1. Department of Nuclear Engineering, Nagoya University, Nagoya 464-01
2. Japan Atomic Energy Research Institute, Tokai-mura, Naka-gun, Ibaraki 319-11
3. Japan Atomic Energy Research Institute, 1233 Watanuki-cho, Takasaki, Gunma 370-12
4. Department of Energy Engineering and Science, Nagoya University, Nagoya 464-01