Engineered barrier development for a nuclear waste repository in basalt: an integration of current knowledge

Sealing performance of bentonite and bentonite/crushed rock borehole plugs

“…Primary advantages for adding ballast material to bentonite are to increase thermal conductivity (Pusch et al, 1980;Dixon et al, 1985), to decrease shrinkage potential, and to increase the bearing capacity of the sealant, minimizing creep or settlement , a suitable composition for such sealant must fulfill the following requirements: (1) low permeability, ( 2 ) low compressibility, ( 3 ) small average pore size to prevent bentonite migration, and (4) some swelling potential. bentonite are to alter the natural geochemical properties as little as possible (Holopainen, 1985) and to reduce the amount of waste rock to be disposed of (Smith et al, 1980).…”

Computed solid phases limiting the concentration of dissolved constituents in basalt aquifers of the Columbia Plateau in eastern Washington. Geochemical modeling and nuclide/rock/groundwater interaction studies

“…The assumption of Fe(OH)3(A) equilibrium can be used to estimate maximum EH values in a similar manner to that used to estimate pH by assuming calcite equilibrium. The Smith et al (1980) use a different approach to estimate redox conditions in the aquifer. They compute a theoretical EH based on a stable mineral assemblage for a basalt system that is poised (E H buffered) by the quartzfayalite-magnetite (QFM) assemblage.…”

Stability of ceramic waste forms in potential repository environments: a review

“…form and/or prevent release of leached radionuclides from the repository, would be devised to provide the necessary protection. Such materials may include sorbent or swelling clays, overpacks (for such purposes as pH buffering), and tunnel backfills, which may incl~de materials other than just crushed repository rock (Smith et al .. , 1980). Although the manmade barriers should counteract detrimental reactions in the repository/wasteform system, tests of the entire assemblage will be required to uncover unexpected and potentially adverse interactions among the natural materia~ , the waste form, and the manmade barriers.…”

“…for the effect in some cases (Smith et al, 1980) is a hydration-spallation process~ in which a layer of material on the waste form gradually hydrates (or is otherwise altered) and spalls away, exposing fresh surfaces that are more susceptible to leaching. Precipitation of phases containing the dissolved material has been advanced as an explanation for the observed decreases in dissolved solids in the leaching solutions.…”