Steel for nuclear reactor vessels - temperature, pressure, corrosion

Reactor steels are special alloys used in nuclear power plants to handle the extreme conditions inside a reactor. In addition to high temperatures and pressures, these steels must also be able to withstand radiation.

Properties and requirements
The most important requirements for a reactor steel are heat and radiation resistance, as well as mechanical strength. These properties are achieved through the composition of the alloy and special manufacturing processes (forging, heat treatment, inspections).

👨‍🎓 Forged parts have a grain flow, similar to the fiber structure of wood. This results in components with superior mechanical properties, including higher tensile strength, improved impact resistance and therefore better overall performance. In addition to weldable stainless steels such as F316L (1.4404), higher-alloy variants of F316L such as 1.4435 or even duplex steels such as F51 (1.4462) are often used for valves and pipe connections in various types of power plants, not only nuclear!

👉 There was already an article published about steel grades and superalloys:
https://www.openpr.com/news/3425250/every-nut-bolt-and-screw-forgings-for-harsh-environments

One of the biggest challenges when using reactor steels is embrittlement caused by neutron irradiation. Neutrons can knock atoms out of the steel grid, causing defects and increasing brittleness. This can affect the safety of the reactor, especially during sudden temperature changes such as during emergency shutdown.

👨‍🎓 The reactor pressure vessels (RPV) consist of weldable low-alloy tempered steels based on manganese, nickel, and molybdenum with alloy additives such as chromium, vanadium, and varying carbon content. In the past, steel grades 1.6310/11 and 1.6751 were used in German nuclear RPVs. After constant improvements in reactor steels over the last decades, the USA and China with the latest variants (grades 3 and 4) of the SA508 steel, France with its 16MND5 and Russia with the 15X2HMΦA now represent a quasi-industry standard for long-lasting nuclear steels for today's reactor pressure vessels worldwide.
All mentioned alloys are very similar, some contain additional B, Cu, P, Si for different reasons. Chinese and Russian RPV contain more Chromium and Nickel. Steel grades in Japan and Korea (SFVV3 or SFCQ1A) are very similar to the other ones.

Source (2022): Table 1 in https://www.ncbi.nlm.nih.gov/pmc/articles/PMC9786578/

Prospects
The future of reactor steels lies in the development of new alloys and technologies that offer even greater resistance to radiation and corrosion. Advances in materials science could allow nuclear power plants to operate more safely and efficiently. Reactor steels play a crucial role in the safety and efficiency of nuclear power plants. Continuous research and development can overcome the challenges associated with their use and extend the life of the reactors.

The author is CEO of a small, but highly certified, drop forge in Western Germany:
https://kb-schmiedetechnik.de/about-us.html and regularly writing popular scientific articles about steel and its varied applications. He is also regularly posting and commenting on LinkedIn: https://www.linkedin.com/in/thomas-henneke-9824b3281/

Thomas Henneke
KB Schmiedetechnik GmbH
Buschmühlenstr. 62
58093 Hagen (NRW)
Germany

👉 corrosion-resistant, non-embrittling, seawater-suitable forgings

KB Schmiedetechnik GmbH is a highly certified German drop forge, located in Hagen (Westphalia) - between the historic "blade & metal" region Solingen and the "soccer city" Dortmund - specializing in small series production of safety-relevant closed die forgings from 200g to 130Kg unit weight of all steel grades including duplex stainless steels, nickel based and titanium alloys according to following standards, norms and certifications:

☢️ nuclear power - atomic energy:
KTA (Germany), EDF/Areva/RCC-M (France)

🧯 pressure equipment like valves:
DESP/DGRL/PED 2014/68/EU, AD 2000-W0

⚗️ boiler systems and piping:
ASME/ASTM, Alstom, Babcock, CNIM, Mitsubishi/Hitachi (MHPS)

⚓️ shipbuilding, naval architecture, ocean engineering:

American Bureau of Shipping (ABS)
Bureau Veritas Marine & Offshore (BV)
Nippon Kaiji Kyokai (ClassNK)
Det Norske Veritas (DNV)
Lloyd´s Register (LR)

Examples are brackets, holders, hoists, hooks, chain links, special screws, pipe connections, pressurised/ pressure-bearing parts, nuclear and hydrogen valves, pieces for boiler systems and nuclear power plants, also seawater-suitable, parts and components for corrosive applications like naval ships, boats, ship technology, corrosion-resistant components, acid-resistant, highly corrosion-resistant forgings for seawater applications, desalination, petrochemicals, fertilizer and food processing, drill equipment, marine and underwater technology, military, defence.

This release was published on openPR.