[ RadSafe ] Re:Source in Twin towers

Brennan, Mike (DOH) Mike.Brennan at DOH.WA.GOV
Tue Oct 6 11:12:34 CDT 2009

According to calculations I did some time ago, pure U-238 has an
activity of 0.000000333 Ci/gm.  Assuming 1,000 kg of DU counterweights
on a plane, that about 0.3 Ci on the plane.  Assuming that the DU is old
enough for ingrowth of Th-234 and Pa-234 (ingrowth of U-234 will be
trivial) that means that the counterweights have a total activity of
about a Ci.  Most of the energy of the decay is in alpha and beta, which
of course means that it is unlikely to have any health consequences for
anyone who does not eat or breath it; two activities that are frowned on
in the crater of an ongoing crash scene.  Protective actions taken to
safeguard against other, much higher risk hazards, in both the short
term and the long term, will be more than adequate to protect people
from the DU hazard.  

On the other hand, it may well be useful to do a rad survey of the scene
early, looking for the counterweights.  I suspect that each
counterweight bares a unique identifier, and given the hardness of
uranium alloys in comparison to many of the other things used in
airplane construction, the counterweights probably have a fair chance of
coming through the crash intact (at least those not directly in an
associated fire).  The exact locations of easily identifiable parts
might well make the crash investigation go faster and reach better
results.  In that case I would give fairly high priority to a survey.
But from a rad safety point of view, I think recovery of the
counterweights and pieces thereof could wait until after all the jagged,
twisted metal has been hauled away. 

-----Original Message-----
From: radsafe-bounces at radlab.nl [mailto:radsafe-bounces at radlab.nl] On
Behalf Of Richardson David (RDE) Colchester Hospital University NHS
Sent: Tuesday, October 06, 2009 1:31 AM
To: radsafe at radlab.nl
Subject: RE: [ RadSafe ] Re:Source in Twin towers

Yes, some large aircraft have crashed (fairly recently) that had DU
counterweights. 747 crashes at Stansted (UK) and Amsterdam (NL) spring
to mind


Best regards
David Richardson
MTO Radiation Protection
Medical Physics
Essex County Hospital
Lexden Road
+44 (0)1206 744579
david.richardson at colchesterhospital.nhs.uk

-----Original Message-----
From: radsafe-bounces at radlab.nl [mailto:radsafe-bounces at radlab.nl] On
Behalf Of Geo>K0FF
Sent: 05 October 2009 17:40
To: radsafe at radlab.nl; Clayton J Bradt
Subject: Re: [ RadSafe ] Re:Source in Twin towers


Have any large planes crashed that DID contain the DU for

>From  a chart on DU counterweights:

DC-10 1000 kg
L-1011 680 kg
747- 850 kg

Additionally, many aircraft parts, including engines are made with
All thorium isotopes are radioactive.

Cd-109, Am-241, Fe-55 could be present in industrial gauges had any been

stored in any of the offices in New York.

It is unlikely that the fire protection system's smoke detectors used
Am-241, as most modern industrial detectors use the photoelectric
method, and other non radioactive methods. It is likely that any extra
battery operated smoke detectors installed by the tenant DO contain
if Pyrotronics industrial smoke detectors happened to have been used in
a central system, they contain 80 uCi of Am 241 each.

Don't get me wrong, I am not a DU alarmist. I actually use DU in my
work, as shielding and as a beta source.

Other building materials of concern are asbestos ( used to fireproof
supports) and mercury ( 1 drop in every fluorescent lamp) One could
surmise that a substantial puddle of liquid mercury existed at the
lowest point in the rubble.

Pictures of thorium airplane parts, counterweights etc. by request. All
taken by myself and with radiation detection equipment shown.

George Dowell
New London Nucleonics Lab 

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