[ RadSafe ] Best technique to detect DU in huge area!!!

[Geo>K0FF]

Hi Dr. Abu-Jarad.

For all practical purposes, Depleted Uranium 238 contains the parent isotope U-238 (alpha decay), daughter Th-234 (beta decay), 
Pa-234m (beta decay), U-234 (alpha decay) and Th-230 (alpha decay). There is also a little residual U-235 left, this being 0.3% or less, plus it's higher daughters. 

All the lower progeny have been removed by the enrichment process.

In my opinion we can disregard the residual U-235 but it is actually measureable. 
Concentrating on the abundant isotopes, we can see that most are NOT particularly strong gamma 
emitters. Most of the photons present come from X-Rays via beta decay/Bremsstrahlung and these are of low 
energy, with this exception: a 1001 keV gamma from the Pa-234m daughter.

Alphas are hard to detect in the field due to their short range in air ( <2 inches), leaving high energy Gammas (Pa-234m), mid energy 
Gammas (U-235) , low energy X-Rays and Betas as the best chance of detection at any distance.  

The FIDLERS you mention are good for low energy X-Rays ( although you mention a 2"X2" crystal unit which 
would be ideal for the 1001 keV photon). True FIDLERS (eg G5) by design have very thin crystals and would 
reject the 1001 keV out of hand. In their usual configuration, FIDLERS don't have any beta sensitivity. and are 
peaked for photons from 10-100 keV. Exception: beryllium windowed probes would probably pass betas to some extent.
Betas and very low energy X-Rays can be blocked by a covering of non contaminated sand, so a probe should be 
selected that will detect betas, low energy photons and high energy photons.

Consider if you will the plastic scintillator probe. These are inherently beta sensitive (with the correct housing 
configuration) and can detect photons over a great energy range. 
Size wise, they can be fabricated in most any shape and dimension. For example,  I have them up to 7 feet long. 
Therefore a single probe or an array of probes could cover a great area all at once. Plastics are also more rugged and would 
stand up to field conditions better than some other scintillator materials.

The 4 foot probe mounted under the front bumper of this Jeep has a door that opens, allowing in extra low energy X-Rays 
and also betas ( Hi Carl).
http://www.qsl.net/k/k0ff/Large%20Area%20Detector/jeep%2520detector.bmp

Such a probe could probably be constructed in any dimension, and more importantly, at a reasonable cost.

The system show on board the Jeep in the link was made by TSA Systems and incorporates the GPS as well as 
radiation control box.

Their link is here:
http://tsasystems.com/contacts/headquarters.html

While the plastic scintillator based system can be configured to respond to a wide range of particles and photon 
energies, it will yield no actual emery dispersion information. To obtain this parameter, a secondary system utilizing 
one of the available technologies ( NaI(Tl), CZT, HPGe) would be recommended to actually identify and quantify any 
isotopes discovered.


George Dowell
New London Nucleonics Lab






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