The Risk Professional: The trouble with radiation - a bad, bad hangover

The trouble with radiation is that it doesn't go away. Well, that is technically incorrect but with plutonium 238 - the type commonly used in nuclear power generation plants - reducing in mass by 50% roughly every ninety years. So, if it starts at one tonne today, there will still be half a tonne of the stuff in almost a century and a quarter of a tonne in almost a century after that and so on.

This is the problem that those advocating nuclear power have not yet come to grips with: the solution most usually applied to "fuel rods" that have ended their useful life is to sink them in water to keep them cool and to reduce their risk of a catastrophic event resulting from a sudden "meltdown" - that's when an otherwise safe nuclear power plant turns into something not unlike a nuclear bomb.

"Spent" fuel rods are often transported - by road or rail - to reprocessing plants. There are just a handful in the world. There they are treated to make them less dangerous and - often - the remaining useless material is then encased in concrete and buried. No one knows how long the concrete will last and what the consequences will be if (when?) it breaks down sometime over the next few hundred years.

In Japan, their problem has been that the pools in which their spent fuel rods were stored suffered damage and the water was disappearing. Some has evaporated as temperatures in the pits rose but some, it now seems likely, escaped. The radiation levels in pools of water around the plant are far outside the norms - and although less than in the landlocked puddles the radiation level in the nearby sea is also far more than it should be.

The authorities put a 30km exclusion zone around the plant but excessive radiation has now exceeded that zone. High levels remain more than 100km from Tokyo but urban areas are now within the reach of higher radioactivity. An increase to a 40km exclusion zone will displace 130,000 people. The smaller, original, zone displaced more than 70,000. The extension of the zone is therefore no small matter - either in terms of logistics or, in due course, compensation.

As fruit and vegetables exported come under scrutiny - in some cases being rejected - the response to the growing radiation threat is coming up short. An acceptable radiation level in vegetables is 100 becquerels per kg but cabbages arriving in Singapore last week the level was approx 900. Other samples in other vegetables were similar or even higher, according to the International Atomic Energy Agency.

There is remarkably little history from which the Japanese can learn (without, of course, considering radiation from US bombs in the 1940s). The most recent case with a similar background is, of course, that of Chernobyl.

For months, English black humour revolved around glow-in-the-dark sheep or lamb that could be bought ready-microwaved. But as always, black humour hides a dark truth.

The Chernobyl reactor in northern Ukraine blew up on 26 April 1996. The fall-out, carried by wind, reached into the Atlantic Ocean some 2200km away. On its way, as clouds dumped their load onto the north west of England, pastures became contaminated with significant levels of radiation. Animals feeding in those pastures showed increased levels of radiation. There were fears (which ultimately proved unfounded) that those animals would develop cancers which might ultimately develop in humans which ate their meat. Fear is often a more serious driver of behaviour than knowing the science, it transpired.

But even though the threat is today regarded as minuscule, routine testing of the pastures shows continued elevated radiation levels - although not sufficient to be regarded as a risk to humans eating the meat nor, more proximately, to the animals themselves.

To put that into some perspective, the 2200 kilometres distance is four hours in a jetliner.

The Philippines government is constantly re-assuring its population that it has identified no significant increase in radiation since the disaster began. But it must not be complacent: it is only slightly outside the 2200km zone this article has somewhat arbitrarily set. In fact, the 2200 km radius (which was not the full extent of the contamination) is almost exactly half-way to Singapore from Tokyo. Shanghai is (un)comfortably within that range. As is the whole of South Korea and much of the North.

As workers pour ever more water into the Japanese reactors to try to buy time while they formulate a plan for what they consider the long term (but is really only the next few decades), the consequences will fall far outside Japan. Korea's meat and dairy industry, China's agriculture in the south east and a host of small island nations are all potential losers in the circumstances.

But, earlier today, the authorities conceded defeat and announced that they would decommission several of the reactors which they now accept they cannot control. However, there will be continued radiation escape as they make the arrangements and apply the solutions.