The VHTR and GFR and their use in innovative symbiotic fuel cycles

This review article is an overview on some recent developments of Generation IV (GEN-IV) gas cooled nuclear reactor performing in the frame of innovative symbiotic fuel cycle mainly by our research group. In fact such reactors, in addition to energy generation, can also improve nuclear fuel exploitation and decrease nuclear waste radiotoxicity mainly by transmutation processes. Transmutation of Trans-Uranic nuclides (TRU) can be carried on in GEN-IV reactors mainly due to their neutronic behaviour and design features. An optimization of the burning process, by using different reactors chains (symbiotic cycles), has been analyzed in order to allow an efficient TRU transmutation with the aims to reduce waste radiotoxicity, optimize raw material exploitation and close nuclear fuel cycle.