At the crippled Fukushima Daiichi nuclear power plant, workers accidentally dropped a large piece of debris into the Unit 3 spent fuel pool on Friday, a little after noon.
The workers were carrying out operations to remove debris with a large remote controlled crane. At the time of the accident, workers were manipulating the control console for the refueling machine, a piece of equipment that weighs almost a thousand pounds.
Tokyo Electric, who is in charge of cleanup operations at Fukushima Daiichi, told reporters that they have not detected any change in radiation levels around the spent fuel pool after the accident.
TEPCO is working to check the 566 spent fuel assemblies in the Unit 3 spent fuel pool to see if any of them have been damaged by the most recent accident. According to decommissioning plans, the utility is scheduled to start removing spent fuel rods from the Unit 3 spent fuel pool in the first half of 2015 at the earliest.
This is not the first time that debris and large objects have been accidentally dropped, pulled, or pushed into the Unit 3 spent fuel pool. Between 2012 and 2013, TEPCO workers used the remote control cranes to remove debris from atop the Unit 3 reactor building, and multiple instances were recorded where operators moving cranes via remote control knocked debris into the spent fuel pool or dislodged other materials on the roof.
In February 2013, workers accidentally knocked the 1.5 ton fuel handling machine mast into the Unit 3 spent fuel pool, and it was later found to have come to rest on top of the spent fuel racks after it narrowly avoided damaging the liner of the spent fuel pool.