[ RadSafe ] Iodine Chemistry of nuclear reactors inemergency cases

Franz Schönhofer franz.schoenhofer at chello.at
Wed Mar 23 18:15:57 CDT 2011

Dear Mike, 

Thank you for inquiry - I remember that we have exchanged in the past a lot
of very fruitful messages!

I apologize for not being up to date on the latest research, because I am
not only retired since some years, but also my department being in charge of
radiation surveillance was taken from me more than 13 years ago - I was
known as not being totally opposed to nuclear power.....

You pose a very good question about the likeliness of atoms finding
together. I cannot answer it definitely, but the answer might be in the
mobility of the atoms in both the lattice of the fuel and outside of it. I
do not have the slightest idea about the diffusion of these "naked" ions and
their probability to find suitable iodine atoms or others. Taking the
fission products curve into account, the most likely element to collide with
I-isotopes should be Cs-137. The activity concentrations in the emissions
are definitevly very different.

As for your final question I am sorry to tell you that I do not know of any
relevant research, even the measurements of different "iodine" species in
the initial phase are extremely rare. This does not mean that they do not
exist yet. The reason for it is that those laboratories in Europe which
would have been able to do them were fully blocked by measurements on food,
precipitation, drinking water, aerosols etc. 7 days a week and 24 hours a
day, related to radiation protection. I-131 in drinking water - if present,
which I doubt on the Fukushima-Tokio accident - will decay very soon.
At least 80% of these measurements were not necessary to establish an
overview on the contamination situation, but were politically wanted.

Sorry, I could go on for hours on lessons learned from the nuclear accident
on Tschernobyl, but since it is past midnight in Vienna I will not.  

Any further questions and especially comments are welcome!

Best regards,


Franz Schoenhofer, PhD
MinRat i.R.
Habicherg. 31/7
A-1160 Wien/Vienna


Thank you for the information. I have copied a few paragraphs from your
message because I have a question about the information in these paragraphs.

Fission products are created as individual atoms so I suppose an individual
atom of radioactive iodine is most likely to react with a different atom and
form an iodide. I suppose it is less likely to find another iodine atom and
form molecular iodine, I2. Is that correct?

So does that mean that after some time, there will only a small amount of
radio-iodine in the chemical form I2? Is most of it in some other chemical
form, perhaps in a form that can be collected as particulates on a filter?

Mike McNaughton
mcnaught at lanl.gov

-----Original Message-----
From: radsafe-bounces at health.phys.iit.edu
[mailto:radsafe-bounces at health.phys.iit.edu] On Behalf Of Franz Schönhofer
Sent: Wednesday, March 23, 2011 3:46 PM
To: 'The International Radiation Protection (Health Physics) MailingList'
Subject: Re: [ RadSafe ] Iodine Chemistry of nuclear reactors in emergency

Now let us go to the facts about iodine: 

One of the chemical speciations is "volatile" iodine, which simply is
molecular iodine, chemically characterized as I2 (two atoms form a
molecule). This is actually very volatile and if I want to smell iodine I
only need to open a semi antique powderflask with elemental iodine - it does
not boil at ambient pressure, but sublimates, which means it transfers from
solid phase directly to gaseous phase. In fact I need not open the flask,
only the glass window to the cupboard where I store it, because it is so
easily volatile.

Two other ones are the ionic forms of iodide I- and less frequently
occurring iodate IO3-. Those are less volatile, but occur in a nuclear

On the long term the organic species like methyl iodide will be formed and
they have a very different impact on the ecosystem.

The ratio of these species is reactor specific and very significant. Studies
exist for BWR, PWR etc. since decades. 

Molecular iodine will be mostly transported as a gas (like the rare gases),
iodide and iodate will be carried exclusively by aerosols. This might
already give you a coarse information about the different ways "iodine"

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