A 3D woven composite component, capable of withstanding extreme temperatures inside a fusion reactor, has been researched as a result of a collaboration between CCFE and the University of Sheffield’s Advanced Manufacturing Research Centre (AMRC).
The work was commissioned by the Joining and Advanced Manufacturing (JAM) programme, which forms one of three Fusion Technology Facilities at CCFE. The AMRC worked with CCFE’s Technical Lead for non-metallics, Dr Lyndsey Mooring, to explore how composite materials could produce components that are stiffer, lighter and easier to manufacture than those currently in use, but which retain the necessary capabilities.
In September, CCFE’s operator the UK Atomic Energy Authority announced the building of a new £22 million fusion energy research facility at the Advanced Manufacturing Park in Rotherham. This includes a test facility that reproduces the thermohydraulic and electromagnetic conditions within a fusion reactor.
Designing a fusion reactor is possibly the most challenging engineering project ever undertaken.
When fusion occurs between atoms of tritium and deuterium, a high energy neutron is released. This then interacts with a much cooler breeder blanket to absorb the energy. The breeder blanket must capture the energy of the neutrons to generate power, but also prevent the neutrons escaping and ‘breed’ more tritium through reactions with lithium contained in the blanket. Each blanket module typically measures approx. 1 x 1.5m and weighs up to 4.6 tonnes.
The current breeder blanket designs that will be tested in the next large international fusion device, ITER, use steel for the structure, and have a network of double walled tubes of 8mm internal diameter and 1.25mm wall thickness to collect the heat. Each one is welded into place and every connection has to be inspected.
Steffan Lea, research fellow at the AMRC Composite Centre, explained: “Currently, the ITER steel modules are limited to approximately 500˚C; CCFE asked us if there was anything we could do to get it up to 600˚C [for future reactor designs]. We set out to see what materials we could use, that would enable higher temperature operation.”
Engineers at the AMRC proposed to make use of high performance ceramic composite materials and to form a 3D woven structure with additive manufacture components. The cooling tubes in the breeder blanket would be integrated into the material and 3D printed parts used to define features such as connectors and manifolds.
Senior Project Manager at the AMRC’s Design and Prototyping Group, Joe Palmer, was involved in the design of the component demonstrator, and said: “To achieve a lightweight, temperature resistant structure, a silicon carbide composite material was chosen for the breeder blanket, with the internal flow channels being created by forming the composite around a disposable core.”
With a computer-aided design model produced, Chris McHugh, Dry Fibre Development Manager at the AMRC Composite Centre, then created a weave design for the composite: “The design I created had multiple weave zones and had multiple layer weaves. The structure needed holes robust enough to include tubes and needed to maintain the preform shape without distortion.
“What we were able to produce on the loom was a 3D woven structure with pockets for the 3D-printed tubes which could be formed into a ridged component.”
Steffan added: “We were able to replace a metallic box, made of different steel components, with a malleable textile fabric which had cooling pipes running the length of it.”
“Using advanced manufacturing, we have integrated the functionality of cooling, simplified the design and removed the welding operation, so lessening the burden of qualification.
Elizabeth Surrey, Head of Technology at CCFE, said: “Designing a fusion reactor is possibly the most challenging engineering project ever undertaken.
“We need to explore manufacturing technologies to satisfy the operational requirements of high temperature, low weight, and high strength structures which use materials offering low nuclear activation.
“For fusion to become a commercial energy source, the structures need to be modular and easily manufactured and provide operational lifetimes of decades.
“Standard manufacturing routes struggle to deliver across all of these requirements. That is why we turned to the expertise of AMRC to investigate the possible application of silicon carbide to this problem.
“Recent advances in silicon carbide manufacturing technology may offer the possibility of using this material in a fusion reactor; it has so many advantages it has to be considered. I was impressed by the progress made at AMRC in such a short time.”
Lyndsey Mooring added: “This successful project has been an excellent first step in demonstrating alternative structural materials and manufacturing routes for scalable fusion reactor components. This opens the design space available for our colleagues and offers problem solving solutions that can assist in realising a future fusion power plant.”
The next step will be the building of a demonstrator that can be tested inside a reactor test facility.