JPH0275782A - Feed condensate pump minimum flow rate circulating system - Google Patents

Abstract

PURPOSE:To suppress the fluctuation in a level of a reactor to an allowable range and to ensure a necessary minimum flow rate of a high pressure condensate pump by a method wherein, in an atomic power plant, when a reactor feed pump is stopped, by means of the delivery pressure of a condensate pump, a minimum flow rate is circulated. CONSTITUTION:The other end of a circulating water pipe 10 branched from the delivery side of an M/DRFP 9 is connected to a condenser 3, and a regulating valve 11 is located in this route. The regulating valve 11 has capacity capable of handling 700ton/h at a delivery pressure of approximate 150kg/cm<2>. A second regulating valve 12 is provided in parallel to the regulating valve 11. The regulating valve 12 has capacity capable of handling a necessary minimum flow rate of 700ton/h equivalent to those of two high pressure condensate pumps 5 at a delivery pressure of approximate 50kg/cm<2> of a high pressure condensate pump 5 in cooperation with the regulating valve 11. During normal running, solely through the opening and closing motion of the regulating valve 11, the fluctuation in a level of a reactor 1 can be suppressed to a value within an allowable range. However, when an abnormal state, e.g., the stop of all reactor feed pumps, occurs, a necessary minimum flow rate equivalent to those of the two high pressure condensate pumps can be ensured by means of the regulating valve 12.

Description

[Detailed Description of the Invention] [Object of the Invention] (Industrial Application Field) The present invention relates to a nuclear power plant, and particularly in a reactor feed water pump configured with one electric motor-driven pump and two turbine-driven pumps. The present invention relates to a feed condensate pump minimum flow circulation system that is provided to circulate the minimum flow rate by the discharge pressure of the condensate pump when all of them are stopped.

(Conventional technology) The reactor feed water pump drive system is based on electric motor drive.
This is done in combination with a turbine-driven system. Of these, electric motor-driven reactor feed water pumps are installed for use during plant start-up or shutdown when turbine-driven reactor feed water pumps cannot be used, or as a backup in case the turbine-driven reactor feed pump fails. Ori,
It is considered desirable to be able to meet all of these requirements by the operation of only one machine.

FIG. 3 shows a nuclear power plant consisting of one electric motor drive and two turbine drive units. That is, steam generated in the nuclear reactor 1 is sent to the turbine 2 and expanded, and at this time a generator (not shown) is turned to generate electrical output.

The steam expanded in the turbine 2 is guided to a condenser 3, where it is cooled by cooling water supplied from the outside and becomes condensed water. This condensate is extracted by a low pressure condensate pump 4,
Further, the pressure is increased by the high pressure condensate pump 5 and sent to the low pressure feed water heater 6, where it is heated by the air extracted from the turbine 2 and the temperature is increased. This temperature-raised condensate is pumped into the turbine-driven reactor feed water pump 7 (hereinafter referred to as T/DRFP).
7), the water is further pressurized and sent as reactor feed water to a high-pressure feed water heater 8 where it is heated to a predetermined temperature and then fed to the reactor 1. Here, the electric motor-driven reactor feed water pump 9 (hereinafter referred to as M/DRFP9) is T/DRFP
7 and is placed in a standby state so that it can be activated immediately in the event of a failure of the T/DRFP 7.

In addition, these high pressure condensate pumps 5 and T/DRFP7
A feed/return pump minimum flow circulation system is installed for the following reasons. In other words, in general, a minimum required flow rate is determined for the pump in order to avoid overheating due to shut-off operation and to continue stable operation. is released to condenser 3. The system that circulates the water supply to the condenser 3 in order to maintain this minimum flow rate is called the water supply and condensate pump minimum flow circulation system. Generally, the other end is connected to the condenser 3 and a control valve 11 is provided in this path to adjust the circulating flow rate.

(Problem to be Solved by the Invention) By the way, with the advent of large-capacity plants in recent years, the capacity of the supply and condensate pump minimum flow rate circulation system is approximately 150 kg/cd at the discharge pressure of M/DRFP9, which is equivalent to the capacity of two high-pressure condensate pumps 5. It has the ability to circulate the required minimum flow rate of 700 tons/h. This is the minimum required flow rate of M/DRFP9 of 800ro.
n/h, and also makes it possible to handle the required minimum flow ff1350 ton/h for one high pressure condensate pump 5 at a discharge pressure of about 50 kg/cd of the high pressure condensate pump 5. However, the prerequisite for handling this capacity is that the number of M/DRFP9s installed is two;
If there is only one unit, it is impossible to maintain the circulation flow rate. This is because if there is an abnormal rise in the water level within the reactor 1 (high water level), the required water supply amount from the reactor 1 will decrease, but at this time, the high pressure condensate pump 5 will However, even if all the reactor feed water pumps are stopped, it is desirable to circulate the minimum flow rate necessary for 2 melees and continue operation. In this case, if there are two M/DRFPs 9, the minimum flow required for two high pressure condensate pumps ff is 1700 ton/h.
It is possible to flow with the discharge pressure of the high-pressure condensate pump 5, but when there is only one M/DRFP9, there is only one supply condensate pump minimum flow circulation system, and the minimum flow rate for one unit is limited. I can't handle it anymore.

