The world is facing the problem of an energy shortage, and China is in the process of industrialization and urbanization; the demand for energy will continue to grow, and the contradiction between energy supply and demand is becoming increasingly prominent. Nuclear power is recognized as a clean energy source in the world. With the development of nuclear power technology, the safety and economy of nuclear power have been improved. China has also increased its investment in nuclear power. The development strategy of nuclear power has been adjusted from "moderate development" to "active development". With the rapid development of the nuclear power industry, the demand for nuclear power valves will continue to expand.
Valves used for nuclear power plants
1. The definition of nuclear power valves
Nuclear power valves refer to the valves used in nuclear island NI, conventional island CI and power plant auxiliary facilities BOP systems in nuclear power plants. There are nuclear safety level Ⅰ, level Ⅱ, level Ⅲ, and non-nuclear level. Among them, nuclear safety level I has the highest requirements. Nuclear power valves are the most used control devices for delivering media, which are an indispensable and important part of the safe operation of nuclear power plants. Power station valves are also called dedicated valves for power stations, which are mainly used on the pipelines of various systems in thermal power plants to cut off or connect pipeline media. Applicable media are non-corrosive media such as water and steam.
2. Advantages of power station valves
The pressure self-tightening seal is adopted, and the two ends of the branch pipe of the valve body are welded.
The sealing surface of the valve seat and disc is made of cobalt-based hard alloy plasma spray welding, which has good wear resistance and scratch resistance.
The valve stem is treated with corrosion-resistant nitriding, which has good corrosion resistance and scratch resistance.
3. The importance of valves in nuclear power plants
In the equipment of nuclear power plants, although the valve is only an accessory, its role cannot be ignored. The valve plays an extremely important role in the normal, safe and reliable operation of the nuclear power plant. It can be said that almost every system of the power plant is inseparable from valves due to the large number of valves used in nuclear power plants. Taking a pressurized water reactor nuclear power plant with two million-kilowatt units as an example, the number of valves needed is about 30,000 sets. Although the investment of valves accounts for about 2% of the total investment of nuclear power plants, the annual maintenance costs of valves in power plants account for more than half of the total maintenance costs. Some of the important valves, such as main steam isolation valves, pressure regulator safety valves and main steam safety valves are also very critical equipment in nuclear power plants. There are also many nuclear-grade valves used in the primary circuit system, which are directly related to the normal and safe operation of the nuclear power plant, and no errors are allowed. According to the accident of nuclear power plants of the International Atomic Energy Organization (IAEA), shutdowns caused by failures of valves, and even nuclear leakage accounts for a large proportion. Therefore, the valve industry must pay enough attention.
Figure 1 Check valves for nuclear power plants
a. Swing check valves b. Spring lift check valves C. Springless lift check valves d. Double plate check valves
