Here's a very quick update as to what's going on.

1.)  I'm here in Tokyo.  As far as Tokyo is concerned, the earthquake was mostly frightening but not devastating.  We were shaken pretty bad but injuries are quite light compared to how things have been going North of us.  Tokyo may encounter brown outs in the near future in order to shuttle power North where the power resources are shut down.  In general, Tokyo is fine.

2.)  I'm a nuclear engineer working here in Japan.  My training is focused on situations which are evolving now in the Fukushima plants.

The most important thing to realize is that the facts that I have available to me are from the news.  They are not significantly detailed and they do not convey a lot of the information that I would need to know to describe the situation clearly.  Much of what I am going to write below is constructed from assumptions based on the scattered facts I can glean from the news.

All of the nuclear plants in the area that have been impacted by the earthquake were shut down immediately.  This is a normal step for such situations.  Very soon after, the tsunami caused by the quake hit the Japanese coast and damaged some of the backup systems at one of the plants.  I know that two plants have had difficulty.  However one plant in particular has been seriously impacted.

After a nuclear power plant shuts down, there is still heat being generated in the core which takes time to decay off.  That heat needs to be removed.  The backup power systems at the plant were not working as they should.

The sequence of events from the point after the tsunami hit are unknown to me.  Based on my knowledge, I will assume that the plant did not have adequate power to continue cooling the core at a rate which was needed.

Based on what I am reading, it appears that the core eventually became too hot and started what is called a metal water reaction.  This is a situation where the zircalloy cladding on the fuel begins to react with the water.  The result is a chemical reaction which releases Hydrogen.

Again, please understand that I am making assumptions about the sequence of events based on the news.

For this particular type of reactor;

The reactor core is inside the reactor vessel.

The reactor vessel is inside a very large 6 inch thick steel pressure vessel.

The pressure vessel is inside the containment building.

The Hydrogen was vented from the reactor vessel and into the primary containment vessel.  Pressure in the containment vessel reached a level which required venting.  At that point, the containment was vented and Hydrogen was released into the containment building.

There is also a possibliity that Hydrogen from the turbine may have also found its way into the containment building.  I have no idea based on the limited facts.

At some point, the Hydrogen ignited and exploded.  This blew apart the containment building.  The primary pressure vessel which contains reactor is still intact and is still doing its job.  The reactor core is still inside the reactor vessel.

I am assuming that the utility determined that the plant was in a condition at which point commercial operation would not be viable in the future.  The utility then decided to pump borated sea water into the reactor to control the decay heat.

This basically means that the water and the boron will control the heat but the plant will never operate again due to the salt and the boron.  Based on the news, I believe the plant is under control and that there will be no more issues.

In the evolution of the Hydrogen release, some radioactive iodine and radioactive cesium has been leaked from the reactor.  The amounts are not known.  The situation is serious but I do not believe that there will be a significant environmental impact and I also believe that in general, people will be safe.

There were some people very seriously injured in the explosion.  There will certainly be some people who will have been exposed to radiation.  But overall, the incident is contained and is now being managed in a way that further damage should be mitigated.

So in summary, some people have been seriously injured.  A few people will have been exposed to radiation but I don't know how serious.  Some radiation has been leaked but I don't believe it will be a major problem.  Finally, the reactor is under control and no cataclysmic catastrophe will be caused.  Multiple safety systems designed to keep the core from getting out of the reactor complex are holding and will not be further compromised.

The second power plant that was suffering problems is also under control.  The utility was able to get cooling to the plant using fresh water.  From what I have gathered, there should be no further issues at that plant.

In terms of food and supplies, I am in the dark.  Tokyo is a significant distance from the truly impacted areas.  I'm sure that as soon as the trains are operating again that supplies will have the needed transit.  The air traffic at Tokyo is operating.  Therefore I conclude that any and all supplies are also being flown in as they're needed.

The Japanese have a lot of stuff setup for this kind of event because they've been predicting this sort of thing for a lot of years.  In addition, we have an earthquake here in Tokyo that I can actually feel about every 15 days.  Therefore earthquakes are expected and the Japanese are constantly vigilant about it.  In that sense, there's probably no other place which is better prepared for this type of disaster.

-Kix