Management of Commercially Generated Radioactive Waste - U.S. ...

4.54.
The exhaust air is monitored to provide early detection of emissions. If container
failure is indicated, the contaminated air is diverted through an adjacent sand filter by
forced draft exhaust blowers. The failed package is removed to a facility for repackaging
or overpacking. Package failure is expected to be rare or non-existent.
Each sleeve contains either four PWR or nine BWR individually packaged fuel assemblies.
The referenced design provides for 1120 sleeves per storage vault and for modular expansion
up to a total of ten vaults. Each vault would store spent fuel containing 2000 MTHM, for a
total storage capacity of 20,000 MTHM.
4.4.1.4 Dry Well Storage of Packaged Spent Fuel
The concept of dry wells (also called dry caissons) for the storage of packaged spent
LWR fuel is similar to concepts already in use for other reactor fuels in both the U.S.
(Hammond et al. 1971) and in Canada (Morrisen 1974). For the conceptual facility here (see
DOE/ET-0028, Section 5.7.7), the spent fuel is packaged in carbon steel canisters and placed
in an underground steel- and concrete-lined caisson. The caisson is then closed with a con-
crete plug. This concept relies upon the soil to conduct the decay heat from spent fuel to
the earth's surface, where it is dissipated to the atmosphere. As in the other packaged
fuel storage concepts, double containment is depended on to maintain radionuclide releases
at negligible levels.
The caisson is designed so that its atmosphere may be monitored and sampled periodi-
cally. Water run-off from the storage area will be collected and monitored (and decontami-
nated, if necessary) before release. Package failure is considered a highly unlikely event;
should it occur, the package is returned to the packaging facility for repackaging or
overpacking.
Each caisson provides a storage space of about 1 m in diameter by 5 m high and contains
either three PWR or six BWR individually packaged fuel assemblies. The design provides for
incremental expansion up to 15,800 caissons, which would store spent fuel containing
20,000 MTHM.
4.4.1.5 Surface Cask Storage of Packaged Spent Fuel
In the surface cask storage concept, packaged spent fuel is stored (outdoors) in a
reinforced concrete radiation shield (cask). This concept has been extensively studied
(ARHCO 1976) and is a straightforward application of existing technology. In the variation
described (see DOE/ET-0028, Section 5.7.8), spent fuel assemblies in carbon steel canisters
are placed in vertical concrete casks located outdoors on concrete pads. Heat is removed
from the fuel by natural convection air flow upward through the annulus between the cask and
the fuel packages.
As in the other packaged fuel storage concepts, double containment limits radionuclide
emissions to negligible levels. Monitoring capability is provided to detect radionuclide
leakage and also to detect increases in exit air temperature, which would indicate blockage