1. Department of Applied Quantum Physics and Nuclear Engineering, Kyushu University, 744 Motooka, Fukuoka 819-0395, Japan
2. Department of Advanced Energy Engineering Science, Kyushu University, 6-1 Kasugakouen, Kasuga, Fukuoka 816-8580, Japan
3. Japan Atomic Energy Agency, 4002 Narita, Ooarai, Higashiibaraki, Ibaraki 311-1313, Japan