An exclusive look at the world’s largest-ever nuclear cleanup

Five years ago, an epic tsunami off the coast of Japan triggered a triple-reactor nuclear meltdown at the Fukushima Daiichi Nuclear Power Plant. Ever since then, 7,000 workers have been laboring round-the-clock on a massive, and unprecedented, cleanup effort. Science correspondent Miles O’Brien takes an exclusive look at ground zero of the greatest nuclear disaster since Chernobyl.