At a recent SCLF conference there was one idea which although it’s a wee bit outside our normal day to day work really caught my imagination, this is the Banana Equivalent Dose for radiation. As anyone who’s ever suffered from cramp after exercise knows, bananas contain potassium. This is why you’ll often see athletes, particularly tennis players, munching bananas before or during an event.
The Banana Equivalent Dose or BED for short is the concept that due to the miniscule quantities of the radioactive isotope Potassium 40 naturally present within a banana it is possible to relate a dose of radiation to the number of bananas you would have to eat to achieve the same dose.
Now before you start to worry and stop eating bananas it must be said that in such tiny quantities there’s really nothing to fear from you’re lunchtime banana. The radioactive potassium 40 exists as a tiny but measurable proportion of the naturally occurring potassium found in bananas which allows you to put radiation exposures into some sort of context. Using this methodology the dose equivalent which you recieve from one banana is about 0.1µSv. So 0.1µSv = 1 Banana.
Therefore your exposure from a chest x-ray is 200 bananas.
The yearly target release for a nuclear power station is 300 bananas.
Ten years of normal background radiation (85% of which comes from natural sources) is about 40, 000 bananas.
A fatal dose of radiation would be about 80, 000, 000 bananas.
And ten minutes next to the Chernobyl reactor core shortly after meltdown is 500, 000, 000 bananas.
Which really is a lot of bananas for anyone to eat!
It’s not a fool proof system but it does make it a bit easier to visualise radiation risks. Let us know if you can think of any other equivalent scales.
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