No restart for undamaged Fukushima reactors

18 December 2013

The two undamaged units at the Fukushima Daiichi plant - units 5 and 6 - are to be decommissioned, plant operator Tokyo Electric Power Company (Tepco) has confirmed. They may be used as mock-ups for testing technologies for inspecting and cleaning up the four damaged reactors there.

Fukushima Daiichi 5 and 6 - 460 (Tepco)
Units 5 and 6 at Fukushima Daiichi were largely undamaged by the earthquake and tsunami (Image: Tepco)

Reactors 5 and 6, about 200 metres to the north of the damaged units 1 to 4, were shut down for periodic inspections at the time of the March 2011 earthquake and tsunami and remained safe throughout, although they too lost power for a time. Both reactors attained cold shutdown with their water temperatures below 100°C within days of the accident.

While all the fuel has now been removed from the reactor of unit 6 and placed in its used fuel pool, fuel still remains in the core of unit 5. Tepco plans to transfer this to the unit's fuel pool by next September.

The operational fate of units 5 and 6 has remained unclear since the accident, but during a visit to the site in September prime minister Shinzo Abe urged Tepco to decide against trying to restart the two undamaged reactors.

Tepco has now announced that it will not restart the units and has applied to the Ministry of Economy, Trade and Industry (METI) to change their operational status to being decommissioned, as of the end of January 2014. It said that the financial implications of decommissioning the units is under examination.

The company is considering using the units as full-size mock-up testing facilities for verifying remote inspection and decontamination technologies for the inside of reactor buildings, as well as equipment for the removal of fuel debris. Tepco said it is in talks with robot manufacturers and research institutions - including the newly-created International Research Institute for Nuclear Decommissioning (IRID) - about the plan.

Unit 5 is a 784 MWe boiling water reactor (BWR) of the identical capacity and design as units 2 to 4. Unit 6 is a slightly larger (1100 MWe) model of BWR, while unit 1 is a smaller (460 MWe) earlier design. All the units started up between 1971 and 1979.

Researched and written
by World Nuclear News