Let’s talk about plutonium

The nightmare at Fukushima just keeps getting worse and worse. There are two reasons behind this failure to contain the disaster: firstly, the Tokyo Electric Power Company (TEPCO), who run the plant, are a management company, not an engineering company; secondly, they are trying to cope with the disaster with woefully insufficient funds. What’s needed at Fukushima is an international team of engineering experts and huge wads of cash. Alas, it seems that the world won’t wake-up to these facts until it is too late.

The latest ‘problem’ that’s been admitted is that of ground water. The Fukushima Daiichi nuclear plant is built on a water coarse (brilliant, huh) and it’s estimated that up to 1000 tons of this water flows beneath the plant and out into the ocean every day (here). TEPCO built a ground wall on the seaward side of the plant to try and contain the ground water, and then pump it out into storage tanks; but they can’t pump it out fast enough and most of the water is going into the ocean. This has been going on almost since the start of the disaster two and a half years ago. It should be noted that this water is flowing through the sub-levels of the three wrecked reactor buildings and is highly radioactive; and by the way, no one knows where the three melted reactor cores are, because neither humans nor robots can get anywhere near them due to the extremely high radiation levels.

So, we have a situation where huge amounts of highly contaminated water is going into the Pacific Ocean. TEPCO regularly tests the sea around Fukushima for radiation and they say the levels are safe. Even if you believe what TEPCO say (and most don’t) you’ll notice that they only ever test for cesium. The devil’s brew that is created by a fission reactor contains a lot more than just cesium. Cesium is one of the elements that are created in abundance, others are iodine, strontium, xenon and barium (here). These all have varying half-lifes, depending on which isotope of each element you’re looking at. Cesium 137, for example, has a half-life of 30 years (making it dangerous for 300 years), whereas iodine 131 has a half-life of about 8 days (in a matter of months it’s gone and no longer a danger); but I’m not going to get into the various isotopes because A) I’m not a nuclear physicist, and B) I want to make this post readable.

In a nuclear reactor you start off with a big lump of uranium (usually uranium 235) in the form of fuel rods, and the fission process creates lots of other elements, most of which are not found in nature. The most abundant fission elements (such as cesium) are in the main beta emitters; ie, the radiation they give off is in the form of beta rays that can penetrate the human body, which makes them quite dangerous. However, the real nasties are the alpha emitters, which are found in much lesser quantities but make up for it by how lethal they are. There are lots of different alpha emitters, but I’ll take the one that most folks are familiar with: plutonium. Named after the planet Pluto, which itself is named after the God of the Underworld, plutonium is one of the most deadly substances on Earth. It’s not deadly in the sense of airborn ionising radiation. Alpha rays don’t reach very far and can’t penetrate a piece of paper and are stopped by a few centimetres of air (you can stand relatively close to an alpha source and be quite safe). It’s deadly because alpha rays are very, very energetic (ie, very, very radioactive) and plutonium isotopes have incredibly long half-lifes. The two best known, because they are used as fuel for nuclear bombs, are plutonium 239 (with a half-life of 24,000 years), and plutonium 240 (with a half-life of 6,500 years). The point about alpha emitters, and in particular plutonium, is that if they get inside your body your chances aren’t good. It’s not just the fact that you’ve got a very energetic/radioactive and long lived isotope nestled up against your cells, but also that plutonium is a highly toxic heavy metal.

Ralph Nader, the American political activist, once famously said that one pound (roughly half a kilo) of plutonium dust spread evenly in the atmosphere would be enough to kill 8 billion people. That claim is often disputed, yet even the nuke brigade don’t shy away from how lethal plutonium is; which brings me back to what’s happening at Fukushima: a Mark 1 Boiling Water Reactor contains 180 tons of fuel, and during its cycle this fuel will produce 700 kilograms of plutonium (here). There are three reactors that have melted down at Fukushima and in total they contain something like 2,100 kilograms of plutonium (reactor No.3 does in fact contain a higher than average level of plutonium, but I’m trying to keep the figures simple). One microgram of plutonium is enough to kill a human if it gets inside the body. There are more than 2 billion micrograms inside those three melted reactor cores, and it looks like much of it is going into the Pacific Ocean, and thence into the food chain; and remember, I’m talking only about plutonium here: there’s a whole host of other nasties in the devil’s brew.

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