[ RadSafe ] Detecting DU at a distance via beta particle emission.

[Emer, Dudley]

George,
DU typically contains: 
U-238 99.8 wt%   87% by activity
U-235  0.2 wt%    1.1% by activity
U-234  0.001 wt% 15.2% by activity

Natural 
U-238 99.3 wt%   48.8% by activity
U-235  0.72 wt%   2.4% by activity
U-234  0.0057 wt% 48.8% by activity

The activity contribution of U-234 to the DU is 15% of the total
activity which is not insignificant. 

In your 2 lb DU cylinder you'd have 303 uCi U-238 and 56 uCi of U-234.

In-growth of the U-234 in 30 years from the 303 uCi of U-238 would be
about 25 nCi.

Dudley Emer
Geophysicist
NATIONAL SECURITY TECHNOLOGIES, LLC
Nevada Test Site - Mercury, Nv  M/S NTS306
Tel:  (702) 295-7808 - Fax:  (702) 295-7761
Pager: 7027945824 at nv.doe.gov


-----Original Message-----
From: radsafe-bounces at radlab.nl [mailto:radsafe-bounces at radlab.nl] On
Behalf Of Geo>K0FF
Sent: Monday, January 07, 2008 12:56 PM
To: Edmond Baratta; radsafe at radlab.nl
Subject: Re: [ RadSafe ] Detecting DU at a distance via beta particle
emission.

">I have a simple question:  If U-235 is removed in the separation from 
U-238,
> why isn't U-234 removed at the same time???
>
> Ed Baratta"

Not all the U-235 is removed, only down to 0.2-0.3%. Sometimes only down
to 
0.4% from 0.711 %. ANY reduction
from the natural ratio of U-238/U-235 qualifies the end product to be
called 
DU. Probably not all the U-234 is removed either, but the U-234 comes
back 
(decay daughter), the U-235 never does . Someone else will have to
comment 
on the U-234 levels initially left in DU metal, if any, I don't know.

Every atom of Pa-234m that decays, turns into U-234. Because of the
great 
disparity between the two half-lives, 1.2 minutes vs. 240,000 years, the

contribution of U-234 to the radiation from DU is minimal.

Bottom line, if you have U-238, you will son have Th-234, Pa-234m and
U-234.

These used to be called Uranium I, Uranium  X1, Uranium X2 and Uranium 
II.(Glasstone)

Yes there are X-ray produced by the beta particles due Bremsstrahlung
that 
can be detected using low energy gamma scintillator probes. That is
another 
subject and I would like to hear from someone who has used this method
in 
practice.
Alpha spectroscopy is the main method for detecting small amounts of DU,
but 
that is not at a distance, therefore yet another (and interesting)
subject.


Same deal with Radium. Assuming a 100% efficient refinement, all the
lower 
daughters will again reach equilibrium in a period of time.
It is inevitable in a decay chain where the parent has a long half-life 
compared to the daughters.

DU will never reach equilibrium in human time scale because U-238 has a
long 
half-life yes, but the daughter U0234 and Th-230 also have long half
lives, 
so the refinement will only result in partial equilibrium.

My interest in DU is only scientific, not political. I am not
anti-radiation 
in any way.

George Dowell
GEOelectronics at netscape.com


----- Original Message ----- 
From: "Edmond Baratta" <edmond0033 at comcast.net>
To: "Geo>K0FF" <GEOelectronics at netscape.com>; <radsafe at radlab.nl>
Sent: Monday, January 07, 2008 2:11 PM
Subject: Re: [ RadSafe ] Detecting DU at a distance via beta particle 
emission.


>I have a simple question:  If U-235 is removed in the separation from 
>U-238, why isn't U-234 removed at the same time???
>
> Ed Baratta
>
> edmond0033 at comcast.net
> ----- Original Message ----- 
> From: "Geo>K0FF" <GEOelectronics at netscape.com>
> To: <radsafe at radlab.nl>
> Sent: Monday, January 07, 2008 1:06 PM
> Subject: [ RadSafe ] Detecting DU at a distance via beta particle 
> emission.
>
>
>
> Detecting DU at a distance via beta particle emission.
>
>
> DU (Depleted Uranium) is uranium with the majority of the U-235
removed, 
> leaving behind U-238 and U-234.
> I prefer to think of DU as refined U-238. The metal has many
industrial 
> and scientific uses, mainly because of its high density, being 1.7
times 
> as dense as lead. A few common uses would be counterweights and
radiation 
> shielding. DU is used in projectiles because of its unique density, 
> pyrophoricity and "self-sharpening" characteristics.
>
> The only progeny present that can be detected at a distance would be 
> Pa-234m, a beta emitter.
> With a maximum energy of  2.28 MeV, the betas would travel
approximately 
> 20-25 feet in air, using the rule of thumb of 10-12 feet per MeV.
> A sensor would have to be appreciably closer than the maximum distance
to 
> detect the beta particles.
>
> Because of self-shielding, DU metal's surface beta rate is in ratio of
the 
> surface size, not the thickness or
> volume of the sample. In other words a thin sheet would have the same
beta 
> surface emission rate as a thick sheet.
> Indeed, DU Slabs are used in the lab to calibrate probes.
>
> The best "calculations" are done in the lab with a DU slab and a
detector! 
> Using a 2 pound cylinder of DU metal and
> a pancake probe, about 6 feet is as far as you can get and still
obtain 
> usable (statistically significant) readings. Any closer and the
readings
> ramp up quickly. With a 100 Cm^2 alpha-beta scintillator on a Thermo 
> ELECTRA alpha-beta meter, the range is extended to about 10 to 12
feet.
>
> George Dowell
> GEOelectronics at netscape.com
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