Fukushima Daiichi nuclear power station located on the Pacific coast in Okuma, Japan, has been undergoing a planned decontamination and decommissioning programme since it was damaged by the 2011 Japan earthquake and tsunami.
Owned and operated by Tokyo Electric Power Company (TEPCO), the 4,696MW nuclear power station comprised six boiling water reactors (BWR).
The reactor units at the power station commenced commercial operation in succession, starting with the unit one that was commissioned in March 1971 through the unit six that started commercial operation in October 1979.
When the disaster struck on 11 March 2011, units one, two and three were in operation, whereas units four, five and six were in outage for periodic inspection.
Units one to four got damaged during the disaster and all reactor units of the plant were brought to cold shutdown in December 2011. Units five and six were permanently shut down in December 2013.
In April 2014, TEPCO formed the Fukushima Daiichi Decontamination & Decommissioning Engineering Company, in partnership with the Japanese Government and key contractors, to implement the decommissioning project, which is expected to take up to 40 years for completion.
Fukushima Daiichi decommissioning project details
Contaminated water treatment, nuclear fuel removal, and radioactive waste management are the three main components of the Fukushima decontamination and decommissioning project.
After the disaster, the reactors were stabilised by cooling through continuous water injection and covered by steel frame reactor covers to prevent radioactive releases.
A Simplified Active Water Retrieve and Recovery System (SARRY) water treatment facility to treat contaminated water, especially for removing Cesium, was brought into operation in August 2011, which was followed by other water treatment facilities including the Multi Radio-nuclide Removal Systems (MRRS) and Advanced Liquid Processing System (ALPS).
Removal of used fuel from spent fuel pools was completed in 2014.
Construction of an impermeable wall, which involved driving 594 steel pipe sheet-piles deep into the earth to block groundwater flow from the plant site, was completed in October 2015.
Removal of highly contaminated water from seawater piping trenches for the reactor units was completed by December 2015.
The immediate next task is to remove melted fuel debris, which is expected to begin by 2021.
Use of robots for Fukushima Daiichi decontamination
Different types of robots including shape-changing robots, crawler robots and, more recently, a submersible robot have been used to figure out the highly radioactive areas inside the reactor buildings.
Remote-controlled robots are expected to be used to perform decontamination of the high-dose radiation area and removal of fuel debris from the reactor pressure vessel.
Financing for Fukushima Daiichi decommissioning
The Fukushima Daiichi nuclear power plant decommissioning and decontamination project including the compensation payout to victims was estimated to cost $195bn in 2017. The decommissioning of Fukushima Daiichi reactors alone was estimated to cost $71bn.
At current estimates, TEPCO is required to contribute $143bn and Japan’s Ministry of Finance will provide $17bn, whereas the remaining $35bn will be provided by other power companies and new electricity providers.
Nuclear Damage Compensation and Decommissioning Facilitation Corporation (NDF) was originally established in September 2011 and reorganised in August 2014 by the Japanese government to manage the fund for supporting the Fukushima Daiichi compensation, decommissioning and decontamination expenses.
NDF had provided $73bn of financial assistance to TEPCO as of July 2018.
Contractors involved with Fukushima Daiichi decommissioning
TEPCO is undertaking the decommissioning work in association with key contractors Hitachi-GE, Toshiba and Mitsubishi Heavy Industries, as well as with collaborative support from international and Japanese government agencies.
Japanese construction company Kajima Construction has been responsible for major clean-up works at Fukushima Daiichi, including the construction of impermeable wall to block groundwater flow from the plant site, as well as the closure of seawater pipe trenches.
The providers of various water decontamination technologies and equipments used at the site are Kurion, Areva, Toshiba, The Shaw Group, and Energy Solutions.
Tokyo Electric Power Company (Tepco) has contracted the US Southwest Research Institute SwRI to explore the use of drones within the reactor containments and assess the situation.
UK-based Createc and Blue Bear Systems collaborated to develop the Remote Intelligence Survey Equipment for Radiation (RISER), a small drone less than 1m in diameter, deployed within the unit three reactor in February 2018.
Toshiba and International Research Institute for Nuclear Decommissioning (IRID) jointly developed a submersible robot called Underwater ROV, which was deployed in July 2017.
Hitachi-GE Nuclear Energy developed two shape-changing robots that were deployed in April 2015.
Quince, Sakura and MHI-HERCULeS robots deployed at Fukushima Daiichi site were developed by Mitsubishi Heavy Industries (MHI) in collaboration with Chiba Institute of Technology (CIT).
The maintenance equipment integrated system of telecontrol robot (MEISTeR) deployed in February 2014 was also developed by Mitsubishi Heavy Industries.
MHI appointed James Fisher Nuclear, a company based in the UK, to develop a prototype device to remotely sample radioactive debris located inside the damaged reactor units, in 2016.
Createc was awarded a contract by Mitsubishi for providing radiation sensors for the identification of fuel debris from the reactor units in 2016.
Atkins was awarded the contract to undertake fire hazard analysis services at the Fukushima Daiichi nuclear power station in June 2015.
The Japan Atomic Energy Agency (JAEA), Hitachi-GE Nuclear Energy and Sugined signed a joint research agreement in July 2015 to develop laser technology for the removal of fuel debris from the damaged reactors at the Fukushima Daiichi nuclear power plant.