JPS58102198A - Condensed water drain recovering system - 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 The present invention relates to a condensate recovery system, and particularly to a condensate recovery system suitable for rust-proof storage measures for condensate and water supply systems of steam turbine power plants.

Conventional plant storage in thermal power plants involves nitrogen gas injection and chemical injection using rust preventive agents. In boiling water reactors, pure water is used as secondary system cooling water, so it is impossible to collect water, and nitrogen filling is difficult when maintaining the gas concentration when there are many inspection equipment and safety issues. Since YJ* is required, it is not used. Therefore, conventionally, the pipes were left full of pure water. In such a case, the quality of pure water deteriorates 1, for example, the conductivity decreases to ts.
g, 4 species, and the dissolved oxygen concentration is dissolved until atmospheric oxygen is saturated (approximately 8 ppm), so cladding (p@ρa e F@jL * r
-FeOOH, etc.), which deteriorates the quality of the stored water. At the same time, these iron claddings may be brought into the reactor during plant start-up, causing damage to equipment, and corrosion products becoming radioactive within the reactor.

They become corrosion product nuclides and adhere to equipment in the reactor system, increasing the surface dose rate of the plant.

Therefore, it is desirable to minimize corrosion of condensate and water supply piping even during the period of shutdown.

As a countermeasure to these problems, consideration is being given to extracting condensate water and water retained in the water supply system, drying it, and eating fat. However, when it comes to I100MW 1st class nuclear reactors) 4C, the amount of water held in the pipes within the system is several hundred tons or more, and a large amount of radioactive drainage must be disposed of.

To explain this in a different way using the example of a conventional plant, the tth
As shown by g, the steam generated in the reactor pressure vessel l passes through the main steam pipe 2, passes through the high pressure turbine 3, and then the low pressure turbine 4.
Turn. Steam exhaust from the low pressure turbine 4 is converted into condensate in a condenser 5 and falls into a condensate reservoir 6 in a condenser s. Thereafter, the condensate passes through a pipe 7 and a valve 8, and is sent to a condensate demineralizer 10 by a condensate purification pump 9, where it is purified. The purified nine-condensate water is sent to the low-pressure feedwater heater 11 by the low-pressure feedwater pump IIK, and further sent to the high-pressure feedwater heater 13 by the high-pressure feedwater pump 12, and after being heated by these feedwater heaters, it is sent to the reactor pressure vessel. Water is supplied to 1. Although the above is currently in operation, there is a concern that corrosion products from each piping and equipment may flow into the reactor when the plant is started up. Corrosion products from these piping equipment are 100~3QQK4
It also becomes mspe. When these flow into the reactor 1, they become radioactive and increase the dose rate of the plant.

An object of the present invention is to provide a condensate drain recovery system that reduces condensate and corrosion of piping and equipment of a water supply system during plant shutdown.

If the outage period is long, it is being considered to extract the water contained in the condensate/water supply and store it in a dry manner.
In the case of a large plan (100 MWe class) K, the amount of water held in the system would be several hundred tons or more, and there was a drawback that the cost of rounding operation would be enormous as it would have to process a large amount of radioactive effluent. The present invention is.

Most of the extracted water is transferred to the main condenser water droplet.

Rounding to be reused during startup will not increase the amount of radioactive waste fluid.

Hereinafter, one embodiment of the present invention applied to a boiling water nuclear power plant will be explained with reference to FIG. After plant shutdown -1 condensate pump population valve 8, outlet valve 15 and.

Close the low pressure water pump population valve 16. Next, the condensate pipe 7,
Water supply pipe 17. The water held in the heater drain pipe 18 is drained by the drain recovery pipe 19 and led to the drain recovery tank 20. Next, the water is led to the inlet of the condensate purification device by driving the pump 21.

After purifying the drain water, it is led to the condenser water reservoir and condensed.

Most of the water stored in the water supply and heater drain piping is stored in the main condenser water reservoir. At the same time, hot drain piping 22
From there, a part of the stored water is drained and recycled, and the drain from the collection tank is transferred from the pump to the condensate desalination 111.
Main heavy water 1 through 0! A closed loop of IK recovery is constructed, and the quality of the stored water is kept under conditions suitable for corrosion protection of carbon steel, that is, the electrical conductivity is 0.05 sl18/c as shown in Figure 3.
ps, maintain 0.8s87as*K. moreover,
As shown in Figure 4, the flow rate of pure water flowing through the pipe is α m
If the temperature is maintained at or above /s@c, corrosion of the piping can be suppressed.゛This is based on the above conductivity conditions (0,055μ8/CF-Q, 3
a8/m ), the corrosion chemical reaction of iron is also suppressed.

This is because the dissolved oxygen S degree in the atmosphere assists this reaction and forms a favorable passive oxide film on the iron surface. Furthermore, if there is no flow in stored water with high dissolved oxygen, pitting corrosion will occur and corrosion will increase, so a constant flow rate must be maintained.

The capacity of the condenser body is approximately 4,000,111', and the amount of water constantly present in the condenser water reservoir and the amount of water present in the condensate, water supply, and heater drain piping are approximately 200 tons and 300 tons, respectively. The capacity of the condenser water droplets is sufficient.

The present invention can also be applied to steam generators other than reactor pressure vessels of boiling water basin nuclear coup plants, that is, steam generators of pressurized water source reactors and fast breeder reactors, and condensate water supply systems to boilers of thermal power plants. .

According to the present invention, 1. When the plant is stopped, retained water in the condensate water supply and heater drain piping can be removed and stored, which is effective because it reduces the amount of corrosion in each piping and suppresses the increase in radioactivity in the plant. .

In the case of carbon steel, what is the corrosion rate when stored in full water?

However, when the water in the pipes is drained and stored, it decreases to about 15% mdm.

In addition, the amount of iron generated in the case of full water storage is approximately 200% over 3 months.
-, but when stored without water, it becomes very low at 60-.

[Brief explanation of the drawing]

Fig. 1 is a system diagram of a condensate water supply system of a BWR plant to explain the prior art, and Fig. 2 is a BWR plant diagram to explain an embodiment of the present invention.
A schematic diagram of a system having a condensate drain recovery system of a WR plant, Fig. 3 is a diagram showing the corrosion mode ratio and conductivity Om ratio of carbon steel, and Fig. 4 is a diagram showing the ratio of corrosion mode to carbon steel. FIG. 3 is a diagram showing the relationship between corrosion rate ratio and flow rate of carbon steel. 5... Main condenser, 6... Main condenser water reservoir, 7...
Condensate piping, 8,15. ll, 16.23...Gate valve. 10... Condensate demineralizer, 7... Condensate piping, 17...
Water supply piping, 19... Condensate drain recovery piping, 20...
Drain recovery tank, 9, 21, 11. 13...pump.

Claims (1)

[Claims] 1. While the plant is out of operation, the first pipe for draining water in the condensate/water supply system piping that connects the condenser and the steam generator, the tank for collecting the drain, and the drain in the tank A condensate drain recovery system comprising a third pipe leading to a condenser and a purifying means provided in the second pipe.