A new microscopic method reveals hidden flaws in reactor welds, unlocking safer, stronger designs for the future of fusion energy.
As the global effort to build the first commercial nuclear fusion power plant intensifies, engineers at the University of Surrey have achieved a significant breakthrough in understanding how welded components perform under the extreme conditions inside a fusion reactor. This advancement provides essential insights that could lead to safer and more durable fusion energy systems.
In partnership with the UK Atomic Energy Authority (UKAEA), the National Physical Laboratory, and scientific instrumentation company TESCAN, researchers developed a cutting-edge microscopic technique to identify hidden weaknesses in welded metals. These internal flaws, formed during manufacturing, can compromise the structural integrity and longevity of reactor components.
The findings, published in the Journal of Materials Research and Technology, focus on P91 steel, a strong, heat-resistant alloy being considered for future fusion reactors. Using a sophisticated imaging method known as plasma-focused ion beam and digital image correlation (PFIB-DIC), the team successfully mapped residual stresses in extremely narrow weld zones that have previously been too small to analyze using conventional tools.
Results showed that internal stress has a big impact on how P91 steel performs – beneficial stress making some areas harder and detrimental stress making others softer, which affects how the metal bends and breaks. At 550°C, the kind of temperature expected in fusion reactors, the metal became more brittle and lost more than 30% of its strength.
Understanding Weld Behavior at Reactor Temperatures
Dr Tan Sui, Associate Professor (Reader) in Materials Engineering at the University of Surrey who is leading the research, said: “Fusion energy has huge potential as a source of clean, reliable energy that could help us to reduce carbon emissions, improve energy security and lower energy costs in the face of rising bills. However, we first need to make sure fusion reactors are safe and built to last.
“Previous studies have looked at material performance at lower temperatures, but we’ve found a way to test how welded joints behave under real fusion reactor conditions, particularly high heat. The findings are more representative of harsh fusion environments, making them more useful for future reactor design and safety assessments.”
Fusion energy – the process that powers the sun and stars – fuses light atoms to release massive amounts of energy. Unlike traditional nuclear power, the materials used, and the radioactive waste produced, are generally short-lived and far less hazardous.
Beyond the lab, the data from the team provides a foundation for validating finite element simulation models and machine learning-powered predictive tools, which have great potential to accelerate the design of fusion reactors like the UK’s STEP programme and the EU’s DEMO power plant project. This will help researchers to refine predictions and focus on the most positive material outcomes, significantly reducing experimental costs.
A Blueprint for Safer Nuclear Materials
Dr Bin Zhu, Research Fellow at the University of Surrey’s Centre for Engineering Materials and a key author of the study, said: “Our work offers a blueprint for assessing the structural integrity of welded joints in fusion reactors and across a wide range of extreme environments. The methodology we developed transforms how we evaluate residual stress and can be applied to many types of metallic joints. It’s a major step forward in designing safer, more resilient components for the nuclear sector.”
With the future commercialization of fusion power on the horizon, the research will play a crucial role in advancing the technologies needed to make it a reality – bringing us closer to delivering secure, low-carbon electricity at scale.
Jiří Dluhoš, FIB-SEM Product Manager at TESCAN, said: “We are proud that our FIB-SEM instruments can be part of such a crucial topic in materials research for the energy industry. Our long-standing collaboration with the University of Surrey to automate microscopic residual stress measurements proves that the plasma FIB-SEM can be successfully used for high-precision machining at the microscale.”
Reference: “Assessing residual stress and high-temperature mechanical performance of laser-welded P91 steel for fusion power plant components” by Bin Zhu, Omar Mohamed, Abdalrhaman Koko, Hannah Zhang, Jiří Dluhoš, Yiqiang Wang, Michael Gorley, Mark J. Whiting and Tan Sui, 1 March 2025, Journal of Materials Research and Technology.
DOI: 10.1016/j.jmrt.2025.02.260
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2 Comments
The research will play a crucial role in advancing the technologies needed to make it a reality – bringing us closer to delivering secure, low-carbon electricity at scale.
GOOD.
Ask the researchers:
How do you understand the fusion power?
According to the topological vortex theory (TVT), fusion power may not only rely on temperature, the interaction mode of vortex fractal structure may be more important.
According to the topological vortex theory (TVT), the energy of the sun may not solely depend on its temperature. For matter on Earth, how it interacts with the vortex fields of the Sun and Earth may be more important.