Safety and environment studies for a European DEMO design concept

•A safety approach is established for EU DEMO including a safety classification scheme.•Accident analyses reveal the need for a large expansion volume with helium cooling.•Minimization of radioactive inventories is being achieved in the DEMO design concepts.•Detritiation and recycling techniques expect to reduce the radioactive waste burden. Pre-conceptual design studies for a European Demonstration Fusion Power Plant (DEMO) have been in progress since 2014. At this stage, while a range of design options are being considered, assessments of the safety and environmental impact of these options are carried out. This is to ensure that the DEMO plant is optimized for safety performance, and that it will demonstrate the favourable safety and environmental characteristics of fusion energy as part of its mission. To this end, safety studies have been under way since the start of the project, to set clear safety objectives and requirements, to analyse the response of the plant to off-normal events, to assess hazardous inventories, to develop strategies to minimize them, and to identify the main potential contributors to environmental releases and to occupational radiation exposure. Development of computer codes and models for safety analysis is accompanied by selected experimental activities focused on improving their validation, and these models have been used for initial studies of postulated accident scenarios, selected by a formal methodology. Studies of key aspects of waste management are also performed, to minimize the waste burden of DEMO and of fusion power plants that will follow.