Salt Disposal of Heat-Generating Nuclear Waste

information, the framework for evaluating a generic salt repository for HLW in
the U.S. is developed.
Current knowledge of thermal effects in salt is based on limited testing and
experience but supports a viable concept of repository operations. Further
evaluation of tunnel deformation and stability, and the effects of excavation and
heating on long-term performance would require development and application of
site-specific constitutive models for the salt. Three-dimensional multiphysics
capabilities are now available which promise advanced capabilities for
performance assessment modeling and field test development.
Thermal, hydrologic, and geochemical considerations suggest that radionuclides
in a salt repository for HLW would not migrate from the disposal horizon. The
majority of radionuclides in the current waste inventory will be
thermodynamically stable as solids and will therefore resist migration. Much of
the inventory will decay before human intrusion would occur. A formal
performance assessment would be used to examine these assumptions for a
specific salt formation or location. A refined evaluation of the isothermal FEPs
list is one of the first research elements proposed, should the U.S. decide to
investigate a salt repository for HLW.
Findings of the evaluations presented in this report are summarized as follows:
1. Many areas of the U.S. have salt formations possessing positive
characteristics for hosting a geologic repository for HLW.
2. International repository programs have advanced repository science for
salt media, and have much to offer if the U.S. resumes investigations for
disposal in salt.
3. Radionuclide transport for salt disposal options is extremely limited
because intact salt is impermeable and because of the healing
characteristics of fractures.
4. Multiphysics modeling is poised to exploit massively parallel
computational hardware for simulation of coupled thermal-hydrologicmechanical
processes in salt. The ability to predict coupled behavior over
long time spans with new computational approaches adds confidence to
any performance assessment.
5. Laboratory testing of intact and granular salt will provide data that will
enhance phenomenological understanding and parameters for thermalhydrologic-mechanical
models.
6. Eventually, an appropriate field test will be needed to prove the principles
of the disposal concept, and to validate the coupled process models.
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