Daybreak and Explosion
First thing this morning I saw the video of an explosion at the Fukushima Daiichi 1 reactor. I spent much of today trying to figure it out. There was clearly a hydrogen fire (you can see the thin blue flames rising rapidly at about 24 seconds into the video.) Beyond that, all was confusion.
The Japanese said that containment was not breached. Others said that the top of the reactor building seemed to be missing: if that wasn't "breaching containment," what was? Meanwhile, the Japanese also talked about the turbine building, and hydrogen fires in turbine buildings are pretty common. (Generators are cooled with hydrogen.) Though I no longer think the explosion is due to a generator fire, a fire in the turbine hall is still mentioned as a possibility in a recent New York Times article. (The turbines and generators are in the same building, called the turbine hall.) Atomic Insights blog also thought the explosion might be in the turbine hall. This blog also has a very informative discussion.
It's been that sort of a day. A day in which it has been very hard to figure out what is happening. When reasonable people don't know WHAT exploded, it's hard to move on from there.
Some Tentative Conclusions
Turns out that the NEI site is probably closest to correct. The outer containment building was breached in the explosion, but the inner containment of the core is intact. They are flooding the inner core with seawater and boron, which will ruin the reactor. Of course, the hydrogen fire probably means the reactor is ruined already: you don't get enough hydrogen to explode unless the fuel is uncovered and overheated.
Speaking of explosions, the top of the reactor building is sort of neat-looking. I mean, it looks too neat. The explosion goes down to a certain level, then stops, nice and even. This puzzled me, though nobody had mentioned it. However, in the comments on the Capacity Factor blog, I found this explanation: The walls that have been destroyed are actually curtain walls of the reactor building steel superstructure (which is seen on image, more or less intact). The containment and the reactor vessel are safe
That explains a lot. The containment part probably begins below those curtain walls.
All day has been like this. Trying to figure out the questions to ask (why such a neat line after an explosion?) and then trying to get the answers.
What Does It All Mean?
I don't know. The Japanese are distributing iodine, which doesn't sound good. On the other hand, when I visited Japan, I saw many people walking about with face masks to prevent disease spread. There wasn't a single piece of garbage on any street. The culture of Japan, as far as I could tell, is very organized, clean, and willing to take precautions. So maybe the iodine is a precaution. But maybe the iodine is a symptom that things are going very wrong. I simply do not know.
I continue to recommend the ANS Nuclear Cafe site for updates. It contains links to many other sites, including English-language Japanese television. In general, the New York Times has some of the best coverage in the main-stream media. I also recommend this thoughtful and balanced article A Japanese Three Mile Island, by Christine Russell at The Atlantic.