FUKUSHIMA – Tokyo Electric Power Co. said Wednesday it had finished removing all used fuel from the storage pool in the reactor 4 building, leaving only less-risky unused material in the pool.
But dismantling the entire facility still has to overcome the high levels of radioactive substances being emitted by reactors 1, 2 and 3, which suffered meltdowns in the wake of the catastrophic tsunami and earthquake in March 2011.
A total of 1,331 spent fuel rod assemblies have now been moved out of the No. 4 building to more stable conditions in a different building. The No. 4 spent fuel pool is on the top floor of the building, which was rocked by a hydrogen explosion early in the crisis.
Tepco has been removing fuel from the pool since last November, starting with 22 of the 202 unused fuel assemblies that were being stored there.
The removed fuel includes three damaged spent fuel assemblies that were in the pool prior to the nuclear disaster.
The remaining 180 unused fuel assemblies are expected to be taken out by the end of the year, Tepco said.
The process takes place underwater, with the fuel assemblies being placed one by one into a transport container. When the container is filled with fuel assemblies, workers use a crane to take it out of the pool and then lower it from the fifth floor. At ground level it is trucked to a safer pool about 100 meters away.
Reactor 4 did not suffer a meltdown after the tsunami struck because it was offline for a periodic inspection and maintenance work.
Even so, the spent fuel pool on the highest floor of the crumbling building was a major source of concern in the early days of the crisis, as the water level was suspected of dropping enough to expose the fuel rods.
Tepco later said the fuel in the pool probably did not sustain major damage.
Removing the fuel from the three other reactors has been hampered by high levels of radiation.
Tepco has said it will delay the start of the process at reactor 1 by two years to 2019. The effort will be rife with challenges, as the utility has no idea where the melted fuel is located inside the reactor.
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