Roof removed from Fukushima Daiichi unit 1 cover

The final roof panel of the temporary cover over the damaged reactor building of unit 1 at Japan's Fukushima Daiichi nuclear power plant has been removed. The walls of the structure remain around the reactor building.

The final roof panel of the temporary cover over the damaged reactor building of unit 1 at Japan's Fukushima Daiichi nuclear power plant has been removed. The walls of the structure remain around the reactor building.

Removal of the final roof panel (Image: Tepco)

In late July, Tokyo Electric Power Company (Tepco) announced that it had removed the first of six roof panels from the cover using a remotely-controlled crane. Each panel is some 7 meters wide and 42 meters long.

Tepco said, "No significant fluctuations in radioactive concentrations [were] found by the dust monitors or from monitoring posts installed at the borders of the site." It added, "After conducting investigations on the condition of rubble and dispersing anti-scattering agents, steel beams will be removed as they obstruct the installation of a water-spraying facility."

The roof of the cover - installed in October 2011 to prevent the dispersal of radioactive materials - has been dismantled to enable rubble to be taken down from the top of the building in preparation for the removal of fuel from the unit's used fuel pool.

Tepco began preparations for its removal last October, which included drilling holes into the cover and spraying an agent to suppress dust scattering. The company temporarily removed one of the roof panels to check the efficiency of the dust suppressant.

The operation to remove the cover had originally been scheduled to start in July 2014. However, it was postponed owing to a problem with a device that controls the circulation of air within the building, as well as a problem with the crane.

The removal of the walls of the cover is scheduled to be completed by the end of next year. Tepco will then install equipment for handling the used fuel before strengthening the surrounding area for heavy machinery and rebuilding a new version of the cover. The entire process is planned to continue for about four years before the removal of used fuel actually begins.

Researched and written
by World Nuclear News