Safe disassembly and storage of radioactive components of JT-60U torus

• We describe the results of the JT-60U disassembly activities, including treatment of the radioactivated materials and safety work during 2009–2012.
• This disassembly was required to newly install the JT-60SA torus at the same position in the torus hall.
• About 13,000 components cut into pieces with measuring the contact dose were removed from the torus hall and stored safely in storage facilities.
• The total weight of the disassembly components reached up to ∼5,400 tons.
• We expect that the project of the JT-60U disassembly has provided the valuable data which will be useful for the disassembly of other fusion devices.

Disassembly of the JT-60U torus was started in 2009 after 18 years of D2 operations and was completed in October 2012 for assembling the JT-60SA torus at the same position. The JT-60U torus was featured by the complicated and welded structure against the strong electromagnetic force, and by the radioactivation due to deuterium–deuterium (D–D) reactions. Since this work is the first experience of disassembling a large radioactivated fusion device in Japan, careful preparations of disassembly activities, including treatment of the radioactivated materials and safety work, have been made. During the disassembly period over 3 years, careful measures against exposure were taken and stringent control of exposure dose were implemented, and as a result, accumulated collective effective dose of ∼41,000 person-day to workers was only ∼22 mSv in total and no internal exposure was observed. About 13,000 components cut into pieces with measuring the contact dose were removed from the torus hall and stored safely in storage facilities. The total weight of the disassembly components reached up to ∼5400 tonnes. Most of the disassembly components will be treated as non-radioactive ones after the clearance level inspection under the Japanese regulations in the future. The assembly of JT-60SA has started in January 2013 after this disassembly of JT-60U torus.