[en] The potential of nuclear energy for sustainable development is based on its competitiveness, environmental friendliness and sustainability of natural resources. The improvements to be achieved relate to cleanliness (by reducing the production of long lived radioactive waste), safety demonstration and sobriety which contributes to minimise the consumption of natural resources. The current level of competitiveness, which is fairly good, has to be maintained. The required improvements benefit from a high efficiency and a simpler architecture of industrial systems; they imply the recycling of nuclear materials and a high efficiency of nuclear combustion. The latter requires a hardened spectrum using fast neutrons, which makes the nuclear core 'omnivorous' as for transuranics. The studies must take into account reactor design, nuclear fuel and fuel cycle. Diverse coolants (water, gas, liquid metals) are considered, with solid fuel (pins, particles) and reprocessing by hydrometallurgical or pyrochemical processes, as well as liquid fuel reactors. Several ways of combining options look promising. The required time before industrial implementation is highly variable. A nuclear fleet can include diversified, specialized components and new applications (hydrogen production) can be envisaged. The R and D programme will rely on the development of simulation power and will imply a strong international cooperation. (authors)