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

4.3 WASTE TREATMENT AND PACKAGING
4.17
This section addresses the treatment and packaging of high-level (including spent
fuel), TRU, and gaseous wastes resulting from the once-through and the reprocessing cycles.
The principal source of the information contained herein is DOE/ET-0028, Technology for Com-
mercial Radioactive Waste Management (DOE 1979), which was prepared in support of this
Statement.(a) The processes described here are not necessarily optimized but are represen-
tative of currently available technology.
The treated waste form and container each provide a barrier to release of radionuclides
after disposal. The functions of the treated waste forms and containers are discussed in
more detail in Section 5.1.2.
4.3.1 Spent Fuel Treatment and Packaging in Once-Through Cycle
In the once-through fuel cycle, the spent fuel is considered to be waste and is treated
to prepare it for disposal. Treatment processes that have been examined range from simply
1) packaging the intact spent fuel assemblies to 2) chopping the fuel assemblies to expose
the fuel, utilizing a process called voloxidation to remove a portion of the volatile radio-
nuclides, dissolving the fuel in nitric acid and finally converting the solution to a solid
by calcination and vitrification.
Encapsulation of intact spent fuel assemblies for geologic disposal is the example pro-
cess assumed in this Statement for the once-through fuel cycle. Three other treatment
methods are also described to illustrate the range of treatment alternatives available.
4.3.1.1 Encapsulate Intact Assembly (Example Method)
A detailed description of the example encapsulation process is contained in DOE/ET-0028
(Section 5.7.3). A similar process is described in ONWI-39 (Appendix C). In both of these
process concepts the intact fuel assemblies are placed in steel canisters that are then
backfilled with helium and welded closed. A flow diagram for the process is shown in
Figure 4.3.1.
The canister and filler materials included in the studies discussed here are only a few
of the potentially applicable materials. Canister materials being considered by DOE include
a variety of metal alloys, ceramics, carbides, forms of carbon, glasses, and cements; poten-
tial filler (stabilizer) materials include a variety of gases, castable solids, and granular
(a) Additional once-through cycle concepts were discussed later in "An Assessment of LWR
Spent Fuel Disposal Options," ONWI-39 (ONWI 1979); this report also contains information
on a reprocessing case which is somewhat different in waste treatment philosophy than
that presented in DOE/ET-0028. Other recent descriptions of reprocessing waste treatment
operations are contained in "Design Integration Study, Spent LWR Fuel Recycle Complex,
Conceptual Design, Case A-1, Separated Streams," DP-CFP-78-121 (SRL 1978) and
"Design Integration Study, Spent LWR Fuel Recycle Complex, Conceptual Design, Coprocessing
Case A-2," DP-CFP-121-79 (Harries et al. 1979). Various methods of waste treatment
and packaging for both fuel cycles are also addressed in "Technical Support of Standards
for High-Level Radioactive Waste Management, Volume B, Engineering Controls,"
EPA 520/4-79-007B (EPA 1977).