Thursday, February 17, 2011

Yes We Have Some Bananas...

...or at least an equivalent dose: Going bananas over radiation:
...A banana equivalent dose is a concept occasionally used by nuclear power proponents to place in scale the dangers of radiation by comparing exposures to the radiation generated by a common banana.

Many foods are naturally radioactive, and bananas are particularly so, due to the radioactive potassium-40. Radiation leaks from nuclear plants are often measured in extraordinarily small units (the picocurie, a millionth of a millionth of a curie, is typical). By comparing the exposure from these events to a banana equivalent dose, a more intuitive assessment of the actual risk can sometimes be obtained.

The average radiologic profile of bananas is 3520 picocuries per kg, or roughly 520 picocuries per 150g banana. The equivalent dose for 365 bananas (one per day for a year) is 3.6 millirems (36 ╬╝Sv).

Bananas are radioactive enough to regularly cause false alarms on radiation sensors used to detect possible illegal smuggling of nuclear material at US ports.[4]...
I've worked with radioactivity and radioactive counters, particularly gamma emitters like K-40, for a long time.  In fact, I did a lame-ass project as an undergraduate measuring potassium in seaweed by measuring the radioactivity from the K-40.  I used to keep a tube of KCl handy to use as a demonstration that the world is full of random sources of radiation (along with the mandatory Coleman Lantern Mantle, source of thorium and daughter isotopes, and some depleted uranium oxide.  I enjoy seeing people panic when they realize radiation is all around them and there is absolutely nothing they can do about because much of their dose is internal (we are a pretty big reservoir of potassium on our own).  It doesn't seem to stick for long, though, and they go back to radio-phobia almost immediately.

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