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Another robot has died in the depths of one of Fukushima’s nuclear reactors, as attempts to locate and remove melted radioactive fuel continue. This is the second robot in two weeks to meet its end in the Fukushima Daiichi nuclear power plant in Japan, the site of a major nuclear accident caused by the devastating 2011 earthquake and tsunami.
The robot’s mission was to investigate the pedestal underneath the Unit 2 nuclear reactor, where melted nuclear fuel is suspected to have fallen. But about 10 feet away from its target, one of the robot’s tank-like treads got stuck, World Nuclear News reports. Tokyo Electric Power Company (TEPCO), which operates the plant, decided to cut the robot’s cable and abandon it inside the reactor. A TEPCO spokeswoman told Phys.org that they don’t yet know whether radiation or debris stopped the robot.
“Scorpion Robot” Obtained Additional Information from Unit 2 PCV: On February 16, the “Scorpion-shaped robot” was inserted into the Unit 2 Primary Containment Vessel (PCV) at Fukushima Daiichi Nuclear Power Station to further investigate the conditions within. It went along the CRD rail that led to the area directly below the Reactor Pressure Vessel called the pedestal area, and obtained additional information such as the PCV interior, deposits conditions, temperature readings, and radiation levels. Even though the robot could not reach the pedestal area, which we had initially planned to investigate, valuable information was obtained which will help us determine the methods to eventually remove fuel debris. The robot was left inside the PCV not to obstruct further investigations, as an option of the original plan, since it stopped over the deposits. TEPCO Holdings will continue to review the information, such as deposits on the CRD rail and conditions inside the pedestal, obtained from this entire investigation. For more photos and information, go to http://photo.tepco.co.jp/en/date/2017/201702-e/170216-01e.html
Posted by Tokyo Electric Power Company Holdings, Incorporated on 16hb Februari 2017
Two feet long and shaped like a scorpion, this robot is equipped with a camera on its front, and another camera on its tail that can whip up and look around. It also sports temperature and radiation sensors. Toshiba and the International Research Institute for Nuclear Decommissioning designed the scorpion robot to scoot on caterpillar treads like a tank through pipes about four inches wide.
It’s now at least the seventh robot to have broken down while investigating Fukushima’s nuclear reactors, which remain highly radioactive. Reuters had counted up to five by March 2016. Last week, a scouting robot was sent in ahead to clear the way for the scorpion robot, but it was pulled back out after about two hours: the camera had been fried by record high levels of radiation estimated to be about 650 sieverts per hour. (For scale, a CT scan exposes you to 0.006 sieverts, and just half a sievert is enough to cause symptoms of radiation sickness.)
This is yet another setback for TEPCO, which still has not succeeded at removing the molten radioactive fuel from three of the four reactors that need to be decommissioned at Fukushima Daiichi. Still, TEPCO officials report that radiation levels measured outside the reactors are not dangerous, and the public is not at risk.