Salt Disposal of Heat-Generating Nuclear Waste

The thermal properties of the crushed
salt backfill correspond to
unconsolidated salt, which produces
higher waste and salt temperatures
than if the crushed salt were assumed
to have thermal properties of intact
salt.
Figure 7. Temperature in the deformed salt repository
at 27 years (Stone et al. 2010)
A deformed mesh plot with contours
of temperature is shown in Figure 7
at 27 years after waste emplacement.
In this example, the access room and
alcove are almost completely closed
by 27 years. The need for the largedeformation,
large-strain mechanics
formulation is clearly shown by the
magnitude of the simulated
deformation. The maximum
temperature at the canister/salt
interface is 408°C occurring at 4.0
years, which is consistent with the
formation of a dry halo of salt around
the waste.
Figure 8. Porosity in the crushed salt backfill at 27
years, from an initial porosity of 0.42 (Stone
et al. 2010)
Figure 8 displays porosity in the
crushed salt backfill at 27 years after
emplacement. The crushed salt
backfill develops a nonuniform
porosity with most of the compaction
occurring near the roof of the alcove.
This variation of compaction is in
qualitative agreement with
measurements of porosity in the
backfill made in the Bambus II
project (Bechthold et al. 2004). The
minimum porosity is 0.12, which is
substantially reduced from the initial
emplaced value of 0.42.
These fully coupled thermalmechanical
calculations help to show
how salt ductility is increased by
heating and the effect on temperature and physical properties. The disposal
alcoves become isolated from the adjacent mining and disposal areas because the
salt aggregate consolidates to an impermeable solid and will be drier than the
native salt because of the heat pulse. Stress differences in the near-field salt and
backfill would be relatively quickly relieved because the deforming salt
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