A nuclear power plant in Japan has exploded.
At 3.30 local time today a nuclear power station in Japan exploded. You can see video of the nuclear explosion in Japan here.
At this stage it is simply not known how serious this explosion will be but it is possible to piece together some points.
The first is that this is not really a nuclear explosion: it's a chemical one.
The difference is important. A nuclear explosion is what happens with a nuclear bomb. We have actual fission, it is the uranium (or plutonium) itself which undergoes a nuclear reaction. This creates vast amounts of radation, new elements and is hugely, massively, destructive. It is absolutely clear that the so called "nuclear" explosion in Japan is not in fact a nuclear reaction.
The damage simply isn't large enough, the plume of smoke is of entirely the wrong shape and the reported amounts of radiation simply are no where near large enough for this to be true.
So it must be a chemical explosion: most likely caused by hot (even melting) uranium coming into contact with water. This would produce hydrogen (the heat of the metal would break the H2O into hydrogen and oxygen) and then that hydrogen itself could explode.
The effect of this is that no new radiation has been created. No new elements: what was already there has been moved around, spread possibly into the surrounding land and atmosphere, but we are absolutely not looking at a runaway nuclear reaction.
The second point is that there will be the inevitable comparisons with the Chernobyl disaster. It is extraordinarily unlikely that the Fukushima explosion will result in anything like the radioactive pollution caused by Chernobyl. For the reactor itself is of an entirely different design. What happened at Chernobyl is that the graphite (a type of carbon, you can liken it to coal) caught fire and it was the plume of smoke from this which spread the radiation across much of Europe. There is no graphite in the Fukushima reactor so such a fire is not possible.
The final point we can make at the moment is that while we don't in fact know exactly what has exploded, the radiation levels do not seem to be all that high. Higher than normal, certainly, but nothing like the results of Chenobyl. This requires a little bit of boring explanation so apologies in advance.
The radiation levels at Chernobyl were of the order of 30,000 roentgens per hour right up next to the plant. No one really has a good idea of what this means but to give you an idea, be exposed to this for a few minutes and you are going to die of radiation poisoning. As reported from Japan, the radiation levels from this nuclear explosion at Fukushima are of the order of 1,000 to 500 microsieverts per hour.
So what's the relationship between a roentgen and a micro sievert? Again, not something that most people could tell you.
30,000 roentgens is about 3,600 sieverts (3,579 actually). There are one million micro sieverts to one sievert. So one thousand micro sieverts is the same as one thousandth of a sievert. So, as far as we can tell at the moment, the radiation coming from the Fukushima explosion is 1/3,600,000 th of the radiation from the Chernobyl explosion. This isn't quite right for a number of complicated reasons (for example, we don't know how far the Japanese radiation will spread, what the total release will be and so on) but it does give an idea of the relative magnitude.
It is 0.00002% of the Chernobyl levels of radiation.
Another way of saying the same thing is that if you were standing at the reactor now you would, in one hour, receive the usual permitted level of radiation for an entire year. About half what you would get if you had a medical CT scan (which is 2,000,- 2,200 micro sieverts). This is of course a very, very, much lower level of radiation than at Chernobyl, where workers got in minutes amounts that killed them.
We will of course find out much more as matters develop. But at present it certainly seems that this is nothing like as bad as Chernobyl was.
It's even possible that the outcome of this explosion will be to show quite how safe nuclear reactors actually are. If, after the seventh largest earthquake ever recorded, and a 10 metre wall of water from the tsunami rips through the place, the result is radiation levels below that from medical devices, well, nuclear power really seems quite safe, doesn't it?
Comments