Re: Spurious LiF light emission - contaminants

["Sandy Perle" <sandyfl@ix.netcom.com>]

> Would you please let us know how these factors could affect readings? This
> may be a variable with which not all persons responsible for assigning, and
> interpreting, ring dosimetry are familiar.
> 
> Chris Alston

There are many factors that affect dosimetry processing and the 
resultant response and reportable dose to the worker. I will mention 
just a few items that are caused by the work environment:

1. Panasonic TLD ... LiBO elements are affected by exposure to 
Hydrogen Sulfide gas. This was a significant issue in the early 1980s 
and was the topic of an NRC I&E Bulletin. It seemed that workers were 
receiving exposures that exceeded regulatory limits. It was soon 
determined that the workers are in an environment where Hydrogen 
Sulfide was present. The belief is that there is a chemical reaction 
with the LiBO elements and a transformation to Lithium Hydroxide 
takes place. This is seen today when laboratory workers use Hydrogen 
Sulfide. There is no efect on the CaSO elements .. and any increased 
response on the two LiBO elemets should be investigated for this 
contaminant.

2. Harshaw & Panasonic TLD ...   (a) Chalk / talcum powder gives off a 
significant amount of light when heated to the temperature that TLDs 
are exposed to .. i.e., 300 degrees F. Power plant workers used to 
rub their hands with talcum powder to facilitate sliding on cotton 
gloves over their hands... IF there were any residual powder on the 
TLD, a very high reading would ensue. (b) Oil on the element, such as 
external or oil from an individual's hand can also result in a 
spurious emission and an erroneous dose reading. 

In summary, it is important to ensure that all bare elements as well 
as the covering, i.e., teflon, be not subjected to any external 
materials .. since the result will more likely than not result in an 
erroneous dose report.

Hope this partly answers Chris's question.



Sandy Perle
Director, Technical Operations
ICN Dosimetry Division
Office: (800) 548-5100 Ext. 2306 
Fax: (714) 668-3149

E-Mail: sandyfl@ix.netcom.com