JP2001208890A - Feed water heater piping system for nuclear power plant - Google Patents

Abstract

PROBLEM TO BE SOLVED: To eliminate a problem such as radiation exposure due to a large quantity of piping by making the capacity of an emergency system smaller than that of a service system in a drain system of a feed water heater in a BWR plant. SOLUTION: In a BWR plant having a service system drain pipes 14a, 14b, 14c successively carrying drain of a high pressure system feed water heater 12, a second low pressure system feed water heater 10, and a first low pressure system feed water heater 9, and having emergency system drain pipes 15a, 15b, 15c discharging the drain of the feed water heater 12, 10, 9 directly to a steam condenser 5, the capacities of the emergency system drain pipes 15a, 15b, 15c are made to be smaller generally by 40% of the capacities of the service system dram pipes 14a, 14b, 14c. Therefore, with decreasing the area of inner surfaces of the emergency system pipes 15a, 15b, 15c, radiation exposure is reduced and safety is improved.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a piping system for a feed water heater for a boiling water nuclear power plant (hereinafter, referred to as a BWR plant).

[0002]

2. Description of the Related Art In a so-called regeneration cycle type turbine plant for heating condensate or feed water sent to a nuclear reactor by steam extracted from a steam turbine, high-pressure and low-pressure feed water heaters are indispensable equipment. is there.

In these feed water heaters, in addition to the bleeding described above, high-temperature fluid condensed by condensing water or heat exchange with feed water by the upper high-pressure feed water heater, that is, drain is recovered by the lower low-pressure feed water heater. Guided to heat water or water supply.

During normal operation, each feed water heater drain is sequentially led to a lower feed water heater by a common drain pipe.
After the heat recovery in the bottom feedwater heater is completed, it is discharged to the condenser, but each feedwater heater drain can also be discharged directly to the condenser by the emergency drain pipe. BW
In the R plant, the capacity of the emergency drain pipe is designed to be the same as the capacity of the normal drain pipe.

An example of a piping system in a conventional BWR plant will be described with reference to FIG. In FIG. 5, reference numeral 1 denotes a nuclear reactor, which is provided with a main steam system for supplying steam generated in the nuclear reactor 1 to the high-pressure turbine 2, the moisture separator 3, and the low-pressure turbine 4. The steam discharged from the low-pressure turbine 4 is condensed by the condenser 5 to be condensed.

The condensate discharged from the condenser 5 via the condensate pump 6 is purified through a condensate purifier 7, and is further pressurized by the high-pressure condensate pump 8, and the first and second low-pressure condensates It is led to the system feed water heaters 9 and 10. Further, a water supply system is provided, which is further pressurized by the water supply pump 11, passes through the high-pressure system feed water heater 12, and sends the water to the reactor 1.

First and second low pressure feed water heaters 9 and 10
The extracted steam is led to the high-pressure feed water heater 12 via the extraction pipes 16a, 16b, and 16c from the low-pressure turbine 4 and the high-pressure turbine 2, respectively, and exchanges heat with condensed water or feed water to form a drain. The drain from the high-pressure feed water heater 12 is guided to the second low-pressure feed water heater 10 through the emergency drain pipe 14a, and the drain is also used for heating the condensate flowing through the feed water piping.

During normal operation of the plant, the drain of the second low-pressure feed water heater 10 is drained by utilizing the pressure difference between the second low-pressure feed water heater 10 and the first low-pressure feed water heater 9, and It is led to the first low-pressure feed water heater 9 via a water level control valve 17b installed in the drain pipe 14b.

However, when the plant is in a low load state when the plant is started and stopped, the pressure difference cannot be sufficiently ensured, so that the drain cannot be discharged from the service drain pipe 14b, and
Feed water heater controller 13 attached to the low pressure feed water heater 10
The system configuration is such that the high water level control valve 18b installed in the emergency drain pipe 15b is opened by b to discharge directly to the condenser. The broken line is a signal sign connecting the controller and the valve.

