JPS61110096A - Reactor water level control method - Google Patents

Abstract

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

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Application of the Invention] The present invention relates to a method and device for controlling the water level of a nuclear reactor. The present invention relates to a reactor water level control method and apparatus suitable for reducing the amount of decrease in reactor water level due to a decrease in reactor water supply flow rate after a failure such as a trip (hereinafter referred to as trip) occurs in a pump in a water supply system.

[Background of the invention]

A conventional nuclear power plant is shown in FIGS. 1 and 2.

Figure 1 shows the main steam system, condensate water supply system, and reactor recirculation control system. The water is purified to an appropriate quality by the device 3, and the high pressure condensate pump 4
The pressure is increased by the low-pressure feedwater heater 5, the pressure is increased by the turbine-driven feedwater pump 7 or the motor-driven water supply pump, the water is heated by the high-pressure feedwater heater 8, and water is supplied to the reactor pressure vessel 9.

The steam generated by the reactor pressure vessel 9 drives the steam turbine 11, rotates the generator G, and generates electricity.

Next, in reactor water level control, single-element control is performed using the reactor water level detector 15 during low loads, and single element control is performed using the reactor water flow rate detector 14, reactor water level detector 15, and main steam flow rate detector during high loads. Three-element control including 16 is performed. load fluctuation,
For transient events, the turbine-driven feed water pump 76 is operated by the steam regulator 12 while the motor-driven feed water pump 6
In this case, the water supply flow rate is controlled and followed by the water supply flow rate control valve 13, and the water level in the reactor pressure vessel 9 is maintained constant.

In addition to controlling the reactor output using control rods, plant output is controlled by the reactor recirculation pump 10 during normal operation.
This controls the core flow rate and reactor output.

In FIG. 1, reference numeral 17 indicates a controller for the reactor recirculation pump 10, the steam control valve 12, and the water supply amount control valve 13.

In the conventional condensate water supply system, if the low-pressure condensate pump 2 or high-pressure condensate pump 4 does not have a backup unit, or if the reserve capacity is small, the low-pressure condensate pump 2 or high-pressure condensate pump 4 trips. In this case, the reactor water level will be controlled as follows.

In other words, when the reactor water level is low and the turbine-driven feed water pump 7 is tripped, the reactor recirculation pump 10 is runback, the reactor core flow rate is reduced, the reactor power is reduced, and the main steam flow rate is reduced. This will prevent the reactor water level from dropping.

However, in this conventional technology, if the low-pressure condensate pump 2 and the high-pressure condensate pump 4 do not have standby units, it is difficult to recover the reactor feed water flow l, and the reactor water level is low and does not recover. ”
The water level could become low and the reactor could scram.

Here, when the low pressure condensate pump 2 and the high pressure condensate pump 4 trip, the downstream pump is also tripped in order to ensure the pushing pressure of the downstream pump. When one of the low-pressure condensate pumps 2 trips, for example, the pushing pressure of water supply decreases, so one high-pressure condensate pump 4 and one turbine-driven water supply pump 7 are tripped. Trips of the low-pressure condensate pump 2 and high-pressure condensate pump 4 are detected by detecting trips of the turbine-driven water supply bongua.

As described above, the conventional technology has a problem in that the reactor scrams every time the condensate water supply system pump trips.

Next, Fig. 2 shows the reactor spray system. In the case where there is only one electric motor-driven water supply pump 6, the electric motor-driven water supply pump 6 is used when the plant is started or stopped. If the feed water pump 6 trips, the reactor feed water is lost and a scram occurs with the reactor water level low and low.

After the reactor scram, there is no cooling water to cool the inside of the reactor, so the water level detector 15 detects "low and low reactor water levels" and starts the cooling water pump 22 shown in FIG. 2. This cooling water pump 22 injects condensate in the condensate storage tank 21 into the reactor pressure vessel 9 to remove heat. At the same time, the high-pressure core spray pump 23 is started based on the "reactor water level" and the condensate in the suppression pool 26 is injected into the reactor pressure vessel 9. cooling water pump 22,
After the pressure inside the reactor pressure vessel 9 is reduced by the high-pressure core spray pump 23, the condensate in the suppression pool 26 is injected into the reactor pressure vessel 9 by the low-pressure core spray pump 24, and the pressure and temperature are further reduced. Perform a stop. In addition,
In FIG. 2, 25 indicates a reactor containment vessel.

