Characterization on the radioactive aerosols dispersed during plasma arc cutting of radioactive metal piping

Shimada, Taro ; Tanaka, Tadao 

In order to understand the production and dispersion behavior of radioactive aerosols during dismantling of nuclear facilities, plasma arc cutting experiments were conducted. Particle size distribution of the aerosols was obtained by sampling air into ELPI which could classify particles into 12 stages of 50% cutoff aerodynamic diameter ranging from 0.007 to 9.9 m. Co specific radioactivity of diameter 0.05 m during cutting of surface contaminated piping indicated the maximum value of approximately 2.7E+4 Bq/g which was fifty times as much as the average value of all of aerosols. That of 9.9m was approximately 100 Bq/g which was the eighth part of the average value. Compared with those for the activated piping, the difference of specific radioactivity between maximum and minimum values were larger in contaminated piping. It is considered that contaminants on the piping were directly melted and vaporized by plasma arc and then condensed into smaller particles.