First off, the real disaster has nothing to do with the Fukushima Nuclear Reactors. The people who really need our help, thoughts, and/or prayers (if you are so inclined), are the thousands (likely tens of thousands or hundreds of thousands) who have been displaced, injured, or killed by the earthquake and resulting tsunami. Any consequences from the reactors will pale next to that - of this, I am absolutely certain.
This page and its children are my attempt to provide better information about the event, based on my knowledge as former DOE on-site inspector, and as a Professor of Nuclear Engineering. This site reflects my work and/or opinions and is the result of my own analysis. It does not represent the position of Colorado School of Mines.
In order to allow better interaction and more rapid updates, I have created a Facebook Page tied to this one. You may find it at http://www.facebook.com/fukushima.nuclear.info.
10:47 PM MST 3/14, Future thoughts will be posted as notes on the Facebook Page.
7:12 PM MST 3/14, It look like there has been an explosion at Fukushima Daiichi Unit-2. The press is reporting that the explosion was inside the primary containment, with some indication that the containment may have been breached. NISA and TEPCO representatives are confirming this. Doses were reported have peaked at 96.5 millirem/hr, assumably at the site boundary. If the main containment been breached, this is not good, though the doses are not yet extreme. Neither TEPCO nor NISA have published updates at this point. I'm waiting for better information. News out of Unit 1 and 3 seems to have stabilized, so if they can get Unit 2 stabilized, we may be seeing that stable end-point. All credible evidence at this point suggests that the public health effects will be small.
12:17 AM MST 3/14, The second hydrogen explosion (technically a deflagration, but that's another topic for another time), was not unexpected. Monitoring at the site boundary shows dose levels of 2-5 mrem an hour, which is elevated, but not severe, now that the evacuation is in place. We are seeing contamination cases in the evacuated populace - I suspect this is probably material that was thrown from the site when the explosion at Unit 1 occured. Venting the primary containment deposited material in the reactor building, which was then thrown into the air by the deflagration. Neither of these is really a mystery. The spike in radiation levels at the site boundary is consistent with this.
8:04 PM MST 3/12, Let's clarify a few points. "Radiation" is energy transmitted in the form of particles or waves. It comes in many forms, including x-rays, gamma rays, beta particles, microwaves, radio waves, and visible light. What we are really concerned about in Japan is "ionizing radiation", which is radiation with enough energy to strip electrons from atoms. "Radioactive material" is any material that emits (ionizing) radiation. "Contamination" is radioactive material anywhere we don't want it. The people who the press keeps reporting as "testing positive for exposure to radiation" are probably people who have been contaminated - i.e., they have dedectible amounts of radioactive material on or in them. (You don't test positive for exposure to radiation.) This may or may not be significant. Most of the time you just clean the contamination off and go about your life. I've tested positive for contamination on more than one occasion (daughter products from radon each time). I haven't seen any units or details from Japan so far, so I can't say how significant the cases are. We are all exposed to ionizing radiation all of the time - approximately 620 millirem a year, on average. There appears to be one operator who picked up ~10 rem, which would not be expected to result in any detectible effects. A chest x-ray give you about 10 millirem, a full dental x-ray about 160 millirem, and a full-body CT scan gives you about 1.5-10 rem. So, if you have ever had a CT scan (this includes myself and my father), then you have probably been exposed to the same amount of ionizing radiation as the worst reported case from the events in Japan - ditto if you have had barium imaging done.
7:22 PM MST 3/12, This picture shows a cutaway view of a boiling water reactor similar to Fukushima Daiichi Unit 1. Compare it to this image of the Unit 1 building after the explosion. The hydrogen explosion apparently occured in the upper part of the building, ripping it apart, but so far there is no evidence that the reactor containment was damaged. The damage looks to be confined to the relatively fragile shell on top of the massive and secure important parts. This is a good example of robust engineering.
6:56 PM MST 3/12, The American Nuclear Society just released a Background document prepared in conjunction with the Atomic Energy Society of Japan. It contains a fairly detailed sequence of events, including a few key points missed by the media. I am reposting it here. One key point to note is that the usage of seawater for emergency cooling was *always* part of the design. It is not an improvised and unanticipated move.
6:42 PM MST 3/12, If you stop to think about it, as far as engineering disasters go, this one is so far low on the scale. On 9/11, a fully-fueled passenger jet was piloted into each of the World Trade Center towers. 2606 people died when engineering failures allowed the support beams to buckle in the resulting fires, causing the buildings to collapse. So far, Fukushima Daiichi Unit 1 has been hit with the fourth largest earthquake in recorded history, slammed by a massive tsunami, and had the top ripped off of it by a hydrogen explosion. Total death toll at/from the reactors so far? One - a crane operator who was apparently killed in the initial earthquake. (And he was actually at Fukushima Daini - a different facilty.)
2:49 PM MST 3/12, The presence of cesium-137 and iodine-131 outside the reactor core probably means that some form of fuel damage has occured. This does not mean that we are looking at a meltdown. Fuel damage can occur long before the ceramic fuel starts to melt. Since the primary containment is intact, and doing its job, the external consequences are minor.
2:38 PM MST 3/12, At this point, it looks the situation is under control. The article pretty much confirms what I have gathered from other sources. Fukushima Daiichi-1 was going to be deconditioned anyways (it and I are of the same vintage), so the seawater injection is a pragmatic decision to sacrifice future operation of the plant to provide assurance of safety. It looks like there may have been some fuel damage, but the offsite consequences are negligable. NHK News just had a picture showing the building before and after the hydrogen explosion. I'll see if I can find it. If you know what you are looking at, it shows just how resilient these structures are.