PLUTONIUM FOUND AT FUKUSHIMA!! Probably from old weapons tests thousands of miles away, but hey, let's wet ourselves anyway
There has also been heavy reporting in the press regarding the discovery of very small amounts of plutonium isotopes at the site – producing less than one Becquerel of radioactivity per kilo of soil. (For context the human body naturally emits radiation around 50 Bq/kg). This is utterly insignificant in a health context but is possibly indicative of fuel damage in the cores – if the isotopes did in fact come from the cores. The levels in three of the five samples are so low, and of such isotopes, that it is quite possible they result from long-ago nuclear weapons tests in the Pacific. Two other samples contain some plutonium-238, a clue that they may be from the no 3 reactor which had plutonium in its fuel.
"[Those two samples] could possibly come from the accident," TEPCO spokespersons told World Nuclear News.
Often these facts have been reported in such a way as to suggest that the Fukushima events have led to contamination levels similar to those following nuclear weapons tests, which is utterly untrue.
Elsewhere, emissions of radioisotopes into the sea are well above normal regulatory limits, though not such as to cause any health concerns. The main health concern is radioactive iodine-131, the isotope which caused the only perceptible public health effects following Chernobyl when millions of children consumed it in contaminated milk, leading to very slightly increased chances of thyroid cancer later in life. As thyroid cancer can almost always be cured successfully, this has resulted only 15 deaths: fewer than one in a million of the affected children and youngsters died.
According to Japan's nuclear safety authorities, the seaborne levels of radio-iodine near Fukushima Daiichi are not such as to necessitate any bans on fish or similar, though all food products from the region (and across Japan) are being radiologically sampled and monitored in case the situation changes. Some bans on produce from the area around the plant have already been instituted, though these are likely to be of brief duration as iodine-131 has a half-life of only eight days – it will all be gone within weeks no matter where it has reached.
Another concern is radioactive caesium. This didn't cause any measurable health consequences following Chernobyl, but it did result in areas of farmland being abandoned for long periods as it has a lengthy half-life. Consequences on this scale seem unlikely in Japan, however, as releases of material from the reactor cores at Fukushima have been tiny compared to that from Chernobyl. In one spot 25 miles from the plant an IAEA team has reportedly measured activity as high as 3.7 megabecquerels from caesium: if you remained within a metre of that spot constantly for 22 years you could acquire a radiation dose sufficient to raise your chances of cancer by a tiny fraction of a percentage point (actually it would take longer, as nearly half of the caesium would have decayed away by then: call it 30 years without breaks. You would also need to ensure that nothing dispersed or washed away the caesium. Your chance of getting cancer would then rise from say 25 per cent or whatever it was to 25.0001 per cent, or similar.)
Having that caesium in your house, in short, would be hugely less dangerous to you than having your bath - you might very easily slip and break your neck in the bath, or accidentally drown yourself. Nonetheless various international "experts" - often anti-nuclear campaigners, in fact - suggest that this means the Japanese evacuation zone should be extended.
Media hysterics continue, with reports that the No 2 core has "melted through the bottom of its containment vessel" published by normally reputable outlets. In fact the IAEA confirms that the temperature at the bottom of the No 2 reactor vessel is just 88 °C.
Some much-needed perspective was offered by the UK's top scientist, who pointed out on Tuesday afternoon that nuclear power is far and away the safest form of energy generation and remains so in the wake of Fukushima.
"Not one person has died from radiation," Sir David King told the Guardian. "Let me put that in context – in the same week, 30 coal miners died. Generating electricity from coal is far more dangerous."
Sir David also made the point that one would subject oneself to more radiation dose by taking a jet flight than by taking a walk around Fukushima Daiichi in its current condition. He was speaking at, and endorsing, the launch of new analysis from Oxford university which urges the UK to reform its current nuclear industry policy of generally not recycling spent nuclear fuel.