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

4.20
Combustible wastes produced during the processing (secondary wastes) are converted to
ashes in an incinerator,- and the ashes are blended with fixation materials and placed into
waste containers. Incineration is accomplished in a molten salt combustion unit followed by
fixation of TRU ashes in aluminum silicate mineral (clay). Noncombustible secondary wastes
are also blended with fixation materials and placed into waste containers. Large pieces of
failed equipment are disassembled or cut into smaller pieces suitable for packaging. The
wastes requiring remote handling are packaged in 0.5 x 3.0-m cylindrical canisters, and the
wastes suitable for contact handling are packaged in 55-gallon drums. The estimated numbers
of these secondary waste packages considered to be TRU wastes are 30 canisters/GWe-yr and
6.5 drums/GWe-yr.
4.3.1.3 Dissolve Fuel and Convert to Glass
A process for dissolution of fuel and conversion to glass is described in ONWI-39
(Appendix C). This process incorporates fuel chopping and dissolution followed by concen-
tration and calcination of the resultant solution followed by vitrification (conversion to
glass) of the calcine. Voloxidation of the chopped fuel is also included in the process, as
described in Section 4.3.1.2. A flow diagram for this process is shown in Figure 4.3.3.
Although glass is the waste form described in ONWI-39, other waste forms such as those dis-
cussed in Section 4.3.2 could also be employed.
The voloxidized fuel is dissolved in nitric acid. During this operation the portions
of the iodine and krypton that were not released to the off-gas system during voloxidation
are evolved. The off-gas treatment process is described in Section 4.3.4.
The dissolution process also allows separation of the fuel cladding hulls from the fuel
itself. The hulls are compacted in small containers with a hydraulic press and several of
these containers are banded together and placed in a 0.5 x 3.0-m cylindrical canister. The
required number of such canisters is estimated to be 17.5 per GWe-yr. The fuel assembly end
fittings are packaged as described in Section 4.3.1.2.
The dissolved spent fuel is concentrated and then spray-calcined. The calcine is then
fed along with glass frit into a continuous ceramic melter for vitrification. The molten
glass that emerges from the melter is collected in canisters which, after cooling, are seal-
welded. The referenced study uses 0.5 x 3.0-m cylindrical canisters; the number required is
estimated to be 141 per GWe-yr. The number of canisters will vary however, depending on the
thermal limitations of the final repository.
The miscellaneous combustible and noncombustible wastes and the failed equipment are
treated the same as in the process described in Section 4.3.1.2. The estimated numbers of
the TRU waste packages in this process are 43 canisters/GWe-yr and 9.4 drums/GWe-yr.
4.3.1.4 Dissolve Fuel for Disposal as a Liquid
The spent fuel treatment and packaging operations described in the preceding three sec-
tions result in waste packages suitable for geologic disposal. These operations could
doubtless be adapted to provide different packages (if required) for disposal by some of the