As a countermeasure to this problem, it is possible to increase the capacity of the water supply and condensate pump minimum flow rate circulation system, but the problem has been that the water level in the reactor 1 fluctuates due to fluctuations in the feed water flow rate when the control valve 11 opens and closes. If this plan is adopted, water level fluctuations in the reactor 1 will further increase, and there is a concern that the water level control will become unstable.

In this way, in order to keep the fluctuations in the water level of the nuclear reactor 1 small due to the opening and closing operations of the control valve 11 during normal operation including startup and shutdown of the plant, it is necessary to make the capacity the same as that of the conventional reactor. - On the other hand, the required minimum flow rate 7 for two high-pressure condensate pumps 5 when the M/DRFP 9 is stopped.
In order to maintain 0.00 ton/h, the capacity must be increased even further than the conventional capacity, and there is a problem in that it is difficult to satisfy both requirements.

Therefore, an object of the present invention is to provide a feed condensate pump minimum flow circulation system that does not allow water level fluctuations in the reactor to exceed an allowable range and that can secure the required minimum flow rate for two high-pressure condensate pumps. It is about providing.

[Structure of the Invention] (Means for Solving the Problems) In order to solve the above problems, the present invention provides at least two condensate pumps and one motor-driven nuclear reactor feed water pump having substantially the same configuration; It has three reactor feed water pumps in combination with a turbine-driven reactor feed water pump, and these condensate pumps and reactor feed water pumps are arranged in a predetermined order on the path from the condenser to the reactor. In the case where similar types are connected in parallel, a circulating water pipe is provided which is branched from the discharge side of the motor-driven reactor feed water pump and reaches the condenser via the first control valve, and a second control valve is provided. The first control valve is arranged in parallel with the first control valve.

(Function) The first control valve in the present invention is basically a conventional control valve, and its capacity is the minimum flow rate required for two condensate pumps depending on the discharge pressure of the motor-driven reactor feed water pump. can be handled.

Therefore, unless an emergency situation occurs in which all reactor feed water pumps are stopped, the first control valve can handle a flow rate that corresponds to all operating conditions.

However, when the motor-driven nuclear reactor feed water pump stops, securing the required minimum flow rate for two high-pressure condensate pumps must depend on the discharge pressure of the high-pressure condensate pumps themselves. In that case,
The capacity is insufficient with only the first control valve, and only in this case, the second control valve is operated to increase the insufficient circulation flow rate.

This makes it possible to avoid the negative effects of increased water level fluctuations in the reactor due to increased capacity, and also to ensure the required minimum flow rate for two condensate pumps.
It can meet two contradictory demands.

(Example) An embodiment of the present invention will be described with reference to FIG.

In this figure, parts that are the same as those shown in FIG. 3 are designated by the same reference numerals, and explanations thereof will be omitted.

In FIG. 1, the other end of a circulating water pipe 10 branched from the discharge side of the M/DRFP 9 is connected to a condenser 3. A control valve 11 is provided in this path, and the circulating flow rate is controlled as in the prior art.

The capacity of this control valve 11 can be about 1 discharge pressure of M/DRFP9 and about 110 discharge pressure.

Furthermore, as a novel configuration according to the present invention, a second control valve 12 is provided in parallel with the control valve 11. Incidentally, hereinafter, the control valve 11 will be referred to as a first control valve in contrast to the second control valve 12.

This second control valve 12 has a high pressure condensate pump 5 discharge pressure of approximately 5
It is assumed that the pump has a capacity that can handle the required minimum flow rate of 700 ton/h for two high-pressure condensate pumps 5 together with the first control valve 11 at 0 kg/cj.

On the other hand, reference numeral 13 indicates a minimum flow rate circulation system control device that operates on the first and second control valves 11 and 12 to open and close them. This minimum flow rate circulation system control device 13
is the suction flow rate signal from the flow rate detector 14 that detects the suction side water supply flow rate of M/DRFP9, T/DRFP7, M/DR
Pump operation number signals from pump operation number detectors 15, 16, and 17 that detect the number of operating FP9 and high-pressure condensate pump 5, respectively, are input, and the first and second control valves 11, 12 are determined by calculations described later. Outputs open/close signals for.

