JPH0534494A - Control of nuclear reactor water level - Google Patents

Abstract

(57) [Abstract] [Purpose] To prevent the reactor pressure vessel from being cooled by the suppression pool water during the reactor scram when the electric motor driven feed pump trips. [Structure] Condensate in the condenser is supplied to the reactor through a condensate water supply system with multiple pumps, and the condensate water supply system also supplies the condensate in the condenser according to the reactor water level detection value when the plant has a low load. To control the reactor water level to the normal water level by controlling the feed water flow rate and the core flow rate by the reactor recirculation pump. Here, when starting and stopping the plant,
When the electric motor driven water supply pump, which is one of the two, trips, the cooling water pump 22 is activated to inject the condensate in the condensate storage tank 21 into the reactor pressure vessel 9 to set the water level in the reactor pressure vessel 9 to the normal level. Control to the water level. As a result, the reactor pressure vessel can be cooled without using unclean suppression pool water.

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 method, and trips a pump of a condensate water supply system when the condensate water supply system has no reserve capacity or has a small reserve capacity. The present invention relates to a reactor water level control method suitable for reducing the amount of decrease in the reactor water level due to a decrease in the reactor water supply flow rate after the occurrence of a failure (hereinafter referred to as trip).

[0002]

2. Description of the Related Art FIGS. 7 and 8 show a conventional nuclear power plant. FIG. 7 shows a main steam system, a condensate water supply system, and a reactor recirculation control system. Condensate condensed by the condenser 1 is boosted by the low pressure condensate pump 2.
The water is purified to an appropriate quality by the condensate purification device 3, is pressurized by the high-pressure condensate pump 4, is heated by the low-pressure feedwater heater 5, is boosted by the turbine-driven feedwater pump 7 or the electric motor-driven feedwater pump 6, and is pressurized by the high-pressure feedwater heater 8. It is heated by and is supplied to the reactor pressure vessel 9. The steam generated by the reactor pressure vessel 9 is the steam turbine 11
Is driven to rotate the generator G to generate electricity.

In the reactor water level control, single element control is performed by the reactor water level detector 15 when the load is low, and when the load is high, the feed water flow rate detector 14, the reactor water level detector 15, and the main steam flow rate detection are performed. The three-element control including the device 16 is performed. Turbine driven feed water pump 7 for load fluctuations and transient events
In (1), the water supply flow rate is controlled by the steam control valve 12 and in the electric motor driven water supply pump 6 by the water supply flow rate control valve 13, so that the water level of the reactor pressure vessel 9 is kept constant.

In addition to controlling the reactor output by the control rod, the plant output is controlled by controlling the reactor core flow rate by the reactor recirculation pump 10 during normal operation to control the reactor output. In FIG. 7, reference numeral 17 denotes 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, the low-pressure condensate pump 2 or the high-pressure condensate pump 2 or the high-pressure condensate pump 4 does not have a reserve machine or has a small reserve capacity. When the pump 4 trips, the reactor water level is controlled as follows. That is,
By "reactor water level low" and "turbine driven feed water pump 7 trip", the reactor recirculation pump 10 is run back, the core flow rate is reduced, and the reactor power is reduced.
The main steam flow rate is reduced to prevent the reactor water level from decreasing. However, in this conventional technique, when the low-pressure condensate pump 2 and the high-pressure condensate pump 4 do not have a backup machine, it is difficult to recover the reactor feedwater flow rate, and the reactor water level does not recover at a low water level. The water level will be low "and the reactor may scrum.

When the low-pressure condensate pump 2 and the high-pressure condensate pump 4 trip, the downstream pump is also tripped in order to secure the pushing pressure of the downstream pump. That is, for example, when one of the low-pressure condensate pumps 2 trips, the pushing pressure of the feed water drops, so one high-pressure condensate pump 4 and one turbine-driven feed water pump 7 are tripped. Then, the trip of the low-pressure condensate pump 2 and the high-pressure condensate pump 4 is detected by detecting the trip of the turbine-driven feed water pump 7.

FIG. 8 shows a nuclear reactor spray system. When there is only one electric motor driven feed water pump 6, the electric motor driven feed water pump 6 is used when the plant is started and stopped. If the feedwater pump 6 trips, the reactor feedwater will be lost and the reactor will scram at "reactor water level low".

