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article imageUnderwater robot probes inside Fukushima nuclear reactor

By Karen Graham     Jul 19, 2017 in Science
Fukushima - On Wednesday, the operator of the crippled Fukushima nuclear power plant began probing inside the contaminated water-filled reactor containment vessel in one of its units, using an underwater robot.
Tokyo Electric Power Company Holdings Inc. (TEPCO), the plant operator, was hoping to find the exact location and condition of the melted nuclear fuel inside No. 3 Reactor, one of the three units that suffered meltdowns in the devastating 2011 earthquake and tsunami.
CTV News is reporting that TEPCO spokesman, Takahiro Kimoto, praised the mission, saying the robot, nicknamed "little sunfish," was able to capture scenes of the damage never before seen. The one piece of evidence they had hoped to find, the melted fuel, was not seen.
The small  radiation-hardened screw-driven submersible robot has a diameter of only 13cm.   and is a...
The small, radiation-hardened screw-driven submersible robot has a diameter of only 13cm., and is a resilient platform for visual inspection of damage status by camera to inspect the interior of Unit 3's primary containment vessel.
Toshiba Corporation
Connected by cables to the outside world, the loaf of bread-sized aquatic robot is mounted with lights and maneuvers through the water using tail propellers, collecting data with two cameras and a dosimeter. The robot entered the structure at 6.30am JST (10.30 BST, 5.30 ET) through a pipe connected to the containment vessel.
The robot was then sent to an area just below the reactor's pressure vessel. Images sent back show damage to multiple structures inside the pedestal and also that some of the support fittings for the CRD housing have fallen. It was discovered that a grate platform that is supposed to be below the reactor core was missing and apparently was knocked down by melted fuel and other materials that fell through from above.
This image captured by an underwater robot shows a part of equipment housing a control rod drive sys...
This image captured by an underwater robot shows a part of equipment housing a control rod drive system of Unit 3 at Fukushima Dai-ichi nuclear plant.
TEPCO
Due to the scope of the examination, the grating above the platform was not examined, said TEPCO. Another exploration will be done on Friday, July 21, based on what officials have learned from today's discoveries. It is important that the missing melted fuel is found in order to assure a safe removal of the highly radioactive substance.
Finding and removing the radioactive fuel is the most critical and dangerous part of the decommissioning process, according to Japan Today. TEPCO has attempted to use remote-controlled robots to see inside the reactors since they began the clean-up after the meltdowns following a massive earthquake and tsunami in March 2011.
This image shows the bottom of the CRD housing within the containment vessel.
This image shows the bottom of the CRD housing within the containment vessel.
TEPCO
Toshiba Corp. and the International Research Institute for Nuclear Decommissioning, or IRID, a government-funded consortium, co-developed the underwater robot, named "Mini Manbo" (miniature sunfish). Toshiba demonstrated the loaf-of-bread-sized robot for the news media at a company test site near Tokyo June 15, 2017.
More about fukushima, Nuclear reactor, aquatic robot, little sunfish, melted fuel
 
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