[en] The focus of this study was to develop recovery technologies in the pyroprocessing. The unit processes of the project can be classified into two groups; electro-refining process to recover uranium and long-lived nuclides, and cathode processing to produce a metal ingot both from a salt-contained metal and from Cd-contained metal. This project has been carried out for the third phase period of the long-term nuclear R and D program, and focused on the development of key technologies of the pyroprocessing such as electrorefining, draw down and cathode processing. Mock-up system of 1 kg-U/batch was built for performance tests which were conducted to ensure the adequacy of the research and development of the pyroprocessing technology. The experiments were carried out through bench-scale inactive tests except for uranium. In particular, the sticking problem was inevitable in the US's Mark-V and PEER electrorefiner. As a result of this study, a graphite cathode was developed, which exhibited self-scraping behavior and did not need scraping step. The design of an electrorefiner could be simplified, and the throughput was enhanced due to an increased cathode area. A long-term R and D plan was established to develop pyroprocessing technology. In the near term, the results of the current project will be utilized in the next phase of the R and D plan ('07 - '10), and long-term wise, is expected to contribute to recovering fuel materials for transmutation in a Gen-IV reactor