MadSci Network: Engineering

Re: Advantages/disadvantages of 90% tungsten vs. lead as a radiation shield

Date: Fri Jul 17 02:34:02 1998
Posted By: Dewey Burbank, Senior Engineer, Chemical Engineering, Cogema Engineering Corp.
Area of science: Engineering
ID: 899138331.Eg

Sorry that I cannot give you a more definitive answer, but I can tell you 
this:  All shielding materials perform similarly when the density of the 
material is considered.  The effectiveness of a gamma shield is pretty 
much directly proportional to the total mass of material in the path of 
the gamma ray.  A lighter (less dense) shielding material will require a 
greater thickness than a heavier (denser) material.  The main variable is 
the total mass or number of atoms of the shielding substance that the 
gamma ray must encounter on its way through the shield.

With this in mind, the difference between the shielding effectiveness of 
tungsten and lead is proportional to their specific gravity (density), 
which is not very much, but their difference in cost is much greater.  If 
lead is not ABSOLUTELY excluded for some other reason, then it will be 
much more cost-effective than tungsten, even though the shielding 
effectiveness may be similar.  Lead is MUCH cheaper than tungsten, and 
therefore is a better shielding material than tungsten, if cost is 
significant factor.

The other consideration is the possibility of activation products if the 
tungsten is exposed to neutrons, because some of the activation products 
can produce gammas of their own that may be more hazardous than the 
original radiation source.  If you would like to discuss this further, 
feel free to Email me at the addresss in the header.

Dewey Burbank

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