The debris is part of a heavy-duty hoist formerly used to move fuel assemblies within the No. 3 reactor building. The hoist collapsed into the pool after a hydrogen explosion in March 2011.
Until now, it lay only partially submerged and was believed to have done little damage to the fuel rods beneath.
But on Feb. 7, Tokyo Electric Power Co. officials said work a day earlier to shift an unrelated steel frame nearby caused “vibrations” which dislodged the hoist. It fell, disappearing beneath the water surface.
TEPCO now plans to drop a video camera into the pool to check whether the hoist has smashed fuel rods below. Officials say 566 fuel assemblies are currently lying in the pool at the No. 3 reactor building.
They insisted there has been no significant change in radioactive concentrations measured in the pool and in the atmosphere since before the latest incident.
However, as reported by Fukushima diary, there has been a significant change in the radiation data, confirming that there may be new damage to the spent fuel- this is stuff that should not be jolted and is precision placed to keep them at certain intervals to moderate the temperature.
Also, the spent fuel pool is meant to be encapsulated by lead and steel to curb the release of radiactivity into the environment.
10 million Bq still reported per hour from the destroyed plant.