1. Nuclear Science and Engineering Directorate, Japan Atomic Energy Agency, 2-4 Shirane, Shirakata, Tokai-mura, Naka-gun, Ibaraki, Japan
2. Sumitomo Metal Technology, Inc., Amagasaki, Japan
3. Institute of Fluid Science, Tohoku University, Sendai, Japan
4. Advanced Nuclear System Research and Development Directorate, Japan Atomic Energy Agency, Ibaraki, Japan