FIG. 2 shows an example of a control circuit in the minimum flow rate circulation system control device 13. When the suction flow rate signal "low" from the flow rate detector 14 and the pump operation number signal "1" from the pump operation number detector 16 are given to the AND circuit 18, the output is passed through the OR circuit 19 to the first A control signal for opening the control valve 11 is output. Further, when the pump operation number signal "0" output from the pump operation number detector 16 and the pump operation number signal "0" output from the pump operation number detector 15 are given to the AND circuit 20, the output is AND If the pump operation number signal "1" from the pump operation number detector 17 is simultaneously inputted to the circuit 21, the AND circuit 21 outputs an OR circuit 1.
9, a control signal for opening the first control valve 11 is output.

Further, when the output of the AND circuit 20 is given to the AND circuit 22 and at the same time the pump operation number signal "2" from the pump operation number detector 17 is input, the AND circuit 22 outputs the second control valve 12. A control signal for opening is output. Under conditions other than the above where the automatic opening condition for the first and second control valves 11.12 is not satisfied, the first and second control valves 11.12 are closed by the control signal from the minimum flow rate circulation system control device 13. It will be done.

According to the above configuration, during normal operation including startup and shutdown of the plant, the suction flow rate is low while the M/DRFP 9 is operating, or the high pressure condensate pump is stopped when the M/DRFP 9 is stopped, or when all T/DRFPs are stopped. The first control valve 11 opens and closes only when one valve is in operation. The required minimum flow rate is ensured by the opening operation of the first control valve 11, and in view of its capacity, its influence on water level fluctuations in the reactor 1 is no different from that of conventional valves.

On the other hand, even when the M/DRFP 9 is stopped, the circulation flow rate is the minimum required flow rate of 700 ton/h for two high-pressure condensate pumps 5.
must be maintained, but M/DRFP9 stoppage, T/R
When all the high pressure condensate pumps 5 of the FP7 are stopped, the second control valve 12 is fully opened, and together with the first control valve 11, the capacity is increased, and the above-mentioned A required minimum flow rate of 700 ton/h for two high-pressure condensate pumps 5 is circulated to the condenser 3 through the circulating water pipe 10.

Thus, according to the above configuration, during normal operation, only the opening and closing operations of the first control valve 11 are performed, so that fluctuations in the water level of the reactor 1 can be suppressed within an allowable range, and there is no concern about water level control. . Moreover, even in the event of an abnormal situation such as all reactor feedwater pumps being stopped, the capacity can be increased using the second control valve 12 to ensure the required minimum flow rate for two high-pressure condensate pumps. and its protection can be ensured.

Note that in the above embodiment, the first and second
The control valves 11 and 12 are configured to change the capacity during normal operation and the capacity in the event of an abnormal situation such as all reactor feed water pumps being stopped. The same effect can be obtained by the same control as in this embodiment by setting the capacity up to the open position as the capacity during normal operation, and setting the fully open position as the capacity in the event of an abnormal situation.

[Effects of the Invention] As explained above, the present invention provides the first circulating water pipe branched from the discharge side of the motor-driven reactor feed water pump and leading to the condenser.
Since the second control valve is connected in parallel with the first control valve, it is possible to suppress water level fluctuations in the reactor within an allowable range. Moreover, it is possible to secure the required minimum flow rate for two high-pressure condensate pumps, and simultaneously meet the requirements for stable water level control in the reactor and protection of the high-pressure condensate pumps.

[Brief explanation of the drawing]

FIG. 1 is a system diagram showing an embodiment of the minimum flow rate circulation system for the water supply and condensate pump according to the present invention, FIG. 2 is a block diagram showing an embodiment of the minimum flow rate circulation system control device according to the present invention, and FIG. FIG. 1 is a system diagram showing a conventional nuclear power plant. 1...Reactor 3...Condenser 5...High pressure condensate pump 7...T /DRFP 9...M/DRFP 10...Circulating water pipe 11...First control valve 12... ...Second control valve 13...Minimum flow rate circulation system control device 14
......Flow rate detector 15.16.17...Number of operating units detector 18.2
0.21.22...AND circuit 19...
...OR circuit application Toshiba Corporation Agent Patent attorney Sasu Suyama −

Claims (1)

[Claims] It has three reactor feed water pumps that are a combination of at least two condensate pumps, one electric motor-driven reactor feed water pump, and two turbine-driven reactor feed water pumps with almost the same configuration. In a system where these condensate pumps and reactor feed water pumps are arranged in a predetermined order on the route from the water tank to the reactor, and similar types are connected in parallel, the motor-driven reactor feed water pumps are A circulating water pipe branched from the discharge side and reaching the condenser is provided via a first control valve, and a second control valve is connected to the first control valve.
A water supply and condensate pump minimum flow circulation system characterized by being arranged in parallel with a control valve.