29 Décembre 2014
Dec. 24, 2014
The operator of the Fukushima Daiichi nuclear power plant has taken a big step toward decommissioning the complex. Tokyo Electric Power Company has removed all nuclear fuel from the storage pool of the crippled No.4 reactor building. NHK WORLD's Mitsuko Nishikawa talked to experts who say the hardest work is still to come.
Spent fuel pulled out from the reactor is cooled in a storage pool on the upper floor of the reactor building. At this stage, it still emits high levels of radiation. If the spent fuel isn't kept cool, it could trigger a meltdown. TEPCO chose to remove fuel from the No.4 building first for two key reasons.
First, a hydrogen explosion in 2011 weakened the structure, giving rise to fears that the cooling pool could collapse.
Second, radiation levels are lower here than in the buildings where a meltdown occurred.
The fuel assemblies had to be kept in water at all times. Workers used a crane to transfer them to radiation-proof casks. They then lifted the casks out of the building and transported them to a more stable pool in another area of the complex.
The workers moved more than 1500 units of fuel, most of it dangerous spent fuel.
"We're satisfied that we've managed to hit a significant milestone on the road to decommissioning Fukushima Daiichi," says Yoshimi Hitosugi, a spokesperson for TEPCO, who reports that the job was completed without any setbacks.
But the biggest challenge is still to come. TEPCO has to remove more than 1,500 other fuel units from the 3 reactor buildings that were hit by meltdowns.
Radiation levels are so high in those buildings that workers can only stay for a short time.
"We have to lower the level of contamination in the reactor buildings so that workers can do their jobs smoothly and safely," explains Hitosugi. "We also need to start building new facilities for the cranes that will remove the fuel. We will start that work next year."
Dealing with the fuel isn't the only challenge TEPCO faces. The utility is also trying to stop tainted underground water from flowing out of the complex. There's still a long, rocky road ahead.