Tritium Distribution in the First Wall of JT-60U

Tritium distribution in the carbon-based plasma-facing wall of JT-60U was examined by imaging plate (IP) technique and full combustion method. The highest tritium concentration was observed at the private region in the divertor. The tritium concentration of the divertor target tiles was lowest. Although significant amount of deposition were observed on the inner divertor tiles, there was no correlation between the deposition layer and the tritium retention in JT-60U. The result of the triton deposition simulation using Orbit Following Monte-Carlo code was consistent with the tritium distribution obtained by the IP technique and the full combustion method. The tritium distribution can be explained by the energetic triton loss due to ripple loss and a slight modification due to high surface temperature of the divertor target tiles. According to the simulation, ~30% of the tritium produced by D-D nuclear reaction in the JT-60U are lost and implanted into the first wall with high energy of up to 1 MeV.