RE: I-131 Volatility Ratio

[Carol Marcus <csmarcus@ucla.edu>]

Dear Jon:



In the days when NRC made it illegal to stabilize NaI-131 against 

volatility when used in nuclear medicine (yes, NRC really did this), I 

measured the volatility of two patient doses which had been kept at room 

temperature.  One was 10% volatile, the other 13%, as I recall.  This was 

without any heat being applied.  (Today, all doses are stabilized.)



Ciao, Carol



At 05:53 PM 1/26/2005, Wesley wrote:

>Jon,

>

>Of course it depends greatly on the chemical and physical circumstances.

>However, I can give you one single quantitative example of how volatile

>radioiodine is.

>

>Some years ago I purposely generated an I-125 iodine vapor in a chemical

>fume hood to test the efficiency of the charcoal filters in the exhaust

>system. I put 5 microcuries of I-125 as NaI in 10 microliters of aqueous

>solution in a small vial and added some stable carrier iodine. I then added

>acid and warmed the open vial with a heat gun for about 15 minutes. In this

>experiment, I attempted to volatilize all of the radioiodine. Based on vague

>chemistry and radiation safety folklore I had expected that essentially all

>of the radioiodine would volatilize. Using a gamma scintillation survey

>meter to measure gamma dose rate at a fixed distance from the vial, I found

>that 80 percent of the activity volatilized and 20 percent remained in the

>vial.

>

>Best regards,

>Wes

>Wesley R. Van Pelt, PhD, CIH, CHP

>Wesley R. Van Pelt Associates, Inc.

>

>

>-----Original Message-----

>From: owner-radsafe@list.vanderbilt.edu

>[mailto:owner-radsafe@list.vanderbilt.edu] On Behalf Of Aro, Jon

>Sent: Wednesday, January 26, 2005 5:25 PM

>To: radsafe

>Subject: I-131 Volatility Ratio

>

>Hi All,

>

>I am looking for the volatility ratio of I-131, essentially the amount

>of airborne activity one would expect from a known activity of I-131.

>I am trying to estimate the exposure an individual would receive as a

>result of radioactive materials being vented through a fume hood.  The

>only isotope that we use where airborne contamination is of concern is

>I-131, as it can be volatile.  After searching Google & hps.org I have

>found nothing.  The "ask the expert" section mentioned that there is no

>"one-size-fits-all" approach to this problem.

>

>Has anyone come across this problem before?   What ratios did you

>find/come up with?

>

>Thanks in advance,

>

>Jon Aro

>Ottawa Hospital

>

>

>

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