Re: re "Puzzler"

["Harold D Snowder"<SNO@inel.gov>]

Having worked in a previous life as a Melter Foreman for U.S. Steel at
numerous steel plants around the U.S. for 7 years I believe I can shed some
plausible explanations on your "puzzler" .  First, steel companies buy
their scrap metal (very few use raw iron ore anymore) from numerous
domestic and foreign sources. I remember seeing everything from scrap truck
trailers, ship hulls, discarded medical equipment, 55 gal. and larger waste
barrels, storage tanks, etc. being melted down in our electric furnaces.
As you can guess, much of this scrap had the opportunity to be exposed to
radioactive (usually natural occurring) materials, especially the  ship
hulls, which transported phosphates, and other ores from distant places.
Having also been a Geologist (my college major) in a prior life, I could
provide you with a  diatribe about natural radioactivity from iron ore and
the carbon coke products used to melt it but will spare you that part.

Consequently, there are two ways the contamination of metal products can
occur. First, it could occur in the melting furnace when the scrap is
combined.   U.S. Steel (and other steel companies) also used to add
radioactive tracers to its molten metal (and no, I don't remember what the
isotopes were although there were technical papers presented on the
process) to monitor the internal currents of the molten metal in order to
minimize wash-out of the refractory brick.  These tracers were naturally
left in the finished product.

Second, in order to galvanize a metal it must be immersed in a "pickling"
solution (consisting of high concentration acids) for several hours. The
pickling solution removes surface scale and etches/impregnates the steel
with the acid (galvanizing).  Since steel companies used large vats to
accomplish this and rarely changed the pickling solutions the residue from
previous steel components mixed with the new. (Kind of like taking a bath
after 200 other people used the same bath water.)
I believe the combination of all these factors could be the answer to your
"puzzler" and explain possible anomolies in why some metal products exhibit
radioactivity and others do not.



                                                   H. Dale Snowder
                                                   Supervisor Health
Physics Instrumention
                                                   Lockheed-Martin Idaho
                                                   Idaho Falls, Idaho