Tokyo Electric Power Co. told nuclear regulators Friday that human error was likely responsible for the highly radioactive water that got pumped into the wrong building at the Fukushima No. 1 power plant in March and that the tainted building is being turned into a makeshift water tank.
According to the hapless utility, workers might have mistakenly turned on the transfer pumps when they were actually trying to turn on the air conditioners in two buildings instead, including the one mistakenly flooded with toxic water.
The switches for the pumps and the air conditioners are on the same power distribution board but were not specifically labeled.
The building erroneously tainted with the radioactive water has since been prepared to serve as a temporary storage space for the tainted water the plant generates on a daily basis to cool its crippled reactors.
Tepco has not been able to confirm that any water leaked from the building, because it has not detected any significant changes in the radiation of groundwater nearby.
Tepco on April 13 found that four pumps inside the two buildings were running even though they were not supposed to be. That means it took more than 20 days to notice the accidental water transfer was under way.
At the Fukushima plant, the water used to cool the three crippled reactors is accumulating in the basements of several buildings. After some filtration, some of it is recycled as coolant while the remainder is stored in tanks for future decontamination. But the plant is rapidly running out of storage space.