Nuclear power station blowdown cooling system

Abstract

The invention relates to the field of nuclear power, in particular to a nuclear power station blowdown cooling system. The nuclear power station blowdown cooling system comprises an inverted-U-shaped pipe connected to an outlet pipeline of a blowdown flash tank, and a surface cooler is installed on the downstream side of the inverted-U-shaped pipe; a second critical cooling device is arranged on the pipeline between the surface cooler and the inverted U-shaped pipe; a downstream pipeline of the surface cooler is provided with a leakage detection device; the blowdown flash tank is connected with an overpressure monitoring device and a first critical cooling device; and the surface cooler is used for cooling sewage in the sewage discharge container by utilizing unit circulating cooling water. According to the invention, the surface cooler is arranged at the downstream of the blowdown cooler, and the hot wastewater with the temperature of 100 DEG C is cooled by using unit circulating cooling water, so that a brand new cooling blowdown system is formed, and the problems of waste of fresh water resources and overtemperature discharge of the hot wastewater caused by short-time insufficient supply of industrial water in the prior art are solved.

Description

Technical Field

[0001] The present invention relates to the field of nuclear power, and in particular to a wastewater cooling system for a nuclear power plant. Background Art

[0002] Nuclear power plant steam turbine buildings generate a large amount of high-temperature, high-pressure blowdown water, which needs to be collected in blowdown expansion tanks. The blowdown water undergoes a secondary flash vaporization at atmospheric pressure, and the flash vapor is discharged into the atmosphere. Simultaneously, the blowdown expansion tanks also contain a large amount of 100°C hot wastewater, which needs to be cooled before being released to the environment. Existing nuclear power plant steam turbine buildings typically use industrial water (fresh water) to mix and cool the 100°C hot wastewater, wasting a significant amount of freshwater resources. When the amount of high-temperature, high-pressure blowdown water is high, there is also a problem of temporary shortage of industrial water, which often results in the final hot wastewater discharged to the environment exceeding the allowable value (60°C). Summary of the Invention

[0003] The technical problem to be solved by the present invention is to provide a nuclear power plant sewage cooling system to solve the problem of waste of fresh water resources and short-term insufficient supply of industrial water leading to over-temperature discharge of hot wastewater in the existing technology.

[0004] The present invention provides a nuclear power plant sewage cooling system, comprising: a sewage expansion tank, an inverted U-shaped pipe, a surface cooler, a pressure detection device, a leakage detection device, a first emergency cooling device and a second emergency cooling device;

[0005] The inverted U-shaped pipe is connected to the outlet pipe of the sewage expansion tank.

[0006] The surface cooler is installed on the downstream side of the inverted U-shaped tube;

[0007] A second emergency cooling device is provided on the pipe between the surface cooler and the inverted U-shaped tube;

[0008] A leak detection device is provided on the downstream pipeline of the surface cooler;

[0009] The blowdown expansion tank is connected to an overpressure monitoring device and a first emergency cooling device;

[0010] The surface cooler uses the circulating cooling water of the unit to cool the sewage in the sewage container.

[0011] In a specific embodiment of the present invention, the elevation of the top of the inverted U-shaped pipe is higher than the water level required to be maintained in the sewage expansion tank.

[0012] In a specific embodiment of the present invention, the surface cooler is a shell and tube heat exchanger, the shell side is the cooled medium, and the tube side is the cooling medium.

[0013] In a specific embodiment of the present invention, the surface cooler is made of duplex steel or stainless steel.

[0014] In a specific embodiment of the present invention, the leakage detection device is a conductivity analysis instrument, which is passed through an online sampling pipeline, passes through its attached constant temperature cooling device, and is finally introduced into a conductivity meter to measure the conductivity.

[0015] In a specific embodiment of the present invention, the leakage detection device is interlocked with the circulating cooling water inlet pipeline isolation device.

[0016] In a specific embodiment of the present invention, the pressure detection device is a pressure gauge.

