Re: Shielding Material

[Karl Smith <ksmith@knorad.com>]

Bob,

 

They use a lot of this line of alloy to make blocker trays for linear accelerators and radiation therapy simulators. They usually cast the blocks in Styrofoam molds and heat it in a big coffee urn. (most often used "cerrobend" or "cerrolow" ` 185 degree F. melt point for safety reasons.) Machines well if you don't let it get too hot. Not as nearly as "squishey" as plain lead.

Just a thought. ~4" stops 1meV. Don't know about plating though.

Available at McMaster-Carr (http://mcmaster.com) retailer.

 

Good Luck

 

Karl Smith

KSmith@KnoRad.com

804-749-4381

 

 

 

Cerrobase: Melting point is 255° F. Composition is 55.5 percent Bismuth, 44.5 percent Lead.



JOHN.RICH@sargentlundy.com wrote: 

I looked at some of the composite materials a while back, and

pound-for-pound lead was still the more efficient gamma shield.



TRANSCO and DUFRANE make "encased" lead shields that have structural

strength and enough interior lead to be efficient shields.

They can be encased in 'most any alloy you want. I don't know how small

the shields can be made but it might be worth your while to talk to one of

them.



john rich

john.rich@sargentlundy.com













"Bob Westerdale" 

.com> cc: 

Sent by: Subject: Shielding Material 

owner-radsafe@list.van 

derbilt.edu 





05/12/04 11:06 AM 

Please respond to "Bob 

Westerdale" 















Greetings...

I've been asked to recommend an alloy for use in the construction of a port

cover for a 400 kV Electron Microscope ( TEM). I usually work with low kV

systems ( ie < 30 kV) where material is much less a factor; This high kV

Instrument presents a challenge in that:

1. The part will be cut from a cube about 5" X 5" x 5", with a

number of high precision machined features, so that machinability is a

serious concern



2. I'd like to be able to plate the part ( Cu-Ni-Cr) for aesthetics



3. I need an alloy with the best beam stopping capability I can

find.



4. I cannot make the whole part out of Pb, as there are some

structural loads that would not be well served by a mushy material. ( and

plating would nearly impossible.)



We've made similar parts in the past out of Leaded brass ( e.g. clock brass

or marine brass) and in some cases 303 or 304 Stainless, I'm hoping that

there might be some more modern materials ( ie tungsten/tantalum or ?

alloys...) that might allow for a less massive solution. Space

is at a premium, and I'd like to avoid a prolonged search for '

Unobtanium '



This component will be headed for Germany, interesting to note that we

cannot allow any exposed Pb surfaces, for fear of toxicity, and the

Radiation leakage at 2" must be less than .1 mR/Hr. (The end-user who told

me this was chain smoking unfiltered Rothmans in a tiny, unventilated

room..... so much for risk perception!)



If anyone has any suggestions/experience I'd be quite grateful!



Thanks,

Bob Westerdale

EDAX Inc.

Mahwah, NJ.









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