Rubble removal progresses at Fukushima Daiichi 3

A hatch weighing some 2.6 tonnes has been removed from the used fuel pool of unit 3 at the damaged Fukushima Daiichi nuclear power plant in Japan. The hatch was one of the largest remaining pieces of rubble in the pool.

A hatch weighing some 2.6 tonnes has been removed from the used fuel pool of unit 3 at the damaged Fukushima Daiichi nuclear power plant in Japan. The hatch was one of the largest remaining pieces of rubble in the pool.

The hatch prior to its removal from the fuel pool (Image: Tepco)

The section of the reactor building that sheltered the service floor of unit 3 was wrecked by a hydrogen explosion three days after the tsunami of March 2011 - leaving the fuel pond exposed and covered by debris including machinery and many twisted steel beams.

Tokyo Electric Power Company (Tepco) said today that the CUW F/D hatch - a hatch on the reactor building operating floor next to the used fuel pool for shielding filter demineralizer in the clean-up water system - had been successfully removed on 15 October. The hatch was clamped within a special jig and removed using wires and a crane, the company said.

Following the removal of the hatch, Tepco plans to employ an underwater camera in the pool to investigate the condition of the 566 fuel assemblies within it.

The hatch's removal follows that of the 20-tonne fuel handling machine in early August. Tepco referred to that equipment as the "largest and most complex piece of rubble" in the fuel pool. Its removal cleared the way for the remaining rubble and the used fuel in the storage pool to be removed.

Once all the larger pieces of rubble have been removed from unit 3's fuel pool, Tepco plans to install a protective cover over the unit to protect it from the weather and prevent any release of radioactive particles during subsequent decommissioning work.

The fabrication of this cover has been under way since November 2013 at the Onahama works in Iwaki city. It has been made in sections so that once it is transported to Fukushima Daiichi, the time to assemble it can be shortened and the radiation exposure to the workers on site can be significantly reduced, Tepco said.

A separate structure will be built to facilitate the removal by crane of used fuel from the storage pool. This 54-metre-tall structure will include a steel frame, filtered ventilation and an arched section at its top to accommodate the crane. Measuring 57 metres long and 19 metres wide, it will not be fixed to the reactor building itself, but will be supported on the ground on one side, and against the turbine building on the other.

The fuel removed from unit 3 will be packaged for transport to the site's nearby communal fuel storage pool, although it will need to be inspected and flushed clean of dust and debris.

Researched and written
by World Nuclear News