Fukushima operator Tepco has published a digest of its three-phase plan to decommission Fukushima Daiichi units 1-4. The process is expected to take 40 years.

Phase one ends with the start of removal of fuel from the spent fuel pools (beginning with unit 4), and is targeted to end in two years (that is, by the end of 2013). In this operation, a fuel handling machine mounted above the pool would place spent fuel into containers under water, and then the reactor’s overhead crane would lower the containers to ground level. Other tasks in phase one include maintaining on-site dose below 1 mSv/yr, maintain stable reactor cooling and accumulated water processing, starting fuel debris removal R&D and decontamination and starting radwaste processing and disposal R&D.

Phase two ends when the removal of fuel debris gets under way. The debris is solidified material from melted fuel, and the process is scheduled to finish in 10 years (that is, by the end of 2021). Other tasks in phase two include completion of spent fuel removal (unit 3 would be the second pool emptied), perform preparations for fuel debris removal, including decontaminating reactor building interiors, fixing PCV leaks and flooding PCVs, continuing stable reactor cooling, completing processing of accumulated water, continuing fuel debris removal R&D, and starting R&D on reactor facility decommissioning. The detailed plan to remove fuel debris consists of these steps: investigation of PCV leaks in early 2015; verify PCV repair technology on-site in early 2016; flood bottom of PCV; verify PCV inspection technology on-site in early 2017; investigate; repair upper parts of PCVs, and then flood them with water; after installing building cover, open RPV head; verify RPV internal inspection technology by mid-2019; investigate; develop removal methodology; develop debris container; establish method to weigh fuel debris; begin removal.

Phase three ends with total decommissioning of the site, in 30-40 years (by 2041-2051). Other tasks in phase three include completing fuel debris removal (in 20-25 years, that is by 2031-2036), and implementing radioactive waste processing and disposal.

However the document says that for now Tepco is working to a three-year plan from a safety directive produced by the government regulator Nuclear and Industrial Safety Agency called ‘Ensuring mid-term safety’. Targets and schedules will be released on an annual basis.

The document also says that Tepco’s on-site project structure, which includes the input of 400 subcontractors, will continue, although it will work with outside agencies for R&D.

The mid-to-long-term roadmap listed the following steps:

-In 2012, the accumulated water processing equipment will have installed a new processing system to remove ‘multi-reactive nuclides’ that cannot be removed with the current caesium decontamination systems.

-By 2014, water shielding walls will be built around the Fukushima Daiichi harbour to protect the sea from radioactive nuclide leaks. Inside the plant’s breakwater, the seafloor will either be dredged or covered, depending on the location, to further reduce the risk of leaks.

-By 2013, the team will develop a plan to establish R&D for post-accident waste.

The mid and long-term roadmap report was drafted by Tepco and the Japanese government agencies Nuclear and Industrial Safety Agency and the Ministry of Education, Trade and Industry’s Agency for Natural Resources and Energy (ANRE).

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