NAMRC Researchers in Residence projects begin

Two researchers are starting projects at the Nuclear AMRC supported by the Researchers in Residence programme.

 Dr Nicolas Larrosa of the University of Bristol is investigating additive manufacture for fusion applications, while Dr Simon Fletcher of the University of Huddersfield in developing new tools to improve machining accuracy for the largest components.

Additive manufacturing for nuclear fusion

Dr Nicolas Larrosa, Lecturer in Structural Integrity at the University of Bristol, will work with the Nuclear AMRC to investigate additively manufactured vanadium components for potential use in nuclear fusion reactors.

Vanadium has long been used as a micro-alloying element in high-strength steels and titanium alloys. In its pure metallic form, or alloyed with a small amount of chromium and titanium, vanadium could be an ideal material for the internal components of a fusion reactor. It is resistant to neutron damage and can withstand the harsh temperatures, stresses and electromagnetic fields experienced in the fusion environment.

Potential applications include the divertor system, which removes waste from the plasma while the reactor is operating. Cladding techniques could also be used to add a functional layer of vanadium to steel structural components. Producing reactor components by additive manufacturing (AM) – where the part is built up from powder or wire rather than being machined down from a solid billet – would allow reactor developers to create more efficient designs, reducing build costs & improving operations.

"Vanadium is very expensive and, with additive, you can achieve a near-net shape with very little scrap," says Larrosa. "You can also achieve very complex geometries which would be impossible using machining or other conventional techniques.

"However, AM parts are characterised by relatively low levels of repeatability and reliability due to a highly variable manufacturing process. Several initiatives were recently launched to benchmark and mitigate the uncertainty of structural properties in AM parts, but there is a notable lack of research on low and high temperature fatigue."

As with any safety-critical reactor systems, developers need to be sure that components produced using innovative techniques don't increase the risks of component failure. Larrosa's research aims to better understand the material properties of additively manufactured vanadium, particularly the mechanisms behind crack formation and propagation.

As a first step, Larrosa will work with two of the centres within the HVM Catapult to produce a series of samples made with different additive techniques. The Nuclear AMRC will produce samples using wire-fed arc and electron beam additive techniques, while the MTC in Coventry will focus on powder-based methods such as selective laser melting. Larrosa will then subject the samples to extensive fatigue testing and analysis to identify which techniques are the most appropriate for fusion applications. "We will compare defects and the structure of how defects are embedded in the sample, and understand what the typical defect arrangement is, which will allow us to create better samples," he says.

AM microstructures are component-dependent, he notes, so a fundamental understanding of the effect of microstructural features on fatigue tolerance is required before AM components and structures can be used in safety-critical applications.

The 30-month project also involves the Culham Centre for Fusion Energy, Henry Royce Institute and University of Birmingham. Ultimately, Larrosa aims to develop engineering rules for the design and structural integrity assessment of additively produced vanadium components. Working with the HVM Catapult provides access to a range of industrial partners, he notes, helping ensure his research is meeting industry needs.

"It gives me a widespread understanding of technology needs and how I can link structural integrity with manufacturing to add value to the final component," Larrosa says. "One of the main advantages of the Catapult is that it brings together academics like me and the final users. It's very applied research, and this gives us the opportunity to interact in a unique place."

NAMRC Researchers in Residence Programme

Researchers in Residence is funded by Research Councils UK to improve knowledge sharing between university-based researchers and the industry-focused Catapult network.

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