12 Juin 2013
June 12, 2013
OKUMA, Fukushima Prefecture--A canopy has been completed over a heavily damaged reactor building at the Fukushima No. 1 nuclear power plant in preparation for removing the spent nuclear fuel inside.
Tokyo Electric Power Co. allowed reporters to tour part of the facility, which experienced reactor meltdowns after the 2011 earthquake and tsunami disaster, on June 11.
The upper part of the No. 4 reactor building was blown off in a hydrogen explosion. The canopy covering it will prevent further leakage of radioactive substances when workers remove spent nuclear fuel from the building.
The No. 4 reactor had been shut down for regular maintenance when the tsunami struck, but its storage pool contains 1,533 spent fuel rod bundles that still generate large amounts of heat.
TEPCO has said it will equip the canopy with a hoist to remove spent nuclear fuel from the pool as part of the decommissioning process at the crippled plant.
The plant operator has also been working to improve the reliability of the reactor cooling system following a series of radioactive water leaks that were found at the plant.
Three reactor buildings currently circulate contaminated water accumulated in the buildings to cool melted nuclear fuel. After radioactive substances and salt are removed, the water is temporarily stored in a 1,000-ton storage tank on elevated land before being put back into circulation.
This water circulation system was set up as a makeshift arrangement and uses about 4 kilometers of pipes.
But a new route for circulating the contaminated water to cool the reactors is almost complete. It will use condensate storage tanks that are designed to turn steam used to rotate turbines for power generation back into water and store it.
The tanks, located between the No. 1, No. 2 and No. 3 reactor buildings and the sea, survived the tsunami two years ago. They were shown to reporters on June 11 for the first time since the disaster.
The length of pipes will be reduced to some 3 km, improving the reliability of the cooling system and reducing the risk of water leakages, TEPCO officials said.