[0017] Compared with the prior art, the present invention provides a nuclear power plant sewage cooling system in which a surface cooler is installed downstream of the sewage cooler, and the unit's circulating cooling water is used to cool the 100°C hot wastewater, forming a brand-new cooling sewage system. The unit's circulating cooling water volume is large and can be recycled, solving the problem of waste of fresh water resources and short-term insufficient supply of industrial water leading to over-temperature discharge of hot wastewater in the prior art. By providing a leak detection device, when a surface cooler leaks, the circulating cooling water can be isolated to prevent the circulating cooling water from leaking into the wastewater discharge pipeline. Emergency cooling devices are provided on the sewage expansion tank and sewage pipeline to avoid the problem of short-term overheating caused by a short-term increase in sewage flow and the slow response of the surface cooler. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] Figure 1 A schematic diagram showing the structure of a nuclear power plant blowdown cooling system;

[0019] In the figure, 1 is a sewage expansion tank, 2 is an inverted U-shaped pipe, 3 is a surface cooler, 4 is a pressure detection device, 5 is a leakage detection device, 6 is a first emergency cooling device, 7 is a second emergency cooling device, and 8 is a circulating cooling water isolation device. DETAILED DESCRIPTION

[0020] In order to further understand the present invention, embodiments of the present invention are described below in conjunction with examples. However, it should be understood that these descriptions are only for further illustrating the features and advantages of the present invention, rather than for limiting the present invention.

[0021] An embodiment of the present invention discloses a nuclear power plant blowdown cooling system, comprising: a blowdown expansion vessel 1, an inverted U-shaped pipe 2, a surface cooler 3, a pressure detection device 4, a leakage detection device 5, a first emergency cooling device 6 and a second emergency cooling device 7.

[0022] The inverted U-shaped pipe 2 is connected to the outlet pipe of the sewage expansion tank 1. The top elevation of the inverted U-shaped pipe 2 needs to be higher than the water level required to be maintained by the sewage expansion tank 1.

[0023] The blowdown expansion tank 1 collects high-temperature, high-pressure media from the nuclear power plant's turbine building. Based on the operating history of existing 1,000-million-ton pressurized water reactor nuclear power units, the turbine building blowdown flow reaches its maximum at 30% load, approximately 600 t / h, with a temperature between 130°C and 180°C. A discharge pipeline is located at the top of the device, connecting it to the atmosphere. Under normal circumstances, the device operates at atmospheric pressure. The collected high-temperature, high-pressure media flashes within the blowdown expansion tank, and the secondary steam from the flash is discharged to the atmosphere through a discharge pipeline at the top, leaving the remaining hot wastewater at 100°C.

[0024] The inverted U-shaped pipe 2 can maintain a certain water level in the sewage expansion tank. The top elevation of the inverted U-shaped pipe needs to meet the minimum water level requirement of the sewage expansion tank 1. The inverted U-shaped pipe 2 prevents flash steam from entering the wastewater discharge pipeline, avoiding equipment failure downstream of the drainage pipeline and causing personal injury.

[0025] Surface cooler 3, installed downstream of inverted U-shaped tube 2, cools the 100°C hot wastewater before it is discharged to the environment. This surface cooler 3 is a shell-and-tube heat exchanger, with the shell side carrying the cooled medium and the tube side carrying the cooling medium. This shell-and-tube heat exchanger offers low resistance and does not affect the wastewater flow rate.

[0026] If the nuclear power plant is located on a coastal site and the cooling medium can be seawater, the surface cooler 3 should use a tube bundle resistant to seawater corrosion, such as duplex steel; if the nuclear power plant is located inland and the cooling medium can be non-seawater, the surface cooler 3 should use ordinary stainless steel, such as 304L.

[0027] In order to prevent the blowdown expansion tank 1 from operating at overpressure due to excessive blowdown volume of the unit in a short period of time, an overpressure monitoring device 4 is provided on the blowdown expansion tank 1 .

