[en] The experimental program of Fast Reactor Safety, in progress at ECN-Petten, includes irradiations of single fuel pins in sodium-filled capsules under simulated loss-of-coolant flow conditions. The main objectives are to determine the failure modes, mechanisms, thresholds and consequences of fuel pin failures under different conditions by varying parameters like: canning temperature, internal pin pressure and burn-up. A brief description will be given of the experiments and the program. Results will be presented of the different failure modes and mechanisms. (author)