The nuclear meltdowns at three reactors in the Fukushima plant were caused when a tsunami knocked out emergency power generation at a plant

The nuclear meltdowns at three reactors in the Fukushima plant were caused when a tsunami knocked out emergency power generation at a plant that was believed to have been built to withstand the quakes and tsunamis that Japan has suffered many times. But the 2011 tsunami was bigger than any seen for more than 1,000 years, since 869, and led to a disaster that the Japanese government once believed was beyond imagination.