Re: Sealed sources: extension of recommended working life

[Fred Axmacher <axmacher@ix.netcom.com>]

I see this problem very much as a liability issue.  Is the savings
generated by non-replacement worth the potential liability of capsule
failure?

The capsule manufacturer has already limited his exposure by
conservatively calculating the durability of the capsule in years on the
basis of what he knows -
    1) The ductility of the casing material and sealed joints
(welded/brazed) that undergo potential  volume changes and radiation
hardening due to decay processes,
    2) The ability of the nuclide in its chemical form to be removed by
leaching.
    3) Operational testing performed as per ISO 2918 (?) that typify the
capsule by five testable criterea.
And by what he doesn't know but can recomend for -
    1) The operational environment.
What doesn't seem to be a factor is the half-life nor the activity
level.
And what particularly doesn't seem to be a factor is real world
experience!

My experience with source manufacturers is that they will gladly
recertify the capsule based on a microscopic visual exam and a leach
test, but only for five years...!

By the way, I find it funny that an Australian should bring up this
question of recertification, in that your government has declared what
the operational life of a sealed source shall be.