Investigation of a New Dry Surface Decontamination Technology with Low-Pressure ArcPlasma and Its Application to Pipe-Shaped Test Pieces

We investigated a dry surface decontamination technology using low-pressure arc plasma for radioactive corrosion product films. The low-pressure arc plasma is produced with a transferred-type DC arc discharge that operates under reduced pressure; here, the cathode is the object to be treated. The cathode spots formed inside the low-pressure arc plasma can melt away the metal oxide film on the surface of the object without significantly damaging the metal substrate. One of the major advantages of this technology is its potential to reduce the amount of secondary waste compared with existing technologies, e.g., decontamination with chemical solutions, because it eliminates the need for a medium. In this report, the dependence of the decontamination performance on the type of plasmasource gas was investigated. Argon, hydrogen, chemically active carbon monoxide, and a mixed gas of CF4/O2 were selected. Consequently, a higher Cobalt-60 removal ratio was obtained with smaller electric charges in the hydrogen low-pressure arc plasma. The low-pressure arc plasma was also applied to pipe-shaped test pieces with a corrosion product film. And eventually, a Co removal ratio exceeding 90% was achieved. The applicability of the dry surface decontamination technology with low-pressure arc plasma for radioactive metal waste with a corrosion product film is demonstrated.