As Japan scrambles to cope with a nuclear reactor damaged in the quake, Josh Dzieza talks to Ron Ballinger, a nuclear expert at MIT about how the plants work, worst-case scenarios, and more. Plus, full coverage of Japan's catastrophe. Shortly after Japan was hit with the double disaster of a magnitude 8.9 earthquake and subsequent tsunami, a possible third reared its head: nuclear meltdown. The quake caused 11 of Japan's nuclear reactors to shut down automatically, including three at the Fukushima Dai-ichi power plant, 170 miles northeast of Tokyo. But the quake also cut Fukushima off from the power grid,...