Swimming robot to probe damage at Japan nuclear plant

YOKOSUKA, Japan (AP) — A Japanese industrial group unveiled Thursday a robot designed for underwater probes of damage from meltdowns at the Fukushima Dai-Ichi nuclear plant after the March 2011 earthquake and tsunami.

The developers say they plan to send the new "mini manbo," or "little sunfish," probe into the primary containment vessel of Unit 3 at Fukushima in July to study the extent of damage and locate parts of melted fuel thought to have fallen to the bottom of the chamber, submerged by highly radioactive water.

"The major advantage is it can avoid various obstacles," said Tsutomu Takeuchi, a senior manager at the nuclear energy division of Toshiba, the electronics and energy company charged with helping clean up the plant.

The other, designed to clear debris for the "scorpion" probe, was called back after two hours when two of its cameras stopped working after its total radiation exposure reached 1,000 Sievert — a level that would kill a human within seconds.

IRID and its partners have designed other basic robots, including a "muscle" arm robot made by Hitachi-GE Nuclear Energy, and a different arm robot made by Mitsubishi Heavy Industries, that are designed to approach the debris from the sides of the reactors.

Scientists need to know the melted nuclear fuel's exact location and understand structural damage in each of the three wrecked reactors to work out the optimum, safest way to remove the fuel.