Distribution Coefficients (K(sub d)) Generated from a Core Sample Collected from the Saltstone Disposal Facility

摘要

Core samples originating from Vault 4, Cell E of the Saltstone Disposal Facility were collected in September of 2008 and sent to the Savannah River National Laboratory (SRNL) to measure chemical and physical properties of the material including visual uniformity, mineralogy, microstructure, density, porosity, distribution coefficients (Kd), and chemical composition. The core samples were taken from grout placed in December of 2007. The saltstone is comprised of blast furnace slag, Class F fly ash, ordinary portland cement, and Deliquification, Dissolution, and Adjustment (DDA) Batch 2 radioactive salt solution. The core sample that was analyzed contained an olive green interior and a gray surface layer indicative that some oxidation had occurred prior to leaching studies. The oxidation condition of the core sample is important because it can impact the measured Kd values. For example, technetium will have lower Kd values or higher solubility values under sub-oxic conditions than under fully anoxic conditions. In this report, results are presented from leaching experiments that were conducted with core sample 3-2 in conditions that are representative of saltstone performance. This study was designed to provide insight into how readily species immobilized in saltstone will leach from the saltstone under oxidizing conditions simulating the edge of a saltstone monolith and under reducing conditions (30 to 60 ppm O2), targeting conditions within the saltstone monolith. Solubility and Kd values were obtained from measurement of the species present in the solid and the aqueous leachate. This work represents the first leaching study performed with a site-specific aged saltstone sample.