Nuclear power plants have been attracting significant attention worldwide as a tool to solve global environmental problems and maintain world energy security without depending on fossil fuels. However, as conventional nuclear power plants are using uranium resources, there is still an energy depletion problem with fossil fuels. In this context, Development on Fast Breeder Reactors (FBR) capable of effectively utilizing uranium resources has started to attract attention worldwide again. As FBR is designated as Japan's "essential national technology," development on FBR is being accelerated. The Japanese government has also started to address the global trend by pushing ahead with discussions on international partnerships with France and the United States. Two years ago, Mitsubishi Heavy Industries (MHI) was selected as the core firm to exclusively undertake FBR development in Japan. MHI has been working on new tasks to develop commercially feasible FBR by setting up Mitsubishi FBR Systems, Inc. (MFBR), which specializes on the study and research and developments (R&D) of FBR.