At least seven robots have been deployed at the Fukushima Daiichi nuclear generating station to assess damage within the three units on site that suffered meltdown events in March 2011. All seven have collected some data en route to the reactor cores in which they were deployed. But all seven have also eventually succumbed to the hostile environments inside the damaged reactor vessels.
The robots have thus far been described as snake-like or scorpion-like, owing to their various abilities to sneak through small spaces, such as entry piping, or to turn corners when needed to do so. Scorpion robots have been designed to fold in half, like a scorpion lifting its tail, to point a light and a camera forward. They could also unfold to a slimmer shape to manage sneaking through tight places.
On Thursday, a Japanese industrial group headed by Toshiba revealed a third robot design, which has quickly been dubbed “the Little Sunfish.” The size of a loaf of bread, fitting comfortably into two outstretched hands close together, the latest robot will swim through the flooded chambers of the reactors in order to collect data to aid in fuel retrieval, the necessary step for eventually cooling the debris down with regards to radiation intensity.
The Little Sunfish is boxy in shape and has propellers for a tail. It is also outfitted with two cameras and a dosimeter.
Previous robots have been abandoned inside the reactors, as technicians feared they would fail at precisely the wrong time if they tried to bring them back. They feared a failure inside an access spot which would, by accident, block the path they needed to keep free so subsequent robots make use of the same entry point.
At least one camera failed within two hours, after its camera had stopped working. By then, it had already been dosed to 1,000 Sieverts, a highly lethal dose for a human.
Besides the smaller, data-collecting robots, Hitachi-GE Nuclear Energy and Mitsubishi Heavy Industries have each designed larger robots designed to do the heavy lifting and breaking down of material that needs to be removed from inaccessible areas.
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