AbstractNuclear and thermal–hydraulic analyses have been performed with the objective to further optimise the high-flux-test-module (HFTM) design. The nuclear analyses showed that the volume of 0.5 l with a damage rate dpa/fpy>20 can be achieved, if the HFTM has a contour like a semi ellipsoid. The thermal–hydraulic analyses focused on the experimental validation of the helium cooling concept. Integral heat transfer experiments revealed that the specimens can be kept at temperatures up to 600 °C. Dedicated experiments are being designed with the objective to provide data for the validation of the direct numeric FE simulation of the helium flow field, the heat transfer and the pressure losses.