Claude’s research interest is multidisciplinary and goes from environmental science to solid state physics. He focuses on the nuclear fuel cycles and their green options. His work deals with nuclear energy and nature with its economic background and the ecological challenges. Claude is also very concerned by nuclear safety giving high priority to this issue in his work. Today he emphasises research on single nano-particle analysis e.g. in repository ground water or in reactor water; on the characterisation of safety relevant fission products in fuels and cladding, and on physical chemistry of actinide isotopes and compounds. He also discusses the raison d’être of a significant fraction of nuclear energy in an optimal energy mixt as well as the place of nuclear energy in a better world.