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

4.4 WASTE STORAGE
4.51
The treated and packaged wastes (Section 4.3) may have to be stored for an interim
period of time before they are finally placed in a repository. With some wastes (e.g.,
spent fuel in the once-through case and high-level waste in the reprocessing cycle case),
interim storage is desirable to allow many of the radionuclides to decay; this lowers the
rate of heat generation and simplifies the final disposal operations. With other wastes,
there is no technical reason for storage prior to disposal, but storage may be required
while awaiting availability of a final repository. With yet another type of waste (kryp-
ton), a special facility may be required to store the waste until its radioactivity has
decayed to a level low enough that it can be released.
4.4.1 'Spent Fuel Storage
Storage of spent fuel is an integral part of both the once-through and the reprocessing
cycles. In both cases, an initial storage period is aimed at allowing short-lived radionu-
clides to decay away; this results in a lowered heat generation rate that facilitates subse-
quent handling operations and also reduces the degree of radionuclide containment required
during the processing operations. Unpackaged spent fuel has been stored in water basins in
the U.S. for many years. The initial storage period was first envisioned as lasting only
about one year, after which the fuel would be reprocessed. However, because of deferral of
reprocessing and the possibility that spent fuel may be sent to disposal without repro-
cessing, and thus require storage until a repository is available, the initial storage
period may now last 20 years or more.
Even longer storage before disposal or reprocessing may be desirable or necessary.
Thus, extended (up to 100 years) storage of spent fuel has also been examined. Advantages
include additional reductions in the radionuclide heat generation rate and the continued
availability of the fuel if the decision is made to reprocess spent fuel.
The extended storage concepts examined here involve prior packaging of the fuel, as
described in Section 4.3.1.1, although it could well be that water basin storage of unpack-
aged fuel would be satisfactory for this purpose also. Only intact spent fuel is consid-
ered here for extended storage; it is assumed that if spent fuel is to be processed to a
different form for disposal, the processing would not be done until the time of disposal.
Four storage modes for packaged intact spent fuel are described briefly here along with the
water basin storage of unpackaged spent fuel. More detailed descriptions are presented in
DOE/ET-0028, Section 5.
Water basin storage is the only method considered in this Statement for unpackaged
spent fuel. The four packaged fuel storage concepts are described here to illustrate the
range of alternatives available to reduce the already negligible impacts of spent fuel stor-
age to even lower values.