It’s now 3:30pm on Friday, 3/18/11. Major problems continue at all 6 Fukushima reactors.
The largest threat of radiation release now seems to come from pools of spent fuel rods. These pools contain much more radioactive material than the reactors themselves. Some genius thought it would be a good idea to store these spent fuel rods in the same containment facility as the reactors. When the reactors created hydrogen explosions that blew apart their outer containment structures, the explosions apparently cracked the pools holding the spent fuel rods. Whoops.
Typically the pools hold enough water to cover the spent fuel by several meters. Even if left uncooled, it would take weeks for enough water to boil off to uncover the spent fuel. Hence the spent fuel pools were not a major concern in the inital stages of Fukushima. However, enough water drained through the cracks in the pool that the spent fuel rods are at risk of being exposed to air. This is very dangerous, as the spent fuel can ignite and spew plumes of radioactive material. The spent fuel in reactor 4 is thought to be presently exposed to air. Incidentally, reactor 4 holds most of the used fuel.
There is perhaps a subtle engineering lesson here. Don’t store something which becomes terrifyingly dangerous if damaged IN THE SAME BUILDING as something that can explode and cause damage. This is why I don’t keep fireworks in the gas tank of my car.
On the bright side, more and more resources keep arriving on site at Fukushima. Power is being reconnected to the original cooling mechanisms of the reactors, and additional water is being directed at the fuel pools. Despite all the doomsaying (here and elsewhere), it is still very possible that the situation could be stabilized. That is, the amount of radiation emitted could be fixed at a tolerable level, and work could begin on reducing it. On the down side, this could already be impossible due to reactor damage, or it could become impossible with a major radiation release from one of many potential sources on site.
If this happens, the macabre option of “entombment” comes into play. Essentially this just means dumping a whole bunch of inhibiting material on the site and then leaving the region alone for at least a few decades. For now, let’s hope this is not necessary.