After the reactor scram, since there is no cooling water for cooling the inside of the reactor, "low or low reactor water level" is detected by the water level detector 15, and the cooling water pump 22 shown in FIG. 8 is started. The cooling water pump 22 injects the condensed water in the condensed water 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 by the “reactor water level low”, and the suppression pool 2
The condensed water in 6 is poured into the reactor pressure vessel 9. After depressurizing the inside of the reactor pressure vessel 9 with the cooling water pump 22 and the high-pressure core spray pump 23, the condensed water in the suppression pool 26 is injected into the reactor pressure vessel 9 with the low-pressure core spray pump 24, and further depressurization and temperature reduction are performed. Then shut down the reactor. In addition, in FIG. 8, 25 shows a reactor containment vessel.

[0009]

In the condensate storage tank 21, the condensate purified by the condensate purifier is always stored or replenished with pure water, so that the condensate is clean, there is no problem. However, since the condensate in the suppression pool 26 is not purified, it is necessary to clean the inside of the reactor pressure vessel 9 when the reactor is restarted after the condensate is injected into the reactor pressure vessel 9. is there. Since the reactor pressure vessel 9 has many internal structures, there is a problem that the working time and cost required for cleaning become enormous.

An object of the present invention is to solve the above-mentioned problems of the prior art, and to prevent the reactor pressure vessel from being cooled by the suppression pool water during the reactor scram when the electric motor driven feed pump is tripped when the plant is stopped. It is intended to provide a reactor water level control method capable of preventing.

[0011]

[Means for Solving the Problems] The above-mentioned object is to detect the trip when the electric motor driven water feed pump trips during operation when the plant is stopped and to start the cooling water pump, and By injecting the condensate in the condensate storage tank and suppressing the decrease in the water level in the reactor pressure vessel,
To be achieved.

[0012]

[Operation] Since the condensate in the condensate storage tank is injected into the reactor pressure vessel by the cooling water pump during a trip, it is possible to prevent the suppression pool water from being injected into the reactor pressure vessel during the reactor scram. ..

[0013]

DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below with reference to the drawings. FIG. 4 shows the main steam system, the condensate water supply system, and the reactor recirculation control system. Condensate condensed by the condenser 1 is boosted by the low-pressure condensate pump 2 and the condensate purification device 3 Is purified to proper water quality by the high pressure condensate pump 4 and is heated by the low pressure feed water heater 5.
The pressure is increased by the turbine-driven water supply pump 7 or the electric-motor-driven water supply pump 6, heated by the high-pressure water supply heater 8, and supplied to the reactor pressure vessel 9. Reactor pressure vessel 9
The steam generated by driving the steam turbine 11,
The generator G is rotated to generate electricity.

Next, in the reactor water level control, single element control is performed by the reactor water level detector 15 when the load is low, and the feed water flow rate detector 14 and the reactor water level detector 15 are used when the load is high.
And the main steam flow rate detector 16 are combined to perform three-element control. Further, load fluctuations and transient events are made to follow by controlling the feed water flow rate by the steam control valve 12 in the turbine driven feed water pump 7 and by the feed water control valve 13 in the electric motor driven feed pump 6, respectively.
The water level of the reactor pressure vessel 9 is kept constant.

Further, in addition to the control of the reactor output by the control rod, the plant output is controlled by controlling the reactor core flow rate by the reactor recirculation pump 10 in the normal operation to control the reactor output.

The pump capacity and number of the condensate water supply system in this embodiment are as follows: low-pressure condensate pump 2 ... 33% × 3 units High-pressure condensate pump 4 ... 33% × 3 units Turbine-driven water supply pump 7 ... 50% × 2 Table Motor driven water feed pump 6 ... 25% x 1 set. In FIG. 4, 17 is a reactor recirculation pump 10, a steam control valve 12, and a water supply amount control valve 1 during normal operation.
3 shows a controller of 3.

