In a fusion power plant, the blanket (the first structure surrounding the plasma) is a critical component since it has to withstand extremely severe operating conditions while insuring tritium self-sufficiency, adequate neutron shielding and coolant temperatures suitable for an efficient power conversion cycle. The candidate blanket concepts selected by the European Union for DEMO use the so-called Eurofer steel as the structural material supporting the blanket. The blanket conceptual design is intended to minimise blanket replacement time and maximise reactor availability. This is achieved by welding together individual modules in order to form a banana-shaped blanket segment, which can be removed from the upper port. Module replacement will require welding procedures in a very confined environment and for this laser welding is currently explored. Eurofer is a ferritic steel, which forms a very hard (see Figure 1), but also less ductile, weld region due to the martensitic phase transformation. Typically, post weld heat treatments are applied in order to mitigate residual stresses and high strength in the weld region. However, this is not possible when repairing blankets and therefore it is important to develop an understanding how such weld structures perform during typical in-service conditions, i.e. during high temperature and irradiation. My project will involve characterising several laser welds performed on variations on Eurofer steels, determining hardness profiles across the weld.