The ongoing disaster of Fukushima will be Japan's and the world's for millenia.

The three molten nuclear cores [corium] each weigh 130 tons and contain several thousand pounds of plutonium. Their location, physical, and radiation properties are unknown because every leaded and leaded glass sensor robot or probe sent down to examine them have never returned. If that's not scary, even if we know their properties, including radioactivity, temperature, and depth, how are we going to remove and isolate them? Some have asserted that a sarcophagus can't be built because the plants sit on the Rim of Fire. The ongoing disaster of Fukushima will be Japan's and the world's, not for forty years, but for milennia.