Reconsolidation of Crushed Salt to 250°C Under Hydrostatic and Shear Stress Conditions

摘要

Design, analysis and performance assessment of potential salt repositories for heat-generating nuclear waste require knowledge of thermal, mechanical, and fluid transport properties of reconsolidating granular salt. To inform salt repository evaluations, we have undertaken an experimental program to determine Bulk and Young's moduli and Poisson's ratio of reconsolidated granular salt as a function of porosity and temperature and to establish the deformational processes by which the salt reconsolidates. Tests were conducted at 100,175, and 250 °C. In hydrostatic tests, confining pressure is increased to 20 MPa with periodic unload/reload loops to determine K. Volume strain increases with increasing temperature. In shear tests at 2.5 and 5 MPa confining pressure, after confining pressure is applied, the crushed salt is subjected to a differential stress, with periodic unload/reload loops to determine E and v. At predetermined differential stress levels the stress is held constant and the salt consolidates. Displacement gages mounted on the samples show little lateral deformation until the samples reach a porosity of ~10%. Interestingly, vapor is vented only for 250°C tests and condenses at the vent port. It is hypothesized the brine originates from fluid inclusions, which were made accessible by heating and intragranular deformational processes including decrepitation.