News & events
Fusion reactor mock-ups can take the heat | 20/12/2016
A CCFE fusion technology project recently passed a major milestone with the first high heat flux testing of divertor components designed and manufactured at Culham.
One of the key areas within Culham's Technology Programme is focussed on the conceptual design of DEMO, the fusion power station that is planned to follow the ITER experiment. This covers a wide variety of work from plasma physics, engineering design of the machine, choice of materials and importantly, divertor studies – a crucial system in a tokamak which is designed to directly intercept the plasma and exhaust heat and waste products.
The DEMO divertor project has now delivered the very first full demonstration at Culham of the application of Virtual Engineering to improve and verify manufacture of components. This rapidly-growing field uses sophisticated computational simulations to test the response and behaviour of a component in the ‘virtual' world, including defects, specific material joining methods and how material properties change with temperature, irradiation and ageing. The results are then validated against real-life small-scale testing of components.
“A fusion reactor will be a huge machine, and real component testing on this scale will be impractical. Nevertheless, we need confidence in the way individual components will perform before we invest in building the full device,” explains Tom Barrett, the mechanical engineer who leads the DEMO divertor activities at Culham.
An ‘ITER-like' divertor design was used as a starting point and improved using ‘design search and optimisation' algorithms. This revealed the potential of a concept called the ‘Thermal Break', in which the properties of the interlayer (between the plasma-facing armour and underlying structure) are manipulated to reduce the stress between the dissimilar materials.
A component demonstrator was produced, and state-of-the-art x-ray tomography (performed at STFC's Rutherford Appleton Laboratory at Harwell) that revealed flaws in the manufacture of the component was then used to create a computational model 'twin' of the manufactured part. This enabled Tom and his team to predict the component's performance under a high heat flux load which crucially allowed improvements to be made to the fabrication procedure.
A fabricated mock-up, 3-D x-ray scan, and simulation ‘virtual twin' of the real component
Six small-scale thermal break divertor mock-ups have now been manufactured at Culham by the Special Techniques Group. As part of a EUROfusion project, the first three have now been tested in the GLADIS ion beam facility at the Max Planck Institute for Plasma Physics in Germany. All three components survived a surface heat flux of up to 25 MW/m2 and 100 heat cycles at 20 MW/m2. The high heat flux test results produce infrared camera surface temperature data, which can be compared with the virtual twin's performance.
CCFE thermal break infrared images under HHF testing in GLADIS (IPP)
Tom Barrett commented: “This is a hugely successful result which has exceeded all expectations. It is testament to the strong team we have at CCFE, proving our strong capability in advanced analysis, materials, fabrication R&D, and project delivery. The next step is to further refine the design following the successful testing and manufacture new mock-ups for phase 2 testing in 2018.”
Elizabeth Surrey, CCFE Head of Technology, said: “Virtual Engineering will be an essential tool in the advancement of fusion power, allowing design and validation to progress in synergy throughout a component's lifetime. I am proud to say that Tom and his team, with others in CCFE, are leading this approach in Europe.”