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

5.37
might be considered adequate to meet the intent of the requirements proposed by the NRC.
Additional details of retrieval and recovery operations are provided in Appendix K.
5.3.1.6 Decommissioning
As mentioned in Section 5.3.1.5, after the readily retrievable period, rooms that have
been filled to capacity with spent fuel are backfilled. The technique selected for the con-
ceptual repository is to fill the rooms with previously excavated crushed rock or with spe-
cially selected backfill material. Standard earth-moving equipment will be used to do this.
This technique was selected as the most economical, and it reduces the amount of mined rock
stored on the surface. With this technique, the rooms are backfilled to within 0.6 m of the
ceiling with crushed rock at approximately 60% of its original density. Other backfill
materials and methods of emplacement are discussed in Koplick et al. (1979).
After all rooms have been filled with spent fuel and are backfilled, the remainder of
the repository underground areas are decommissioned. All corridors and underground areas
are backfilled in the same manner as emplacement rooms. After this is completed, the repos-
itory shafts are decommissioned by filling to the surface and sealing. Combinations of
crushed rock, clay, and concrete may be used for this purpose. Because the procedures to
be used are highly site and media specific, they are not described in this generic Statement
(see Koplick et al. (1979)).
Repository decommissioning is complete when the surface facilities are decontaminated,
perhaps dismantled, and the repository location is monumented.
5.3.2 Reprocessing Fuel Cycle Repository
A geologic repository operating for disposal of fuel reprocessing wastes in the repro-
cessing fuel cycle would be required to receive high-level waste (HLW) and various remotely
handled TRU (RH-TRU) and contact-handled TRU (CH-TRU) wastes. The characteristics of these
wastes from reprocessing commercial fuel are described in Section 4.3. Defense program
wastes could be accommodated in geologic repositories in a manner similar to that described
here for these commercial fuel cycle reprocessing wastes. Characteristics and quantities
of these wastes are described in Appendix I. While these latter wastes differ from those
from LWR fuel reprocessing, the differences (mainly older and cooler, smaller quantities of
high-atomic-number actinides and different chemical form) produce wastes with lower radia-
tion intensities and lower heat output. Thus, repository placement criteria would be less
stringent for defense wastes than those for commercial wastes and they could therefore be
accommodated in the same repositories.
5.3.2.1 Design Bases
As described in Section 5.3.1.1 for the once-through fuel cycle repository, waste
emplacement is subject to thermal loading criteria for a given type of waste and rock. The
limits listed in Table 5.3.4 for the reprocessing fuel cycle repository are two-thirds of
the calculated permissible criteria described in Appendix K.