THE POSSIBILITY OF RADIOACTIVE DUST COLLE CTION IN FUSION-REACTOR BY USE OF THERMOPHORETIC FORCE

A large amount of radioactive dusts are generated in fusion reactors a s a result of sputtering and/or plasma disruption, and they adhere and deposit in the vacuum vessel. The condition in the vessel is in high vacuum of 10(-4) Torr order as well as strong electromagnetic field. O nce the vacuum condition is destroyed to collect the dusts, the vacuum pumping of the huge vessel requires at least several days or a week. Therefore, it is necessary for an economical operation to collect the dusts without destroying the vacuum. In this research, a dust collecti ng system that makes use of thermophoresis phenomenon known as a raref action effect of gas is proposed and its experimental verification is performed to examine its possibility. The system is very simple, namel y, temperature gradient is made by setting a low temperature plate clo se to another high temperature wall on which the dusts are deposited a nd the dusts are recovered onto the low temperature plate by the therm ophoresis phenomenon. It has been found that, in principle, it is poss ible to collect the radioactive dusts by weakening adhesive force whic h acts on the dusts and raising temperature gradient enough.