[ RadSafe ] Po210 -RE: Legitimate uses in weighing standards

stewart farber radproject at sbcglobal.net
Wed Dec 20 11:27:20 CST 2006

Aside from the many comments on the thread about Po-210 use as a poison 
[which I've not read in detail], there is a use for small Po-210 anti-static 
devices I've not seen mentioned -perhaps missed it.  I once used a Po-210 
brush in removing static from very small poly bottles used to dispense 
radioactive liquids [for making standards] before they were weighed in a 
Mettler balance.

Since the weight of the liquid dispensed from these mini poly bottles [sort 
of like a baby doll bottle holding only a few ml] was very slight [a few 
drops weighing a small fraction of a gram] any variation of the before and 
after weight of the poly bottle which could be introduced due to static 
charge on the bottle could introduce an unknown error into the calculated 
activity of a spike  vs the "true" activity. If the mg dispensed is in error 
due to a weighing error, the activity added can be in error [too high or too 
low -can go both ways], and the spiked "known" activity concentration is not 
what it is calculated too be.  The effect of static in weighing small items 
can be a significant contributor to uncertainty.

Stewart Farber, MS Public Health
Consulting Scientist
Farber Technical Services
1285 Wood Ave.
Bridgeport, CT 06604
[203] 367-0791 [office]
[203] 522-2817 [cell]
email: radproject at sbcglobal.net

----- Original Message ----- 
From: "North, David" <DNorth at Lifespan.org>
To: <radsafe at radlab.nl>
Sent: Wednesday, December 20, 2006 11:30 AM
Subject: RE: [ RadSafe ] RE: 15000 units of Po210

Remembering from when I owned such anti-static brushes for photography, the 
Po-210 is sealed inside tiny ceramic beads, roughly the size of fine sand 
grains, which are fixed onto a metal strip by lacquer or some such adhesive. 
The strip is then behind a small metal cage to protect the mounted beads.

David L. North, Sc.M., DABR
Associate Physicist
Medical Physics
Main Bldg. Rm 317
Rhode Island Hospital
593 Eddy St.
Providence, RI 02903
fax: (401)444-4446
dnorth at lifespan.org

> ----------
> From: radsafe-bounces at radlab.nl on behalf of Bernard L. Cohen
> Sent: Wednesday, December 20, 2006 10:50
> To: Jim Hardeman
> Cc: radsafe at radlab.nl
> Subject: Re: [ RadSafe ] RE: 15000 units of Po210
>     Does anyone know how the Po-210 sources are securely sealed without
> stopping the alpha particles which are used to eliminate static electic
> charges? The seal must really be secure because escaping Polonium is
> highly volatile and once released it spreads everywhere.
> Jim Hardeman wrote:
> >Folks --
> >
> >I went back and looked at Georgia's Rules and Regulations for
> >Radioactive Materials ... NRC's and most states' regulations for
> >exemptions and the like should be similar (if not identical).
> >
> >As I indicated in an earlier e-mail, the exempt quantity for Po-210 is
> >0.1 microcurie (good memory on my part!). There is, however, a provision
> >for general licensure for static elimination devices containing sealed
> >Po-210 sources up to 500 microcuries ... I'm not sure as to these
> >particular devices (I'm not in our materials program) but normally
> >persons selling generally licensed devices are required to report to the
> >radiation control authority in a particular jurisdiction the names,
> >addresses, etc. of persons or firms acquiring such devices within their
> >jurisdiction ... and this notification requirement may vary from one
> >jurisdiction to another. The distinction between an exempt source and
> >one acquired under a general license may be subtle, but the general
> >license does at least allow for "some" ability to backtrack. But the
> >bottom line is, yes, it is is legal for "anyone" to own a static
> >elimination device containing up to 500 uCi Po-210 ... and for that
> >matter, there's no legal restriction against "anyone" possessing more
> >than one (1) of these devices.
> >
> >My $0.02 worth ...
> >
> >Jim Hardeman
> >Jim_Hardeman at dnr.state.ga.us
> >

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