Approaches to safety, environment and regulatory approval for ITER

Abstract

International Thermonuclear Experimental Reactor (ITER) Engineering Design Activities (EDA) in safety and environment are approaching the point where conceptual safety design, topic studies and research will give way to project oriented engineering design activities. The Joint Central Team (JCT) is promoting safety design and analysis necessary for siting and regulatory approval. Scoping studies are underway at the general level, in terms of laying out the safety and environmental design framework for ITER. ITER must follow the nuclear regulations of the host country as the future construction site of ITER. That is, regulatory approval is required before construction of ITER. Thus, during the EDA, some preparations are necessary for the future application for regulatory approval. Notwithstanding the future host country's jurisdictional framework of nuclear regulations, the primary responsibility for safety and reliability of ITER rests with the legally responsible body which will operate ITER. Since scientific utilization of ITER and protection of the large investment depends on safe and reliable operation of ITER, we are highly motivated to achieve maximum levels of operability, maintainability, and safety. ITER will be the first fusion facility in which overall ‘nuclear safety’ provisions need to be integrated into the facility. For example, it will be the first fusion facility with significant decay heat and structural radiational damage. Since ITER is an experimental facility, it is also important that necessary experiments can be performed within some safety design limits without requiring extensive regulatory procedures. ITER will be designed with such a robust safety envelope compatible with the fusion power and the energy inventories. The basic approach to safety will be realized by ‘defense-in-depth’. The first priority will be in the prevention of accidents through the intrinsic features of the facility, quality assurance throughout, in design, construction, operation and maintenance, and appropriate provisions for human factors. Nevertheless, the plant will be designed to be ready for anomalous events. In addition, public will be protected with appropriate mitigative features, even for extremely unlikely and unforeseen hypothetical accidents to add safety margins as appropriate. Current safety design approaches are introduced in this paper, including a global methodology, off-normal plasma termination, decay heat removal, and containment and confinement strategies.