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INVESTIGATION OF BREACHED DEPLETED UF6 CYLINDERS
J. H. DeVan
Martin Marietta Energy Systems. Inc.
Oak Ridge, Tennessee USAABSTRACT
In June 1990, during a three-site
inspection of cylinders being used
for long-term storage of solid
depleted UF6, two 14-ton cylinders
at Portsmouth. Ohio, were discovered
with holes in the barrel section of
the cylinders. An investigation
team was immediately formed to
determine the cause of the failures
and their impact on future storage
procedures and to recommend
corrective actions.
Subsequent investigation showed that
the failures most probably resulted
from mechanical damage that occurred
at the time that the cylinders had
been placed in the storage yard. In
both cylinders evidence pointed to
the impact of a lifting lug of an
adjacent cylinder near the front
stiffening ring, where deflection of
the cylinder could occur only by
tearing the cylinder. The impacts
appear to have punctured the
cylinders and thereby set up
corrosion processes that greatly
extended the openings in the wall
and obliterated the original crack.
Fortunately, the reaction products
formed by this process were
relatively protective and prevented
any large-scale loss of uranium.
The main factors that precipitated
the failures were inadequate spacing
between cylinders and deviations in
the orientations of lifting lugs
from their intended horizontal
position.
After reviewing the causes and
effects of the failures, the team's
principal recommendation for
remedial action concerned improved
cylinder handling and inspectionprocedures. Design modifications
and supplementary mechanical tests
were also recommended to improve the
cylinder containment integrity
during the stacking operation.
INTRODUCTION
Depleted uranium hexafluoride (UF6)
produced at the uranium enrichment
gaseous diffusion plants has been
stored in steel cylinders since the
diffusion plants first went into
production more than 40 years ago.
As the number of cylinders became
significant, each of the three
diffusion plants created outdoor
storage yards as long-term depleted
UF6 repositories. These yards
consist of concrete or compacted
gravel storage pads, with lower
cylinders positioned on wooden or
concrete saddles and a second level
of cylinders supported by the lower
level. In June 1990, during
inspections at Portsmouth, Ohio, two
steel cylinders, each containing
14 tons of depleted UF6, were
discovered with holes in the barrel
section of the cylinders. The holes
in both cylinders appeared to have
originated very close to the
stiffening ring nearest the valve
end. An investigating team was
appointed and, in association with
Portsmouth personnel, developed
action plans to permit detailed
examinations of the cylinders and
their contents, as well as an
assessment of the environmental
impact of the incidents on the
storage yard and neighboring
cylinders. Evidence was gathered
through the process of removing the
failed cylinders from the storage
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DeVan, J. H. Investigation of breached depleted UF sub 6 cylinders, article, January 1, 1991; Tennessee. (https://digital.library.unt.edu/ark:/67531/metadc1058239/m1/2/: accessed June 8, 2024), University of North Texas Libraries, UNT Digital Library, https://digital.library.unt.edu; crediting UNT Libraries Government Documents Department.