A remote-controlled robot has safely returned with a tiny piece of melted fuel it collected from inside one of three damaged reactors at the tsunami-hit Fukushima Daiichi nuclear power plant for the first time since the 2011 meltdown. The mission is not over until it’s certain that the sample’s radioactivity is below a set standard. If the radioactivity exceeds the limit, the robot must go back inside the reactor to find another piece. Fukushima Daiichi lost its key cooling systems during the 2011 earthquake and tsunami, causing meltdowns in its three reactors.
