On May 11, 1996,
ValuJet Flight 592 crashed shortly after takeoff in the Everglades near
Miami, Florida, killing all 105 passengers and 5 crew members. The National
Transportation Safety Board determined that the probable cause of the
accident was a fire in the airplane's cargo compartment that was started
by the activation of at least one of the oxygen generators being improperly
carried as cargo. This crash is a vivid example of the potential for
tragedy that can result from the transport of undeclared "dangerous
goods."
The expired but
unexpended oxygen generators were identified as "airplane parts," instead
of being properly classified as hazardous materials and specially packaged
and handled to mitigate the hazards. "Proper classification, labeling,
and packaging are important to safety," says Scott Ludwig, leader of
the Transportation Technologies Group in ORNL's Chemical Technology
Division. The group is located at the National Transportation Research
Center (NTRC).
Rick Rawl, one
of the group's members, has spearheaded the development of the Hazardous
Materials Transport Expert System, which tells users what type of package
is required for a product, as well as how to properly classify, label,
and ship the package to meet regulations. "If a user wants to know how
to safely package, label, and ship a substance—even an unusual
mixture of substances such as a combination of acetone and hydrochloric
acid—our software can provide the answers," Rawl says.
Since 1960 the
Transportation Technologies Group has been evaluating the ability of
packages to protect their contents from damage and prevent the contents
from escaping in case of accidents. The researchers have focused on
containers of radioactive materials, including spent nuclear fuel. To
meet federal regulations, any container for transporting a significant
quantity of radioactive materials must be designed so that none of the
material escapes, even if the container is involved in a rail or truck
accident.
The ORNL group
has conducted drop tests of packages of various designs to determine
which ones best contain and protect their contents following a severe
impact. Casks and other containers have been dropped 200 feet from ORNL's
Tower Shielding Facility and, more recently, 30 feet from a mobile crane
onto a specially designed, unyielding steel-and-concrete pad. The dropped
packages and their contents are photographed and evaluated to determine
the extent of damage and the potential for leaks of radioactivity.
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A
lead-steel cask made by Nuclear Assurance Corporation is dropped
30 feet in this drop test at ORNL using a crane. The cask is designed
to hold spent nuclear fuel. Its impact limiter is made of balsa
wood and redwood. Other casks have impact limiters made of steel
honeycomb. Insets: The edge of the cask is deformed as a result
of the impact on the drop test pad—a steel armor plate supported
by 5 feet of concrete on bedrock.
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"There have been very
few transportation accidents involving radioactive materials," Ludwig
notes. "One accident happened on December 8, 1972, in nearby Lake City,
Tennessee, when a truck rolled over and a cask of spent fuel fell to
the ground. Unfortunately, the driver was killed. But the cask was not
damaged, and no radioactivity was released to the environment."
"We will continue drop
tests at the NTRC," says Larry Shappert, who has been conducting drop
tests of packages for 40 years. "We have the capability at the NTRC
to drop 10,000-pound pack-ages from 30 feet onto a newly designed impact
pad. We also have an impact pad inside the packaging lab which can be
used to test small packages."
To guide designers
and shippers of casks of radioactive materials, Shappert in 1998 prepared
the Radioactive Materials Packaging Handbook, 350 copies of which
have been published. It provides information on shielding, criticality,
heat transfer, testing, and operation, as well as Department of Transportation
and Nuclear Regulatory Commission regulations.
Shappert currently
advises the Defense Logistics Agency on what needs to be done to properly
package and ship 55-gal. drums of radioactive materials and special
chemicals that could be sold. He also tests the effectiveness of special
materials designed to cushion the contents against the shock of an impact
by absorbing its energy. These materials, called impact limiters, are
usually made of steel honeycomb, redwood, or balsa wood.
"At the NTRC,
our program will be expanded to test packages for hazardous chemicals
and high-value commodities, such as television sets and other electronic
devices," Ludwig says. "We hope to offer packaging advice to local companies."
"In the NTRC lab
we will have a vibration table to shake packages and a compression testing
device to squeeze them," Rawl says. "For example, the vibration table
will allow us to shake a TV set until it breaks. In this way, we'll
know the level of vibration the package should be designed for to protect
the TV against transportation-related damage."
The group's computer
center at the NTRC provides information that will help shippers minimize
the effects of transportation accidents, although rare, involving radioactive
materials. Users can access an NTRC server that hosts Transportation
Routing Analysis Geographic Information Systems (TRAGIS). This software
package selects interstate and state-preferred routes for radioactive
materials carriers that avoid heavily populated areas. The computer
service, which provides the latest census information, is used in conjunction
with risk codes such as RADTRAN. Thus, users can calculate the potential
total radiation exposure of all drivers and the public who live within
a half mile of the truck, rail, or waterway route taken by the vehicle
carrying radioactive materials. The information is useful for environmental
impact statements and other risk assessments.
So, if you're
looking for a useful transportation-related software package or a package
test, you may find it at the NTRC.
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Related Web
sites
ORNL's
Transportation Technologies Groups
ORNL's
Chemical Technology Division
ORNL's
Tower Shielding Facility
National Transportation
Safety Board