The water level control valve 17b is a feed water heater controller.
When fully closed due to malfunction of 13b, the normal drain pipe 14a,
Emergency drain tube 15b having the same capacity as 14b, 14c
Since the entire drain amount can be discharged to the side, the system configuration is such that operation can be continued without affecting the reactor output.

As described above, in the current BWR plant in which the reliability of the feed water heater controller 13 is ensured, the flow of the drain through the emergency drain pipes 15a, 15b and 15c is basically caused by the start of the plant. This is a limited case when stopping.

[0012]

However, in the case of the prior art, the emergency drain pipes 15a, 15
Designing the 15b and 15c with the same capacity as the regular drain pipes 14a, 14b and 14c is problematic in that the economy is impaired, the piping surface area is unnecessarily large, and it is not preferable from the viewpoint of reducing the exposure of the plant. .

The present invention has been made in order to solve the above-mentioned problems, and it is intended to optimize the capacity of an emergency drain pipe and to reduce radiation exposure, assuming that the operation of a BWR plant is performed continuously. Economical by reducing the amount of piping
An object of the present invention is to provide a piping system of a feed water heater for a nuclear power plant which is excellent in stability.

[0014]

According to a first aspect of the present invention, there is provided a main steam system for supplying steam generated in a nuclear reactor to a high pressure turbine and a low pressure turbine, and condensing steam discharged from the low pressure turbine with a condenser. The condensate is guided to a first low-pressure system feedwater heater, a second low-pressure system feedwater heater and a high-pressure system feedwater heater for heating, and the heated condensate is fed to the reactor. A first extraction pipe for extracting steam from the high-pressure turbine and transferring it to the high-pressure feed water heater, and a first low-pressure feed water for extracting steam from the low-pressure turbine. Heater and second
A second bleed pipe and a third bleed pipe which are respectively transferred to the low-pressure system feedwater heater, and the drain water of the high-pressure system feedwater heater, the first low-pressure system feedwater heater and the second low-pressure system feedwater heater An emergency drain pipe returning the condenser to the condenser, and a normal system branching from the emergency drain pipe of the high-pressure feed water heater and sequentially flowing into the secondary side of the second low-pressure feed water heater. A drain pipe, wherein the capacity of the emergency drain pipe is smaller than the capacity of the normal drain pipe.

According to the first aspect of the present invention, a plurality of stages of feed water heaters, a pipe line for transferring the drain of the upstream stage feed water heater to the downstream stage feed water heater (a common system drain pipe), and an upstream stage feed water heater In a BWR plant having a pipe (emergency drain pipe) for directly discharging drain to a condenser, the volume of the emergency drain pipe is made smaller than the capacity of the normal drain pipe to reduce the physical quantity and the amount of water in the pipe. The surface area can be reduced.

According to a second aspect of the present invention, the capacity of the emergency drain pipe is approximately 40% of the capacity of the service drain pipe, or the drain amount of turbine extracted steam of the feed water heater. It is characterized by the following.

According to the second aspect of the present invention, the capacity of the emergency system drain pipe is set to about 40% of the capacity of the service system drain pipe, or the drain amount for the steam extracted from the turbine is set as follows. The physical quantity and the surface area in the pipe can be reduced.

The invention of claim 3 is characterized in that a remote control valve is provided from the first bleed pipe to the third bleed pipe or the service drain pipe. According to the third aspect of the present invention, in a BWR plant having an emergency drain pipe, by providing a remotely controllable bleed stop valve in the bleed line, drain is prevented from flowing into the turbine, and damage to the turbine is prevented. Prevention can protect the turbine. Further, it is possible to detect that the water level of the feed water heater has become equal to or higher than a predetermined value with respect to the valve means, and forcibly interlock the valve to completely close the valve.

According to a fourth aspect of the present invention, the drain valve of the high-pressure feed water heater or the drain water level of the first low-pressure feed water heater or the second low-pressure feed water heater is equal to or more than a specified value. , And an interlock that is forcibly closed upon detecting that the power supply has been turned off is provided.

