1. Graduate School of Engineering Osaka University; 2-1 Yamadaoka, Suita Osaka 565-0871 Japan
2. Research Institute of Nuclear Engineering University of Fukui; 1-2-4 Kanawa-cho, Tsuruga Fukui 914-0055 Japan
3. Center for Exploratory Research Research and Development Group Hitachi, Ltd.; 1-280, Higashi-koigakubo, Kokubunji Tokyo 185-8601 Japan
4. JST, PRESTO; 4-1-8 Honcho, Kawaguchi Saitama 332-0012 Japan