Small edit: I just read that some of the damaged reactors at the nuclear plant in question was about to be decommissioned anyway. I may have overstated the power loss of Japan’s electric grid.
Small Edit number 2: For the more technically minded, here is a rather complete description of what happened at the Fukushima plants. Keep exploring the posts on this blog. Probably one of the most accurate sources of information on this situation out there.
Small edit number 3:Here is a link to a chart prepared by Randall Munroe, the author of the webcomic xkcd. THis chart shows the relative strengths of different kinds of exposure to radiation. It is so clear it should put many of your misconceptions about radiation in perspective. It certainly did for me.
A horrible tragedy as you might have heard. Here is a brief summary. Not only there was damage caused directly by the earthquake ranking 8.9 on the Richter scale, there was devastation on a very large scale caused by the tsunami that ensued. The water advancing on the land has been filmed from an helicopter. It is terrifying to see the mass of water relentlessly pushing into the land, never indicating that it is slowing down.
That is not the end of the story. The earthquake and tsunami damaged the Fukushima Dai-ichi nuclear power plant, which has now been subject to a few hydrogen explosions. The situation is terrible. Not only people have lost their homes, jobs, friends and family members (2414 confirmed deaths), Japan may be deprived of a substantial portion of its electric power grid for a long period of time. That makes it very hard to get back up. If you feel the need to help, Phil Plait has compiled a list of organisations through which you can donate to help. Personally, I will be giving money through the account CERN has set up for the occasion. And by the way, I hope you realize that it’s not because Japan is a rich nation that it doesn’t need our help.
There are two things that seriously infuriate me in the spectrum of reactions we have seen in the western world to the Japan disaster. First, there is this kind of stupid people. Please, if you think God is wrecking Japan to convert atheists, check yourself in a mental institution and never go anywhere near children. But there is also this kind of smart-ass. Green Peace is jumping at the occasion to further its political agenda.
I think the first category of reaction doesn’t need any more deliberation. It’s just plain stupidity. However, for the second point, it is worth taking some time to explain a few things about nuclear power plants.
I think that after the Large Hadron Collider and the International Space Station, nuclear power plants are the most advanced pieces of successful engineering humanity has come up with. The thing is, nuclear reactors are fairly simple. They are a really neat way of controlling an avalanche reaction by neutrons to generate tons of heat. They consist of a given number of parallel rods containing pellets of uranium. The rods are standing in heavy water that slows down the neutrons coming out of the uranium pellets. The distance between the rods is carefully controlled such that the neutrons are slowed down at just the right speed when they reach a neighbouring rod. Why is the speed of the neutrons so important? Because if the neutrons go too slow, they won’t have enough energy to provoke the production of more neutrons. If they go too fast, they just whizz by, they pass right through the rod.
You can see now that stopping a nuclear reaction is fairly easy: separate the rods. Even bringing them closer would do the job. In addition to this, you can just flush the heavy water and replace it with ordinary water. Ordinary water captures neutrons instead of just slowing them down. You can also insert slabs of absorbing material between the rods. These are only the ways I remember of stopping nuclear reactions. Four years ago, one of my fellow undergraduate physics student who just became an employee at the Gentilly II nuclear power plant in Québec was kind enough to come back to the physics department to explain all he knew about the plant. He talked for more than two hours, interrupted by our questions. This is why nuclear power plants are such wonders of engineering. You never see the end of all the safety features implemented. I wish I remembered more.
In any nuclear power plant, each of the safety measures I told you about (and much more), are implemented in one way or another, always with a lot of redundancy (so that if one trigger mechanism fails, it can still be fired by another mechanism). A nuclear reaction in a typical nuclear reactor can be stopped in a manner of seconds.
Nuclear power plants around the world are programmed to kill the nuclear reactions in case of an earthquake. Once the reactor is shut down, there should be no danger of nuclear meltdown or radiation leakage from the reactor. There was one reactor meltdown at Fukushima Dai-ichi because of failure in cooling, but it is contained. By the way, the link I just provided has plenty of information on the safety of nuclear power plants. In particular, it says:
It should be emphasised that a commercial-type power reactor simply cannot under any circumstances explode like a nuclear bomb.
Like I said, the explosions that occurred at the nuclear power plants in Japan were hydrogen explosion. They had nothing to do with the reactors. They may have damaged the reactors, but remember that the reactors are shut down. Also, people over there are closely monitoring the situation and ready to intervene if radiation ever leaks. They are also making sure that water is being circulated around the rods to cool down the reactor. They had problems with this at some point since the flood damaged back-up generators (used to pump the water), but it seems to be under control now.
For more information on this, have a look at Phil Plait’s blog post on this exact topic, and this excellent article by Ford Vox, telling us about new nuclear technologies, orders of magnitude safer than what we already have. Please forgive my own inaccuracies. I strongly encourage you to keep reading on this, and if you feel kind, you can correct me in the comments.