In this case, the condensate storage tank 21 always stores condensate purified by the condensate purification device or is replenished with pure water, so the condensate is clean and there is no problem.

However, since the condensate in the suppression pool 26 has not been purified, it is necessary to clean the inside of the reactor pressure vessel 9 when restarting the reactor after injecting the condensate into the reactor pressure vessel 9. It is. Since the reactor pressure vessel 9 has a large number of internal structures, there is a problem that the work time and cost required for cleaning become enormous. [Object of the Invention] The object of the present invention is to solve the problem of Another object of the present invention is to provide a reactor water level control method that solves the technical problems and prevents reactor scram when the pump of the condensate water supply system trips during normal operation. Another object of the present invention is to provide a reactor water level control method capable of preventing cooling of a reactor pressure vessel by suppression pool water during a reactor scram when an electric motor-driven water pump trips. It is an object of the present invention to provide an atomic f water level control device that can reliably implement these control methods and reduce equipment costs.

[Summary of the invention]

A first aspect of the present invention is to detect the trip when a pump in a condensate water supply system trips, and to compare the number of operating pumps in the condensate water supply system with the load of the plant, and to The feature is that when the number of operating units is insufficient, the reactor recirculation pump is run back, the reactor core flow rate is reduced, and the reactor output is reduced.
With this configuration, it is possible to prevent reactor scram when the pump of the condensate water supply system trips during normal operation.

The second aspect of the present invention is to detect the trip when the motor-driven water pump trips during plant startup and shutdown, start the cooling water pump, and install a condensate storage tank in the reactor pressure vessel. The feature is that internal water is injected to suppress the amount of water level drop in the reactor pressure vessel. With this configuration, during plant start-up and shutdown, reactor scram when the motor-driven water supply pump trips, etc. It is possible to prevent the reactor pressure vessel from being cooled by suppression pool water.

Further, the third aspect of the present invention is to detect the trip when the pump of the condensate water supply system trips, and to compare the number of operating pumps of the condensate water supply system with the load of the plant, This system is characterized in that it is equipped with a runback determination device that runs back the reactor recirculation pump when the number of operating pumps is insufficient.With this configuration, the first invention can be reliably carried out, and the condensate A standby pump for the water supply system can be omitted.

Furthermore, the fourth invention of the present invention is that when the electric motor-driven water supply pump trips during operation when the plant is started or stopped,
It is characterized by the provision of a 7372 determination device that detects the trip and starts the cooling water pump.
With this configuration, the second aspect of the invention can be carried out reliably, and a standby machine for the motor-driven water supply pump can be omitted.

[Embodiments of the invention]

Embodiments of the present invention will be described below with reference to the drawings.

3 to 5 show an example of a water level control device and its functions for carrying out the first aspect of the present invention.

Figure 3 shows the main steam system, condensate water supply system, and reactor recirculation control system. The water is purified to an appropriate quality by the device 3, and the high pressure condensate pump 4
The pressure is increased by the low-pressure feedwater heater 5 , the pressure is increased by the turbine-driven feedwater pump 7 or the motor-driven feedwater pump 6 , the water is heated by the high-pressure feedwater heater 8 , and water is supplied to the reactor pressure vessel 9 .

The steam generated by the reactor pressure vessel 9 drives the steam turbine 11, rotates the generator G, and generates electricity.

Next, in reactor water level control, single-element control is performed using the reactor water level detector 15 during low loads, and single element control is performed using the reactor water flow rate detector 14, reactor water level detector 15, and main steam flow rate detector during high loads. Three-element control including 16 is performed. In addition, load fluctuations and transient events are followed by controlling the feed water flow rate by the steam control valve 12 in the turbine-driven water feed pump 7 and by the feed water control valve 13 in the motor-driven water feed pump 6, respectively. Reactor pressure vessel 9
The water level is kept constant.

Furthermore, in addition to controlling the reactor output using the control rods, the plant output is also controlled by the reactor recirculation pump 1 during normal operation.
0 controls the core flow rate and reactor output.

