"TOKYO — Japan's nuclear crisis intensified dramatically on Wednesday after the authorities announced that a second reactor unit at the stricken Fukushima Daiichi plant in northeastern Japan may have ruptured and appeared to be releasing radioactive steam.
The break, at the No. 3 reactor unit, worsened the already perilous conditions at the plant, a day after officials said the containment vessel in the No. 2 reactor had also cracked.
Such were the radiation levels above the plant, moreover, that the Japanese military put off a highly unusual plan to dump water from helicopters — a tactic normally employed to combat forest fires — to lower temperatures in a pool containing spent fuel rods that was overheating dangerously."