Nuclear power valve - the key to the operation of nuclear power plants

     In nuclear power plant equipment, although the valve is only an accessory, its role can not be ignored, because the valve plays an extremely important role in the normal, safe and reliable operation of the nuclear power plant.

Nuclear power valve definition

    Nuclear power valves are valves used in nuclear power plants in nuclear island NI, conventional island CI, and power plant auxiliary facility BOP systems. From the security level, it is divided into nuclear safety level I, level II, level III, and non-core level. Among them, nuclear safety class I has the highest requirements. Nuclear power valves are used in nuclear power plants with a large number of medium conveying control equipment, which is an indispensable and important part of the safe operation of nuclear power plants.

The importance of valves in nuclear power plants

    Although the valve is only an accessory in the equipment of the nuclear power plant, its function cannot be ignored, because the valve plays an extremely important role in the normal, safe and reliable operation of the nuclear power plant. Because the use of valves in nuclear power plants is large, it can be said that almost every system of the power station can not be separated from the valve. Taking a pressurized water reactor type nuclear power plant with two sets of millions of kilowatts as an example, the valve usage is about 30,000 units.
    Although the investment in valves accounts for about 2% of the total investment of nuclear power plants, the annual maintenance cost of power plants on the valves accounts for more than half of the total maintenance. Some of the important valve products, such as main steam isolation valves, regulator safety valves and main steam safety valves, are also critical equipment in nuclear power plants.
    There are also many applications in the primary loop system. The various nuclear grade valves are directly related to the normal and safe operation of the nuclear power plant, and no errors are allowed. According to the International Atomic Energy Organization (IAEA) nuclear power plant accident case, the shutdown or shutdown accident caused by valve failure and failure, and even the nuclear leakage accounted for a large proportion, so it must cause sufficient attention in the valve industry.

Nuclear power valve classification introduction

    A pressurized water reactor type nuclear power plant equipped with two sets of millions of kilowatt units is a relatively common and reasonable configuration. It consists of Nuclear Island NI, Conventional Island CI and Power Plant Auxiliary Facilities BOP (Balance of Plant). Three parts, of which the nuclear island NI includes the nuclear steam supply system NSSS (Nuclear Steam Supply System) and the nuclear island auxiliary facility BNI (Balance of Nuclear Island).
    NI is the core of a nuclear power plant, where nuclear energy is converted into heat and a large amount of steam is produced to provide electricity. CI is the main force of nuclear power plants, where heat is converted into electrical energy (including the entire process of steam turbine power generation until power output). Although BOP is not the protagonist, it is also indispensable like the screws on the equipment. In the nearly 30,000 valves, the three parts are used in a ratio of approximately 43.5% for NI, 45% for CI, and 11.5% for BOP.
    It can be seen that the CI uses a large amount of valves, compared with the same class of thermal power unit valves, which is characterized by a large diameter specification, and the pressure and temperature parameters are not too high. Therefore, from a technical point of view, the difficulty is relatively lower than that of the NI valve. The BOP valve is not only less in quantity, but also less technically difficult. This section only provides a brief introduction and analysis of some aspects of the NI part of the valve.
    NI valves are mainly classified into gate valves, globe valves, check valves, ball valves, butterfly valves, diaphragm valves, safety valves, pressure reducing valves, steam traps, and regulating (control) valves. According to the proportion of the total quantity used, the order is about 33.6% for the shut-off valve, 26.2% for the diaphragm valve, 12.8% for the ball valve, 7.2% for the check valve, 5.7% for the butterfly valve, and about 5.0% for the gate valve. About 3.5%, safety valve is about 2.5%, steam trap is about 0.3%, pressure reducing valve is about 0.2%, and other valves are about 3%. According to the nuclear safety (specification) level, the valves can be divided into nuclear 1, 2 and 3 and non-nuclear, accounting for 2.3%, 30%, 22% and 45.7% of the total number of NI valves.