Salt Repository Seal Materials: A Synopsis of Early Cementitious Materials Development

摘要

Development of seal materials for radioactive waste repositories in evaporite rocks spans ten years. Experimental mixes have been tested under both laboratory and field conditions in halite, anhydrite, and accompanying clastic strata. Physical properties of the mixtures gradually improved through these experiments, leading to development of mixtures we now commonly call the BCT Series of mixtures. Two of these mixtures, BCT-1F (a salt-saturated mixture) and BCT-1FF (the equivalent mixture without salt), were developed for use in the Bell Canyon test in New Mexico, although only the BCT-1FF formulation was used in the field test. Other grouts, studied subsequent to Bell Canyon field emplacement, have provided more data about mineralogy, and physical performance as a function of compositional and curing variables. The interface between grout and rock has been studied on a limited basis, including some simulated boreholes and concretes. For those properties that have been tested, including expansion and compressive strength, the BCT-1F and -1FF and related grouts appear to meet preliminary performance criteria. Other properties, such as thermal expansion and creep, require additional attention. Four classes of grouts are established by chemistry and expansive mechanism: (1) non-expansive; (2) chloride expansive; (3) sulfate expansive; and (4) mixed expansive mechanisms. Additional study of evaporite-compatible mixtures, especially concretes, is recommended, under constant simulated shaft conditions. Characteristics of grout/rock interfaces, and mechanisms of expansion also require further study. 83 refs., 15 figs., 30 tabs. (ERA citation 10:026849)