Journal of Nuclear Fuel Cycle and Waste Technology

In this study, plasma processing of metal surface is experimentally investigated to enhance the surface decontamination efficiency and to find out the reaction mechanism. Cobalt, the major contaminant in the nuclear facilities, and three fluorine-containing gases, CF4/O2, SF6/O2, and NF3 are chosen for the investigation. Thin metallic disk specimens are prepared and their surface etching reactions with the three plasma gases are examined. Results show that the maximum etching rate of 17.2㎛/min. is obtained with NF3 gas at 420℃, while with CF4/O2 and SF6/O2 gas plasmas those of 2.56㎛/min. and 1.14㎛/min. are obtained, respectively. Along with etching experiments, constituent elements of the reaction products are identified to be cobalt, oxygen, and fluorine by AES (Auger Electron Spectroscopy) analysis. It turns out that the oxygen atoms are physically adsorbed ones to the surface from the ambient not participation ones during the analysis after reaction, which supports that the surface reaction of cobalt is mainly to be a fluorination reaction.

Keywords

Metal surface decontamination,cobalt,reactive plasma etching,Auger electron spectroscopy