Source of DU

["Bolling, Jason E" <bollingje@ports.usec.com>]

The source of any depleted uranium must be from a uranium enrichment

facility.  Depleted uranium cannot be created without simultaneously

enriching other uranium.  Natural enrichment uranium (0.711% U-235 in the

form of UF6 gas) is used as the feed stream.  Both enriched and depleted

uranium is withdrawn from the stream to maintain the mass balance.  The

depleted uranium is referred to as TAILS and can range in enrichment from

0.25% to 0.4% U-235.  The only production facilities for enrichment of

uranium in the US are in Oak Ridge, Tennessee (undergoing decommissioning),

Portsmouth, Ohio (in cold standby), and in Paducah, KY (operational).  All

of these facilities use the gaseous diffusion method of isotopic enrichment.

Usually, the feed stream to these plants is UF6 made from mined uranium ore.

However, when the US actually had a reactor fuel reprocessing program

(before President Carter halted it) some UF6 was being generated from

reprocessed reactor fuel.



As previously mentioned on the list, the fuel reprocessing effort allowed

minute quantities of contaminates within the reprocessed uranium that made

its way into the UF6 feed stream.  The primary contaminate is Technetium-99,

however, as already mentioned, some small amounts of trans-uranic elements

like plutonium, neptunium, and others have been detected at the ppb level.

Once this reprocessed feed stream is fed into a gaseous diffusion cascade,

the light elements are quickly separated from the heavy elements.  Because

the diffusion cascade separates elements based on isotopic mass, the

elements heavier than uranium preferentially remain in the depleted uranium

TAILS.  These TAILS were then used to create the depleted uranium munitions

now in service.



So, while it is true that some DU contains trace amounts of isotopes

generated in a nuclear reactor, all DU must have come from one of the US

enrichment facilities.  Because US enrichment facilities use the gaseous

diffusion method, the trace isotopes present in DU are those that are

heavier than uranium.  As already mentioned on the list, those isotopes are

radioactive with shorter half-lives than uranium and are easily detected.



Just thought I'd add a little background to this whole DU issue.



Jason Bolling

NCS Manager

USEC, Inc.

Portsmouth Gaseous Diffusion Plant



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