[ RadSafe ] I-131 Spill Neutralization

Marcel Schouwenburg M.Schouwenburg at tudelft.nl
Fri Apr 4 02:43:25 CDT 2008

Hi John,

I've no reference by hand, but the first formulation you mention is, as
far as I know, the most common.

It does'nt really matter whether you use 0.1 N or 0.01 N sodium
hydroxide (both solutions are commonly used in stock iodine solutions).
A small practical advantage is that when using 0.01 N sodium hydroxide
there is a smaller change to overshoot in pH.

The purpose of (cold) sodium iodide is to replace the hot iodine ions
with cold iodine ions facilitating the removal of the spoiled activity
(as is eg used in salt separating columns).

With kind regards,

Marcel Schouwenburg
Head / Lecturer Training Centre Delft, Health Physicist, expert level 2
National Centre for Radiation Protection (Dutch abbr. NCSV)
RadSafe Moderator & Listowner
Manager Quality Assurance Reactor Institute Delft (RID)

Delft University of Technology
Faculty of Applied Sciences / Reactor Institute Delft
Mekelweg 15
NL - 2629 JB  DELFT
The Netherlands
T: +31 (0)15 27 86575
F: +31 (0)15 27 81717
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E: m.schouwenburg at tudelft.nl


-----Original Message-----
From: radsafe-bounces at radlab.nl [mailto:radsafe-bounces at radlab.nl] On
Behalf Of Cormack, John (FMC)
Sent: vrijdag 4 april 2008 9:27
To: radsafe at radlab.nl
Subject: [ RadSafe ] I-131 Spill Neutralization

Hi Folks.
Does anyone out there know the correct formulation for sodium
thiosulphate solution widely recommended for I-131 spill neutralization,
and/or a reference for this? I've seen it variously specified as:
0.1 N sodium thiosulfate + 0.1 N sodium hydroxide ( to bring the pH up)
+ 0.1 N sodium iodide
the same as above , except that 0.01 N sodium hydroxide is specified
rather than 0.1 N.
Sometimes the sodium iodide isn't mentioned , so I'm wondering what
purpose it serves.
I'd be grateful for any information that anybody can give.
John Cormack 
Chief Medical Scientist 
Division of Medical Imaging 
Flinders Medical Centre 
Bedford Park 
South Australia 5042 
Telephone :       (08) 8204 4642 (National) 618 8204 4642
Fax:                  (08) 8204 5450 (National) 618 8204 5450
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