Friday, March 18, 2011

Articles about radiation: Complex reality of the radioactive pollution.

As a departure from the primary topic of this blog, I am going to publish a few articles about radiation, to display support for the people affected by the terrible disaster that is unfolding in Fukushima.

Complex reality of the radioactive pollution:

There is a map that everyone must see before thinking about pollution from Fukushima.

The most common misconception is imagining contamination as having a neat falloff or smooth distribution. The distribution is smoothed over time but remained this unsmooth even after a decade. There could be a spot where you measure high levels of radiation, few meters away the levels can be normal, and few more meters away the level may be high again.

You shouldn't think of it as of contamination with 'radiation' that 'radiates' around. No, it is a contamination with dirt that goes around the way dirt does; the dirt itself is radioactive and can expose you either from outside over distance, or from inside through ingestion, inhalation, food chain, etc. The reactor pollutes environment with radioactive dirt. The radioactive dirts radiates the radiation. The radiation from the dirt does not itself make anything radioactive.

The 'radiation levels', unduly exact numbers in microsieverts/hour, are not a measurement of environment pollution with radioactive isotopes from the accident. They are merely an *indication* of a fact of pollution.
A counter would measure drastically different values whenever clean counter is held up in the air, the counter is directly held to a surface that has been collecting dirt from the air (and here it would drastically depend to the position of this surface), or the counter is allowed to collect dirt from the air [however that would pollute the counter]. The alpha and beta activity as measured by a counter held to a surface will drastically depend to the amount of *non* radioactive dirt that is mixed with radioactive dirt.

The meaningful pollution values are that of estimated curies (or becquerels) of particular isotope per square kilometre, per cubic metre of air, per cubic metre of water, etc. To measure air pollution by radioactive dust you have to run specific volume of air through the filter, then measure radioactivity of the filter.
Different isotopes have different presence in the human body even at same environmental concentration.
Furthermore, the radiation levels on the surfaces fall off quickly in first few rains even for long living isotopes due to the radioactive dirt being washed off and mixed up with a deeper volume of soil (picture radioactive dirt sitting on surfaces affecting the geiger counter a lot, then same radioactive dirt mixed up with soil and groundwater, largely not reaching the geiger counter; with a significant fraction of that dirt being washed off into rivers and then dispersed in the sea).

When you live 500km away from Chernobyl and you know of everyday things such as radioactive boars in Germany thousands kilometers away from Chernobyl, which are radioactive beyond permissible limits for meat because the boars eat truffles which concentrate radioactive isotopes, while humans and other animals whom do no routinely eat radioactive truffles (or radioactive boars) are not even remotely as much contaminated as those boars, you tend to appreciate the complexity of radioactive environment pollution which can't be represented by a mkSv/h number. Elsewhere, you do not know such things.

That is to say, the issue of pollution is very complicated and it is far more difficult to measure pollution than to hold a Geiger counter to something. So far I haven't seen any pollution figures from area around Fukushima. Only readings from Geiger counters indicating the fact of pollution.
Understandably, after earthquake and tsunami, they have other issues to be concerned with.

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