1. Nuclear Professional School, School of Engineering, The University of Tokyo, 2-22 Shirakata Shirane, Tokai-mura ,
Naka-gun, Ibaraki 319-1188, Japan
2. Department of Nuclear Engineering and Management, School of Engineering, The University of Tokyo, 7-3-1 Hongo, Bunkyo-ku, Tokyo 113-8656, Japan
3. Horonobe Underground Research Center, Japan Atomic Energy Agency, Hokushin 432-2, Horonobe-cho, Hokkaido 098-3224, Japan
4. Nuclear Fuel Cycle Engineering Laboratories, Japan Atomic Energy Agency, 4-33 Muramatsu, Tokai-mura, Ibaraki 319-1194, Japan