Excessive rad levels on a package

[Tony Hedges <loui19@vcomm.net>]

Radsafers,

I refere to an over exposure event when receiving a package in a recent
post.  I have received a number of requests for more information on this
event. I ran across this event while reading the NRC's Quarterly Report to
Congress on Abnormal events at radioactive material licensees.  The report
number is NUREG-0090 Vol. 18 No. 3 "Abnormal Occurances, 3rd Quarter CY95".
Here it is for you entertainment:

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AS 95-5 "Importation of a Package Having Excessive External Radiation into
the United         States from the Republic of Korea"

Date & Place - December 20, 1994; Omnitron International, Inc; Edgerly,
Louisiana.

Nature & Probable Consequences - Omnitron International received a package
of radioactive material with external radiation levels approx. 18 times
higher than allowed by the U.S. Department of Transportation (DOT).  The
package was one of two packages received from a shipper in the Republic of
Korea.  Each package contained an Iridium-192 source in the form of a wire
that had an activity of approx. 16,650 megabecquerel (450 millicurie).

The high radiation levels were discovered during a routine survey of the
packages upon receipt by Omnitron personnel.  The package had radiation
readings of 37 millisievert (mSv) (3700 mrem) per hour at its surface and
1.4 mSv (140 mrem) per hour at 1 meter.  The maximum levels allowed by DOT,
which regulates the transport of radioactive material in the US, are 2
mSv/hr (200 mrem/hr) at the surface and 0.1 mSv/hr (10 mrem/hr) at 1 meter.

Omnitron notified the State of Louisiana's Radiation Protection Division of
the event. Inspectors from the State agency found that the package had a
narrow beam of radiation from its top surface of approx. 180 mSv/hr (18
rem/hr), and 22 to 37 mSv/hr (2.2 to 3.7 rem/hr) at other surface locations.
The radiation levels were approx. 4 times the levels measured at the surface
of the container ("overpak") in which the package arrived.

During the ensuing investigation by State and Federal agencies, it was
learned that the packages arrived in the US at LA International Airport and
were subsequently sent by truck to a Continental Freight facility in
Houston, Texas where they were cleared by Customs.  After being placed in
"overpaks" by a repackager, the packages were sent by Federal Express truck
from Houston to Omnitron International in Edgerly, Louisiana.  (It should be
noted that at least eight companies [two brokers, two trucking companies,
one repackager, and three freight forwarders] handled the packages in the US
before they left Houston.)

The investigation also determined that at least 32 people in the US were
probably exposed to the excessive radiation from the package.  The estimated
doses for the people who received maximum exposure are as follows: (1) LA
International Airport to Houston, Texas, 5.82 mSv (582 mrem); (2) Houston,
Texas, (freight companies, brokers, and a repackager) 46.13 mSv (4613 mrem);
and (3) Houston, Texas to Edgerly, Louisiana, 0.84 mSv (84 mrem).  The
maximum estimated dose was received by an employee of a Texas repackaging
firm because the packages were stored near the employee's workbench for a
day or more while the "overpaks" were constructed.

Cause or Causes - The State of Louisiana's Radiation Protection Division
concluded that the reason the one package had an excessive radiation profile
was that the source wire was not secured in the safe or completely shielded
position.  This suggests an improper preparation for shipment and a failure
to perform a proper radiation survey by the shipper in the Republic of
Korea.  There was no indication of damage to the pacakge, or any evidence to
suggest that the source changed position during shipment.  The source wire
was properly secured in the shielded position for the second package.

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That's it...

Tony Hedges
RPT
loui19@vcomm.net