Nuclear power is a safe, clean, economical, and reliable energy source. Replacing some fossil fuel generation with nuclear power not only preserves fossil fuels for long-term use, thus benefiting the environment, but also reduces fuel transportation costs. This is of great significance to the implementation of sustainable development strategies.
Nickel-based high-temperature alloy materials have been used in the nuclear power field for a long time. They are mainly used as heat transfer tubes, component frames and compression springs in pressurized water reactor steam generators, as well as superheater and reheater heat transfer tube components in high-temperature gas-cooled reactors and some fast reactors.
Reactor Loop Materials
The loop piping in a pressurized water reactor (PWR) is the channel that maintains and controls the coolancirculation.
Its primary function is to contain the high-temperature, high-pressure, and highly radioactive coolant, ensuring
reactor safety and normal operation.
The materials used for the loop piping should possess the following properties: strong resistance to stress
corrosion, intergranular corrosion, and uniform corrosion; a stable matrix structure with few inclusions; sufficient
strength, ductility, and thermal resistance; good casting and welding properties; mature production processes; low
cost; and prior experience in similar applications.
Incoloy 800H (UNS N08810)
Incoloy 800H offers excellent high-temperature performance, creep resistance, and comprehensive weldability.
It is widely used in heat exchange fins, brackets, and fixtures in heat exchange equipment; steam turbines
and forgings in the nuclear power industry; and polysilicon cold hydrogenation equipment for solar power
plants.
Fast Reactor Steam Generator Materials
A fast reactor steam generator is a sodium-water heat exchanger consisting of two components: a steam generator and a superheater. Because the superheater tubes are filled entirely with steam, they are less susceptible to stress corrosion, allowing for a wider range of materials than steam generator tubes. When steam superheats exceed 490°C, austenitic stainless steel or nickel-based alloys, such as 316, 304, or Inconel 600, are often used.
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Conel 600 (UNS N06600)
This nickel-chromium alloy is resistant to high-temperature oxidation corrosion, chloride ion stress corrosion,
cracking and corrosion in high-purity water, and corrosion in sulfur-containing alkalis. It can be used at
temperatures up to 1093°C. It is widely used in heaters, heat exchangers, evaporators, stills, and other
equipment in the nuclear power, petrochemical, and heat treatment industries.
High-Temperature Gas-Cooled Reactor Steam Generator Materials
High-Temperature Gas-Cooled Reactor steam generators are a spiral tube bundle structure, installed inside a prestressed concrete pressure vessel. The reheater and superheater operate at higher temperatures, so the heat transfer tubes are made of Inconel 690 alloy. The steam generator and economizer operate at lower temperatures (450-340°C), so 2.25Cr-1Mo steel is typically used for the heat transfer tubes. Austenitic stainless steel is not suitable due to its tendency to stress corrosion.
Inconel 690 (UNS N06690)
Inconel 690 alloy offers excellent resistance to intergranular corrosion and intergranular stress corrosion
cracking. It is primarily used for heat transfer tubes in steam generators used in pressurized water reactor
(PWR) nuclear power plants. Since its introduction in the 1990s, no reports of damage have been reported
for Inconel 690 alloy used in PWR steam generator heat transfer tubes.
Spacer Grid Materials
Spacer grids were originally made of austenitic stainless steel, but are now primarily made of nickel-based alloys or zirconium alloys. Nickel-based high-temperature alloys are the most commonly used of the three materials mentioned above due to their excellent corrosion resistance, high yield strength, tensile strength, and endurance strength, as well as good processing properties. High-temperature alloys used for grids include Inconel 718, Inconel 625, and Inconel X-750
Inconel 718 (UNS N07718 / GH4169)
Inconel 718 is a precipitation-hardened nickel-iron-chromium alloy with high high-temperature strength and
excellent creep resistance. It is primarily used in aerospace, gas turbines, and nuclear power. It can be used to
manufacture aircraft engine turbine blades, guide vanes, turbine disks, combustor liner, and compressors.
