Activities for accident termination at Fukushima Daiichi Nuclear Power Station and mid and long-term plan for decommissioning

'Road toward accident termination at Fukushima Daiichi NPS' was published by TEPCO in April 2011 and it showed two steps. Step 1 targeted at steady decreasing trend of radiation level within three months after its publishment and Stage 2 was controlled release of radioactive materials and big reduction in radiation level within three or six months after Step 1 completion. Step 1 was confirmed in July 2011 and Step 2 was attained in December 2011 conforming to special ten issues. After completion of Step 2, Government/TEPCO mid and long- term activity council was established to setup mid and long-term activity roadmap and its progress management. Roadmap was divided into three phases of (1) two years, (2) within ten years and (3) 30 - 40 years later. Phase 1 was the period until the start of fuel unloading from spent fuel pools; phase 2 was that of fuel debris unloading and phase 3 was that of decommissioning completion. Activities within three years ware planned in details with possible time target and those after fourth year was rough time target dependent on future site condition and state of R and D. Now R and D on 14 themes (19 proposed) was under progress. Activities were classified into eight items: (1) reactor cooling and accumulated water processing, (2) prevention of ocean contamination, (3) radioactive waste control and reduction of radiation level at the site boundary, (4) site decontamination, (5) fuel unloading from spent fuel pool, (6) fuel debris unloading, (7) reactor dismantling and (8) radioactive materials disposition and processing. (T. Tanaka)