This cutaway diagram shows the central reactor vessel and thick concrete containment in a typical boiling water reactor of the same era as Fukushima Daiichi 1 (image: www.world-nuclear-news.org)

While it is axiomatic that we don’t have all the details at any given time this post is going to attempt to keep everyone updated. Last night Scarecrow, Lobster and Prof Foland in particular did a great job keeping everyone up to speed on the apparent rupture of the Unit 2 reactor at Daiichi Nuclear Power Station. You can find those articles and threads at the links below.

Japan Nuclear Watch: Third Explosion, Possible Cracked Containment At Unit 2

Japan Nuclear Watch: Ministry Press Conference On Third Explosion And Fire At Unit 4

There was also a fire and perhaps explosion at Unit 4 of the same complex. Unit 4 had achieved cold shut down status, meaning that the rods were all in, and the reactor had cooled down for the high temperatures of power production to “cold” status.

That does not mean that it is room temperature, but rather that as long as it is still covered with water it will not be in danger of melting and that they do not have to monitor the production of steam.

It is still unclear at this time what happened at that unit but speculation is that the spent fuel rods which are stored in a cooling pond until they are shipped our for reprocessing were exposed. This would have caused them to heat up and perhaps burst into flame. I have to admit here that I thought that this was really unlikely to happen, but as we are all finding there is a lot that can go wrong when buildings are exploding.

As of now (7:30 EST) the Japanese officials are reporting that the radiation level at the plant, which had spiked to 11,930 microsiervets, has dropped to 596 per hour. A quick word on ‘sievert units”.

In a year from natural sources you will receive around 1,000 microsiervets, the levels at that plant at the highest reported spike were 11 years worth per hour.

Why the drop in the radiation levels? The current thinking is that the some of the rods burned and released the radioactive materials contained in them directly into the atmosphere. There was a intensive and desperate firefighting effort at the Unit 4 site and it seems to have been effective.

It is possible that the holding pool only partially drained or that there were only a relatively small number of rods in the pool. In any case it seems that this particular problem is resolving. However each of the six reactors at Daiichi have these spent rod ponds and there is still potential that they could be damaged, drain and burn, if that is indeed what happened.

In response to the increased radiation threat TEPCO (Tokyo Electric Power Company) has withdrawn all but 50 of the workers at the plant. The 50 staying behind are, of course taking great risk with their lives to try to stay with and control the conditions at the plant.

It is still unclear if the explosion at Unit 2 breached the reactor vessel or the containment structure. Either are very bad news. If it breached the reactor vessel (where the actual reactor sits) that would reduce the pressure inside and make keeping cool water over the rods much harder, if not impossible. But that is not at bad as if it has breached the steel and concrete containment structure, at that point you would be in the middle of a full melt down with pellets of uranium scattered on the floor of the reactor building and being to melt and run together.

The good news (such as it is) at this point is that there has been the reported decrease in radiation at the site. This tends to indicate that if there is a breach it is small at this time, which gives some small possibility of containing the reaction. The full nightmare scenario is a total loss of control.

Between the recent events and the venting of radioactive steam at the plants the area which increased levels of radiation are being detected continues to grow. Yesterday the level of radiation in Tokyo (about 40 mile away) had doubled from normal levels. It is still relatively low but the increase is noticeable.

170 miles away, the USS George Washington, in harbor at Yokosuka, detected increased radiation levels. The statement form the U.S. Navy did not give a level but detection of any increased radiation shows just how far this is spreading.

I think it is important to note that there are many people in the world who get higher than average exposure to radiation and are not always adversely affected. Working in mining or around nuclear power plant, as an X-Ray technician or even just living somewhere where there is more background radiation than normal. They do have increased health risks but exposure to some increased radiation for a small time is not a guarantee of ill health.

It is particles like radioactive Iodine that, if taken up into the human system will deposit and do the long term damage. This is the real worry. So far the plants have released smallish levels of these particles, but if there is another fire or one or more full breaches that will change, and drastically.

Nuclear accidents do not happen in an instant. They may start that way, but they evolve over days as desperate actions race to prevent the physics of heat and radioactive decay from getting the upper hand. This event is continuing and will continue for at least a few more days.

All of this is the emergency part of this disaster. While this is still unfolding it is probably unseemly to mention economics but that part of the crisis is playing out and I’d be remiss if I did not say something about it. Today the Nikkei index fell 10%. European stock markets are falling and the Dow Jones Industrials is set for a sharp sell off.

Japan is the worlds 3rd largest economy and it looks set for a major collapse. That is not surprising given their hat trick of disasters, but if their economy collapses that has the strong possibility of restarting the world wide recession that the U.S housing bubble and lack of regulation caused. Just another factor to keep your heartburn going this morning.

I have mentioned it before and I will mention it again; if you have the means there is going to be a huge amount of clean up and relief needed by the Japanese people. Please consider giving to the Red Cross or any relief group you favor. This is a time to remember that we are all humans, and we are all in this together.

UPDATE:

MSNBC is reporting that TEPCO officials are asking for assistance from the US and Japanese military in the form of helicopters to preform water drops at the site. This comes on the heels of the IAEA reporting that radiation levels at the plan are now lethal after five hours of exposure.

Taken together these two facts tend to indicate that they are not having success in cooling the Unit 2 reactor.

There have also been reports that the cooling pools at the Unit 5 and 6 reactors are warming. This leads to worry that they will also evaporate and expose spent rods being held there prior to reprocessing. There were 783 rods being housed in the cooling pool at Unit 4. No word yet on the number of rods being housed at the other two reactors.

More as events evolve

The floor is yours