|MadSci Network: Engineering|
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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