How DU was used in the production of Pu

["Stokes, James" <StokesJ@ttnus.com>]

I may be wrong, but there appears to be a lack of understanding by some on
how DU and low enriched U were actually processed in the production of Pu.
A better understanding would explain some of the "facts" we have or have not
been reading about.

"Production" reactors were used to produce Pu for defense programs
applications. The fuel for those reactors were recycled.  As the U-235 was
depleted, the fuel was raised back up to the appropriate enrichment by
BLENDING woth more hoghly enriched uranium.  It was not done by sending back
through the GDP facilities.  "Sweetner" material, of a much higher
enrichment level, was used to restore it to fuel grade enrichment.

Seperate from that DU metal was manufactured into "target" material.  That
materials purpose was to absorb neutrons, to become Pu.  The Pu was then
chemically extracted, and we should all recognize that no process is 100%
efficient.  Therefore there would be trace levels of Pu in the DU that was
recycled.  Since U-236 is a by product of this process, the concentration of
U-236 in the material, was an indicator of how many times it had been
recycled.  Each "batch" of material had its own isotopic "fingerprint",
which indicated how many times it had been recycled, and how efficient the
chemical extraction process worked.  When the extraction process did not
work so well, the Pu residual levels were "high", and it became the limiting
isotope for handling purposes.  Operationally, this was called POOS
material,(Plutonium out of specification).

The GDP in Porstmouth and Paducah did provide the "makeup" material for
loses in the system, but the majority of the material was recycled between
the production reactors, the chemical refinery and the metals foundry, once
it was introduced into the production stream.

UO2 and UO3 became UF4 which became U-metal which was irradiated, PU
extracted, and the cycle started over again.

The used of DU as a product itself was used in Hydroshots, and later the
penetrator program.  Depending on where that DU came from, its isotopic
profile would be different.  There were other applications of DU in defense
programs, but I don't believe that it is publically available knowledge,
therefore let me not discuss them.

I have no opinion about the material I stated above, but if I did, I assure
you that it would be my opinion alone.
************************************************************************
The RADSAFE Frequently Asked Questions list, archives and subscription
information can be accessed at http://www.ehs.uiuc.edu/~rad/radsafe.html