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View Full Version : Gold, versus Lead, as a radiation shield?


Ranchoth
02-11-2004, 08:01 PM
Not so odd a question, this time...how would Gold compare to Lead, if used as a radiation shield? Would it offer more protection for it's weight? Or less? Would it not work at all?



Ranchoth

scr4
02-11-2004, 08:40 PM
Not so odd a question, this time...how would Gold compare to Lead, if used as a radiation shield? Would it offer more protection for it's weight? Or less? Would it not work at all?
It's pretty much the same. Lead is slightly more effective (more stopping power for the same weight), but the difference is only about 1%.

I can't think of any reason to use gold for radiation shielding, considering the high price. Besides lead, the only other material I've seen used is tungsten. It's useful when the shield needs to be mechanically strong.

toadspittle
02-12-2004, 09:37 AM
Isn't gold foil used for radiation shielding on spacecraft?

AndrewL
02-12-2004, 09:42 AM
How effective would a large tank of liquid mercury be as a radiation shield?

curly chick
02-12-2004, 10:23 AM
How effective would a large tank of liquid mercury be as a radiation shield?

Surely that would depend on what the tank was made of
If the tank wasn't resistant, then the mercury would be all over the floor at the first hint of radiation.
If the tank was made of something resistant, then why would you need the mercury?

toadspittle
02-12-2004, 10:33 AM
How effective would a large tank of liquid mercury be as a radiation shield?

A large mass of ANYTHING is generally a good radiation shield. Piled-up dirt--or plain water--are both good radiation shields. The problem for engineers is finding something that will stop particles and rays that is still small. (i.e., the lead vest you wear at the dentist's office during X-rays)

toadspittle
02-12-2004, 10:37 AM
The rocket engines of American space shuttles are lined with gold- brazing alloys to reflect heat, and the lunar modules of the Apollo programme that put men on the moon were shrouded with gold foil acting as a radiation shield.

http://www.gold.org/discover/knowledge/aboutgold/industrial_uses/

toadspittle
02-12-2004, 10:49 AM
As a footnote, it appears that gold's radiation-shielding abilities are due to its high reflectivity--not necessarily to the sort of absorption abilities that a nice big slab of lead possesses.

robby
02-12-2004, 11:09 AM
What kind of radiation are you concerned about? As you are comparing gold to lead, you are probably talking about electromagnetic radiation in the X-ray or gamma range.

If you are trying to shield a nuclear reactor, not only are you concerned with gammas, but you also need to shield against neutrons. In this case, the best shielding is a material containing hydrogen, such as plastic or water. Actual reactors use all of the above (lead, plastic, and water).

Surely that would depend on what the tank was made of
If the tank wasn't resistant, then the mercury would be all over the floor at the first hint of radiation.
If the tank was made of something resistant, then why would you need the mercury?
What do you mean by "resistant?" Materials don't disintegrate at the "first hint of radiation."

swansont
02-12-2004, 07:49 PM
What kind of radiation are you concerned about? As you are comparing gold to lead, you are probably talking about electromagnetic radiation in the X-ray or gamma range.

If you are trying to shield a nuclear reactor, not only are you concerned with gammas, but you also need to shield against neutrons. In this case, the best shielding is a material containing hydrogen, such as plastic or water. Actual reactors use all of the above (lead, plastic, and water).



Boron-10 is often added to some of the materials, as it has a significant neutron absorption cross-section.

Carnac the Magnificent!
02-12-2004, 11:07 PM
A large mass of ANYTHING is generally a good radiation shield. Piled-up dirt--or plain water--are both good radiation shields. The problem for engineers is finding something that will stop particles and rays that is still small. (i.e., the lead vest you wear at the dentist's office during X-rays)

IIRC, cosmic radiation cuts through anything like it wasn't there.

scr4
02-13-2004, 12:34 AM
My above post refers to gamma rays, sorry I forgot to mention that.

A large mass of ANYTHING is generally a good radiation shield. Piled-up dirt--or plain water--are both good radiation shields.
In X-rays there is quite a bit of difference. At 60-100 keV energy range (typical for medical and security equipment), lead is about 50 times more effective than the same mass of water. Gold is about 90% as efficient as lead in this energy range. Mercury is somewhere between gold and lead.

You can find the exact number on the NIST XCOM (http://physics.nist.gov/PhysRefData/Xcom/Text/XCOM.html) database. It gives you the mass attenuation coefficient. X-ray transmission is exp(- u d), where u is the mass attenuation coefficient and d is the density of the material, in grams per square centimeter.

Ranchoth
02-13-2004, 02:07 AM
What kind of radiation are you concerned about? As you are comparing gold to lead, you are probably talking about electromagnetic radiation in the X-ray or gamma range.

Mostly Alpha radiation. (I think (http://people.howstuffworks.com/nuclear-power1.htm)) It'd be as shielding for a piece of Highly Enriched Uranium, (http://boards.straightdope.com/sdmb/showthread.php?t=238188&highlight=ranchoth) about 90% U-235.

Shalmanese
02-13-2004, 07:29 AM
Mostly Alpha radiation. (I think (http://people.howstuffworks.com/nuclear-power1.htm)) It'd be as shielding for a piece of Highly Enriched Uranium, (http://boards.straightdope.com/sdmb/showthread.php?t=238188&highlight=ranchoth) about 90% U-235.

Alpha radiation can be shielded with a piece of paper.