Could brazil nuts really trigger a radiation leak alarm at a nuclear powerplant?

[dstarfire]

In one episode of QI, while talking about foods that are faintly radioactive, Stephen Fry mentions that if you walked into a nuclear powerplant with a pocket full of brazil nuts it would probably set off the radiation leak. This sounds suspiciously like an exaggerated story (like ‘a tooth left in cola overnight will almost completely dissolve’).

[Ethilrist]

Should be simple enough to test. Need answer fast?

[engineer_comp_geek]

My first thought when reading the OP was “how can Brazil nuts possibly be radioactive?” And so, being curious, I went googling.

First of all, the mechanism behind it is fairly simple. A lot of plants will pick up naturally occurring radioactive elements from the soil that they grow in, and Brazil nut trees are no exception. What does make Brazil nut trees exceptional is that they have a very extensive root system, and because of this, they will pick up more radioactive elements than other plants with much smaller root systems.

The soil in Brazil tends to have a bit more radioactive elements in it than soil from many other parts of the world. So Brazil nuts not only pick up more radioactive elements from the soil than other plants, but they are also grown in an area where radioactive elements are more highly concentrated than in other parts of the world.

Ok. Simple enough. That explains why Brazil nuts have more radioactivity than most other foods.

The next thing I found was that a lot of Bazil nuts aren’t grown in Brazil these days, and those that are grown in places like Bolivia that don’t have the higher concentration of radioactive elements in the soil, which makes those Brazil nuts much less radioactive than the ones that are grown in Brazil. According to one web site, over 50 percent of Brazil nuts come from Bolivia these days.

I then found this page:

http://www.orau.org/PTP/collection/consumer%20products/brazilnuts.htm

This page does give the same basic info as Wikipedia and other pages:

As might be expected, the reported concentration of Ra-226 and Ra-228 vary, but overall, the radium concentrations in Brazil nuts are 1000 times higher than those in other foods.

However, earlier in the article it says this:

To be specific, the radium in Brazil nuts is a mix of Ra-226 and Ra-228. Of course, the various decay products of Ra-226 and Ra-228 are also present. Although the radioactivity is not high enough to be detectable with a simple survey instrument, a one to five minute count on the powdered meat of the nut with a pancake GM or ZnS detector connected to a scaler will indicate that the beta and alpha activities are significantly above background.

If you can’t detect the higher levels with a survey meter, it’s not going to set off the leak detectors in a nuclear power plant.

ETA: However, if you keep a bag of Brazil nuts in your shirt pocket all day long, next to your dosimeter, your dosimeter is going to show abnormally high radiation exposure by the end of the week.

[samclem]

[sub]Since the OP is answered…[/sub]
Nuts! Hot nuts! Get 'em from the [del]peanut[/del] Brazil nut man.

[quiltguy]

If the radiation doesn’t get ya’, the high selenium content will. :eek:

[LSLGuy]

So just what is the US RDA for Radium?