Re: ABCNEWS.com: Hundreds of Radioactive Devices Missing

[D J Hornsey <bssdjh@BATH.AC.UK>]

  Franz,

     You are correct that the so called Betalightsare filled with about

0.5TBq (13 Ci) of tritium gas, and for that reason in the UK they were

placed on an Exemption Order to the Radioactive Substances Act. This meant

that we did not require authorisation to either acquire or dispose of

them. Some recent work (unpublished) by the enforcing authority of the

above act has shown that a high percentage of the tritium has exchanged

and is now bound to the phosphor or its components. When damaged some gas

escapes but a lot (no idea how much) is bound and presents a potential

contamination hazard. The betalights have effectively been removed from

the Exemption Order and we now require authorisation for them. I assume it

is that bound contamination that resulted in the expensive cleanup that

was reported and the dose the collector. 

  As we all know, and certainly from my own experience,tritium is a very

labile element and exchanges easily. Labelling by the Wilzbach technique

using the energy of beta decay is commonly used to prepare labelled

molecules and I have always assumed that the betalight was a mini Wilzbach

system, so, perhaps we should not be surprised that there is a significant 

level of bound tritium in them.     



  Regards,



     David.



 **************************************

 * David J. Hornsey, Radiation Safety.*

 * South Building,                    *

 * University of Bath                 *             

 * Claverton Down,                    * 

 * Bath BA2 7AY. UK.                  *

 *                                    *

 * tel:01225 826540                   *

 * fax:01225 826779                   *  

 * e-mail: d.j.hornsey@bath.ac.uk     *

 **************************************





************************************************************************

You are currently subscribed to the Radsafe mailing list. To unsubscribe,

send an e-mail to Majordomo@list.vanderbilt.edu  Put the text "unsubscribe

radsafe" (no quote marks) in the body of the e-mail, with no subject line.

You can view the Radsafe archives at http://www.vanderbilt.edu/radsafe/