Alpha emitters, Geiger Counters
– a clarification on monitoring for radioactive pollution
The principal alpha-emitting nuclides of interest are Plutonium and Uranium. To all intents and purposes only specialised and expensive scintillation counters like the DP2 Elektra can detect them in the environment. Even then the detector window must be within 2cm of the radioactive particle. You won’t do this many times because the window on the DP2 is so thin that a blade of grass will make a hole in it, and then it has to be repaired. Cheaper (but still costly) instruments such as the Gamma Scout which claim to detect alphas might possibly have some marginal response if a particle was on the detector window, but you will still have no way to tell what it was responding to. Gamma signals will swamp any alphas anyway. If you don’t believe our advice on this, here’s another view
There is a cause for concern. As we have already said, it is more than likely (in fact quite certain) that Plutonium and Uranium are part of the fallout mix. If the gamma signal goes above background you have to assume there are particles floating about that you definitely do not want inside your body. The problem with alpha-emitting particles is that although the range of their radioactive decays is very short, they are immensely destructive, killing cells and potentially mutating the DNA of cells which survive. The standard ICRP model of radiation risk takes an average of the energy of those decays as if it were distributed across large volumes of tissue and concludes that the risk is low. This is as stupid as believing that because it’s safe to warm yourself by the fire it’s equally safe to absorb the same amount of heat by eating a red-hot ball bearing.
At the date of writing we still know of no information from Japan on alpha emitters from the disaster. This is a serious dereliction of duty to the public.
This page was posted 20th March 2011 in response to a message from the UK Foreign and Commonwealth Office suggesting that Geiger Counters do detect alpha emitters.