Thursday, April 7, 2011

Camels, last straws, mutations, strict EPA standards, and common sense.

Suppose you have a large number of camels under slightly varying, very heavy loads of various things; about 40% of camels break their backs from overload.
You add extra straws to each camel's load, by accident. You observe a slight increase in the camel's probability of suffering the broken back - perhaps when you add 1000 grams of extra weight, the increase is from 40% to 41% . The common sense tells you to expect increase of 0.1% when you add 100 grams, and 0.001% when you add 1 gram - if you can plot a smooth curve of camel deaths versus weight, you would expect that you can approximate the curve with a line at small ranges - and you can expect that even if you add a single extra straw, there is a possibility that it would be the last for some unlucky camel.

Humans suffer from cancer, at a lifetime rate of approximately 40%; cancer is understood to be caused by a long, improbable sequence of mutations within a single cell's lineage. There is a very large number of mutations constantly occurring in the human body - vast majority of them not caused by external carcinogens.

Carcinogens, however, add a small number of extra mutations. Carcinogens are not expected to have safe doses - as the mutations are past the safe mutation rate - and the standards on the known carcinogens (including radiation) are thus extremely strict. No extra straws should be added to camels already at the risk.

The EPA standards for carcinogens - including radioactive contamination - are thus set to be as low as technically feasible. Strictness of the standard is not related to the danger, but to the ease of prevention. When those are exceeded, it is unacceptable, but is not a very big deal for you personally.

The EPA's standard for radioactive iodine in drinking water, in particular, is about 0.111 Bq/L . When this is exceeded by a big factor of 100, that is entirely unacceptable in the sense that the nuclear reactors have not performed as well as was deemed technically feasible - and that is entirely unacceptable because it can cause a few extra deaths in large population. But it is, in itself, not a reason to be afraid.

There is a second set of standards, set by relative threat to human life. Those are substantially more permissive. When food products exceed those standards, however, products have to be disposed of. Those standards are typically in the range of hundreds Bq/L. When those standards are exceeded, there is a sufficiently high risk to human life as to implement active measures to prevent consumption of contaminated food or drink.

Note: the camels are only an allegory. Of course the mechanics of back breaking and cancer are very different. However, both represent the situation where the normal is already unsafe and the extra risk is small.

Wednesday, April 6, 2011

Nuclear accident management in Japan - I just don't understand it.

There's the things I simply do not understand about Fukushima nuclear disaster.

1: Lack of high range radiation meters - the ">1000 milliSievert/hour" figures that keep cropping up.
2: Complaints by the Japanese government on the inaccurate measurements performed by TEPCO. Why the government did not have it's own experts on site doing the measurements? Surely they should have some sort of nuclear war or terrorism response team that is trained for measurements of very high levels of contamination. If they don't - US does. The contamination levels are millions times higher than what TEPCO routinely deals with.
3: Why the situation is being controlled entirely by TEPCO?
4: How the spent fuel pool in reactor 4 ran dry and caught fire (the major source of radioactive release into atmosphere) ?
5: Where are the US and French (Areva) experts and what are they doing?

Lithuania - the country where I live - operated 2 nuclear reactors.

The reason I felt reasonably safe about that is - I knew that if something happened, it would have been handled by the entire European Union, using the immense resources of a region that is a largest producer of nuclear power worldwide.
There is no question that my local electrical utility would not be able to handle reactor accident. But I believe that in Europe vastly larger resources would be available. If I thought that in a case of a nuclear reactor accident in some small country in EU they would not have robots and high range radiation measurement devices on site the next day - if I had any doubts that EU's handling of such accident, combined with a natural disaster, would be vastly better than Japan's - I would be an anti nuclear advocate.

If I thought that in the event of one in a thousand years disaster, the reactors could fail here like they did in Japan - and the spent fuel pools would simply run dry if reactor basements get flooded - I would be an anti-nuclear advocate. Because it is in the disaster when nuclear power may be the most beneficial - the nuclear plant can run for a year without refuelling, providing the power to rebuild the infrastructure after the disaster. The renewable energy sources are unfortunately very fragile and vulnerable in the event of disaster. The fossil fuel sources require constant supply of the fuel. Nuclear reactors should be the energy source to rely on in the face of unprecedented disaster - not the amplifiers of severity.

This is an example of nuclear power plant that did provide shelter to the people who lost their homes, instead of contributing to their suffering. Had the Fukushima plant been built to proper standards, the nuclear power would have been the saviour in the face of disaster - but sadly, that was not the case and the nuclear power did show it's less than beneficial side.