R&D on in-vessel dust and tritium management in ITER

In a tokamak, plasma-wall interactions can result in production of dust. During operation, the tritium present in the Vacuum Vessel (VV) can then be trapped in the in-vessel materials but also in dust. The vacuum vessel represents the first confinement barrier to this radioactive material. In the event of a postulated accident involving ingress of steam into the VV, hydrogen could in principle be produced by chemical reaction with hot metal and dust. If the ingress of air into the VV is also postulated, reaction of air with hydrogen and/or dust cannot be completely excluded and could lead to a possible explosion which could challenge the VV tightness. In order to prevent such accidents and their radiological consequences, limitations on the accumulation of dust and tritium in the VV and on the air ingress are imposed. Correlatively, ITER has defined a strategy for the control of in-vessel dust and tritium inventories based on both measurement and removal techniques. In this context, this paper reports on the status of tasks under F4E responsibility aiming at developing some of the measurement systems and necessary R&D for the validation of the ITER strategy.