1. Department of Science Education, Division of Educational Sciences, Graduate School of Humanities and Social Sciences, Hiroshima University, 1-1-1 Kagamiyama, Higashi-Hiroshima 739-8524, Japan
2. Fast Reactor Cycle System Research and Development Center, Japan Atomic Energy Agency, 4002 Narita, Oarai, Higashi-Ibaraki 311-1393, Japan