According to the fourth aspect of the present invention, in the nuclear power plant having the emergency drain pipe, the service drain pipe is provided with a remotely operable valve means to shut off the inflow of the upstream feedwater heater drain. . Further, it detects that the drain water level of the downstream feed water heater has reached a specified value or more with respect to the drain shutoff valve, and forcibly interlocks and closes. Thereby, the water level control can be continued, and the safe operation of the plant can be performed.

[0021]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS A first embodiment of a piping system of a feed water heater for a nuclear power plant according to the present invention will be described with reference to FIG. In FIG. 1, the same portions as those of the conventional technique shown in FIG. 5 are denoted by the same reference numerals, and duplicate description will be omitted. This embodiment is different from the conventional example in that the emergency drain pipe 15 is used.
a, 15b, and 15c are replaced with the common drain pipes 14a, 14b, and 14c.
c is smaller than the capacity of c.

As shown in FIG. 1, during normal operation, the drain of the high-pressure system feed water heater 12 utilizes the pressure difference with the second low-pressure system feed water heater 10 to adjust the water level attached to the service system drain pipe 14a. It is collected by the second low-pressure feedwater heater 10 via the valve 17a.

The drain of the second low-pressure feed water heater 10 utilizes the pressure difference with the lower first low-pressure feed water heater 9 and passes through the water level control valve 17b attached to the service drain pipe 14b. The first low-pressure feed water heater 9 collects the water. During normal operation,
The probability that the drain will flow through the 40% capacity emergency drain pipes 15a and 15b is extremely low. These emergency drain pipes 15a, 15b
Drain flows in the following cases.

That is, the drain flows through the emergency drain pipes 15a and 15b because the pressure difference between the high-pressure feed water heater 12 and the second low-pressure feed water heater 10 is small when the plant is started or stopped. In response to a signal from the feed water heater controller 13a attached to the high pressure feed water heater 12, the high water level control valve 18a attached to the emergency drain pipe 15a is automatically opened and discharged directly to the condenser. Is the case.

Similarly, the drain flows through the emergency drain pipe 15b because the pressure difference between the second low pressure feed water heater 10 and the lower first low pressure feed water heater 9 is small, and the second low pressure The signal from the feed water heater controller 13b attached to the system feed water heater 10 automatically opens the high water level control valve 18b attached to the 40% capacity emergency drain pipe 15b and directly connects to the condenser 5 This is the case when it is discharged.

Therefore, it is economically advantageous to design the capacity of the emergency drain pipes 15a, 15b, 15c, which are used only during limited operation, to be the same as the capacity of the service drain pipes 14a, 14b, 14c. According to the first embodiment, the capacity of the emergency drain pipe 15a of the high-pressure feed water heater 12 and the capacity of the emergency drain pipe 15b of the second low-pressure feed water heater 10 are set to the respective ordinary capacity. By making the capacity smaller than the capacity of the system drain pipes 14a and 14b, the economic effect can be enhanced.

Next, a second embodiment of the present invention will be described with reference to FIG. In this embodiment, the emergency drain pipe 15 is used.
In principle, a, 15b, 15c should be used only when starting and stopping the plant, and emergency drain pipes 15a, 15b, 15c
Of the design capacity of the common system drain pipes 14a, 14b, 14c
40%.

In the preceding BWR plant, it has been confirmed that the flow of the drain of the feed water heater is switched from the emergency system side to the regular system side at about 30% of the plant output. , The volume of piping can be reduced by 40%. During normal operation, the feed water heater controller 13
In the event that any abnormalities occur when a, 13b, and 13c are malfunctioning, and the emergency drain pipes 15a, 15b, and 15c must be used, the reactor power is reduced. The operation can be continued.

Next, a third embodiment of the present invention will be described with reference to FIG. The second low pressure feed water heater 10 will be described as an example. The bleed steam from the low-pressure turbine 4 flows into the second low-pressure system feedwater heater 10 through the bleed pipe 16b, and exchanges heat with condensed water to form a drain. Also, a second low pressure feed water heater
Drain from the high-pressure system feed water heater 12 is supplied to 10 from a service system drain pipe 14a via a water level control valve 17a.

