Tokamak dust, characterisation and removal studies

Dust and flakes are generated during operation of next step tokamaks such as ITER by plasma interaction with plasma facing components. Accumulation of this particulate engenders potential safety problems, the main ones being chemical reactivity (hydrogen), mobilisation of radioactive dust in a loss of vacuum event, and tritium retention within the plasma chamber. The present prediction for the annualised particulate generation rate is many times more than the currently foreseen safety limits for in-vessel dust inventory. Thus, means may have to be provided to remove particulate on a routine basis. If a vacuum break is needed for batch particulate removal, the resulting reduction in tokamak availability may be unacceptable. Ideally, means should be provided to collect and remove particulate without breaking the vacuum, on a quasi-continuous, intra-shot basis. Vibratory conveying (VC) is one approach to particulate removal. This paper reports initial characterisation of surrogate materials used to emulate tokamak particulate, preliminary results from a small-scale VC test rig, and concepts for implementing VC in a tokamak, (C) 2001 UKAEA. Published by Elsevier Science Ltd. All rights reserved.