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

Edmond Baratta edmond0033 at comcast.net
Mon Jan 7 14:11:54 CST 2008

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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