UPDATE 11:39: Here is a excellent video that explains what has happened so far.  Very nice graphics of the core and pictures of what happened after the explosion.  Mention of 90 people being tested for radiation poisoning so far, etc.

Also here is an excellent link to a twitter feed about the situation that Greenpeace is providing.

Al Jazeera is reporting that the situation at the Fukushima nuclear power plant could be very serious.

Peter Hayes, the executive director of the Nautilus Institute for Security and Sustainable development in Melbourne, described the situation as “dire”.

“It’s still possible that the reactor workers can stabilise the situation if power is brought back, if coolant is brought into the reactor,” he told Al Jazeera, but warned that “we’re really right at the precipice of a massive nuclear crisis”….

Radiation 1,000 times above normal was detected in the control room of one plant in the early hours of the morning.

The quake, which measured 8.9 on the Richter scale, cut the supply of off-site power to the plant and diesel generators intended to provide back-up electricity to the cooling system.

“The events that occurred at these plants, which is the loss of both offsite power and onsite power, is one of the rarest events to happen in a nuclear power plant, and all indications are that the Japanese do not have the situation under control,” said Edwin Lyman, a nuclear expert at the Union of Concerned Scientists, a US-based nonprofit organisation.

Here is a wonderful point by point recap by the World Nuclear News that takes you through what happened and explains each step.*

Also BBC News is doing a credible job of following the story and often reverts to show video of the massive explosion that rocked the plant several hours ago.

I want to stress this may all be contained but in case there is any fallout this is a graphic depiction of how fast it would get here. (UPDATE THIS GRAPHIC HAS BEEN DISCREDITED)

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*Thanks to Mark Chapman for sending me the link