Decontamination Process Using CF4-O2 Microwave Discharge Plasma at Atmospheric Pressure.

Abstract

Application to decontamination is proposed of microwave discharge plasma in carbon tetrafluoride and oxygen mixture at atmospheric pressure. Preliminary cold experiments were conducted using cobalt oxide deposited on stainless steel plate. Fluorine atoms proved to be generated in high concentration in the plasma, which fluorinated the deposited metal oxide into volatile gaseous form. Upon plasma irradiation during about 200 s, the cobalt oxide deposit was removed to 100% from plate surface. Thermodynamic equilibrium calculations on CF₄-O₂ systems containing cobalt served to elucidate the mechanism of metal oxide removal by microwave discharge plasma, and similar calculations on systems containing actinides (U, Pu etc.) and lanthanides (La, Gd etc.) indicated that the process should be applicable also to the removal of these radioactive elements. It is concluded from the experimental and calculated results that decontamination is basically feasible with the proposed method of using microwave discharge plasma in a CF₄-O₂ system at atmospheric pressure.