Storage
A discussion of depleted UF6 cylinder storage activities
and associated risks.
Management Activities for Cylinders in Storage
The long-term management of the existing DUF6 storage cylinders
and the continual effort to remediate and maintain the safe condition of the
DUF6 storage cylinders will remain a Departmental responsibility
for many years into the future. The day to day management of the DUF6
cylinders includes actions designed to cost effectively maintain and improve
their storage conditions, such as:
- General storage cylinder and storage yard maintenance;
- Performing regular inspections of cylinders;
- Restacking and respacing the cylinders to improve drainage and to allow
for more thorough inspections;
- Repainting ends of skirted cylinders and repainting cylinder bodies as needed
to arrest corrosion; and
- Constructing new concrete cylinder storage yards and reconditioning existing
yards from gravel to concrete to improve storage conditions.
Health Risks from Cylinder Storage
Under normal conditions, the main risk from cylinder storage is to cylinder
yard workers from exposure to low-level external radiation in the vicinity of
cylinders. The radiation levels measured on the outside surface of filled depleted
UF6 storage cylinders are typically about 2 to 3 millirem per hour
(mrem/h), decreasing to about 1 mrem/h at a distance of 1 ft (0.3 m). The radiation
exposures of the workers are carefully monitored and limited to stay well under
applicable guidelines and regulations. Appendix
D of the PEIS reports that the historical dose to cylinder yard workers
has been less than 200 mrem annually, much less than the regulatory limit of
5,000 mrem/yr and less than the DOE administrative control limit of 2,000 mrem/yr
for workers. (For more details on risks from continued storage, see also Appendix
D of the PEIS.)
Once depleted uranium has been converted from UF6 to a more stable
form such as uranium oxide or UF4, the risk associated
with accidents during storage and handling is greatly decreased because of the
reduced chemical reactivity and solubility of the conversion products compared
to UF6. The PEIS evaluated long-term storage of uranium oxide. Under
normal operating conditions at an oxide storage facility, there would be a small
increase in cancer risk for workers due to exposure to external radiation from
the uranium oxide; however, good work practices would minimize the exposure
and the risk. Even under extreme accident conditions, such as if a storage facility
building were damaged in an earthquake, the risk of immediate chemical injury
to the general public and to workers from exposure to released uranium oxide
would be small.
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DUF6 Guide