The water level control device shown in FIG. 6 includes a runback judging device 31. This runback determiner 31
A trip of the pump is detected by the number of operating low-pressure condensate pumps 2, high-pressure condensate pumps 4, turbine-driven feedwater pumps 7 and electric-motor-driven feedwater pumps 6, and the feedwater flow rate signal from the feedwater flow rate detector 14, and the reactor is recirculated. It is determined whether or not the pump 10 needs to run back, and the reactor recirculation pump 10 is run back when necessary.

FIG. 5 shows the decision logic of the runback decision device 31. All three low pressure condensate pumps 2 are operated during 100% load operation of the plant. At this time,
From the water supply flow rate detector 14, it is sent to the runback determination device 31 that the water supply flow rate at 100% load is being supplied. In this operating state, when one low-pressure condensate pump 2 trips, a trip signal enters the runback determiner 31, and the runback determiner 31 has the water supply capacity of the pump as the operating load as can be seen from FIG. It is determined that 100% is insufficient, and the reactor recirculation pump 10 is run back to reduce the reactor output. As a result, the water level drop in the reactor pressure vessel 9 can be reduced and the reactor scrum can be prevented.

During operation at 66% load, if three low-pressure condensate pumps 2 are in operation, the initial load is 66% even if one unit is tripped. Since this is possible and the reactor water level does not drop, the runback determination unit 31 does not runback the reactor recirculation pump 10. If one of the low-pressure condensate pumps 2 is tripped during operation, the water supply capacity is insufficient, so the runback determiner 31 causes the reactor recirculation pump 10 to run back and the reactor pressure vessel 9 Reduce the amount of water level drop. As a result, it becomes possible to prevent the reactor scrum. As can be seen from FIG. 5, the runback determiner 31 operates similarly when the high-pressure condensate pump 4 and the turbine drive feedwater pump 7 trip.

As described above, in the runback determination device 31 of this embodiment, when the pump of the condensate water supply system is tripped, the number of operating pumps is compared with the water supply flow rate as the load of the plant. When the number of operating pumps is insufficient, the reactor recirculation pump 10 is run back to reduce the water level drop in the reactor pressure vessel 9 and prevent reactor scram. As described above, the runback determiner 31 of this embodiment shows the case where the flow rate of the feed water is used as the load determining element of the plant, but in addition, the output of the generator, the pressure after the first stage of the high pressure turbine, etc. are properly set. You may employ | adopt what can detect the load of a plant.

FIG. 6 shows the difference in water level control characteristics between the embodiment and the prior art. The prior art is indicated by a chain line, and the change according to the embodiment is indicated by a solid line.
It shows the change when the low-pressure condensate pump 2 trips during load operation. As can be seen from FIG. 6, in the prior art, the "water level" of the reactor pressure vessel 9 becomes "low and low" about 50 seconds after the low-pressure condensate pump 2 has tripped, which may cause a reactor scrum. However, in the above-mentioned embodiment, the amount of decrease in water level is small, the recovery is quick, and the reactor scrum can be avoided.

FIG. 1 is a diagram showing a condensate injection system for injecting condensate into a reactor pressure vessel and a suppression pool water injection system for injecting condensate in a suppression pool after a reactor scrum. The case where the electric motor driven water supply pump does not have a backup machine is shown.

In the water level control device shown in FIG. 1, the condensate in the condensate storage tank 21 is injected into the reactor pressure vessel 9 by the cooling water pump 22. On the other hand, high pressure core spray pump 2
3 and the low-pressure core spray pump 24 are used to inject the condensed water in the suppression pool 26 into the reactor pressure vessel 9.

In the present invention, in the above apparatus, when the electric motor driven water supply pump 6 that is operated when the plant is stopped is tripped, the runback determiner 31 detects the trip and activates the cooling water pump 22. It is characterized by doing.

FIG. 2 shows the decision logic of the runback decision device 31. An example of the reactor water level control method of the present invention will be described with reference to FIGS. 1 and 2. When the electric motor drive water supply pump 6 trips during operation when the plant is stopped, the run-back determination device 31 activates the cooling water pump 22 to transfer the condensate in the condensate storage tank 21 into the reactor pressure vessel 9. Immediately injects, suppresses the decrease in water level, high-pressure core spray pump 23, and low-pressure core spray pump 24
Is prevented and the inside of the reactor pressure vessel 9 is prevented from being contaminated by the condensate in the suppression pool 26.

