1. Research Laboratory for Nuclear Reactors, Tokyo Institute of Technology, Ookayama 2-12-1-N1-14, Meguro-ku, Tokyo 152-8550, Japan
2. Technical Department, Tokyo Institute of Technology, Ookayama 2-12-1-N1-14, Meguro-ku, Tokyo 152-8550, Japan
3. Department of Energy Sciences, Interdisciplinary Graduate School of Science and Engineering, Tokyo Institute of Technology, Nagatsuta-cho 4259-G3-35, Midori-ku, Yokohama, Kanagawa 226-8503, Japan