2014 年 49 巻 4 号 p. 180-189
The Japan Atomic Energy Agency (JAEA) planned to apply the clearance system to slightly contaminated concrete debris with radionuclides, which was generated from the modification of the Japan Research Reactor No. 3 (JRR-3) in the Nuclear Science Research Institute (NSRI) of JAEA. The modification work was conducted from 1985 to 1990 and the generated concrete debris has been stored as radioactive waste in interim storage facilities in the NSRI. This is the Japanese first application of clearance system to concrete debris and stored waste. We established procedures for measuring and evaluating the radioactivity concentration of sored concrete debris. In 2008, the authority approved these procedures for clearance. Since 2009, we have been measuring and evaluating the radioactivity concentration of concrete debris, using the approved procedures. By the end of 2012, the authority had confirmed the correctness of our measurement and evaluation results on about 2,600 tons of concrete debris. About 1,800 tons of those cleared concrete were recycled to flat surface subsidence in the NSRI caused by the Great East Japan Earthquake, and also used as base material to construct new buildings and parking lots in the NSRI.