Thermal topology optimisation of a plasma facing component for use in next-generation fusion reactors

The ITER tokamak, the experimental fusion reactor designed to be the first to produce net energy, has had a monoblock concept selected for use as a plasma facing component in the divertor region. This design currently consists of a CuCrZr cooling pipe surrounded by a copper interlayer and embedded in a tungsten armour plate. Additive manufacturing may facilitate a geometry capable of greater efficiency through the introduction of greater design freedom whilst maintaining compatibility with the monoblock concept. This is achieved through the addition of high conductivity material to the armour domain surrounding the coolant pipe. Finite element simulation of the heat transfer system combined with a topology optimisation methodology has been used to find the optimal distribution of high thermal conductivity material (such as Cu) for three thermal objectives: minimising temperature and thermal gradient, and maximising conductive heat flux. The topology optimisation relies on a density-based approach which makes use of the globally convergent method of moving asymptotes technique [1]. The optimised geometries have been tested for both steady state operation and transient heat flux events for both a symmetric, flat monoblock design and an asymmetric component designed to minimise leading edges. In high heat flux transient events, the optimisation resulted in temperature reductions of over 200K and reduced thermal gradients. These techniques may be used to help protect divertor components from damage in future devices.