1. Japan Atomic Energy Agency, Nuclear Fuel Cycle Engineering Laboratories 4-33 Muramatsu, Tokai-mura, Naka-gun, Ibaraki 319-1194, Japan
2. Japan Atomic Energy Agency, Advanced Nuclear System Research and Development Directorate, 4-33 Muramatsu, Tokai-mura, Naka-gun, Ibaraki 319-1194, Japan