Each of the drains is provided with a second low-pressure feed water heater.
The mixed drain is formed in 10 and is discharged to the first low-pressure system feed water heater 9 at the lower stage. In the present embodiment, the capacity of the emergency system drain pipe 15 is reduced to only the turbine bleed air portion of the drain. The capacity is set to be recoverable by the water dispenser 4 to reduce the amount of piping.

That is, the emergency drain pipes 15a, 15b, 15
In (c), the drain from the high pressure feed water heater 12 in the upstream stage cannot be discharged. Therefore, if the reactor is not affected by the drain from the high-pressure feedwater heater 12 at the upstream stage, the reactor can be operated while maintaining the reactor output.

Next, a fourth embodiment of the present invention will be described with reference to FIG. In this embodiment, a bleed stop valve is provided in a bleed pipe 16 connected between the high-pressure turbine 2 and the high-pressure feedwater heater 12.
19a, and a bleed stop valve 19b is provided in the bleed pipe 16 connecting the low-pressure turbine 4 and the second low-pressure feedwater heater 10.

In this embodiment in which the capacity of the emergency drain pipes 15a, 15b, 15c is set to 40% of the capacity of the service drain pipes 14a, 14b, 14c, for example, the second low-pressure feed water heater
If the water level control valve 17b of 10 is fully closed for some reason, the drain discharge is performed even if the high water level control valve 18b installed on the emergency drain pipe 15b is fully opened by a signal from the feed water heater controller 13b. Due to lack of capacity, low pressure feed water heater
As the drain water level of 10 continues to rise, the drain flows backward through the bleed pipe 16b, flows into the low-pressure turbine 4, and damages the turbine.

However, according to the present embodiment, from the viewpoint of protecting the turbine, the bleed stop valves 19a, 19a for isolating the bleed pipes 16a, 16b from the high-pressure turbine 2 and the low-pressure turbine 4 are provided.
By providing 19b, the high-pressure turbine 2 and the low-pressure turbine 4 can be protected.

Next, a fifth embodiment of the present invention will be described with reference to FIG. In this embodiment, as shown in FIG. 2, a drain shutoff valve 20 is provided between a water level control valve 17a attached to a service drain pipe 14a and the second low-pressure feedwater heater 10. If the capacity of the emergency drain pipes 15a and 15b is set to the capacity of the turbine bleed air, for example, if the water level control valve 17b of the second low-pressure feed water heater 10 is fully closed for some reason, the second The drain water level of the low pressure feed water heater 10 rises.

Even if the high water level control valve 18b installed on the emergency drain pipe 15b is fully opened by the signal from the feed water heater controller 13b, the ability to discharge the drain from the high pressure feed water heater 12 on the upstream side There is no. Therefore, low-pressure feedwater heater 10
It is necessary to continue the rising of the drain water level, flow backward through the bleed pipe 16b, flow into the low-pressure turbine 4, and damage the turbine.

In the present embodiment, a drain shutoff valve 20 for blocking drainage from flowing into the lower feedwater heater is provided in the service system drain pipe of the feedwater heater, and the drain water level of the feedwater heater 10 is controlled. It is intended to control to a specified value. According to the present embodiment, all the feedwater heater drains are directly discharged to the condenser, so that the plant thermal efficiency is reduced, but the reactor can be operated without lowering the reactor output.

Next, a sixth embodiment of the present invention will be described with reference to FIGS. In this embodiment, the bleed tube 16 is used.
The bleed stop valve 19 (19a, 19b) installed in each of the a and 16b is input to the interlock in response to a signal from the feed water heater controller 13 (13a, 13b) and is automatically fully closed.
The other parts are the same as in the first embodiment.

According to the present embodiment, when the water level of the feed water heater rises abnormally, the bleed stop valve 19 (19a,
Since 19b) is fully closed, it is possible to increase the reliability of preventing the drain from flowing into the high-pressure turbine 2 and the low-pressure turbine 4.

