Re: Working life of sealed industrial sources

["Wesley M. Dunn" <WDUNN@brc1.tdh.state.tx.us>]

For what its worth, neither I nor my boss recall a source failure
due to corrosion or age.  Devices, yes.  The actual source, no.  Of 
course, if the device becomes too old to use, the source may also be 
"retired".

The second part of your question was sidestepped in the United 
States for well logging sources.  The Nuclear Regulatory Commission 
required that every well logging source used after July 15, 1989 be 
doubly encapsulated and meet prototype testing standards (based on 
the current ANSI Standard). The Agreement States were required to 
adopt similar requirements (effective in Texas on Jan 1, 1993).  

This shut out use of the very old sources.  However, the NRC did 
provide for a "Generic Exemption" of certain source models that did 
not meet the letter of the reg (e.g., the source model had been in 
production before the ANSI standard was finalized).

The only other restriction that I am aware of is the requirements (by 
Texas) that sources and devices have a safety evaluation performed.  
WHile this excludes the very oldest of sources, the Registry 
of Radioactive Sealed Sources and Devices (SSD: Maintained by the 
NRC) includes many very old sources.  

Note that the leak test requirement is a performance based standard: 
if it leaks, it gets removed.  If it doesn't leak, it can still be 
used, regardless of the "suggested life".

Wes

> Date sent:      Mon, 7 Oct 96 02:40:38 -0500
> Send reply to:  radsafe@romulus.ehs.uiuc.edu
> From:           radgovwa@wt.com.au
> To:             Multiple recipients of list <radsafe@romulus.ehs.uiuc.edu>
> Subject:        Working life of sealed industrial sources

> For the longer half life sealed industrial sources used in density or
> level gauges, well logging, etc. (e.g. Cs 137, Am241), source
> suppliers may recommend a working life of perhaps 10-15 years before
> replacement even though there may be no apparent physical
> deterioration of the source encapsulation when tested.
> 
> Is anyone aware of any incidents of leakage of the radioactive
> material from such sources (other than that due to accident etc) which
> could be attributed to corrosion or other age related failure of the
> encapsulation?  
> 
> Are any regulators permitting variations to the working life
> recommended by the source suppliers?
> 
> Radiation Health Section
> Health Department of Western Australia
> e-mail radgovwa@sage.wt.com.au

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Wesley M. Dunn, CHP                        512-834-6688
Deputy Director, Licensing                 512-834-6690 (fax)
(Texas) Bureau of Radiation Control        wdunn@brc1.tdh.state.tx.us
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