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1. Development trend of nuclear power units: According to analysis of available data, in the construction of nuclear power plants, the capacity of these units is moving in the direction of 1.3 million, 1.4 million, and 1.5 million kilowatts abroad. Domestically, it is mainly developing in the direction of 800,000, 900,000, and 1,000,000. Nuclear power equipment will develop in the direction of larger size, higher parameters, and improved performance. 2. Development trends of nuclear power valves: With the development of the nuclear industry, there are increasing demands for larger size, higher parameters, better performance, as well as greater reliability and safety in nuclear power plant equipment. This requires nuclear power valves to be able to adapt to this trend as well. The specific types and parameters of valves used in nuclear power are as follows: (1) Gate valves without stuffing boxes: a) Hydraulically driven gate valves. The valve uses the pressure of water itself to push the piston open or close; its nominal diameter is DN350, 400 mm ； Working pressure: PN17.5MPa ； Operating temperature: 315°C. b Fully enclosed electric gate valve. The valve should be equipped with a specially designed enclosed motor, which uses an underwater-operating internal planetary reduction mechanism to move the gate open and closed. Nominal diameter of the valve: DN100~800mm ； Working pressure: PN2.5~45.0MPa ； Operating temperature: 200~500°C. (Note: The advantages of the above two types of glandless gate valves are: no packing seal, which eliminates potential leakage points, and at the same time reduces energy consumption. Disadvantages: complex structure, high cost. ) ⑵ Shut-off valve: Used as a shut-off valve in auxiliary pipelines. This valve generally comes in three types of structures, namely the packing-type globe valve, the bellows-type globe valve, and the metal diaphragm-type globe valve. The medium for this valve is water and steam with moderate parameters (moderate temperature and pressure) ； Nominal diameter: DN10~150mm. ⑶Butterfly valve: Butterfly valves used in systems for conveying air media within cooling systems and containment structures. This valve generally comes in three types: a coaxial directly-connected rubber-lined butterfly valve, an eccentric metal-sealed butterfly valve, and a double-acting metal-sealed butterfly valve (in which the butterfly disc is separated from the sealing surface before rotating). Nominal diameter of the valve: DN≤2500mm ； Working pressure: PN＜4.0MPa ； Operating temperature: 100~150°C. In addition, the nominal diameter of quick-close butterfly valves used in air duct systems, ranging from DN400 to 1200 mm, is also considered a direction for development. ⑷Pilot-operated safety valve with detector: Pilot-operated safety valves equipped with detectors, used in the nuclear island system. By using a pilot-operated safety valve equipped with a detector, it is possible to adjust the positions of the two contacts responsible for controlling release and medium filling, based on the sensitive relationship between pressure and spring force; this approach helps to prevent jamming issues from occurring structurally. This valve features a directly-acting valve disc structure with spring pre-tensioning and diaphragm sealing, ensuring reliable sealing. Nominal diameter of the valve: DN600mm ； Operating pressure: PN1.265MPa. ⑸Check valve-type isolation valve: A check valve-type isolation valve used in steam systems, whose structure is similar to that of a lift-type check valve. Nominal diameter of the valve: DN64~800mm (21/2in~30in) ； Operating pressure: PN1.0~42.0MPa (Class600~2500) ； Operating temperature: -29~1050°C. ⑹Main steam isolation valves: Main steam isolation valves and main feedwater valves for the nuclear island and the conventional island, with a nominal diameter of DN800mm ； Nominal pressure: 40.0 MPa ； Temperature 700℃ ； In addition, safety valves that meet seismic requirements, high-vacuum solenoid valves with soft and hard seals for nuclear fuel extraction, and overhead-type nuclear power ball valves are also nuclear power valves that need to be developed urgently.