The possibility of radioactive dust collection in fusion reactor by use of thermophoretic force

A large amount of radioactive dusts are generated in fusion reactors as 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. Once 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 collecting system that makes use of thermophoresis phenomenon known as a rarefaction effect of gas is proposed and its experimental verification is performed to examine its possibility. The system is very simple, namely, temperature gradient is made by setting a low temperature plate close to another high temperature wall on which the dusts are deposited and the dusts are recovered onto the low temperature plate by the thermophoresis phenomenon. It has been found that, in principle, it is possible to collect the radioactive dusts by weakening adhesive force which acts on the dusts and raising temperature gradient enough.