In this paper some major achievements of two nuclear systems thermal-hydraulics methods development and application research activities are presented. Both methods development and ADS thermal-hydraulic design main results are described. Radial subassembly temperature profiles are given and data concerning the optimisation of peripheral pin circumferential thermal gradients are also talked over. IFMIF liquid Lithium Target was modelled and analysed basing on the most recent design parameters. Temperature and boiling margins profiles were outlined and critical design issues have been discussed.