13 Feb (NucNet): A robot sent into the Unit 2 primary containment vessel (PCV) at the Fukushima-Daiichi nuclear power station has measured radioactivity as high as 650 sieverts per hour (Sv/hr), Tokyo Electric Power Company (Tepco) has said.
Tepco said the robot had been sent into the PCV on 9 February 2017 to clear a path for a “scorpion” robot to further explore the inside of the PCV.
Tepco said “various safety precautions” were taken to ensure that radiation remained inside the PCV and to protect the robot.
The robot and its cameras are designed to withstand 100 Sv/hr for 10 hours and the time it spends inside the PCV is being adjusted as necessary.
Tepco said on 8 February 2017 that the radiation level in the Unit 2 PCV may have reached as high as 530 Sv/hr, but that reading was only an estimate based on analysis of images from the robot with a margin of error of 30%.
Tepco said those images were “intriguing”, but further examination was necessary before it could be verified that they showed fuel debris from the March 2011 accident.
That estimate of 530 Sv/hr far exceeded the previous high of 73 Sv/hr recorded at the reactor following the accident. At this level of radioactivity, a person could die from the briefest of exposures.
At the time Tepco said it would not be surprised if even higher radiation levels were found there, but only actual measurements would tell.
Tepco said there had been no change to radiation readings outside the PCV.
