The radioactivity of bismuth

[emcelhannon]

How would one calculate and illustrate the harmlessness of the ridiculously long half life of Bi. Can we compare it to the sun, an X-ray, metal detector, smoke alarm, my mother in laws glare?

I'd like to be able to prove it with math if anyone here knows how.

 

Thank you,

Ernie

[John Cuthber]

If I were concerned about any of those other sources of radiation (I'm not), I could reduce my net exposure by hiding behind a big lump of bismuth.

 

It is damn near impossible to actually show that Bi is radioactive because it's roughly a billion times less radioactive that uranium.

[emcelhannon]

Thank you for your reply. I'll use the comment about hiding behind a lump. I know it's harmless, but comparing it to uranium will not put my customers at ease. I need numbers to show that it's less damaging than a light bulb, (something already perceived as harmless).

[Greg H.]

Well, if it helps at all, bismuth is safe enough to be used in a variety of consumer products:

 

Bismuth compounds account for about half the production of bismuth. They are used in cosmetics, pigments, and a few pharmaceuticals, notably Pepto-Bismol. Bismuth has unusually low toxicity for a heavy metal. As the toxicity of lead has become more apparent in recent years, there is an increasing use of bismuth alloys (presently about a third of bismuth production) as a replacement for lead.¹

It's also used to make low metling point alloys for such things as automatic sprinkler systems², so chances are, your customers (whoever they are) are already using, have used, or at least been exposed to products with bismuth in them on a recurrent basis.

1 - Bismuth - Wikipedia

2 - Bismuth - More Uses

[John Cuthber]

I wouldn't use a light bulb because it's a slightly different sort of risk so it might be thought of as misleading.

 

Perhaps this would work.

According to this page

 

http://en.wikipedia.org/wiki/Abundance_of_elements_in_Earth%27s_crust

there's about 2 parts per million of uranium or, if you like,2 grams of uranium in each tonne of the earth's crust.

so if the only source of radioactivity in dirt were the uranium (and it isn't - there are other contributors like potassium and thorium) dirt is about 2 millionths as radioactive as pure uranium.

So the bismuth, which is a thousand million times less radioactive than the uranium, is about 500 times less radioactive than average dirt.

 

Actually, the ratio is rather bigger than 500

There's about 5 times more thorium than uranium in dirt but it's about 3 times less radioactive so the radiation from Th is comparable with that from Thorium.

So the dirt is about 500 times more radioactive than Bismuth.

Then there's another factor. The decay products.

The immediate products of radioactive decay of uranium are themselves radioactive.

And then there is a chain of further reactions until you get to something stable so, for each decay due to uranium there will (eventually) be about 15 decays from the so called daughter products.

So for naturally occurring uranium (with all the decay products) the total radioactivity is about 15 times that due to just the uranium.

Bismuth's decay product is stable so there isn't a similar multiplication factor.

So now the dirt is about 15,000 times more radioactive then the bismuth.

 

People don't generally worry about dirt being radioactive.

 

Having said all that, Greg's comment about pepto bismol might convince some people better.

Edited August 19, 2012 by John Cuthber

[StringJunky]

Bismuth is considered an environmentally safe alternative for lead split-shot used in fishing. Lead shot below a certain size (1oz) is illegal to use in the UK as lost shot that remains in the swan and other waterfowl feeding areas causes them to have cumulative lead-poisoning when they grub around.

 

It's a lot safer than lead and most people have some notion of that particular metal's toxicity.

[emcelhannon]

Everybody's afraid of lead, so saying that bismuth is safer isn't very comforting. Bismuth sub silicate is used in medicine, and that works sometimes. Still, saying that a pharmaceutical co. thinks its safe enough to sell in Papto isn't as good as the numbers about dirt. That one ought to relax just about everybody.

 

But I don't know about radioactive potassium. What do you mean?

 

Much obliged to all.

[John Cuthber]

Quite a lot of elements contain small amounts of radioactive isotopes. Potassium is probably the best known example.