Tepco engineers have cleared away the top section of Fukushima Daiichi unit 4’s reactot building, ready for work to start on the overbuilding they need for fuel removal.
Unit 4 was heavily damaged by a hydrogen explosion and the used fuel pond has had to be supported by the installation of steel beams and concrete. The pond also contains more fuel than the others on site because the entire core load of fuel had been stored there for maintenance work when the natural disasters struck on 11 March 2011.
For these reasons unit 4’s pond represents one of the biggest hazards on the site, and tackling it by removing the fuel is one of Tepco’s highest priorities. This will involve the construction of a new building over and around unit 4 containing ventilation, filtration and handling gear. To make this all possible, Tepco have had to clear the remains of the roof from the service floor on the fifth level.
The refuelling building will house equipment and provide a safe path for fuel removal
Underwater inspections in the pond have shown most of the fuel to be undamaged, but the pond contains a lot of dust and debris which will complicate its removal. Currently the top of the pond is protected by a metal cover.