Tokyo Electric Power Co. said Wednesday that radiation levels exceeding 10 sieverts have been detected in the flooded basement of reactor 1 at the crippled Fukushima No. 1 nuclear plant, a development that will hamper its decommissioning.
Radiation from the basement water was found to be as high as 10,300 millisieverts an hour, a deadly intensity that will deliver the maximum annual dose in only 20 seconds and sicken anyone who is exposed within minutes.
“Workers cannot enter the site and we must use robots for the demolition,” Tepco said.
Tepco took samples from the basement by inserting a camera and surveying instruments through a drain hole in its ceiling.
Tepco said the radiation level in unit 1, the first of the three reactors hit by hydrogen explosions and meltdowns during the crisis, is 10 times higher than in units 2 and 3, which also suffered meltdowns.
The high radiation is a result of the poor state reactor 1’s core was left in after the meltdown.
The core meltdowns at three of the plant’s six reactors occurred after the March 11, 2011, earthquake and tsunami plunged the poorly protected plant into a blackout and destroyed its cooling systems.
The decommissioning of reactors 1 to 3, as well as unit 4, which didn’t have a meltdown, is expected to take 40 years and will require the use of new technologies.