Decommissioning of accelerator facility. Example of the Tanashi Branch, High Energy Accelerator Research Organization

The decommissioning of the Tanashi Branch was the first example of the decommissioning of a large accelerator complex including electron, charged particle and heavy ion accelerators in Japan. In order to perform the decommissioning work safely and properly, various radiation and radioactivity measurements were performed. Several methods of decontamination were also planned and tried. Careful evaluation of residual radioactivity in various materials was very important for reducing the radioactive waste. Many kinds of accelerator components and shielding materials were transferred and reused at the various accelerator facilities of universities and research institutes. All accelerators were decommissioned perfectly within a year. After removal of all buildings, vacant land was changed to the park. The decommissioning of electron synchrotron and cyclotron facilities is introduced in this report. (author)