Cleaning and inspection experience of UF6 30B cylinders

Operational experience on cleaning and inspection of UF6 30B cylinders started in 1985 is described. Cleaning results show that surface radiation rate of cylinders ranging from 1 μSv (0.1 mrem) ∼ 0.7 mSv (70 mrem) per hour before washing is reduced to 0.2 μSv (0.02 mrem) ∼ 1.5 uSv (0.15 mrem) per hour after washing. Average weight of wet precipitate containing uranium is less than 3 kg per cylinder, which are higher than originally expected. This precipitate is put into polyethylene packs, which contain some 3 kg per pack in average and whose surface radiation dose rate ranges from 0.07 mSv (7 mrem) to 0.85 mSv (85 mrem) per hour. The average amount of process liquid waste is approximately 0.6 m3 per cylinder, and after treatment its α and β radioactivity become <7.4 x 10-3 Bq (2 x 10-7 μCi)/cm3 (α) and <1.1 x 10-1 Bq (3 x 10-6 μCi)/cm3 (β) respectively. Radiation control results such as personnel dose rate, airborne concentration in the restricted area and that of gaseous effluent from the stack and so on are also presented. The radiation dose rate of the operators is very low in both whole body dose and skin dose