The nuclear crisis in Japan – what I know so far

As you might have heard on the news there are some troubles with a nuclear plant in Fukushima. First of all, I live in Tokyo. Tokyo is about 300 kilometers away from Fukushima so we are absolutely at no risk where we are. They have upgraded the evacuation zone in Fukushima to 20 kilometers recently and that is to keep everyone 100% safe.

What happened was that because of the earthquake the power plant lost external power. In other words they have a blackout right there at the moment. Let me show you a quick picture from Wikipedia.

Boiling Water Reactor

This is a schematic of the type of reactor we’re talking about. A Boiling Water Reactor. When the power fails several things in this image stops working, but the only important thing is point number 16. That is the pump that pumps in water from the sea which in turns cools the water that is in the reactor. The Union of Concerned Scientists have written a good article on what has happened so far.

Basically as I said, they lost power. Then they have diesel generators on-site to provide backup-power. As soon as the earth-quake happened all the reactors shut down, but they still produce heat. What then happened was that the whole area got flooded from the Tsunami and the diesel-generators failed. To my understanding they are now completely without power (and have been for some time) and the pumps (at point 16) can’t pump in “coolant” (seawater that is). This causes the water inside the reactor to rise in temperature and pressure. The rise in pressure caused this to happen:

That is clearly not good. But it is not dangerous in itself. I’m just speaking out of my own belief there but the tank that holds the fuel and the boiling water is encased in concrete. When the pressure rises too high that causes the metal (which is flexible) to expand and finally break the concrete (which is not flexible) that it is encased in. Because concrete isn’t soft it doesn’t slowly break and give way, it builds up tension until it can’t possibly hold anymore and then releases all the tension at once. Causing what you see in the video.

However, according to recent news the inner container is still supposed to be undamaged.

There are two very bad potential outcomes. All the water inside the tank has been in contact with the fuel rods and is thus radioactive. It contains traces of a bunch of bad radioactive materials that are waste-products of nuclear fission. The first really bad thing that can happen is that the inner container breaches and lets out all that steam. Fortunately steam would condense pretty quickly and fall down pretty quickly. The affected radius would likely not be very large.

The second bad thing that can happen is a meltdown; that’s when the fuel rods stop being sufficiently cooled by surrounding water and the radioactive fuel which is normally hard material shaped in rods (number 2 in the figure above) start melting and thus dripping down to the bottom of the tank and melting through the steel container and into the underground containment facilities. The containment facilites are reported to be intact so really it shouldn’t be a problem. But having several thousand degrees warm material lying around melting through steel, concrete and earth is a large potential hasard simply because it can leak into the ground-water or it can start a fire that could be used to carry the radioactive steam high into the air and thus spread it out.

So in summary; containment tank exploding: causes local damage. Meltdown: causes no damage in itself but could itself be a cause of a third and by far worst possibility, fire.

The last thing is still very, very unlikely of happening. This is purely my speculations, as there have been very little information released on this so far. You can read this CNN article if you want to know more.