[ RadSafe ] funniest DU scare story ever !

[Stewart Farber]

Hello all,

For authoritative information on this point, see the HPS "Ask the Experts" 
[link and text below]  to see that the 7 mg/cm2 (dermal) dose rate at 
CONTACT [emphasis added] with a thick [depleted] uranium slab in metal form, 
which includes both beta and gamma contribution, is generally assumed to be 
in the range of 200 to 230 mrad/h--depending on depletion or enrichment.

As distance from the slab increases, the  4 and 7 mR/hr for gamma at the 
surface of the slab will quickly fall away to insignificant levels.

Stewart Farber
=======================

http://www.hps.org/publicinformation/ate/q161.html

Answer to Question #161 Submitted to "Ask the Experts"
Category: Radiation Basics - Beta Radiation

The following question was answered by an expert in the appropriate field:

      Q: I'm having a very hard time finding solid information about the 
radiation field intensities expected at the surface of a depleted uranium 
slab. We are hoping to use such a slab to test and calibrate beta detectors 
to establish their beta dose rate response. Such a technique is often 
mentioned in the literature, but I find very little said about what sort of 
beta-dose rate to expect at the surface of such a slab. Obviously the exact 
alpha, beta, and gamma intensities will depend on the precise makeup of this 
particular batch of depleted uranium, but it would be nice to find a 
discussion of the general ranges expected for each as well as some examples 
of how others perform such calibrations. The few mentions I see of this 
range in the area of 210 to 235 mR/hr beta-dose rate at the surface and 
somewhere between 4 and 7 mR/hr for gamma at the surface of the slab. (The 
alpha will be unimportant since we'll have the slab covered by thin (5 mil) 
mylar to minimize potential contamination). If someone has a good reference 
for this, or a site URL which discusses this, I'd really appreciate any 
information. Thanks.

      A: The 7 mg/cm2 (dermal) dose rate at contact with a thick uranium 
slab in metal form, which includes both beta and gamma contribution, is 
generally assumed to be in the range of 200 to 230 mrad/h--depending on 
depletion or enrichment. The value is mostly dependent on the beta 
contribution and will therefore vary depending on additional layers of 
absorber. The following is an excellent reference for published data on 
natural and depleted uranium (no, I am not the author of the paper):

      Preferred Reference:
        a.. Coleman, R.L.; Hudson, C. G.; Plato, P. A. Depth-dose curves for 
90SR and natural and depleted uranium in mylar. Health Phys. 44(4): 395-402; 
1983.
      Other References:
        a.. Handbook of Safety Procedures for Processing Depleted Uranium, 
Army Material Command Handbook, No. AMCHDBK-385-1.1-89, Department of the 
Army, Washington, D.C. The relevant charts from the handbook are shown in 
Question #5 of the 1997 ABHP Exam (the view at this Web site is in a 
not-completely-clear format).

        b.. Radiological Health Handbook, Bureau of Radiological Health, 
Jan. 1970, Page 204. Rules of thumb for dose rates at the surface of uranium 
materials (no supporting data).
      Robert L. Coleman
      Oak Ridge National Laboratory

----- Original Message ----- 
From: "John Andrews" <andrewsjp at chartertn.net>
To: <denison8 at wowway.com>
Cc: "RADSAFE" <radsafe at radlab.nl>
Sent: Thursday, May 25, 2006 12:38 AM
Subject: Re: [ RadSafe ] funniest DU scare story ever !


> denison8 at wowway.com wrote:
>
>> Anybody got a ref for the exposure rate from a kilo of DU (I'm at home 
>> without my books).  Off the top of my head I'd guess no more than a 
>> couple of mrem.
>>
>> At 20:55 -0400 5/24/06, Jaro wrote:
>>
>>> http://www.space.com/astronotes/astronotes.html
>>> May 24
>>> Florida Couple Finds Depleted Uranium in Old NASA Tool Box




-- 
No virus found in this outgoing message.
Checked by AVG Free Edition.
Version: 7.1.392 / Virus Database: 268.7.0/345 - Release Date: 5/22/2006