[0028] The sewage expansion tank 1 is also provided with a first emergency cooling device 6. When the received high-temperature medium exceeds the design allowable value, for example, the temperature of the waste liquid after flash evaporation exceeds 100°C, overpressure may occur. According to the pressure monitoring device 4, the emergency cooling device 6 is opened in a chain to ensure the safe operation of the sewage expansion tank 1 and avoid overheating of the sewage finally discharged into the environment.

[0029] A second emergency cooling device 7 is provided on the pipeline between the surface cooler 3 and the inverted U-shaped tube 2, and a leakage detection device 5 is provided on the downstream pipeline of the surface cooler 3;

[0030] The leak detection device 5 is a conductivity analysis instrument that is introduced into a conductivity meter through an online sampling pipeline, after passing through its attached constant temperature cooling device, to measure conductivity. The circulating cooling water on the tube side of cooler 3 contains many impurities. If a leak occurs in the heat exchange tube bundle of cooler 3, the monitored conductivity will increase abnormally. Therefore, the leak detection device 5 can be used to perform online detection of leaks in the heat exchange tube bundle. If the tube-side cooling medium leaks to the tube side, the leak detection device 5 interlocks with the circulating cooling water inlet pipe isolation device 8, which can cut off the circulating cooling water supply and simultaneously activate the emergency cooling device 7, which uses mixed cooling with industrial water to ensure that the system discharge does not exceed 60°C.

[0031] The nuclear power plant sewage cooling system described in the present invention has been applied in the Tianwan Nuclear Power Plant, and has a good circulation cooling effect, saves costs, and avoids waste of resources.

[0032] The above embodiments are only intended to help understand the method and core concept of the present invention. It should be noted that, without departing from the principles of the present invention, a number of improvements and modifications may be made to the present invention by those skilled in the art, and such improvements and modifications also fall within the scope of protection of the claims of the present invention.

[0033] The above description of the disclosed embodiments is intended to enable one skilled in the art to implement or use the present invention. Various modifications to these embodiments will be readily apparent to one skilled in the art, and the general principles defined herein may be implemented in other embodiments without departing from the spirit or scope of the present invention. Therefore, the present invention is not limited to the embodiments shown herein but is intended to conform to the widest scope consistent with the principles and novel features disclosed herein.

Claims

1. A nuclear power plant sewage cooling system, characterized in that: include: Blowdown expansion tank, inverted U-shaped pipe, surface cooler, pressure detection device, leakage detection device, first emergency cooling device and second emergency cooling device; The inverted U-shaped pipe is connected to the outlet pipe of the sewage expansion tank. The surface cooler is installed on the downstream side of the inverted U-shaped tube; A second emergency cooling device is provided on the pipe between the surface cooler and the inverted U-shaped tube; A leak detection device is provided on the downstream pipeline of the surface cooler; The blowdown expansion tank is connected to an overpressure monitoring device and a first emergency cooling device; The surface cooler uses the circulating cooling water of the unit to cool the sewage in the sewage container.

2. The nuclear power plant sewage cooling system according to claim 1, characterized in that: The elevation of the top of the inverted U-shaped pipe is higher than the water level required to be maintained in the sewage expansion tank.

3. The nuclear power plant sewage cooling system according to claim 1, characterized in that: The surface cooler is a shell and tube heat exchanger, with the shell side being the cooled medium and the tube side being the cooling medium.

4. The nuclear power plant sewage cooling system according to claim 3, characterized in that: The surface cooler is made of duplex steel or stainless steel.

5. The nuclear power plant sewage cooling system according to claim 1, characterized in that: The leakage detection device is a conductivity analysis instrument, which is passed through an online sampling pipeline, passes through its attached constant temperature cooling device, and is finally introduced into a conductivity meter to measure the conductivity.

6. The nuclear power plant sewage cooling system according to claim 1, characterized in that: The leakage detection device is interlocked with the circulating cooling water inlet pipeline isolation device for control.

7. The nuclear power plant sewage cooling system according to claim 1, characterized in that: The pressure detection device is a pressure gauge.

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