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Hi-tech Brillo pads answering a hot fusion problem

-Nick Holloway, Tom Barret, Culham Center for Fusion Energy

When a CCFE engineer Tom Barrett and colleagues embarked on a European-wide project to design a key component to protect fusion reactors from thermal damage, they never expected their solution could come in the form of a household object.

The component in question is the exhaust system of the 'DEMO' prototype power plant. Known as the divertor, it is a trench where the hot fusion plasma will be deliberately deposited. Doing so enables heat to be conducted away while controlling impurities, and is a way of managing the ejection of power and helium waste.

Divertor target mock-ups manufactured at CCFE, in collaboration with KIT in Germany. © CCFE (Click to view larger version...)
Divertor target mock-ups manufactured at CCFE, in collaboration with KIT in Germany. © CCFE
The divertor surface will be dotted with thousands of small tungsten blocks, forming the divertor targets. Millimetres below these targets, a water coolant flow removes the waste heat and regulates the divertor's temperature, and so the structural integrity of these components is critical. Damage to the coolant pipe will mean the coolant leaks out and the whole reactor has to shut down for costly repairs. So Tom and his colleagues' job is to find a way of separating the very hot tungsten (1,500 degrees C) from the not-quite-so-hot cooling water (a mere 200 degrees C). One idea is to focus on the so-called 'interlayer' between the tungsten armour and cooling structure.

The Brillo-pads team. © CCFE (Click to view larger version...)
The Brillo-pads team. © CCFE
"We think the layer between the two surfaces has to be spongey, but also act as a thermal barrier as well as survive the high heat flux," Tom explains. "From our analysis it looks like a good material for the job is a kind of felt made from copper — a bit like a Brillo pad you'd use to clean your dishes."

Read the whole story on CCFE website.


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