[en] During the last 30 years the nuclear fuel used in French PWRs has shown satisfactorily results concerning nuclear safety but unexpected events have occurred: clad failures, mis-positioning, errors in the fuel loading, fretting wear, corrosion or deformation. All this feedback experience must be taken into account in the development of new fuels. The French nuclear safety authority (ASN) has developed 4 axis of work: 1) the prevention of generic deficiencies, 2) the progress in safety (the level of safety must always be better), 3) the demonstration of safety (generally based on a complex and combined series of calculations concerning neutron transport, thermohydraulics and mechanics, and 4) the physical limits of the fuel (in order to take into account all the consequences of a modification, for instance an increase of the burn-up implies consequences about the handling and storage of the spent fuel. (A.C.)