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

Geo>K0FF GEOelectronics at netscape.com
Mon Jan 7 12:06:50 CST 2008

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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