RE: thoriated tungsten -Reply

["Kent N. Lambert" <lambert@auhs.edu>]

On 22 Dec 97 at 16:18, Charris, Rafael G. SSgt wrote:

> If this worker is a user of licensed source though, could not a dose
> from this unlicensed welding rod be counted against the regulatory
> limits, since part of his dose comes from a licensed source?

Yes, you are absolutely correct if the user is also exposed to 
licensed material.   20.1001(b) "It is the purpose of the regulations 
in this part to control the receipt, possession, use... of licensed 
material by any licensee in such a manner that the total dose to an 
individual (including doses from licensed and unlicensed radioactive 
material and from radiation sources other than background radiation) 
does not exceed the standards for protection against radiation 
prescribed in this part."   

Taking this to an extreme, here's a question:  How much exposure 
does it take to trigger this?  If a cardiologist walks by the 
nuclear cardiology department on her way to coffee everyday, and she 
gets an annual exposure of 1 millirem from licensed activities 
(calculated, not measured) does this mean that the NRC dose limits 
apply?  What if she gets 10 millirem annually from catheterization 
procedures subsequent to a nuclear medicine imaging study?  Or 110 
millirem from responding to a code on a patient that has a 
brachytherapy implant?  What if a cardiology fellow receives minimal 
exposure (less than the mda of the film dosimeter) during a rotation 
into nuclear cardiology?  The answers to these have significant 
implications since many state radiation control agencies permit the 
use of Webster's formula for fluoroscopists but its use is not 
recognized by the NRC.

Kent N. Lambert, M.S., CHP
lambert@auhs.edu
Allegheny University of the Health Sciences
Hahnemann Division
Radiation Physics and Safety, MS 106
Broad and Vine Streets
Philadelphia, PA  19102-1192

215-762-8768 (voice)
215-762-7683 (fax)  

Disclaimer:  All opinions are well reasoned and insightful.
Needless to say, they are not (necessarily) the opinions of my employer.