Re: H-3 Exit Signs

["JERRY ROSEN" <rosen@rso.radsafe.pitt.edu>]

The mechanism for contamination by "rapidly diffusable" H2 gas is 
relatively straight forward.  It readily diffuses into any gas 
permeable surface.  Unfortunately, it doesn't diffuse out as readily, 
leading to long term outgassing and smearable contamination.

> Subject:       H-3 Exit Signs

> Contrary to what is commonly thought and what is promoted by the sign
> manufacturers/vendors, when a gas-filled sign is broken, the 5 Ci to 50 Ci
> (= 2 x 25 Ci back-to-back) of H-3 doesn't just escape and dilute harmlessly
> into the environment.
> 
> I don't know the mechanism, but the fact is that a single gas-filled H-3
> exit sign can create removable contamination in excess of 2,000 dpm/100 sq.
> cm over hundreds of square feet.  In my opinion, this constitutes a
> significant HP concern because of the contamination problem in an
> unrestricted area (even if the dose is "insignificant").
> 
> To those HPs who still don't see this as a problem, let's just say one
> broken sign can create the need for a $10K to $30K clean-up using outside
> consultants and/or significant resources if handled in-house, not to mention
> the negative PR.
> 
> 
> 
> >>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>
>   Jeffrey S. Mueller, M.S., CHP                  E-mail = jmueller@ucla.edu
>   UCLA Radiation Safety Office                Telephone = 310/206-8204
>   1010 Veteran Avenue, 2195 WMB                     FAX = 310/206-9051
>   Box 951765                                      Pager = 800/233-7231 #93565
>   Los Angeles, CA 90095-1765
> <<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<
> 
> 
Jerry Rosen

University of Pittsburgh
Phone:  412-624-2728
Fax:    412-624-3562
Email:  Rosen@radsafe.pitt.edu