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

7.27
The number of equivalent 30-year-life plants utilized through the year 2040 was used
to estimate resource requirements rather than number of plants started up. (Average utili-
zation or capacity factor for a reprocessing plant was assumed to be 80% of on-stream design
capacity and for a MOX fuel-fabrication plant a 65% factor was assumed.) It was assumed
that the balance of the facilities started up would be utilized for continuing requirements
outside the boundaries of the systems studied here. Both the number of startups and equiv-
alent 30-year-life plants are shown in Table 7.3.9.
The number of repositories required is sensitive to the geologic medium. In the case
of spent fuel, for example, the criteria utilized in this Statement indicate that the under-
ground area required to store wastes in salt or shale is approximately twice that needed to
store wastes in granite or basalt. For the reprocessing cycle wastes, salt compares favor-
ably with granite and basalt, but shale requires on the order of twice the area required for
the other three media examined. Taking into account the range of requirements for the four
media considered here, Table 7.3.10 shows the range of 800-hectare (2,000-acre) repositories
required for both the once-through and the reprocessing cycles. Further details can be
found in Appendix Tables A.10.1 and A.10.2.
Although the range of requirements shown in Table 7.3.10 results largely from the range
of geologic media considered, the range is also affected by the age of the waste. An older
waste generates less heat and, as a consequence, permits somewhat more efficient use of
repository space. The effect of waste age on repository capacity is discussed in
Section 5.3.3.
Since significant improvements may yet be possible in both the once-through cycle
repository concept and the reprocessing cycle repository concept, conclusions regarding
relative repository requirements by fuel cycle should be considered as preliminary. The
generally larger repository requirement for reprocessing wastes (salt is an exception)
results from the additional placement area required for TRU wastes. (An illustration of the
relative repository area requirements for each waste type can be found in DOE/ET-0028,
Vol. 4, Tables 7.4.2 and 7.5.3.)