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RE: Re DU source and Gulf Illness
The reason to consider using reprocessed Uranium as a feed to the enrichment
process is that the U-235 concentration is still higher than natural levels.
Commercial LWRs do not burn the Uranium to levels where the U-235 content
would be less than the natural level. So the residual Uranium is still
slightly enriched.
Reprocessed Uranium does have higher levels of the other Uranium isotopes
present and their significance depends on what question you are asking. For
example U-232 is a poison to the reactor and must be accounted for in the
fuel design. As I remember it, U-236 decay begins to provide a significant
gamma component and can change the HP aspects of the fuel fab plant, at
least if allowed to build up in a fuel cycle that routinely recycled Uranium
from the reprocessing plants.
If the reprocessed Uranium has a U-235 content lower than natural ( i.e. so
it would be called depleted) it would not be sent back to the enrichment
plant. Nor would there be any incentive to take the extra step to make it
into the UF6 chemical form since we already have so much UF6 tails at the
enrichment plants already. The normal route to Uranium metal production is
to convert UF6 to U metal. The only reprocessing plant that would have
resulted in the recycled Uranium coming out directly as UF6 was the Morris,
IL plant and that never went into operation.
As noted by others, the chemical and physical steps to recycle Uranium
obtained from the reprocessing operations will result in the chemical
separation of most of the fission product and actinide contaminants.
However some do carry over, most notably the Tc-99. As an example of a
concentrating mechanism, when you sublime the UF6 out of a
transport/storage container the remaining heel in the container tends to
contain the Tc-99 and other fission products. That is one step where you
can get a concentrating mechanism for the contaminates. My experience is
that if you want to know where the Tc-99 went you follow what happened to
the heels.
While the DU metal can contain trace quantities of the contaminates, I see
no realistic mechanism where it would have higher concentrations than we
have experience in the U fab plants. And as noted these levels do not
significantly increase the overall radiation levels.
A. Joseph Nardi, Supervisory Engineer
Westinghouse Electric Company
P. O. Box 355
Pittsburgh, PA 15230
Telephone: 412-374-4652
FAX Number: 412-374-3357
email: nardiaj@westinghouse.com
> ----------
> From: RuthWeiner@AOL.COM[SMTP:RuthWeiner@AOL.COM]
> Reply To: RuthWeiner@AOL.COM
> Sent: Friday, April 11, 2003 10:24 AM
> To: Lessler.Richard@epamail.epa.gov; radsafe-digest@list.vanderbilt.edu
> Cc: BobCherry@AOL.COM
> Subject: Re: Re DU source and Gulf Illness
>
> I may be off base, but it seems to me that irradiated fuel from a reactor
> would contain sufficient fission products that it could not be used for
> enrichment and therefore not be used to produce DU. If one taleks
> material from Pu production (which stopped 14 years ago) and .strips out
> the fission products (essentially, material that has been reprocessed)
> there might be some actinides left. However, all actinides do not form
> hexafluorides like uranium. The biggest non-natural component of DU is
> most likely another uranium isotope. But these would be present in trace
> amounts and on;ly U232 has a specific activity of any significance at all.
> Uranium forms UF6 because the +6 odixation state of U is quite stable,
> unlike the +6 oxidation state of Pu, for example.
>
>
> RuthF. Weiner, Ph. D.
> ruthweiner@aol.com
>
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