Radiation levels inside a damaged reactor at the Fukushima Daiichi nuclear power station are at their highest since the plant suffered a triple meltdown almost six years ago. The facility’s operator, Tokyo Electric Power, said atmospheric readings as high as 530 Sieverts an hour had been recorded inside the containment vessel of reactor number 2.
The extraordinary radiation readings highlight the scale of the task confronting thousands of workers, as pressure builds on TEPCO to begin decommissioning the plant, a process that is expected to take over four decades.
Just a single of one Sievert is enough to cause radiation sickness and nausea; 5 Sieverts would kill half those exposed to it within a month, and a single dose of 10 Sieverts would prove fatal within weeks.
Previous measurements of the radiation inside the containment vessel had pointed to an exposure level of 73 Sieverts per hour.
TEPCO has also revealed that image analysis showed a hole in metal grating beneath the same reactor’s pressure vessel. The one-meter-wide hole was created by nuclear fuel that melted and then penetrated the vessel after the tsunami knocked out Fukushima Daiichi’s backup cooling system.
“It may have been caused by nuclear fuel that would have melted and made a hole in the vessel, but it is only a hypothesis at this stage,” Tepco’s spokesman Tatsuhiro Yamagishi told AFP.
“We believe the captured images offer very useful information, but we still need to investigate given that it is very difficult to assume the actual condition inside.”
The bottom line is, until now, TEPCO has never been able to approach this area of the containment vessel because all earlier attempts to manually drive robots ended in failure long before the vehicles reached this point. You can see for yourself in the image below.
Yamashiki warned that the complete reduction of the radiation will take hundreds of thousands of years. However, looking on the bright side, he said, “right now, the radiation level is much lower since the reactor hasn’t been active for a while.”
It will not be an easy problem to solve because the radiation is so horrifically severe. It is enough to kill a human with only very brief exposure, but robots are not necessarily safe either. At levels this high, a robot would only be able to operate for two hours before radiation ravages its internals and renders it useless.
TEPCO hopes to find and start removing the fuel by 2021.