Salt Disposal of Heat-Generating Nuclear Waste

closure have been constrained by the computational effort and complexity. The
advanced suite of SIERRA Mechanics codes has been developed at Sandia to run
on massively parallel computing hardware, to address these past limitations
(Edwards 2002).
Hampel and coworkers (Hampel et al. 2010) recently summarized numerical
simulations for the design and stability analysis of underground openings in rock
salt. Several partners performed benchmark analyses using various constitutive
models. Their benchmark calculations and comparisons of isothermal results from
joint projects showed that the constitutive models captured deformational
phenomena in rock salt below and above the dilatancy boundary.
Based on the developments at Sandia National Laboratories with SIERRA
Mechanics and the developments described by several German salt researchers, it
would appear that different teams have collected extensive experimental data and
theoretical knowledge for simulating the mechanical deformation of rock salt.
Several advanced constitutive models have also been developed and applied. The
strong temperature dependence of salt deformation and the thermal influence on
reconsolidation need to be reevaluated soon if the U.S. chooses to investigate the
salt disposal option. For the calculation and assessment of the tightness of the
geological barrier rock salt around a repository, further effort is also to be made in
the investigation and modeling of salt damage healing and the corresponding
reduction of permeability.
Coupled thermal-mechanical benchmark 3-D simulations could be performed in
order to calculate the evolution of stresses, strains, dilatant volumetric strains, and
damage around a potential repository for heat-generating radioactive wastes in
rock salt. Useful outcomes would include advancing the technical baseline
regarding the processes described in the U.S./German salt repository workshop,
and performing appropriate code benchmark calculations, ultimately leading to an
in situ test for model validation. U.S./German collaborations continue with a goal
to hold an integrated salt repository workshop each year.
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