The application of the carbon isotope separation method using plasma chemical reactions in carbon monoxide plasma for the recovery of 14 C from the graphite moderator of a dismantled Japanese gas-cooled reactor, Tokai Power Station, was evaluated numerically. The 14 C separation factor of 4.6 in one unit stage was estimated through the numerical simulation of a kinetic model in CO plasma. The calculated results show that the 14 C concentration in the cascade tail flow can be reduced to the environmental standard recommended by the International Commission on Radiological Protection (3 Bq/cm 3) and to the natural abundance level (1:3Â10 À4 Bq/cm 3) in 3 and 16 stages in the stripping section, respectively, and the amount of 14 C-enriched CO flow can be reduced to 1/10 3 and 1/10 6 of the feed CO amount in 9 and 19 stages in the enriching section, respectively. In the case of 3-stage processing in the stripping section and 9-stage processing in the enriching section, it is estimated that the total energy consumption by the plasma generator would be about 15 kW and the maximum inner diameter of the plasma reactor in the cascade would have to be about 60 cm.

The application of the carbon isotope separation method using plasma chemical reactions in carbon monoxide plasma for the recovery of 14 C from the graphite moderator of a dismantled Japanese gas-cooled reactor, Tokai Power Station, was evaluated numerically. The 14 C separation factor of 4.6 in one unit stage was estimated through the numerical simulation of a kinetic model in CO plasma. The calculated results show that the 14 C concentration in the cascade tail flow can be reduced to the environmental standard recommended by the International Commission on Radiological Protection (3 Bq/cm 3 ) and to the natural abundance level (1:3Â10 À4 Bq/cm 3 ) in 3 and 16 stages in the stripping section, respectively, and the amount of 14 C-enriched CO flow can be reduced to 1/10 3 and 1/10 6 of the feed CO amount in 9 and 19 stages in the enriching section, respectively. In the case of 3-stage processing in the stripping section and 9-stage processing in the enriching section, it is estimated that the total energy consumption by the plasma generator would be about 15 kW and the maximum inner diameter of the plasma reactor in the cascade would have to be about 60 cm.