Fukushima Unit 2 Decommissioning

The decommissioning work at unit 2 of Fukushima Daiichi has been moving at a significant pace in recent years. Unit 2 was spared from the kind of hydrogen explosion damage that ripped through units 1, 3, and 4. This provided more opportunities to install equipment and work in some areas of the building.

Unit 2 has had a handling building installed along the side of the refueling floor level in the same area as the damaged blow-out panel. This access provided the means to remove equipment and decontaminate the refueling floor level. Even with this extensive work completed, the radiation levels on the refueling floor are unsafe for workers.

Spent Fuel Removal Scheduled: FY 2024-2026
Fuel Debris Removal Scheduled: FY 2021*
Fuel debris removal appears to have been deferred since this date was reported earlier in 2021

Spent Fuel Removal

There is a detailed plan for remote removal of the spent fuel from unit 2’s pool.

Airlock building installed to gain access to the refueling floor and for clean-up activities.

Initial plans involved removing the roof and walls of the refueling floor in order to install a building to remove the spent fuel. This plan was scrapped by 2019 for safety reasons and was replaced with a plan that left the original building largely intact but installed a second platform onto the refueling floor level.

fukushima daiichi unit 2 spent fuel removal building

Spent fuel removal building published by TEPCO in 2019

This defueling building includes a negative air pressure system with HEPA filtration and a hatch to transport spent fuel casks down to the ground level. Internal equipment including cranes and a rail system will be operated remotely.

fukushima daiichi unit 2 fuel removal crane and rail

Fuel cask removal rig and rail to be installed inside unit 2’s refueling floor.

Unit 2 Spent Fuel Removal Articles

Fukushima Daiichi Unit 2 Spent Fuel Pool Inspected
Fukushima Unit 2 Spent Fuel Pool Inspection
SimplyInfo.org Annual Report; Unit 2
Fukushima Unit 2 Has A Spent Fuel Removal Plan
Fukushima Unit 2 Spent Fuel Removal Plan May Drastically Change
Fukushima Unit 2 Refueling Floor Inspection Results
Fukushima Unit 2 Refueling Floor Work Progresses, Poses Risks
Fukushima Unit 2 Wall Removal Begins
Fukushima Unit 2 Decomm Progresses
TEPCO Erects Mystery Platform Around Unit 2 Fukushima Daiichi

Fuel Debris Removal

TEPCO has completed multiple inspections inside the reactor pedestal of unit 2. At least a portion of the fuel debris is located there. A future inspection to attempt to remove samples of fuel debris is planned with a deferred start date due to the pandemic. An elaborate plan to use a retractable arm and a series of hot cells to remove the fuel debris from the pedestal is in place. Research and development work began before the pandemic including a fully constructed robot arm, a hot cell, and some other equipment. We detailed this plan in our 2021 annual report.

The diagrams below from TEPCO and IRID help illustrate the fuel removal process.

An access tunnel is planned to be installed inside the reactor building to provide a contained route from the containment hatch to the hot cell and airlock cells.
fuel debris would be moved from containment through the tunnel. The fuel debris is packed into a shielded container, then moved out through the delivery cell.

The above diagram shows the retractable arm inside containment and the interface between the containment wall and the fuel debris removal cells.

The above diagram explains the secure tunnel that will be used to route fuel debris out of the reactor building. The top left image shows a prototype created for testing. This tunnel also has to bridge from outside the reactor building to the containment structure to avoid placing additional load on the building.

The images and diagrams above show an isolation room and robot that would be used to open the X6 hatch into containment in an isolated manner. This would prevent the release of radioactive dust. Photos of the isolation room are from a test run with the equipment at unit 5.

Above diagram of the retractable arm design. that will be installed in containment to remove fuel debris. The end of the arm can be equipped with different cutting and collecting devices.