Safety issues to be taken into account in designing future nuclear fusion facilities

Highlights: • Assess if decay heat removal is a safety function. • Re-study accidents considered for ITER and identify those specific to DEMO. • Limit tritium inventory and optimize main gaseous tritium release routes. • Take into account constraints related to requirements of waste disposal routes. - Abstract: For several years now, the French "Institut de Radioprotection et de Sûreté Nucléaire" has been carrying out expertise of ITER fusion facility safety files at the request of the French "Autorité de Sûreté Nucléaire". As part of the lengthy process which should lead to mastering nuclear fusion, different fusion facility projects are currently under study throughout the world to be ready to continue building on the work which will take place in the ITER facility. On the basis of the experience acquired during the ITER safety expertise, the IRSN has carried out a preliminary study of the safety issues which seem necessary to take into account right from the earliest design phase of these DEMO facilities. The issues studied have included the decay heat removal, exposure to ionizing radiation, potential accidents, and effluent releases and waste. The study shows that it will be important to give priority to the following actions, given that their results would have a major influence on the design: assess if decay heat removal is a safety function, re-study the accidents considered in the context of the ITER project and identify those specific to DEMO, and optimize each of the main routes for gaseous tritium releases.