The nuclear industry uses stainless steel in a variety of components: reactors, heat exchangers, turbines, radioactive sludge ponds, and more.
The components used are generally made of stainless steel, a material that provides maximum corrosion resistance, has a long lifetime and thus provides reliability with little to no maintenance.
Stainless Steel Grades and Cobalt Restrictions for Nuclear Applications
Due to the peculiarity of nuclear environments, the most common grades of stainless steel are 1.4307 (304L) and especially 1.4404 (316L). Occasionally it happens that the application demands also higher austenitic grades or high yield grades like duplex stainless steel.
In addition to the grade, the stainless steel quality has often further restrictions with regards to the chemical composition. In particular the level of cobalt it contains may have limitations. A general maximum level of 0.2% is acceptable, but at times it can be restricted to a maximum content of 0.05%. This is because cobalt contains an isotope that, when irradiated by nuclear materials, becomes radioactive and deteriorates.
The requested maximum amount of Cobalt has serious implications with regards to the melt of the raw material itself. Stainless steel is recycled to 95% and mostly from scrap. The more stringent the Cobalt content limitations are, the less scrap can be used and thus the more expensive and difficult-to-find the material becomes.
Meeting Strict Standards for Nuclear Stainless Steel Sections
Due to the nature of the application, the quality standards are among the strictest of all. Montanstahl has a long experience in handling production of steel sections and components for the nuclear industry.
Each project demands its own specific requirements: a production plan is mutually agreed with the customer and it meticulously defines each production step with the relevant procedures. This includes non-destructive tests (NDTs), which are scrupulously protocolled for the final documentation and will be included in the lifetime record.
Both the Quality Department and the Production Departments are trained and accustomed to handling the production of profiles with augmented controls, inspections and related paperwork with hold and witnessing points, third party inspections – all of which are pre-requisites in the nuclear industry.
These sorts of products follow a dedicate production flow and are accompanied by a specifically appointed and certified project manager.
What technologies are used
Montanstahl is able to use all its available production technologies, choosing with the customer the most suitable for the specific application. The required profiles may be produced by hot rolling, hot extruding, or laser welding. In addition, there is the possibility to further tighten the products tolerances using a hot rolled, hot extruded or laser welded pre-shape and then cold drawing it to achieve the required dimensions and tolerances.
Where stainless steel is used in the nuclear industry
Containment vessels are critical components in nuclear power plants, responsible for holding the reactor core and preventing the release of radioactive materials. These vessels must be able to withstand high pressures, temperatures, and radiation levels, which is why they’re constructed using materials that can withstand these extreme conditions. Stainless steel is the preferred material for building containment vessels in nuclear reactors because of its excellent strength, durability, and resistance to corrosion.
Piping systems are used in nuclear reactors to transport coolant, fuel, and other materials throughout the reactor. These piping systems must be able to withstand high pressures and temperatures, as well as the corrosive effects of radioactive materials flowing through them. Stainless steel is the preferred material for piping systems in nuclear reactors because of its high resistance to corrosion.
Stainless steel piping systems are made using high-quality, corrosion-resistant stainless steel alloys, which are designed to withstand the harsh environments found in nuclear reactors. These alloys are resistant to pitting and crevice corrosion, which can occur due to the contact of materials with radioactive fluids. Stainless steel pipes also help maintain the integrity of the system, preventing leaks and other issues that could lead to dangerous situations.
Fuel rods surround nuclear fuel pellets and are responsible for containing fuel and protecting it from the reactor environment. The material used to make rods must be strong, durable, and resistant to corrosion, radiation, and extreme temperatures. Stainless steel is used as a fuel rods material due to its excellent mechanical properties and corrosion resistance.
Stainless steel fuel rods help maintain the integrity of the fuel, thus reducing the risk of a nuclear accident. The strength and durability of stainless steel also make it an ideal material for use in fuel rods, as it can withstand the extreme temperatures and pressures that occur in a nuclear reactor.
Stainless steel is also used in the construction of storage tanks for nuclear waste. Thanks to its high resistance to corrosion, it’s the ideal material for storing radioactive waste, which can be highly corrosive. Stainless steel storage tanks help ensure that radioactive waste is safely contained and transported.
Beside from concrete, lots of structural load bearing parts are made from stainless steel structural sections like beams, channels, angle bars and hollow sections. This is valid both for the reactor core and all surrounding services, like fuel rod storage and preparation. Several structural sections are only available on the market in welded execution, which lead the nuclear industry to introduce additional safety and quality requirements for laser welded structural components.
In 2013 Sellafield Ltd. released a new issue of its specification: “Fabrication of Plant & Equipment (Carbon Steel & Stainless Steel) General Duty”, including laser beam welding as an acceptable welding method. And today the laser welding technology is fully accepted and compliant for the production of sections and parts in the nuclear industry worldwide.
The Essential Role of Stainless Steel in Ensuring Safety and Reliability in the Nuclear Industry
In conclusion, stainless steel is an essential material in the nuclear industry due to its exceptional strength, durability, and resistance to extreme temperatures and radiation. Stainless steel is used in the construction of containment vessels, piping systems, fuel cladding, storage tanks and load bearing structures, all critical components of a nuclear reactor.
The use of stainless steel in the nuclear industry helps ensure the safety and reliability of nuclear reactors, preventing accidents and protecting the environment.
As the demand for clean and sustainable energy sources, such as nuclear energy, continues to grow, the use of stainless steel in the nuclear power plants is likely to increase.
Montanstahl has supplied stainless steel profiles for the nuclear industry in almost all relevant European Countries, plus the USA and China. We are considered a reliable and competent partner for supplying stainless steel sections into the nuclear sector.