Kai Kaletsch eic at shaw.ca
Fri Dec 15 08:50:22 CST 2006

```Hi Bernard,

I don't think the statement "...The enrichment process takes U-235 from 0.7%
to about 3.5% so the DU should have 1/5 as much U-235 as natural uranium.
..." follows  logically. In order to balance U-235 quantities, you must
balance percentages of U-235 in the mixture multiplied by quantities of the
mixture.

For example, if you start with 1000 t of natural U and end up producing 1 g
of 3.5% U-235 enriched U, you will not see any significant depletion in the
1000t - 1g of material that are left.

Dan McCarn mentions an interesting mechanism about the U234/U238 ratios in
ground water. I don't think it can be used to explain such a huge increase
in U-234 activity in global average DU. We have close to 100% recovery in
ores leached in a mill. Even in ISL operations, they try for +75% recovery.
I think, if the recovery is low, the explanation is that macroscopic pieces
of ore don't get contacted by the solution. So, you probably leave both U234
and U238 in the ground.

Best Regards
Kai

----- Original Message -----
From: "Bernard L. Cohen" <blc+ at pitt.edu>
To: "Michael McNaughton" <mcnaught at lanl.gov>
Sent: Thursday, December 14, 2006 1:24 PM
Subject: Re: [ RadSafe ] Pepto-Bismol

> Natural uranium should have the same alpha activity from U-238 and U-234
> (they are in secular equilibrium).. The enrichment process takes U-235
> from 0.7% to about 3.5% so the DU should have 1/5 as much U-235 as natural
> uranium. Enrichment shoud remove a  somewhat larger fraction of U-234 (it
> is lower in mass) than of U-235, so the U-234 alpha activity in DU should
> be somewhat less than 20% of that in natural uranium. Even if it was 20%,
> it would be 0.2/ (1+0.2) = 17% of the total alpha activity. How can it be
> as much as 28%?
>
> Michael McNaughton wrote:
>
>> According to figure 2.2 of DOE-STD-1136-2004, about 28% of the total
>> alpha activity of DU is U-234.
>>
>> At 06:01 PM 12/13/2006, John R Johnson wrote:
>>
>>> What do you mean by "pure depleted uranium"? Producing U-238 without
>>> U-234 is very difficult.
>>
>>
>> Mike McNaughton
>> Los Alamos National Lab.
>> email: mcnaught at LANL.gov or mcnaughton at LANL.gov
>> phone: 505-667-6130; page: 505-664-7733
>>
>>
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