In this photo taken on Oct. 3, 2008, the No. 1 reactor, center, of the Fukushima Daiichi Nuclear Power Plant in Okumamachi, Fukushima Prefecture, is seen. A strong earthquake on Friday, March 11, 2011 knocked out power at the plant, and because a backup generator failed, the cooling system was unable to supply water to cool the 460-megawatt reactor. An official with Japan’s nuclear safety commission said Saturday, March 12, 2011 that a meltdown at the plant is possible. (AP Photo/Kyodo News)RICHARD T. PIENCIAK, Associated Press
The nuclear crisis in Japan has developed rapidly on many fronts, making it difficult to track the threads. What are the dangers? Will the situation improve? Can the reactors be cooled?
The crisis began Friday when a magnitude-8.9 earthquake and tsunami cut off regular electricity to the oldest unit at the Fukushima Dai-ichi nuclear complex, 170 miles (270 kilometers) northeast of Tokyo.
Since then more reactors – at more nuclear sites – have lost at least some cooling ability, increasing concerns about possible meltdowns.
Some questions and answers about the crisis in Japan: