The design of the equipment and confinement barriers of ITER-FEAT should be consistent with the basic safety requirement that-no emergency plan involving evacuation of the nearby population is required in case of the worst credible accident. Extensive probabilistic and deterministic analyses have been done to select abnormal event sequences, and to ensure that all potential consequences are within project guidelines. The paper deals with the work done for the tritium systems. A Bottom-Up methodology based on component level Failure Mode and Effect Analysis has been applied to point out accident initiators. Once possible accident sequences have been identified, detailed deterministic analyses on bounding events confirmed that the accidents in tritium plant are not a concern from a safety point of view. The no-evacuation goal of ITER-FEAT is attained also for accidents where 'ultimate safety margin' are challenged, as in case of hydrogen-air reactions in cold box or in hard shell, enclosing the process equipment of the isotope separation system. (C) 2002 Elsevier Science B.V. All rights reserved.