced without controlling the core flow rate by the recirculation pump 10, and the decrease in the reactor water level is suppressed and the initial water level is quickly restored, thereby suppressing fluctuations in the reactor water level. It is possible to avoid unnecessary reactor scrum.

The eleventh embodiment corresponds to claim 5, and most of the configuration is almost the same as that of the first embodiment, but the water level control device (not shown) includes a drain pump operating condition monitoring device and a water level fluctuation suppression determination. It is configured to include a device.

As a function of this configuration, in the water level control device, the drain pump operating state signal S ₁ from the drain pump 19 is input, and the drain pump operating state monitoring device causes the drain pump 19 to be stopped and the standby state. If the drain pump 19 is not started, the drain pump abnormality signal S ₂ is output to the water level fluctuation suppression determination device. In the water level fluctuation suppression determination device, when the drain pump abnormality signal S ₂ is input, the recirculation pump speed reduction request signal S ₃ is output to the recirculation pump rotation speed control device 24, and the recirculation pump 10 is operated. The rotation speed is reduced to a predetermined value.

Due to the lowering of the speed of the recirculation pump 10, the coolant flow rate in the reactor 8 is reduced at an appropriate speed to reduce the reactor output. This reduces the reactor power without operating the control rod 11, suppresses the decrease in the reactor water level, and quickly restores the initial water level, thereby suppressing fluctuations in the reactor water level and reducing unnecessary atoms. The furnace scrum can be avoided.

The twelfth embodiment corresponds to claim 6, and most of the configuration is almost the same as the first embodiment, but a drain tank water level gauge (not shown) is installed in the drain tank 18, and the same is not shown. The water level control device includes a drain tank water level detector and a water level fluctuation suppression determination device. As a function of this configuration, the drain tank water level gauge installed in the drain tank 18 constantly monitors the water level of the drain water in the drain tank 18, and outputs this drain water level signal to the water level control device.

The water level control device outputs a drain water level lowering signal to the water level fluctuation suppression determining device when the drain water level falls below the set value in the drain tank water level detector. The water level fluctuation suppression determination device that receives this drain water level decrease signal outputs a selective trip request signal of the recirculation pump 10 to the recirculation pump rotation speed control device 24, and at least one or more recirculation pumps. Trip.

By stopping at least one of the recirculation pumps 10, the flow rate of the coolant in the reactor 8 is appropriately reduced and the reactor output is reduced. This reduces the reactor power without operating the control rod 11, suppresses the decrease in the reactor water level, and quickly restores the initial water level, thereby suppressing fluctuations in the reactor water level and reducing unnecessary atoms. The furnace scrum can be avoided.

The present invention is not limited to the above-mentioned embodiment, and for example, the reactor power reduction request signal S
Based on ₄ , the selection control rod insertion request signal S ₅ sent out by the timer 23 is used as a request signal for stopping a plurality of recirculation pumps 10 to further reduce the core flow rate, thereby reducing the reactor output and the reactor steam flow rate. You can also let it. Further, instead of using the timer 23, the output due to the decrease in the feed water temperature and the gradual increase in the reactor steam flow rate are detected to detect that the reactor water level drops below the maximum feed water capacity, and the insertion of the selection control rod,
It is also possible to activate the recirculation pump stop function.

That is, the decrease behavior of the reactor water level itself is detected, it is judged that the gradually increasing reactor steam flow rate exceeds the feed water flow rate, or the feed water temperature almost corresponding to the reactor output is set as a set value. It is a determination that the value is below. Further, by adding a water level lowering signal of the drain tank 18 to the operation state monitoring of the drain pump 19, it is possible to determine the abnormality of the drain pump 19 earlier.

In addition to the above, the scope of the present invention is not changed,
Of course, various modifications can be made. Furthermore, in the present invention, a drain pump that does not involve starting a standby machine
Even if there is a partial loss of the feed water flow rate and its temperature due to the stop of one or two units in 19, the fluctuation of the reactor water level can be suppressed and unnecessary reactor scrum can be avoided.

