AbstractAll the alternatives considered for the reduced technical objectives/reduced cost international thermonuclear experimental reactor (RTO/RC ITER) foresee, as one of the methods for additional heating and current drive, the use of neutral injection. Two atomic deuterium beams, with 1 MeV energy and each with at least 16.7 MW power, are the reference for the engineering design of the system. The design of NB system developed for the ITER final design report (FDR) [1] is being modified to comply with the reduced size of the machine and to incorporate, if possible, some design improvements and simplifications. The analyses of overall power distribution and the maximum power densities on each of the beamline components have been updated. To obtain 16.7 MW neutral beam power, 35 MW ion beam power at the exit of the accelerator is necessary. Therefore, about 18 MW are deposited on the beamline components. Moreover, during the commissioning of the injectors, and the high voltage conditioning of the beam source, the full beam power is dumped and measured on a calorimeter. The beamline requires actively cooled high heat flux (HHF) components to exhaust high power density (up to 15 MW/m2) in steady state conditions. The operative life of this components (30 000 beam-on/beam off cycles, without replacement) requires, primarily, the verification of thermal fatigue safety margins. This paper describes the most relevant aspects of the mechanical design of the HHF components, focusing on the thermal and mechanical verifications.