The evidence indicates that all of the spent fuel pools at Fukushima Daiichi are intact and there are no cracks that contributed to a loss of cooling water for used nuclear fuel assemblies. This is substantiated by observations around the storage pool areas, and the ability to re-establish cooling water levels.
Loss of water in the spent fuel storage pools at Fukushima Daiichi was primarily caused by sloshing of the water during the earthquake and evaporation when the sources of cooling water to the storage pools was temporarily interrupted. Alternative means of providing cooling water to the storage pools was established to ensure that the fuel was covered with water and safely maintained.
As part of its long-term stabilization plan, Tokyo Electric Power Co. is reinforcing the spent fuel storage pool structure in reactor 4 as a precautionary measure.
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