M. Sakane (Department of Mechanical Engineering, Faculty of Science and Engineering, Ritsumeikan University, 1-1-1Nojihigashi Kusatsu-shi Shiga, 525-8577, Japan)S. Mukai (Power Reactor and Nuclear Fuel Development Corporation, 4002 Narita-cho Oarai-cho Ibaragibun Ibaragi,311-13, Japan)