Re: Pressure Buildup in PuBe Sources

[TDC@ehssun.lbl.gov]

We have some PuBe sources from the 50's (239) and 60's (238).  All the ones
from the 50's went back to Mound in the mid '60's for recanning after a few
incidents from internal pressure build-up.

This subject was bought up at the 1994 DOE Plutonium Vulnerability Study.
At the study we learned that the problem of pressure build up in the 50's
sources was NOT from alpha decay but from incomplete oxidation of the Pu.
When Pu get oxidized it expands with great pressure.

As part of the mid 60's recanning process - oxidation was completed - as I
understand it.

Additionally we have had all our sources radiographed twice.  The last time
about 10 years ago - and there is no sign of buldging containments.

Pu 238 neutron sources remain the best to use for technical reasons.  They
have low anisotrophy (less than Ambe - but not less than CmBe), They have a
lower associated gamma than AmBe, They are well documented in the
literature (better than CmBe) and they have a more useful halflife than Cf
(and a narrower spectrum too).  Additionally for an accelerator lab - these
are the highest energy neutrons we can get from an isotopic source (that we
can have tracability on).

BUT Pu is "bad" politically because of all the publicity - so standards
organizations are not including it as a recommended source for reasons
that I believe are totally political - despite the technical superiority.

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