The capacity and number of pumps in the condensate water supply system in this example are as follows: Low-pressure condensate pumps 2...33*X3 high-pressure condensate pumps 4...33%*3 Turbine-driven water supply pumps 7...50%* 2 electric motor driven water pumps 6
...25 *X1 unit.

In FIG. 3, reference numeral 17 indicates a controller for the reactor recirculation pump 10, steam control valve 12, and water supply amount control valve 13 during normal operation.

The present invention is characterized in that the apparatus is provided with a run pack determiner 31. Then, a low pressure condensate pump 2, a high pressure condensate pump 4, a turbine-driven water supply pump 7
Based on the number of motor-driven feed water pumps 6 in operation and the feed water flow rate signal from the feed water flow rate detector 14, a trip of the pump is detected, and the need for a run pack of the reactor recirculation pump 10 is determined. The circulation pump 10 is configured to be able to be run-packed.

Next, FIG. 4 shows the determination logic of the run pack determiner 31, and an example of the method of the present invention will be described with reference to FIGS. 3 and 4.

When the plant is operating at a load of 100 cm, the low pressure condensate pump 2
All three cars are operated. At this time, the water supply flow rate detector 14 sends to the run pack determiner 31 that water is being supplied at the 100% load water supply flow rate.

In this operating state, when one low-pressure condensate pump 2 trips, a trip signal is sent to the run pack determiner 31, and as can be seen from FIG.
It is determined that the water supply capacity of the pump is insufficient to the operating load of 100%, and the reactor recirculation pump 10 is run back to reduce the reactor output. Thereby, the amount of water level drop in the reactor pressure vessel 9 can be reduced and reactor scram can be prevented.

If three low-pressure condensate pumps 2 are in operation during 66% load operation, the initial load is 66% even if one trips, so it is possible to supply water to the reactor with two low-pressure condensate pumps.
Since the reactor water level does not decrease, the run pack determiner 31 does not cause the reactor recirculation pump 10 to run back. If 11 units of the low pressure condensate pumps 2 trip while 2 units are in operation, the water supply capacity is insufficient, so the
1 turns on the reactor recirculation pump 10 to reduce the amount of water level drop in the reactor pressure vessel 9. As a result, it becomes possible to prevent reactor scrams.

As can be seen from FIG. 4, the run pack determiner 31
Even when the high-pressure condensate pump 4 and the turbine-driven water supply pump 7 trip, they operate in the same way.

In this way, in the car/puncture determination device 31 of this embodiment,
When a pump in the condensate water supply system trips, the number of operating pumps is compared with the water supply flow rate as the plant load, and when the number of operating pumps is insufficient, the reactor recirculation pump 10 is turned on/back. This reduces the amount of water level drop in the reactor pressure vessel 9 and prevents reactor scram.

As mentioned above, the gin-back determiner 31 of this embodiment uses the feed water flow rate as the plant load determination factor, but other factors such as the output of the generator and the pressure after the first stage of the high-pressure turbine can also be used to properly determine the plant load. A device that can detect the load may be adopted.

Next, FIG. 5 shows water level control characteristics according to the prior art and the embodiment of the present invention. In FIG. 5, the conventional technique is shown by a dashed line, and the change according to the embodiment of the present invention is shown by a solid line, which shows the change when the low pressure condensate pump 2 trips during 100% load operation.

As can be seen from FIG. 5, in the prior art, after the low pressure condensate pump 2 trips, the reactor pressure vessel 9
There was a possibility that the water level would be low and a reactor scram would occur, but in the embodiment of the present invention described above, the amount of water level drop is small and the recovery is quick, making it possible to avoid a reactor scram. .

Next, FIGS. 6 to 8 show an example of a water level control device for carrying out the second aspect of the present invention and its functions.

Figure 6 shows the condensate injection system that injects condensate into the reactor pressure vessel after a reactor scram, and the sublet pool water injection system that injects condensate from the sublet/pool. Indicates a case where the water supply pump does not have a spare unit.

