As of 5 pm local time:
Fukushima Daiichi Nuclear Power Station:Increase of radiation at site boundary:
Units 1 to 3: shutdown due to earthquake
Units 4 to 6: outage due to regular inspection
* The national government has instructed evacuation for those local residents within 10km radius of the periphery.
* The value of radioactive material (iodine, etc) is increasing according to the monitoring car at the site (outside of the site). One of the monitoring posts is also indicating higher than normal level.
* Since the amount of radiation at the boundary of the site exceeds the limits, we decide at 4:17PM and we have reported and/or noticed the government agencies concerned to apply the clause 1 of the Article 15 of the Radiation Disaster Measure at 5PM.
* In addition, a vertical earthquake hit the site and big explosion has happened near the Unit 1 and smoke breaks out around 3:36PM. Our two employees and two cooperation workers who had been working for the foundation of safety are suffered and they are all sent to the hospital.
* We continue endeavoring to secure the safety that all we can do and monitoring the periphery.
At 2:46PM on March 11th, turbines and reactors of Tokyo Electric Power Company's Fukushima Daiichi Nuclear Power Station Unit 1 (Boiling Water Reactor, rated output 460 Megawatts) and Units 2 and 3 (Boiling Water Reactor, Rated Output 784 Megawatts) that had been operating at rated power automatically shutdown due to the Miyagiken-oki Earthquake.
After the shut down, the values of radioactive materials (iodine, etc) measured by the monitoring car have been increasing. Increase in the measured value has also been recognized in one of the monitoring posts.
Furthermore, today at 3:29PM, radiation dose measured at site boundary has exceeded the limiting value. Therefore, at 4:17PM, it was determined that a specific incident stipulated in article 15, clause 1 has occurred.
We will endeavor to secure the safety and alongside, continue monitoring the environment of the site periphery.
Noriyuki Shikata, Director of Global Communications at the Japanese Prime Minister's office, is on Twitter (@norishikata). His latest tweet:
In spite of the blast at 15:36 at Fukushima , no damage to the container housing the reactor occurred. Radioactive level fell after that.
It may be that the containment vessel hasn't ruptured, but there's a leak somewhere, probably not a big one. That's my conclusion. The only two American commentators I'm following are Mark Hibbs (@carnegienpp) and Dan Yurman (@djysrv). Others are panicky or downright inaccurate.
Update: Here's a set of good interviews. Other Reuters reports have been inaccurate, though.
The leak may be a breached fuel rod, and, judging from the relatively small amounts of radiation that have been released, probably only one or two. That plus a leak in the primary coolant system (or a deliberate release to decrease the pressure) would account for what is being seen.
Second update: The Nuclear Energy Institute has a page of information and links, constantly updated.
Matt Wald of the New York Times has a pretty good explanation of how the explosion probably occurred. Further update: Japanese authorities are now saying that the explosion was in the reactor building but that the containment vessel is intact.
The US Nuclear Regulatory Commission is keeping in touch with Japanese authorities and has some background information here.
Third update: Satellite photos. I haven't spent a lot of time on these, and they're from before the explosion. The damage seems to be from the tsunami.
Fourth update: Good article on how to understand what's going on at Fukushima from a reporter who was at Three Mile Island.
Fifth update: Press release from Tepco on status as of 2 am March 13 Japan Time.