How can you create a plan to clean up a nuclear reactor meltdown if you have no idea what you’re dealing with because it’s far too dangerous to go inside? At Wired, Vince Beiser reports on the  little robot that bravely went where no human could: to document the extent of the damage at the Fukushima Daiichi nuclear power plant so that Japanese scientists can figure out how to clean it up.

Human beings couldn’t go into the heart of Fukushima’s reactors to find the missing fuel, though—at least not without absorbing a lethal dose of radiation. The job would have to be done by robots. But no robot had ever carried out such a mission before. Many had already tried and failed. Debris tripped them up. Yard-thick concrete walls threatened to block their wireless signals. Radiation fouled up their microprocessors and camera components. And so it fell to Matsuzaki, a shy-eyed , 41-year-old senior scientist with Toshiba’s nuclear technology branch, to help build a machine that wouldn’t end up as another one of the robot corpses already littering the reactors.

The Fukushima cleanup is a project far bigger and more complex than those of even the world’s worst previous nuclear catastrophes. Chernobyl was literally covered up: The Soviets simply encased the whole thing in concrete and steel. Three Mile Island was tiny by comparison. Only a single reactor melted down, and none of its fuel escaped. “Fukushima is orders of magnitude more difficult,” says Lake Barrett, an American who oversaw the cleanup of Three Mile Island and who signed on as a consultant to Tepco and the Japanese government in 2013.

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