Accomplishment of JT-60U disassembly work dealing with radioactive components

Ikeda, Yoshitaka; JT-60 Team

The upgrade of the JT-60U to the superconducting tokamak "JT-60SA" has been carried out to contribute the early realization of fusion energy. Disassembly of the JT-60U tokamak was required so as to newly install the JT-60SA torus at the same position in the torus hall. The JT-60U tokamak was featured by the radioactivation due to deuterium-deuterium (D-D) reactions of 1.510 (n) in total. About 13,000 components with a total weight of more than 5,400 tonnes were removed from the torus hall and stored safely in storage facilities with recording the data such as dose rate, weight and kind of material, so as to apply the clearance level regulation in future. It was confirmed that the main radioactive material of the disassembly components was the stainless steel and that its dose rate was almost background level (0.1 micro Sv/h) at 10m far from the vacuum vessel. The assembly of JT-60SA tokamak has started in January 2013 after this disassembly of the JT-60U tokamak.