That is, according to the first embodiment and the second embodiment, after the drain pump 19 is stopped and the deceleration of the recirculation pump 10 is started due to the standby machine not being started, the selection control rod is inserted after a predetermined time, or Stop at least one recirculation pump 10. As a result, the reactor steam flow rate can be reduced to a lower level.Therefore, even if the output gradually increases due to the decrease in the feedwater temperature, the reactor steam flow rate is suppressed within the feedwater capacity range and the Make sure that the reactor water level does not drop. Therefore, it is possible to avoid a reactor scrum due to a decrease in reactor water level.

According to the third embodiment, the eleventh embodiment, and the twelfth embodiment, the speed-reducing function of the recirculation pump 10 prevents the feed / condensate pump 13 from being automatically stopped and the water level lowering beyond the normal operating range thereafter. It operates by detecting the stoppage of the drain pump 19 itself, detecting the inactivation of the drain pump standby machine, or detecting the drop of the drain water level in the drain tank 18 without waiting until the detection.

Therefore, the reactor steam flow rate is reduced more quickly after the drain pump 19 is stopped, and the mismatch with the feed water flow rate is suppressed to the minimum, so that the fluctuation of the reactor water level is alleviated. To be done. Therefore, it is possible to avoid the reactor scrum due to the drop in the water level during the transition caused by this mismatch.

According to the fourth embodiment, by detecting the stop of the drain pump 19 and the detection of the standby unit non-operation, the selected control rod 11 is inserted and the reactor steam flow rate is made sufficiently low. It is possible to suppress a decrease in reactor water level due to partial loss of temperature. Therefore, the reactor scrum due to the lowered water level can be avoided.

According to the fifth and sixth embodiments, after the fluctuation of the water level immediately after the partial loss of the feed water flow is settled, the reactor steam flow rate exceeds the feed water capacity and the reactor water level rises due to the gradual increase of the output accompanying the decrease of the feed water temperature. Even if the water level drops, it is detected and at least one recirculation pump 10 is stopped, or the selective control rod is inserted to suppress the reactor steam flow rate within the water supply capacity range and lower the reactor water level. Try not to do it.
Therefore, it is possible to avoid the reactor scrum due to the decrease in the reactor water level.

According to the seventh embodiment and the eighth embodiment, even if the reactor steam flow rate exceeds the water supply capacity due to the gradual increase in the output due to the decrease in the feed water temperature after the water level fluctuation immediately after the loss of the feed water flow rate is settled, this By detecting and stopping at least one recirculation pump 10, or by inserting the selective control rod 11, the reactor steam flow rate is suppressed within the water supply capacity range so that the reactor water level will not drop. . Therefore, it is possible to avoid the reactor scrum due to the decrease in the reactor water level.

According to the ninth and tenth embodiments, after the water level fluctuation immediately after the loss of the feed water flow rate is settled, the decrease in the feed water temperature is detected by the predetermined temperature setting, and the recirculation pump 10 is reduced. Even if one or more units are stopped or the selective control rods 11 are inserted, the reactor steam flow rate is suppressed within the water supply capacity range so that the reactor water level does not drop. Therefore, it is possible to avoid the reactor scrum due to the decrease in the reactor water level.

[0112]

As described above, according to the present invention, in the water supply / condensation system of a nuclear power plant, one or two drain pumps without stopping the standby machine are stopped due to a decrease in the water level of the drain tank or the like. Even when a partial loss of the reactor water supply flow rate and its temperature occurs, the reactor water level is stably controlled to avoid unnecessary reactor scrum, improving the operating rate of the nuclear power plant and stabilizing the power supply. There is an effect that the supply is done.

[Brief description of the drawings]

FIG. 1 is a block configuration diagram of a reactor water level control device according to a first embodiment of the present invention.

FIG. 2 is a flow chart of reactor water level control according to the first embodiment of the present invention.

FIG. 3 is a comparative characteristic curve diagram of transient response characteristics when the drain pump is stopped according to the first embodiment of the present invention and a conventional example, (a) is a reactor output and a core flow rate, and (b) is a feed water flow rate and a reactor. Steam flow rate, (c) shows reactor water level.

FIG. 4 is a conventional transient response characteristic curve diagram when a drain pump is stopped, where (a) shows reactor power and core flow rate, (b) shows feed water flow rate and reactor steam flow rate, and (c) shows reactor water level. .

