[ RadSafe ] Natural Uranium - Isotope Abundance (UNCLASSIFIED)

[Falo, Gerald A Dr KADIX]

Classification:  UNCLASSIFIED 
Caveats: NONE

Randy,

I second what Bob Cherry states below especially with regard to your
measurements.  Given the fairly narrow range of composition values (See
below.), the measurement uncertainty can be larger than the natural
variation especially when measuring small amounts.  

Unfortunately, I know of no NRC or DOE documents the natural variation
in the ratio.

In "Isotopic Compositions of the Elements 1997," prepared by K.J.R.
Rosman and P.D.P. Taylor for the International Union of Pure and Applied
Chemistry (IUPAC), the range of natural variations (atom percent) for
the uranium isotopes are:

U234: 0.0059 - 0.0050 (atom %)
U235: 0.7202 - 0.7198 (atom %)
U238: 99.2752 - 99.2739 (atom %).

There's a note "geologically exceptional specimens are known in which
the element has an isotopic composition outside the reported range."

The report can be found at:
http://www.iupac.org/reports/1998/7001rosman/iso.pdf.

NIST has a table at: http://physics.nist.gov/PhysRefData/Compositions/
but the table doesn't seem to have a range of values.

I hope this helps.

Jerry


-----Original Message-----
From: radsafe-bounces at radlab.nl [mailto:radsafe-bounces at radlab.nl] On
Behalf Of bobcherry at satx.rr.com
Sent: Wednesday, October 24, 2007 2:34 PM
To: Redmond, Randy (RXQ)
Cc: radsafe at radlab.nl
Subject: Re: [ RadSafe ] Natural Uranium - Isotope Abundance

>If my results are greater
>than  0.711 percent U-235, then it's enriched; if my results are less 
>than 0.711 percent, then it's depleted.
To quote the great Lee Corso, "Not so fast, my friend."
Be sure to consider uncertainty in your results and uncertainty in the
natural variation in relative abundance of uranium isotopes. Choose
acceptable values for type I and type II errors and then see what you
have.
Bob

----- Original Message -----
From: "Redmond, Randy (RXQ)" <redmondrr at y12.doe.gov>
Date: Wednesday, October 24, 2007 10:37 am
Subject: [ RadSafe ] Natural Uranium - Isotope Abundance
To: radsafe at radlab.nl 

> Background
> 
> - NRC regulations define depleted uranium as uranium with U-235 
> abundance less than 0.711 percent.
> - DOE STD 1136-2000 Table 2-1 gave U-235 weight percent as 0.72 and 
> stated that the range of the weight percent of U-235 in the natural 
> environment could vary from 0.61 to 0.81 percent.
> - The range stated in 1136 was deleted - DOE STD 1136-2004. 
> 
> My dilemma
> 
> To prove that I have not technology enhanced (added radioactivity to) 
> the uranium in various substances (my facility deals with DU and EU), 
> I am being currently held to 0.711 percent. If my results are greater 
> than 0.711 percent U-235, then it's enriched; if my results are less 
> than 0.711 percent, then it's depleted. Does anyone know of a NRC or 
> DOE document that can be cited which establishes a range for U-235 in 
> natural uranium? Establishing baseline information on every material 
> is not an option..
> 
> Thank you,
> 
> Randy Redmond
> BWXT Y-12
> Radiological Engineering
> 865-574-5640
> 
> 
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Classification:  UNCLASSIFIED 
Caveats: NONE