"In a fusion reactor, a large problem is the resistance to heat of a part of the reactor called the divertor, where waste material from the reactor is removed. In this part, the heat flux density can be so high that tungsten, from which the divertor is made, will crack, melt or erode away. A solution is to use liquid metals in the divertor, which will not crack and can be replenished. Additionally, these liquids take up excessive heat by vaporizing and radiating, an effect called vapor shielding. But early designs using for example a wire mesh to soak up liquid lithium are not yet suitable for use in a real reactor.
I designed a 3D-printed matrix from tungsten with capillary channels in which the liquid metal is contained. It is resistant to the various loads such as the power and neutron fluxes and can handle a temperature gradient very well.
Using the linear plasma generator Magnum-PSI at DIFFER we showed that using tin as the liquid metal, this divertor design can withstand almost double the required heat flux density in steady state operation of the reactor, and even three times that for so-called slow transients. Another obstacle that remains is the resilience to very short plasma disruptions, which give much higher heat flux densities, but the early results look promising.
As an engineer, I take up design challenges such as the ones the European DEMO project is facing, much more than the physics challenges of ITER. I am happy that I was able to convince the team at DEMO that my divertor design is feasible and may solve many of their challenges. We are now building a prototype of this divertor using various 3D matrix materials.”
This interview was published in the DIFFER Annual report 2019, available online.