Overview of goals and performance of ITER and strategy for plasma–wall interaction investigation

Recent progress in experiments, modeling and theory has increased confidence that ITER can achieve its goal of high Q (>10) in inductive operation. Further, experimental results in the ‘improved hybrid’ regime suggest a possibility of high Q (>10) operation in a long pulse (>1000 s) with benign ELMs. However, considerable uncertainty still exists in the prediction of several key aspects; for example, tritium retention, disruption, impurity control, ELMs, SOL transport and dust. ITER requires flexibility of operation scenarios at least in the early operation phase to accommodate uncertainties in prediction, to explore wide operational spaces and to incorporate newly developed control schemes. Because of these uncertainties conservative assumptions are adopted in performance predictions, and step-wise implementation of reactor-relevant plasma-facing material, such as tungsten, are planned.