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article imageRadiation in Fukushima reactor No. 2 reaches 'unimaginable' level

By Karen Graham     Feb 3, 2017 in Science
Radiation levels in reactor No. 2 at the Fukushima nuclear power plant have inexplicable soared to the highest readings recorded since the plant was crippled by a triple meltdown almost six years ago.
Not only will the findings delay the process of decommissioning the plant, but the cost of the actual work will undoubtedly skyrocket. There are also concerns that the some of the melted fuel that escaped the pressure vessel is lingering nearby, according to Gizmodo.
Tokyo Electric Power Co. (TEPCO) said on Thursday that the maximum estimated radiation level near what is believed to be melted fuel in the reactor was 530 sieverts per hour, the highest recorded so far since the triple meltdown in 2011. One sievert is the unit measurement for a dose of radiation and will cause illness if absorbed all at once, while 8 sieverts will result in death, even with treatment.
Investigation area inside the pdestal in Reactor No. 2
Investigation area inside the pdestal in Reactor No. 2
TEPCO's findings are the result of studying images taken from a video camera attached to a pipe that was inserted into reactor No. 2 on Jan. 30. TEPCO officials also confirmed they had found two holes on grating for maintenance work below the bottom of the reactor’s pressure vessel.
“The holes were likely made when the melted nuclear fuel fell from the pressure vessel and melted the grating,” a TEPCO official was quoted as saying by Asahi Shimbun.
Measurements of radiation levels were taken at three different spots inside the reactor's containment vessel and ranged from 20 on up to 530 Sieverts per hour. Tepco says the levels were estimated based on the extent of the disturbances in the images caused by the radiation.
Even though a TEPCO official said, “there is a margin of error because radiation levels were not measured directly,” the company believes the scattered melted nuclear fuel inside the containment vessel was emitting high levels of radiation.
This is a satellite image of Dai Ichi Power Plant  showing damage after an Earthquake and Tsunami. T...
This is a satellite image of Dai Ichi Power Plant showing damage after an Earthquake and Tsunami. This photo was taken on March 14, 2011 at 11:04 am local time, 3 minutes after an explosion.
Photo courtesy DigitalGlobe
Regardless of if these are estimated levels, they are exceedingly high this long after the initial incident took place. Bottom line - According to the National Institute of Radiological Sciences, medical professionals are not prepared to handle patients exposed to the radiation levels currently being experienced at the plant.
The high levels of radiation will curtail any dismantling at Fukushima, which includes the removal of fuel debris. The dismantling was expected to begin in 2021 and take about half-a-century. An additional problem is finding out where the melted fuel ended up. It has been assumed that most of the melted fuel had remained inside the reactor’s pressure vessel.
But with finding the holes in the grating, officials aren't so sure anymore, so they plan on sending in an investigative robot, called Sasori (scorpion) later this month to take more measurements of radiation levels in various areas and collect more images of the scattered fuel.
Hole in grating is clearly visable.
Hole in grating is clearly visable.
But even sending the robot inside will present challenges. The robot is supposed to use the circular grating that measures 5.0 meters (16.4 feet) in diameter, to maneuver around inside the containment vessel, but one of the holes eaten through the grating measures 1.0 X 1.0 meters (3.2 X 3.2 Feet). This is not good for a robot that is 59 centimeters (23 inches) long and 9 cm (3.5 inches) high.
If things could be any worse, Gizmodo also writes that the Sasori robot was designed to withstand exposure of up to 1,000 total sieverts. Earlier use of the robot when levels were 73 Sieverts an hour allowed it to run for about 10 hours. So at 530 Sieverts, the robot may last two hours, if they are lucky.
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