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

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of air ports. Failed packages would be returned to the packaging facility for canister
repair or replacement, as necessary; this is considered to be an improbable event.
Each storage unit is about 3.3 m (10 ft) in diameter and about 7.6 m (25 ft) high.
Each unit provides a storage envelope of about 1 m in diameter by 5 m high, and contains
either four PWR or nine BWR individually packaged fuel assemblies. A large number of stor-
age units would be located at one site; the referenced design provides for incremental
expansion up to a total of 11,200 storage units, which would store spent fuel containing
20,000 MTHM.
4.4.2 High-Level Waste Storage
In the reprocessing cycle case where the fuel to be reprocessed has been out of the
reactor only a few years, the storage of high-level waste either as a liquid or a solid is
desirable to provide additional time for the heat generation rate to decrease. Another
potential reason for storage of high-level waste could be to bridge the (possible) gap
between waste generation and repository availability. The high-level waste could be stored
as a liquid and then be solidified just before repository emplacement, or it could be
solidified immediately and then stored in that form until it could be placed in a reposi-
tory, or it could be stored as a liquid for part of the time and as a solid for part of the
time (although the latter case would doubtless be more expensive).
Except for moderate volumes of surge storage in shielded processing facilities, the
only method given serious consideration anywhere for interim storage of liquid high-level
waste is storage in large underground tanks. Many methods, however, appear suitable for
storage of high-level waste after it has been solidified. Solidified high-level waste pack-
ages can be stored similarly to spent fuel in water basins, in air cooled vaults, in dry
wells, and in casks stored on the surface (ERDA-76-43 1976). Additional details on the
storage of liquid high-level waste and of solidified high-level waste in water basins and
in sealed casks can be found in DOE/ET-0028 (Section 5).
In the example waste management system considered in this Statement for the reproces-
sing cycle case, spent fuel is reprocessed 1.5 years after discharge from the reactor. The
resultant high-level liquid waste is solidified immediately (except for a minimal surge
storage period) and the solidified high-level waste is stored for 5 years in a water basin
at the reprocessing plant. When further storage is required pending repository availa-
bility, the waste is stored in sealed casks. Certain other waste disposal concepts under
consideration (i.e., rock melting and well injection) dispose of high level waste as a
liquid. Implementation of one of these concepts may require substantial liquid high-level
waste storage facilities.
4.4.2.1 Tank Storage of Liquid High-Level Waste
Storage of liquid high-level waste in large subsurface tanks has been practiced for
over 30 years in several countries. Most of the U.S. experience has involved storage of
government-produced defense program wastes; the tanks built initially were single-walled,