working life of sealed industrial source

[stephane_jeanfrancois@Merck.Com (Stephane Jeanfrancois)]

REPLY: It will always depends on the location and used of such sources. It 
is a well known fact that some device may need a window change (mylar or 
other) each 5 hours of work (laminated steel industry).

In mining, these gauges are exposed to corrosive elements and may need 
replacement. (it is cheeper to purchase a whole new unit).

In any case, I don't think I would follow the supplier's recommendation to 
change it after x years. Leakage (leak test are mandatory) would be my only 
reason to change a source (or difficulty in calibration due to strenght of 
the source). I never heard of a source that was leaking due to other reasons 
then a direct hit of some kind. The only problem you may find  with 
corrosion is sudden peaks of radiation in some spots (the shielding is not 
alway uniformly applied either)

Stephane Jean-Francois phys. Eng.
RSO Merck Frosst Canada
stephane_jeanfrancois@merck.com

______
you wrote:
" 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