Monday, June 13, 2011

Name That Decay Chain!

There are a lot of studies comparing different energy sources and risk. A lot of the risk is more political than real. Popular opinion means a lot to politicians. Actual risk seems to get lost in the politics.

One comment I saw today was based on a coal versus nuclear study. A large part of the study was a pole of people living near nuclear or coal power plants. That is a big part of the decision of course, what will people vote for, but education of the real risks involve is not as big a deal as I think it should be.

A coal power plant emits a lot of stuff if not scrubbed and filtered. Then if it is scrubbed and filtered, the ash and particulates contain stuff that can be nasty. Heavy metals are a big concern, with radiation a little bit of a concern that looks to be over emphasized.

Coal contains traces of Uranium and Thorium, plus other natural radioactive isotopes. Natural isotopes are generally very long lived, but a there are a few short lived isotopes in the natural decay chains.

For some odd reason, long lived isotopes have a bad reputation. Statistically, it is the short lived ones that are nasty. The short lived are more likely to decay releasing ionizing energy. Uranium-238 has a half life of 4.5 billion years. So a few atoms of Uranium-238 are essentially stable in a biological environment. You would have to ingest a fairly large amount of Uranium-238 to have any radiation harm. It would likely be more harmful as a poisonous heavy metal than a radiation hazard. Think about it. It takes 4.5 billion years for half of the ingested amount to decay. If you ingested 4.5 billion atoms of U-238, 2.25 billion would decay in 4.5 billion years, so only 2.25 would decay per year in your body. Compare 2.25 per year to 4400 per second beta decays normal for a 160 pound (about 75 kilo)person, and that ain't a lot, even if U-238 is 60 times more harmful than K-40. Plutonium-239 is only supposed to be 100 times more harmful than potassium 40, so that makes sense.

I need to build a biological decay table to make it easier for people to compare radiation risk by isotope. Then maybe people can start focusing more on the real risks. A biological decay table would b e the probability of harmful decay energy per microgram of isotope. Then everyone could compare fallout danger to the banana dose or Brazil nut dose.

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