Decommissioning program of JRR-2

Japan Research Reactor No.2(JRR-2), heavy water moderated and cooled tank type research reactor with maximum thermal power of 10 MW, was used over 36 years, and was permanently shut down in December, 1996. Afterward, dismantling report was submitted to the STA, and dismantling was begun in 1997. Decommissioning of JRR-2 is planned in 11 years from 1997 to 2007, and the program is divided into 4 phases. Phase 1 had already been ended, phase 2 is being executed at present. Reactor body will be removed in phase 4 by one piece removal or caisson techniques. On reactor building, it is planned to use effectively as a hot experimental facilities after decommissioning ends. How to treat heavy water and primary cooling system contaminated by tritium becomes an important problem to lead decommissioning to success because JRR-2 is heavy water reactor. On heavy water, transportation to foreign country is planned in phase 2. On primary cooling system, it is planned to remove and dispose the majority in phase 3, and tritium decontamination with technique established by the proof test is planned before them. As a preparation for them, various investigation and examination are being advanced at present. (author)