[1] Decommissioning and Radioactive Waste Management Head Office, Japan Atomic Energy Agency, 4-49 Muramatsu Tokai‐mura, Naka-gun, Ibaraki, 319-1112, Japan
[2] Department of Applied Energy, Graduate School of Engineering, Nagoya University, Furo-cho, Chikusa-ku, Nagoya-shi,464-8603, Japan
[3] Horonobe Underground Research Center, Japan Atomic Energy Agency, 432-2 Hokushin, Horonobe-cho, Teshio-gun, Hokkaido, 098-3224, Japan