Dust Combustion Safety Issues for Fusion Applications

摘要: This report summarizes the results of a safety research task to identify the safety issuesand phenomenology of metallic dust fires and explosions that are postulated for fusionexperiments. There are a variety of metal dusts that are created by plasma erosion anddisruptions within the plasma chamber, as well as normal industrial dusts generated in themore conventional equipment in the balance of plant. For fusion, in-vessel dusts aregenerally mixtures of several elements; that is, the constituent elements in alloys and thevariety of elements used for in-vessel materials. For example, in-vessel dust could becomposed of beryllium from a first wall coating, tungsten from a divertor plate, copperfrom a plasma heating antenna or diagnostic, and perhaps some iron and chromium from the steel vessel wall or titanium and vanadium from the vessel wall. Each of theseelements has its own unique combustion characteristics, and mixtures of elements mustbe evaluated for the mixture's combustion properties. Issues of particle size, dusttemperature, and presence of other combustible materials (i.e., deuterium and tritium)also affect combustion in air. Combustion in other gases has also been investigated todetermine if there are safety concerns with "inert" atmospheres, such as nitrogen. Several coolants have also been reviewed to determine if coolant breach into the plasmachamber would enhance the combustion threat; for example, in-vessel steam from a watercoolant breach will react with metal dust. The results of this review are presented here.