Decontamination of radioactive metal surface by atmospheric pressure ejected plasma source

An atmospheric pressure ejected plasma source has been developed and applied to the decontamination of cobalt-contained oxide layer on metal surfaces. A helium-based discharge with relatively low gas temperature of approximately 200∼300 °C has been used for the decontamination. Small amounts of CF₄ and O₂ gases are added into helium plasmas as reactive species for carbonylation and fluorination of cobalt. Treatments are performed with various operating parameters such as RF power, treatment time and CF₄/O₂ gas flow ratio and so on. Decontamination ratios of approximately 95% have been achieved through both gasification and solidification. With the increased reactive gases, the decontamination processes are expedited via gasification, and decontamination ratios solely by gasification have reached up to approximately 70%, indicating the necessity of extra effort of removing solidified powder components.