[Explanation of symbols]

1,25 ... Reactor output (curve), 2,26 ... Core flow rate (curve), 3,27 ... Feed water flow rate (curve), 4,28 ... Reactor steam flow rate (curve), 5,29 ... Reactor water level (Curve), 6 ... initial water level, 7 ... reactor scrum value, 8 ... reactor, 9 ... reactor core,
10 ... Recirculation pump, 11 ... Control rod, 12 ... Control rod drive mechanism,
13 ... Condensation water pump, 14 ... Water supply heater, 15 ... Condensation water, 16 ...
Water supply, 17 ... Drain water, 18 ... Drain tank, 19 ... Drain pump, 20 ... Water level control device, 21 ... Drain pump operating state monitoring device, 22 ... Water level fluctuation suppression determination device, 23 ... Timer, 24
... Recirculation pump rotation speed control device, 30 ... Start of selection control rod insertion, S ₁ ... Drain pump operation status signal, S ₂ ... Drain pump abnormality signal, S ₃ ... Recirculation pump speed reduction request signal, S
₄ ... reactor power reduction request signal, S ₅ ... selected control rod insertion request signal, S ₆ ... speed control signal.

Claims (6)

[Claims] 1. A drain of a feed water heater inserted in a feed / condensation system for feeding a coolant to a reactor, a control rod in a core, a plurality of recirculation pumps for circulating a coolant in the core, and a condensate system. In a boiling water nuclear power plant equipped with a drain pump to be collected in, when the drain pump is stopped by detecting the operating state of the drain pump and the spare drain pump does not start, the rotation speed of the recirculation pump is set to a predetermined value. A reactor water level control device, characterized in that a water level control device is provided which suppresses fluctuations in the reactor water level by inserting the selection control rod after a predetermined period of time and reducing the speed. 2. A drain of a feed water heater inserted in a feed / condensation system for supplying coolant to a reactor, a control rod in a core, a plurality of recirculation pumps for circulating a coolant in the core, and a condensate system. In a boiling water nuclear plant equipped with a drain pump for recovery, the operating state of the drain pump and the reactor water level are detected, the drain pump stops, and the standby drain pump does not start. A reactor water level control device, which detects that the reactor water level has dropped and trips at least one of the recirculation pumps to suppress fluctuations in the reactor water level. 3. A drain of a feed water heater inserted into a feed / condensation system for supplying coolant to a reactor, a control rod in a core, a plurality of recirculation pumps for circulating a coolant in the core, and a drainage system. In a boiling water nuclear power plant equipped with a drain pump to be collected in the above, when the drain pump is stopped by detecting the operating state of the drain pump and the reactor steam flow rate and the feed water flow rate, and the standby drain pump does not start, Reactor water level control characterized by detecting that the reactor steam flow exceeds the feed water flow after a certain time and tripping at least one of the recirculation pumps to suppress fluctuations in the reactor water level apparatus. 4. A drain of a feed water heater inserted in a feed / condensation system for supplying coolant to a reactor, a control rod in a core, a plurality of recirculation pumps for circulating a coolant in the core, and a drainage system. In a boiling water nuclear plant equipped with a drain pump that collects the water, the feed water temperature after a prescribed time when the drain pump stops operating and the standby drain pump does not start by detecting the operating state of the drain pump and the feed water temperature. Is lower than a set value and trips at least one of the recirculation pumps to suppress fluctuations in the reactor water level. 5. A drain of a feed water heater inserted in a feed / condensation system for feeding a coolant to a reactor, a control rod in a core, a plurality of recirculation pumps for circulating a coolant in the core, and a drainage system. In a boiling water nuclear power plant equipped with a drain pump for recovery to, when the drain pump is stopped by detecting the operating state of the drain pump, the recirculation pump is lowered to a predetermined rotation speed to reduce the reactor water level. A reactor water level control device, which is provided with a water level control device that suppresses fluctuations in temperature. 6. The drain water of a feed water heater inserted in a feed / condensation system for supplying a coolant to a reactor, a selective control rod in the core, a plurality of recirculation pumps for circulating a coolant in the core, In a boiling water nuclear plant equipped with a drain pump for collecting in a water system, when the water level in the drain tank is detected and the water level in the drain tank falls below a set value, the recirculation pump is lowered to a predetermined rotation speed. A reactor water level control device comprising a water level control device for suppressing fluctuations in the reactor water level.