Re: Radioactive material on CV990 ?

Date:         16 Oct 97 11:59:50 
From: (James Matthew Weber)
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>I don't know about the 990, but I've heard that the 747-100 has some
>uranium in the outer wings to dampen flutter that was identified in
>flight testing.  This may just be an unsubstantiated rumor, though.

>>- Are there other examples where radioactive materials are employed in
>>civil a/c ?
>Most elements have radioactive isotopes or contain trace amounts of
>radioactive elements, so just about everything in an airliner is
>slightly radioactive.  238U might not be much worse than more common
>materials given its long half-life.

Actually 737-300/400/500 use tungsten weights in the wingtips.
Tungsten is nearly as dense as uranium, but is much more difficult to
fabricate. My recollection is 10kg per wingtip.

Let me put the radioactivity issue into perspective. The risk for pure
Uranium is as a toxic heavy metal.  In that regard it is every bit as
dangerous as other heavy metals. The radioacivity risk is trivial by
comnparison.I have personally handled fuel pellets (uranium oxide) for
a reactor prior to use with my bare hands. The bullets used in the
GAU-8 cannon on the A10 are U238, and require no radiation protection
or precautions.

It is considered safe to do so as a radioactive material before it has
been in a reactor. (once it has been in a reactor, you get fission
products that have much shorter half lives, so are much much more
serious radiation hazards.

U238 has a half life comparable to Potassium 40. I think you would
find most people horrified to discover that a very sizeable portion of
the potassium in their body (Close to half)  is in fact K-40. In my
University days I was involved in a project where we tried to image
people using the K40 in their body. Turns out to be just about
impossible, the quantities involved are modest, and with a 4 billion
year half life, it doesn't decay very fast. At best what we were
looking far was only marginally above background, and even trace
contamination (which was a real problem for us, since it was done in
the nuclear medicine department at a large University Hospital) was
enough to completely hide the K40 decay we were looking for. (Moral of
the story is don't make you lead shielding for the floor out of pigs
used to transport radio-isotopes!!)