Basic Research Needs for Geosciences - Energetics Meetings and ...

PANEL REPORT: CHEMICAL MIGRATION PROCESSES IN GEOLOGIC MEDIAThe hypothetical perturbed environment near emplaced nuclear wastein a geologic repositoryThe longevity of engineered materials in proposed nuclear waste repositories such as YuccaMountain strongly depends on the environments to which they are subjected (Steefel 2004).The pH, chemical composition, oxidation state, and transport of liquid water to the engineeredmaterials, along with transport of organic and inorganic gases into the repository as a functionof time and temperature, are critical parameters controlling environmental stability. Dust orrubble on engineered material surfaces may experience high temperatures, radiation fields andchemical gradients. Moisture and volatile gases may be added to or removed from the dustand rubble, possibly resulting in deliquescent brine formation and reactions that corrode thewaste package materials, prevent corrosion, release wastes to the repository, sorb releasedspecies, or precipitate released contaminants. The surrounding geochemical environment islikely to be influenced by properties of the engineered materials, creating a feedback loop.Heat flow and rates of contaminant release, the degree of oxidation and generation of acidicgases from corrosion processes, and the effects on permeability and mineralogy of thesurrounding rock must all be factored into the evolving environment.Courtesy of Carl Steefel, LBNLAbove: Key processes within waste emplacement drift. Below: Surface processes on topof waste package.30 Basic Research Needs for Geosciences: Facilitating 21 st Century Energy Systems