beta shield sources

[Mayumi Yagi]

Nicholas, 
Is it possible that you are using a lead-impregnated plexiglas shield?  
We have a couple on hand in our lab for 125I work, as well as "normal" 
plexiglas for 32P.  You can't use the lead ones for 32P work--they will 
generate Brehmstrallung radiation, as you seem to be seeing.  The lead 
ones are slightly more yellow than the non-lead guys (they look more 
"aged", presumably due to the lead).  The regular ones damp down 32P 
effectively (though if you're looking at high levels, not completely).

Mayumi

On 2 Nov 1995, NICHOLAS THEODORAKIS wrote:

> In article <rjordan-2510951356100001 at linus.radonc.washington.edu>,
> Rob Jordan <rjordan at tezcat.com> wrote:
> >Can anyone email me some companies/catalog/etc. phone numbers that have
> >good selections of beta shielding devices.  I'm looking primarily for
> >boxes, containers, shields, etc. of various sizes, but every <insert
> >common lab supply catalog here> catalog that I've looked in has a page or
> >two at best.  I mean something like Acme Radiation Saftely Supply would be
> >perfect.
> >
> >Thanks-
> >Rob      rjordan at u.washington.edu
> 
> Well, I don't have a recommendation (many lab supply vendors sell them),
> but I do have an observation that I hope will generate some discussion. 
> We have some plastic beta shields from Owl Scientific around the lab; 
> when we were doing some rad. surveys with a monitor that has probes for
> both beta- and gamma rays, we noticed that 32P kept behind the shield
> generated a lot of bremstrallung (spelling?) gamma radiation when it hit 
> the plastic (which did block the betas, BTW).  I almost think it would 
> safer not to use the shield.  Has anybody else noticed this with their 
> beta-shields?  Any comments?
> 
> Nick
> 
> -- 
> ++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
> 			Nick Theodorakis
> 			ntheo at welchlink.welch.jhu.edu
> 			Johns Hopkins Medical School, Baltimore, MD
> 
>