Tungsten Query

Hi All,
I need to find a tungsten foundry or a source for tungsten sheet to make some radiation shielding for a prototype PET scanner. The head
of the program has decided not to use lead and has asked me to design and build the shielding. We want to use the tungsten alloy with the highest density that is economically available. From my research so far I believe we will be using one of the K18** alloy's but I'm not sure if magnetism is an issue for us or not. The energy level we are using is 511 KeV.
The problem that I am running into is that we only need a handful of pieces and no one that I have talked to so far seems terribly interested. I need 8 elliptical strips with a length of ~26" and a width of 3.5" to 7.5", the thickness will be .25" for four of the pieces and .094" for the remaining four pieces.
I realize that most tungsten parts are formed by powder metallurgy and that would probably be best, but, we do have a high-quality water jet available so if I have no other options and I can find sheet material we can make the parts here.
Any help or suggestions you can give me on a supplier or material selection would be greatly appeciated.
Thank you in advance, Dave Wilson
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snipped-for-privacy@lycos.com (Dave Wilson) wrote in message

First off, I'm not a materials scientist, so weigh that against what I'll suggest.
Could you use Bismuth? it's nearly as dense as lead and not toxic (as far as I know.. and Bismuth Subsalicylate is the active ingrediant in Kaopectate).
One possiblity that might make Bismuth a bad choice is it's strong diamagnetism (supposed to be the strongest of all elemental metals). If heavy electromagnetic fields are near (how many Teslas would you say?), it might have the unwanted behavior of being strongly pushed around.
http://www.webelements.com/webelements/elements/text/Bi/phys.html
Good luck finding your solution. If you find a cool vendor that can deliver small tungsten part orders, please post contact info. I'm looking for simple tungsten tubes with maybe some minimal machining and I can't afford to buy hundreds of them. Grinding Tungsten must take forever.
you could try isotope 217.. http://www.ohiovr.com/xfer/roby.mp3
Cheers, Scott
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aSkeptic wrote:

You'd probably be much happier with an epoxy loaded with tungsten powder. It's a great deal cheaper, much easier to make into complex shapes, and almost equivalent from a mass point of view--the epoxy is so light compared with the tungsten that 20% binder is only about 2% extra mass. You'd gain some vibration damping as well.
Cheers,
Phil Hobbs
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NO!
Bismuth subsalicylate is the active ingredient in PeptoBismol.
The active ingredients in KaoPectate are PECTin and KAOlin (Duh)
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No. The active ingredients in KaoPectate *used to be* Kaolin and Pectin. Kaopectate *now* contains bismuth subsalicylate. (Read the label, Kevin.)
-Unomor
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I'm willing to believe they offer the pink stuff under their brand name, but I haven't bought any in decades. Can't read a label I ain't got, and I'm not about to run out to a drug store to check. If they now put that pink stuff in there, then the name is false advertising AFAI'm concerned.
Besides which, what are salicylate-sensitive people supposed to take for their guts?
Are you sure that ALL FORMS of Kaopectate are now based on bismuth subsalicylate? Or do they just offer that pink stuff under their own brand name while making the original formula available also?
I'll have to check the next time I'm at a store carrying these things.
In either case I don't believe that bismuth subsalicylate preparations are very useful for radiation shielding in the conditions needed by the OP.
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AFAIK, there is no more Kaopectate which doesn't contain bismuth subsalicylate. (I discovered this the hard way, looking for something safe to give a dog with diarrhea. I wanted kaolin/pectin for the purpose, and couldn't obtain it....) Perhaps salicylate people have to get along with loperamide. I don't know. I agree that the disappearance of kaolin/pectin available OTC is counter-rational. I also agree that bismuth subsalicylate would not be useful as radiation shielding.
Unomor
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Not any more it seems
http://www.ohiovr.com/xfer/testrender.jpg
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snipped-for-privacy@yannitell.com (aSkeptic) wrote in message

what the hell???
Sorry
I ment to post this link:
http://www.ohiovr.com/xfer/kaopectate.JPG
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What about Na tungstate (harmless powder) encased in stacks of some tubings, at least for a scaled experiment?
J.J.
snipped-for-privacy@lycos.com (Dave Wilson) wrote:

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Dave Wilson wrote:

You should contact Plansee <http://www.plansee.com/index_ENG_HTML.htm in Austria. Use of SI units is preferred.
Michael Dahms
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Have you tried Rembar in New York?
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Thank you for all the information so far. I checked out the Plansee website and did not find much information. I will contact them to see if I can get some useful input and a quote.
Regarding the Bismuth, even though it has a higher atomic number, the tungsten has about twice the density. Lead and Tungsten are THE materials of choice for radiation shielding in this application. Because of design requirements we are limited to tungsten on this project. Also, because of the nature of the detectors being used we have to use the thin, flat, planar sheet and cannot do the shielding by stacking material.
So, I'm still looking for information that will point me in the direction of tungsten suppliers that can provide the 8 pieces in the shapes mentioned, or, flat sheet tungsten in .25 and .095 that are large enough so we can cut the shapes on a water jet.
Thank you again, Dave Wilson
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