Radiation levels of up to 530 Sieverts per hour were detected inside an inactive Reactor 2 at the Fukushima Daiichi nuclear complex damaged during the 2011 earthquake and tsunami catastrophe, Japanese media reported on Thursday citing the plant operator, Tokyo Electric Power Company (TEPCO).
A dose of about 8 Sieverts is considered incurable and fatal.
A hole of no less than one square meter in size has also been discovered beneath the reactor’s pressure vessel, TEPCO said. According to researchers, the apparent opening in the metal grating of one of three reactors that had melted down in 2011, is believed to be have been caused by melted nuclear fuel that fell through the vessel.
The iron scaffolding has a melting point of 1500 degrees, TEPCO said, explaining that there is a possibility the fuel debris has fallen onto it and burnt the hole. Such fuel debris have been discovered on equipment at the bottom of the pressure vessel just above the hole, it added.
The latest findings were released after a recent camera probe inside the reactor, TEPCO said. Using a remote-controlled camera fitted on a long pipe, scientists managed to get images of hard-to-reach places where residual nuclear material remained. The substance there is so toxic that even specially-made robots designed to probe the underwater depths beneath the power plant have previously crumbled and shut down.
However, TEPCO still plans to launch further more detailed assessments at the damaged nuclear facility with the help of self-propelled robots.
Earlier this week, hopes for a more efficient cleanup at Fukushima were high, as the plant operator announced a portion of nuclear fuel debris responsible for a lot of the lingering contamination from six years ago may have finally been found.