Next, a seventh embodiment of the present invention will be described with reference to FIGS. In the present embodiment, the drain shutoff valve 20 installed in the service system drain pipe 14a is input to the interlock by a signal from the feed water heater controller 13a and is automatically fully closed. In addition, other parts
This is the same as in the first embodiment.

According to the present embodiment, when the water level in the second low-pressure feed water heater 10 rises abnormally, the drain flowing from the high-pressure feed water heater 12 is automatically shut off.
Even if the capacity of the emergency drain pipe of the second low-pressure feed water heater 10 is only for the extracted steam, the water level control can be continued, and the reliability for stable operation of the plant can be increased.

[0042]

According to the present invention, it is possible to optimize the capacity of the emergency drain line (reduce the amount of material), and to contribute to the reduction of the exposure to the plant by reducing the surface area of the piping, which is excellent in economy and safety. And a drain discharge device for a BWR plant.

[Brief description of the drawings]

FIG. 1 is a piping diagram showing first to fourth embodiments of a piping system of a feedwater heater for a nuclear power plant according to the present invention.

FIG. 2 is a piping diagram showing a fifth embodiment of a piping system of a feedwater heater for a nuclear power plant according to the present invention.

FIG. 3 is a block diagram showing a control example according to a sixth embodiment of the present invention.

FIG. 4 is a block diagram showing a control example according to a seventh embodiment of the present invention.

FIG. 5 is a piping diagram showing a piping system of a conventional feed water heater for a nuclear power plant.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Reactor, 2 ... High pressure turbine, 3 ... Moisture separator, 4 ...
Low-pressure turbine, 5: condenser, 6: condensate pump, 7: condensate purification device, 8: high-pressure condensate pump, 9: first low-pressure feedwater heater, 10: second low-pressure feedwater heater , 11 ... feed water pump, 12 ... high pressure feed water heater, 13 ... feed water heater controller, 14
… Regular drain pipe, 15 emergency drain pipe, 16 bleed pipe, 17 water level control valve, 18 high water level control valve, 19 bleed stop valve, 20 drain drain valve.

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI Theme coat ゛ (Reference) G21D 3/04 G21D 1/00 Q E

Claims (4)

[Claims] 1. A main steam system for supplying steam generated in a nuclear reactor to a high-pressure turbine and a low-pressure turbine, and steam condensed from a steam discharged from the low-pressure turbine in a first low-pressure system. A feed water heater, a second low-pressure feed water heater, and a high-pressure feed water heater, which are sequentially heated to supply a heated condensate to the nuclear reactor. A first extraction pipe for extracting steam from the turbine and transferring the steam to the high-pressure feed water heater; and a first low-pressure feed water heater and a second low-pressure feed water heater for extracting steam from the low-pressure turbine. And a second bleed pipe and a third bleed pipe which are respectively transferred to the condenser and the drain water of the high-pressure feed water heater, the first low-pressure feed water heater, and the second low-pressure feed water heater, respectively. Emergency drain pipe to return to the A service drain pipe which branches off from an emergency drain pipe of the high pressure feed water heater and sequentially flows into the secondary side of the second low pressure feed water heater, and the capacity of the emergency drain pipe is reduced. A piping system for a feed water heater for a nuclear power plant, wherein the piping system has a capacity smaller than a capacity of the service drain pipe. 2. The capacity of the emergency drain pipe is approximately 40% of the capacity of the service drain pipe, or the drain amount of turbine extraction steam of the feed water heater. A piping system for a feed water heater for a nuclear power plant according to claim 1. 3. The piping of a feed water heater for a nuclear power plant according to claim 1, wherein a remote control valve is provided from the first bleed pipe to the third bleed pipe or the service drain pipe. system. 4. The remote control valve according to claim 1, wherein the drain water level of the high-pressure feed water heater or the drain water level of the first low-pressure feed water heater or the second low-pressure feed water heater has exceeded a specified value. 2. The piping system of a feed water heater for a nuclear power plant according to claim 1, wherein an interlock for detecting and forcibly closing is provided.