Fuel removed from damaged N-plant
Work has started to remove radioactive fuel rods from a reactor at Japan's crippled Fukushima Dai-Ichi nuclear power plant, a crucial first step toward a full clean up of the earthquake and tsunami-damaged plant.
The Unit 4 reactor was offline at the time of the March 2011 disaster, and its core did not melt as Units 1-3 did. But hydrogen explosions blew the roof and walls off the building and weakened the structure, leaving it vulnerable to earthquakes.
Tokyo Electric, known as TEPCO, has since reinforced the building, but experts say keeping so many fuel rods in a storage pool in the building still poses a major safety risk.
"The operation is an important step toward decommissioning Fukushima Dai-ichi, which would take 30-40 years," TEPCO president Naomi Hirose said.
TEPCO has built a massive steel structure next to and partly over Unit 4 to mount cranes for the operation. It will take at least until the end of 2014 to finish moving the 1,533 sets of fuel rods, including 202 unused sets, to a safer location. Each set includes about 60-80 fuel rods containing uranium-based fuel pellets.
The unused fuel rods will be taken first, and then the more radioactive spent fuel. Finally three sets of rods that are slightly damaged will be removed. The storage pools in Units 1-4 contain a total of 80 sets of rods with slight damage, most of which occurred years ago.
The operation is delicate. Experts say the fuel rod sets may have been damaged or jammed by small pieces of debris that fell into the pool during the explosions. Some have also raised concern about a major earthquake hitting during the removal work.
Two other reactors, Units 5 and 6, were also offline at the time of the disaster and eventually went into normal shutdown. They are also expected to be decommissioned.