The level of nuclear radiation detected at the troubled Fukushima nuclear plant in Japan spiked on Thursday to its highest level since the triple core meltdown in 2011.
In March 2011, multiple reactors at the Fukushima Daiichi power plant spiraled out of control after a 42-foot tsunami overwhelmed the plant’s sea walls, rendering the vital systems used to cool the plant’s six reactors inoperable. Ultimately, fuel meltdowns occurred at three reactors, releasing vast amounts of radioactive matter and resulting in the world’s worst nuclear disaster since Chernobyl.
On Thursday, the Tokyo Electric Power Company (TEPCO), the investor-owned utility that operates the Fukushima reactors, reported that it detected a radiation level of 530 sieverts per hour in the containment vessel of reactor 2 at the Fukushima No. 1 power plant.
A sievert is a measure of the health effect of low levels of ionizing radiation on the human body.
Even a brief exposure to 530 sieverts of radiation would kill a person. Exposure to only one sievert is enough to result in infertility, loss of hair and cataracts. According to the National Institute of Radiological Sciences, exposure to a mere four sieverts of radiation would typically be lethal for one out of every two people. The highest level of radiation detected previously at the Fukushima reactor was 73 sieverts per hour.
According to the Japan Times, the reading was taken near the entrance to the space just below the pressure vessel, which contains the reactor core. The extremely high radiation levels suggest that some of the melted fuel that escaped the pressure vessel is nearby.
TEPCO had planned to deploy a remote-controlled robot to assess conditions inside the containment vessel. But, considering the extreme radiation levels, it is unclear whether it will be able to do so.
The robot is designed to withstand exposure of up to 1,000 sieverts. Based on the calculation of 73 sieverts per hour, the robot could run for more than 10 hours, but 530 sieverts per hour means it would be rendered inoperable in less than two hours.
William Pentland is a Partner at Brookside Strategies, LLC, a consulting firm in Portland, Maine that focuses on issues in utility regulation, market strategy and energy policy.