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.