Background Radiation: What & Where Are Trace Amounts Coming From?

[zoobyshoe]

What's the nutshell story on background radiation? It sounds like there is a small level of nuclear radiation coming from the soil just about everywhere. Is this the case? What is it coming from? Are there trace amounts of radioactive elements pretty much all over the place?

 

[Bystander]

Originally posted by zoobyshoe
What's the nutshell story on background radiation? It sounds like there is a small level of nuclear radiation coming from the soil just about everywhere. Is this the case?

Yup

What is it coming from? Are there trace amounts of radioactive elements pretty much all over the place?

Yup. Snoop around on "crustal abundance."

 

[zoobyshoe]

OK. I've been to two sites. Too much to wade through.

Anyone interested in expounding on background radiation?

 

[russ_watters]

Originally posted by zoobyshoe
OK. I've been to two sites. Too much to wade through.

Probably need to refine that google search. Try "background radiation exposure environement." The fist site is the http://www.ocrwm.doe.gov/factsheets/doeymp0337.shtml

More than 80 percent of the radiation we are exposed to comes from such natural sources as sunlight, soil, and certain types of rocks. Cosmic rays filtering down through the atmosphere, and radon gas filtering up through the soil, are sources of natural radiation. This radiation is called background radiation. It is present everywhere, all the time and varies greatly depending on our geographical location.

In addition, people are exposed to radiation from man-made sources such as color televisions, smoke detectors, computer monitors, and X-rays. These sources account for less than one-fifth of our total radiation exposure. But, there is no difference between natural radiation and its effects and man-made radiation and its effects.

THIS site has a small chart saying what you get from certain things such as a plane trip across the country (5mrem) and a chest xray (10mrem).

I looked for what environmentalist websites say on the subject, but only found a handful of dead links. Its not surprising to me though since its existence tends to counter arguments against things like nuclear power. (check out the mkaku forum for how a poster named "theroyprocess" ignores any mention of background radiation)

 

[zoobyshoe]

Thanks Russ, that level of info is more what I'm looking for.

I did actually search "crustal abundance + background radiation" and came up with sites that were more technical than I could grasp overall.

There was much mention of "radionuclides". This, I get the feeling, is different than there being a lot of uranium or plutonium specks scattered everywhere.

Your quotes mentioned radon as the primary source of BR from the soil, which is something the sites I found didn't do.

I'm curious as to what causes it to leave the ground when it does?
Even though it's a gas, it's got a heavier nucleus than gold.

-zoob

 

[Nereid]

I'm curious as to what causes it to leave the ground when it does? Even though it's a gas, it's got a heavier nucleus than gold.

There used to be an experiment which high school physics teachers did to teach gas diffusion. A gas jar full of H₂S was opened at the front of the class, and students asked to put their hands up when they first smelled the 'rotten eggs'. Radon can move from its place of creation by gas diffusion.

Besides that, gases in soil move in response to pressure differences ('the wind'), which is partly how water vapour (for example) moves upwards through the soil, drying it out. Radon is 'just another gas'.

There are plenty of naturally occurring radionuclides besides thorium and the various isotopes of uranium (and their daughter decay products, including radon?).

You've heard of 'carbon dating'? The technique is based on ¹⁴C, which is produced by cosmic rays interacting with nitrogen atoms in the air. The radioactive carbon (it has a half-life of ~5,700 years) becomes part of living things, through photosynthesis in plants (which get eaten, etc) ... yes, you are radioactive! Here's a link:
http://science.howstuffworks.com/carbon-141.htm

⁴⁰K (potassium) is another naturally occurring radionuclide, and yes, those bananas which are 'high in potassium' are also radioactive.

 

[zoobyshoe]

Originally posted by Nereid
You've heard of 'carbon dating'? The technique is based on ¹⁴C, which is produced by cosmic rays interacting with nitrogen atoms in the air.

This is a surprise! Alchemy?

⁴⁰K (potassium) is another naturally occurring radionuclide, and yes, those bananas which are 'high in potassium' are also radioactive.

Meaning plants tend to prefer to take in the radionuclide over the conventional element?

 

[russ_watters]

Originally posted by zoobyshoe
Meaning plants tend to prefer to take in the radionuclide over the conventional element?

No, that just means that since some potassium is radioactive, the more potassium you eat, the more radioactive potassium you eat.

 

[Nereid]

zooby wrote (re the production of ¹⁴C): This is a surprise! Alchemy?

Yes zooby, essentially all nuclear reactions are alchemy.

When a cosmic ray collides with an oxygen or nitrogen nucleus (say) in the air, a cascade of secondary particles is produced. Some of the secondaries are neutrons. A neutron with the right energy may interact with a ¹⁴N to produce ¹⁴C:

n + ¹⁴N -> ¹⁴C + ¹H

More details:
http://en2.wikipedia.org/wiki/Radiocarbon_dating

Here's a proposed Polish high school project on cosmic rays; very nice.

It includes the following sentence: "At the separate detector level (4 separate pieces of information per mini array) the secondary cosmic ray particle flux can be constantly measured. The intensity is about 170 counts per second for 1m² detector (corresponding to 6 penetrating and ionising particles passing per second per human head or 1 particle per hand)."
http://www.u.lodz.pl/~wibig/maze/eu_e.htm

 

[zoobyshoe]

Originally posted by Nereid
When a cosmic ray collides with an oxygen or nitrogen nucleus (say) in the air, a cascade of secondary particles is produced. Some of the secondaries are neutrons. A neutron with the right energy may interact with a ¹⁴N to produce ¹⁴C:

n + ¹⁴N -> ¹⁴C + ¹H

Thanks, Nereid. I can follow this explanation. Prior to this I just had the vague notion that carbon-14 was something that was just hanging around. It is a surprise to find out it is constantly being created, and in this fascinating way.

Here's a proposed Polish high school project on cosmic rays; very nice.

Yes, great project. The high schools I attended were too light on science to get into anything this cool.