Here, as can be seen from FIG. 2, when the electric motor driven feed water pump 6 trips in parallel with the turbine driven feed water pump 7, the plant operation can be continued,
Since it is not necessary to start the cooling water pump 22, the runback determiner 31 sets the load of the plant within the operating range of only one motor-driven feed water pump, that is, in the present embodiment, only when the load is 25% or less. The cooling water pump 22 is started. The load is detected by the water supply flow rate detector 14.

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

FIG. 3 shows the difference in the water level control characteristics between the embodiment shown in FIGS. 1 and 2 of the present invention and the prior art. The prior art is indicated by a dot-dash line and the change according to the embodiment of the present invention is shown by a solid line. Indicate. Further, FIG. 3 shows the reactor water level change when the electric motor drive feed pump 6 trips during operation at 25% load operation of the plant. As you can see from Figure 3,
In the prior art, the reactor water level becomes the starting water level of the high pressure core spray pump 23 after about 60 seconds. However, according to the embodiment of the present invention, the water level decrease amount is small and the water level is recovered, and the high pressure core spray pump It is possible to avoid starting 23. As a result, it is possible to prevent contamination of the reactor pressure vessel 9 due to the injection of condensate in the unpurified suppression pool 26.

[0029]

According to the present invention, when the plant is started or stopped,
When the electric motor driven water supply pump trips during operation, the trip is detected, the cooling water pump is started, the condensate in the condensate storage tank is injected into the reactor pressure vessel, and the Since the amount of decrease in water level is suppressed, there is an effect that contamination of the reactor pressure vessel due to injection of unpurified suppression pool water can be prevented when the reactor is scrammed.

[Brief description of drawings]

FIG. 1 shows an embodiment of a reactor water level control device for carrying out the present invention, in which a connection relationship between a runback determiner and a reactor spray system constituting the reactor water level control device is shown. FIG.

FIG. 2 is a diagram showing a decision logic of a runback decision device shown in FIG.

FIG. 3 is a diagram comparing and comparing the water level control characteristics of the conventional reactor water level control device shown in FIG.

FIG. 4 is a diagram showing a connection relationship between a runback determiner configuring a reactor water level control device and each system of a nuclear power plant.

5 is a diagram showing a determination logic of the runback determiner shown in FIG.

FIG. 6 is a diagram comparing and comparing the water level control characteristics of the conventional reactor water level control device shown in FIG. 4;

FIG. 7 is a diagram showing each system of a nuclear power plant for explaining a conventional reactor water level control method.

FIG. 8 is a diagram showing a conventional nuclear reactor spray system.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Condenser, 2 ... Low-pressure condensate pump which comprises a condensate water supply system, 4 ... High-pressure condensate pump, 6 ... Electric motor drive water supply pump, 7 ... Turbine drive water supply pump, 9 ... Reactor Pressure vessel, 10 ... Reactor recirculation pump forming a reactor recirculation system, 11 ... Steam turbine, 14 ... Feed water flow rate detector, 15 ... Reactor water level detector, 16 ... Steam flow rate detector, 21 Condensate storage tanks constituting the nuclear reactor spray system, 22 ... Cooling water pumps, 23 ... High pressure core spray pumps, 24 ... Low pressure core spray pumps, 25 ...
Reactor containment vessel, 26 ... Suppression pool, 31 ...
A runback detector that constitutes the reactor water level control device.

Claims (1)

Claims: 1. Condensate in a condenser is supplied to a reactor through a condensate water supply system having a plurality of pumps, and at the time of low load on the plant, the reactor water level detection value In a reactor water level control method for controlling a reactor water level to a normal water level by controlling a feed water flow rate to a reactor by a condensate water supply system and a core flow rate by a reactor recirculation pump, one of the pumps at the time of starting and stopping a plant is used. When the electric motor driven water supply pump, which is one of the two, trips, the cooling water pump is started and the condensate in the condensate storage tank is injected into the reactor pressure vessel to control the water level in the reactor pressure vessel to the normal water level. A water level control method for a reactor.