The work toward decommissioning of unit 1 through 4 of Fukushima Daiichi Nuclear Power Station of Tokyo Electric Power Company Incorporated

Since accident at Fukushima Daiichi nuclear power station (NPS), TEPCO had made strenuous efforts to settle the accident under the cooperation of the government and others concerned. At present, various works towards decommissioning had been done according to the revised mid-and-long-term roadmap decided by 'Council for the Decommissioning of TEPCO's Fukushima Daiichi NPS' on June 27, 2013. This article described present state and future perspective of decommissioning works based on mid-and-long-term action plan. 'Cold shutdown condition' was maintained at Units 1-3. The RPV bottom temperature and the PCV gaseous phase temperatures at Units 1-3 were ∼30-50degC (as of August), and maximum total release rate of radioactive materials was ∼0.01 billion Bq/h and radiation exposure dose at site boundaries was 0.03 mSv/year. Highly radioactive water accumulated in the building basement had been treated to be used for reactor cooling and contaminated water generated in this process was treated and stored. Several countermeasures against accumulated water increased by groundwater intrusion were prepared so as to mitigate sea water contamination and reduce the impact of radiation on the area outside the power station. According to revised mid-to-long-term roadmap towards the decommissioning of Units 1-4, current activities were: (1) preparation for fuel removal from the spent fuel pool and (2) R and D for fuel debris removal and radioactive waste processing and disposal. R and D consortium International Research Institute for Nuclear Decommissioning (IRID) was founded on August for R and D for nuclear decommissioning, advancing international/domestic alliance for decommissioning and human resource development for nuclear R and D. (T. Tanaka)