Some amount of tokamak dust will be inside the ITER vacuum vessel as a result of routine sputtering, disruptions, and possibly maintenance-related activities. The three plasma-facing materials (beryllium, carbon, tungsten) will give rise to a dust mixture with radiological, chemically toxic, and chemically reactive hazards. The project has evolved an approach to ensuring that the public is protected via confinement, limiting chemical reactions, and limiting the dust inventory. This paper provides an overview of the dust safety limits, production, removal, and surveying methods.

A common approach for design and safety regarding an important uncertain parameter is to establish a predictive "design curve" based on the best available information. The design and safety analyses are done on the basis of this design curve, e.g., material properties subject to radiation damage. Validation efforts are required during operation to ensure that the parameter stays within the predictive design curve or corrective actions must be taken.

For dust, the fundamental approach is a predictive rate of dust production as a function of material (Be, C, W), location, number of pulses, and number of disruptions. Such things as periodic global surveys of dust (as now being done in some current tokamaks) and local surveys of dust (such as grab samples) will validate the predictive rate during operation. The rates are compared against dust inventory limits, which are themselves a function of material (Be, C, W) and location. The location impact relates to various postulated event sequences involving temperature increases for different in-vessel surfaces, as well as the potential for dust mobilization (challenging radiological confinement). The dust inventory on replaced components such as the divertor is reset upon replacement. Dust may need to be removed more frequently, suggesting partial cleaning of some locations where the dust accumulation is relatively high and the dust limits are relatively low. The balance of production , limits, and cleaning may be quantified separately for different materials and different locations.