[ RadSafe ] Re: Utah Board considering banning DU

Brennan, Mike (DOH) Mike.Brennan at DOH.WA.GOV
Thu Jun 11 12:35:57 CDT 2009

If you look at the decay chain, and think about DU vs. natural uranium
(Unat), it is easy to see that DU is and will remain much less
radioactive by weight for equivalent forms (metallic, uranium
hexafluoride, etc).  The final activity by weight or volume depends on
what form the U is in and how much of the containing material is

On the equivalent form basis, there is a very useful rule of thumb
concerning the equilibrium between a radioactive isotope and its decay
products when the half-life of the parent is much longer than that of
the daughter.  For all practical purposes the activity of the parent and
the daughter reach equilibrium in 7 half-lives of the daughter.  

Applied to U238, this means that if you started with pure U238 (not
possible, of course, but useful to examine the situation) the first
daughter Th234, will reach equilibrium about 150 day after you started.
The second daughter, Pa234, with a half life of 1.2 minutes, can be
viewed as in-growing at about the same rate as Th234.  Thus if you are
measuring activity of the DU you are planning to dispose of more than 6
months after the DU was separated, you will already be measuring the
next two links in the chain at the maximum activity that they will

The next link, U234, is a little trickier.  If you started with pure
Pa234 you would never reach equilibrium between it and its daughter
U234, because the half-life of U234 is much longer.  However, if you are
starting with DU you have a system where Pa234 is being produced as fast
as it decays, so U234 can eventually reach equilibrium with the activity
of the DU.  Equilibrium will be reached in seven half-lives of U234, or
in about 1,680,000 years.  Over a shorter period, say the next 10,000
years, the amount of U234 that in-grows will be trivial compared to the
amount of U238 that you started with.  

Unat, on the other hand will already be in equilibrium between U238 and
234, with a sprinkling of U235.  Again, even if the Th234 and Pa234 were
removed in the processing, they would grow back and reach equilibrium
within 6 months.  So on a equal weight basis in the same form, Unat is
more radioactive than DU, at least for the next million years or so.  

On the other hand, the ore is potentially much worse, as it is out
gassing radon, and can reach mind-bending levels if care isn't taken
with ventilation (I recall reading about "dog-hole" mines with radon
levels in the hundreds of thousands of pCi/l, with the closest thing to
respiratory protection being the filter of the cigarette the miners
smoked as the dug with pick and shovel.  

-----Original Message-----
From: radsafe-bounces at radlab.nl [mailto:radsafe-bounces at radlab.nl] On
Behalf Of Roger Helbig
Sent: Wednesday, June 10, 2009 8:41 PM
To: Mario Bettolo
Cc: radsafe at radlab.nl
Subject: [ RadSafe ] Re: Utah Board considering banning DU


Thank you.  If you just look at the decay cycle, that may appear to be
true, but the decay cycle only shows what the daughter products are and
not how plentiful that they will be at a given time and as a result the
analogy is really bogus.  Some of the daughter products are gamma
emitters; they are not produced for thousands of years into the decay
cycle and then only half of half of half of -- etc. of all the U238
reaches that equilbrium point at any given time - Remember, there is
U238 in every backyard all over the world; there is U238 in every body
of water all over the world; there is
U238 in every breeze of air all over the world.  U238 was used to
determine the age of 1000 year old Antarctic ice deep in the icecap - it
has always been on earth and always will be - It is junk science being
peddled by pseudo scientists on a mission - their mission is to outlaw
DU (which probably is completely OK with the military because the most
modern tanks need something else than a DU kinetic energy penetrator to
defeat them) and then make the users of DU in the Gulf War and in Iraq
in 2003 out to be outlaws.

Roger Helbig

I am copying your question and my reply (which is an semi-educated
amateur in comparison to genuine PhD Health Physicists with the coveted
CHP (Certified Health Physicist) after their name who inhabit that list
and their colleages with or without equal alphabet soup following their
name) on the RADSAFE list of radiation protection professionals
including a couple Uranium Geologists, etc. that is hosted by the
University of Delft in The Netherlands so you may receive some other far
more informative replies.

On Wed, Jun 10, 2009 at 12:00 PM, Mario Bettolo <mabettolo at yahoo.com>

>  This email contains my personal thoughts only, and should not be 
> taken as a professional opinion.
> http://www.sltrib.com/utah/ci_12556404
> I thought you would find this article interesting.
> The main contention of the group asking for the ban is that DU becomes

> more radioactive over time - essentially leaving the Class A waste 
> designation and becoming Class B and/or C.  Do you have any concise 
> information about that?
> Thanks,
> -Mario
> This email contains my personal thoughts only, and should not be taken

> as a professional opinion.
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