The water level control device shown in FIG.
The condensate inside the reactor pressure vessel 9 is transferred to the reactor pressure vessel 9 by the cooling water pump 22.
Pour water inside. On the other hand, a high pressure core spray pump 23,
The condensate in the suppression pool 26 is injected into the reactor pressure vessel 9 by the low-pressure de-core spout V-pump 24 .

The present invention provides that the device is configured such that when the motor-driven water supply pump 6 that is operated when the plant is started or stopped trips, the runback determiner 31 detects the trip and starts the cooling water pump 22. It is a feature.

Next, FIG. 7 shows the determination logic of the runback determiner 310, and an example of the method of the present invention will be explained with reference to FIGS. 6 and 7.

If the motor-driven water supply pump 6 trips during operation during plant startup/stop, the run bank determiner 31 starts the cooling water pump 22 and immediately transfers the condensate in the condensate storage tank 21 into the reactor pressure vessel 9. This prevents the inside of the reactor pressure vessel 9 from being contaminated with condensate in the suppression pool 26 by injecting it into the reactor pressure vessel 9 to suppress the amount of water level drop and prevent the high-pressure core spray pump 23 and the low-pressure core spray pump 24 from starting. .

Here, as can be seen from FIG. 7, if the motor-driven water supply pump 6 trips while operating in parallel with the turbine-driven water supply pump 7, it is possible to continue the plant operation, but it is necessary to start the cooling water pump 22. Therefore, the runback determiner 31 starts the cooling water pump 22 only when the load of the plant is within the operating range of only one motor-driven water supply pump, and in this embodiment, the load is 25% or less. The load is detected by the water supply flow rate detector 14.

In this embodiment, the load of the plant is set at the upper limit of the operating range of the motor-driven water supply pump 6, and the upper limit is set at 25 inches, but the load is not limited to this value. Furthermore, as a starting condition for the cooling water pump 22, a reactor water level drop signal can be extracted and used.

Next, FIG. 8 shows water level control characteristics according to the prior art and the embodiment of the present invention. In FIG. 8, the prior art is shown by a dashed line, and the changes according to the embodiment of the present invention are shown by a solid line.

Further, FIG. 8 shows a change in the reactor water level when the motor-driven water supply pump 6 trips during operation when the plant is operating under a 25-inch load.

As can be seen from FIG. 8, in the conventional technology, the reactor water level reaches the startup water level of the high-pressure core spray pump 23 after about 60 seconds, but according to the embodiment of the present invention, the amount of water level drop is small, and The water level also recovers, making it possible to avoid starting the high-pressure core spray pump 23.

As a result, an unpurified suppression pool 26
Contamination of the reactor pressure vessel 9 due to condensate injection inside the reactor pressure vessel 9 can be prevented.

〔Effect of the invention〕

According to the first aspect of the present invention described above, when the pump of the condensate water supply system trips, the trip is detected, and the number of operating pumps of the condensate water supply system and the load of the plant are calculated. In comparison, when the number of units in operation is insufficient, the reactor recirculation pump is run back, the core flow rate is reduced, and the reactor output is reduced, so reactor scram due to tripping of the pump in the condensate water supply system is avoided. It has the effect of preventing

Further, according to the second aspect of the present invention, when the motor-driven water supply pump trips during plant startup and shutdown, the trip is detected, the cooling water pump is started, and the cooling water is pumped into the reactor pressure vessel. Since the condensate in the condensate storage tank is injected to suppress the amount of water level drop in the reactor pressure vessel, there is no possibility of contamination of the reactor pressure vessel due to injection of unpurified suppression pool water during reactor scram. This has the effect of preventing this from occurring.

Furthermore, according to the third aspect of the present invention, when a pump in the water supply system trips, the trip is detected, and the number of operating pumps in the condensate water supply system is compared with the load of the plant. However, since a runback determination device is provided to run back the reactor recirculation pump when the number of operating pumps is insufficient, it has the effect of reliably implementing the first invention, and also improves the efficiency of the condensate water supply system. Since a spare pump can be omitted, equipment costs can be reduced.

Furthermore, according to the fourth aspect of the present invention, there is provided a gin-back determination device that detects a trip and starts the cooling water pump when the motor-driven water supply pump trips during operation of the motor-driven water pump when the plant is started or stopped. Therefore, in addition to having the effect of reliably carrying out the second invention, it is also possible to omit a standby unit for the electric motor-driven water supply pump, thereby reducing equipment costs.

