Fukushima Daiichi operator TEPCO said Wednesday that it had completed the task of removing 400 metric tons of spent fuel from the plant's Unit 4 storage pool that was among the most threatening aspects of the catastrophic events of March 2011, when the six-reactor nuclear plant was rocked by an earthquake and tsunami.
While Units 1,2 and 3 suffered partial meltdowns, Unit 4 was offline for routine maintenance, when the disaster struck. Unit 4, consequently, did not suffer from a meltdown event, but a hydrogen explosion badly damaged the building that held its storage pool, which was on the top floor of the building.
The company, which began removing the assemblies in November 2013, said there were 180 unused fuel assemblies that still needed to be removed, but this was a far less risky task than the one just completed, which involved moving 1,331 spent fuel assemblies.
The milestone in the plant's cleanup is nowhere near to closure for the disaster. Units 1, 2 and 3 still contain highly radioactive materials. It was recently decided that operations to remove fuel from Unit 1 would be delayed for two years. That is expected to begin in 2019.
The 1,331 removed assemblies have now been placed in a ground-level pool and will be assessed for potential leaks, the Japan Times reported.