[ RadSafe ] RE: Airborne Monitoring for Cl-39

Demopoulos, Paul pdemopoulos at af.umaryland.edu
Tue Nov 17 10:54:11 CST 2009

Dear Jim,

>From what you are saying about the irradiation, Argon will produce Cl39 by the reaction A40(γ,p)Cl39. From an old reference off the internet: "the threshold was found to be 14.2 Mev. The Cl39 activity was found to have two beta-particles of energies 2.96 and 1.65 Mev, and two gamma-rays of energies 1.31 and 0.35 Mev, the low energy gamma-ray having a conversion coefficient of 0.05." 

>From this information you could have several options if the Cl-39 in the air is the only radionuclide. 

One could be that you can sample the air through a bubbler system similar to C-14/H-3 samplers ran at Universities (with dilute NaOH for C-14) and run the sample through an LSC. The high energy Betas would be detected with about a 100% efficiency.  

The modification to the usual C-14/H-3 type system would be for the Chlorine gas bubbler you may want to use the following OSHA method or a 0.1% sulfamic acid solution for the Chlorine gas:


You could also try by setting up a NaI system to monitor for the gammas or if possible a HPGe.


Paul J Demopoulos
Radiation Safety Officer - EHS
University of Maryland at Baltimore
714 West Lombard Street
Baltimore, MD 21201
Phone: 410-706-6281
Fax: 410-706-1520
email: pdemopoulos at af.umaryland.edu

-----Original Message-----
From: radsafe-bounces at radlab.nl [mailto:radsafe-bounces at radlab.nl] On Behalf Of Tracy, James W.
Sent: Tuesday, November 17, 2009 10:51 AM
To: radsafe at radlab.nl
Subject: [ RadSafe ] Airborne Monitoring for Cl-39


I am looking for information for performing airborne monitoring for Cl-39.  We are operating an accelerator and plan to irradiate liquid Argon for an experiment.  This will result in the production of Cl-39 via gamma activation.  I expect some of the Cl-39 to change from liquid to gas and become airborne.  We have local ventilation that will exhaust this out of the building via a stack.  I want to monitor the stack effluents during this operation.

My question is how do I sample this?  Normally, I would sample the stack with a filter paper and charcoal cartridge.  But with the chlorine being a gas, I'm not sure what collection efficiency I would have.


Jim Tracy
Health Physicist

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