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RE: I-131 Volatility Ratio
Dear all,
I agree it depends on the chemical form of the iodine.
NaI is not volatile. However, I- (iodide) may be oxidised to I2 (iodine).
I2 may either
(i) evaporate,
(ii) react with iodide to form I3- (triiodide) or
(iii) hydrolyse
In acid, where HIO is formed, the hydrolysis of I2 is reversible, but in a basic solution [IO]- (hypoiodite) is formed, which disproportionates into non-volatile [IO3]- (iodate).
Therefore, either a reducing agent (e.g., thiosulphate) or base will prevent the evaporation of iodine.
Kind regards,
Arvic Harms
Dr Arvic Harms
Quality of Life Division
National Physical Laboratory
Hampton Road
Teddington TW11 0LW
Middlesex
United Kingdom
E-mail: arvic.harms@npl.co.uk
Tel ++44 20 8943 8512
Fax ++44 20 8614 0488
> -----Original Message-----
> From: Wesley [mailto:wesvanpelt@att.net]
> Sent: 27 January 2005 01:54
> To: 'Aro, Jon'; 'radsafe'
> Cc: WesVanPelt@att.net
> Subject: RE: I-131 Volatility Ratio
>
>
> 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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