In the nuclear islands and conventional islands of PWR nuclear power plants, most of the components are made of steel materials. Except for the nuclear fuel cladding, the control rod drive mechanism and the steam generator heat transfer tube which are made of zirconium alloy and nickel-based alloy, the rest of the equipment is made of steel materials.

1. The main pipeline of the loop

It is an important barrier to prevent nuclear reaction fission products from leaking to the containment under normal, abnormal, accident and test conditions of nuclear power plants. Therefore, the main pipeline of nuclear power must be able to withstand high temperature, high pressure and corrosion. The main pipeline of the primary circuit of the third-generation PWR AP1000 nuclear power plant is made of integrally forged 316LN austenitic stainless steel.

2. Reactor pressure vessel

The reactor pressure vessel operates under harsh conditions such as high temperature, high pressure, fluid erosion and corrosion, and strong neutron irradiation, and its design life is not less than 40 years and cannot be replaced. Pressure vessel materials must meet the following special requirements: sufficiently high purity, density and uniformity, appropriate strength and good toughness and plasticity, excellent resistance to radiation embrittlement and ageing resistance, excellent weldability, hot and cold Processing performance and excellent corrosion resistance. A508-3 is currently the material of choice for the pressure vessel of large pressurized water reactors.

3. Steam generator

The function of the steam generator is to transfer the heat from the primary circuit coolant from the reactor to the secondary circuit medium and turn it into steam to drive the steam turbine to generate electricity. The shell of the steam generator (including the upper head, the upper cylinder, the lower cylinder and the cone) is made of ferritic steel plate; the U-shaped heat transfer tube has been widely used in Ni-based alloys such as 690 and 800; the tube plate adopts Forged from high-strength low-alloy steel, the coolant side of the primary circuit is a stainless steel surfacing layer.

4. Nuclear valve

Nuclear-grade valves are a key accessory in nuclear power equipment. They are connected to more than 300 sub-systems of nuclear power plants. The main types are gate valves, globe valves, check valves, butterfly valves, safety valves, main steam isolation valves, ball valves, diaphragm valves, and pressure reducing valves. Valves and control valves, etc.

The materials selected for nuclear valves generally need to have good corrosion resistance, radiation resistance, impact resistance and intergranular corrosion resistance. Therefore, low-carbon or even ultra-low-carbon austenitic stainless steel is used as the main material in some main systems. And select some alloy materials with high strength, good toughness, high temperature and high pressure resistance, erosion resistance and abrasion resistance to make valve stem or sealing surface and other parts.

According to the choice of valve body material, stainless steel valves account for about 55%.

5. Heap internals

The internal components of the reactor refer to all the structural parts in the pressure vessel except the fuel assembly and related parts. It has a wide range of parts, complex structure, high precision requirements, and needs to withstand tests such as high temperature and high pressure, neutron radiation, and coolant corrosion. Therefore, the principles for selecting materials for the internal components of the reactor are generally: appropriate high strength, good plasticity and toughness, impact resistance and fatigue resistance; neutron absorption interface and neutron capture cross-section, and small induced radioactivity; radiation resistance, corrosion resistance and Coolant compatibility is good; thermal expansion coefficient is small; good welding and machining process performance.

The main structural material of the second-generation PWR nuclear power plant is generally austenitic stainless steel, such as 304L, 304LN, 321, 347, and 310. The bolt material is 316LN, 321H stainless steel, and some special parts are made of martensitic stainless steel. , Such as 1Cr13 compression spring. The third-generation pressurized water reactor AP1000 nuclear power plant has greater power and longer life, and has stricter requirements on the composition and performance of the internal components of the reactor. The main structure is made of forged F304 and F304H austenitic stainless steel, and the compression spring is made of improved 403 martensitic stainless steel.