[Brief explanation of drawings]

Figure 1 is a diagram showing each system of a nuclear power plant to explain the conventional reactor water level control method, the second cause is a diagram also showing the reactor spray system, and Figure 3 is the first invention of the present invention. A diagram showing an example of a reactor water level control device for implementing the above, and showing a connection relationship between a runback determiner that constitutes the nuclear p water level control device and each system of a nuclear power development plant, Figure 4 is a diagram showing the determination logic of the runback determiner shown in Figure 3, Figure 5 is a diagram comparing the water level control characteristics of the conventional technology and the reactor water level control system shown in Figure 3; FIG. 6 shows an embodiment of a reactor water level control device for carrying out the second invention of the present invention,
FIG. 7 is a diagram showing the connection relationship between the runback determiner and the reactor spray system that constitute the reactor water level control device; FIG. 7 is a diagram showing the determination logic of the runback determiner shown in FIG. 6;
FIG. 8 is a diagram comparing the water level control characteristics of the prior art and the reactor water level control device shown in FIG. 6. 1...Condenser, 2...Low pressure condensate pump constituting the condensate water supply system, 4...High pressure condensate pump, 6...
The electric motor-driven water supply pump, 7... The turbine-driven water supply pump, 9... The reactor pressure vessel, 10... The reactor recirculation pump constituting the reactor recirculation system, 11...
・Steam turbine, 14... Water supply flow rate detector, 15...
・Reactor water level detector, 16...Steam flow rate detector, 2
1... Condensate storage tank constituting the reactor spray system, 22... Cooling water pump, 23... High pressure core spray pump, 24... Low pressure core spray pump, 25...・Reactor containment vessel, 26... subretention pool, 31... runback determiner that constitutes the reactor water level control device.

Claims (1)

[Claims] 1. Reactor water level control that supplies condensate in the condenser to the reactor through a condensate water supply system having a plurality of pumps, and controls the core flow rate using a reactor recirculation pump. In the method, when a pump in the condensate water supply system fails, the failure is detected, and the number of operating pumps in the condensate water supply system is compared with the load of the plant, and it is determined that the number of pumps in operation is insufficient. A nuclear reactor water level control method, characterized in that the reactor recirculation pump is runback at times to reduce the reactor core flow rate and reactor output. 2. Condensate in the condenser is supplied through a condensate water supply system that has multiple condensate pumps, an electric motor-driven water supply pump installed downstream of these pumps, and a turbine-driven water supply pump installed in parallel. In a reactor water level control method that supplies water to the reactor, controls the reactor core flow rate using a reactor recirculation pump, and injects condensate from the condensate storage tank into the reactor pressure vessel using a cooling water pump, when the plant starts or stops. , detecting a failure when the electric motor-driven water pump fails during operation;
A reactor water level control method characterized in that the cooling water pump is started to inject condensate in a condensate storage tank into the reactor pressure vessel, thereby suppressing a drop in the water level in the reactor pressure vessel. 3. In a reactor water level control system that has a plurality of pumps and includes a condensate water supply system that supplies condensate in a condenser to the reactor, and a reactor recirculation pump that controls the reactor core flow rate,
When a pump in the condensate water supply system fails, the number of operating pumps that detect the failure and are in operation in the condensate water supply system;
A nuclear reactor water level control system, comprising a runback determination device that compares the load of a plant with a plant load and runs back the reactor recirculation pump when the number of operating pumps becomes insufficient. 4. It has multiple condensate pumps, an electric motor-driven water supply pump installed downstream of these pumps, and a turbine-driven water supply pump installed in parallel, and supplies condensate in the condenser to the reactor. In a reactor water level control system, the reactor water level control system includes a condensate water supply system that controls the reactor core flow rate, a reactor recirculation pump that controls the reactor core flow rate, and a cooling water pump that injects condensate in the condensate storage tank into the reactor pressure vessel. A nuclear reactor water level control system, comprising a runback determination device that detects a failure and starts the cooling water pump when the motor-driven water supply pump fails during operation when the plant is started or stopped.