SOAR: A MODEL FOR SCOPING OF OPTIONS AND ANALYZING RISK VERSION 1.0 USER GUIDE

ion: Reduction and representation of the essential and complex components of a feature, event, or process into a simplified form for inclusion in a model. An abstraction is intended to maximize the use of limited computational resources while allowing a sufficient range of sensitivity and uncertainty analyses. Advection: The process in which solutes, particles, or molecules are transported by the motion of flowing fluid. Ambient: Undisturbed, natural conditions. Anoxic: Pertaining to the existence of reducing conditions; often due to minimal or no oxygen present. Aqueous: Pertaining to water, such as aqueous phase, aqueous species, or aqueous transport. Backfill: Materials used to fill in an excavated, open area after emplacement of waste. Breach: A penetration in the waste package. Center for Nuclear Waste Regulatory Analyses (CNWRA): A federally funded research and development center in San Antonio, Texas, sponsored by the U.S. Nuclear Regulatory Commission (NRC), to provide NRC with technical assistance for the repository safety program. Cladding: The metal outer sheath of a fuel rod generally made of a zirconium alloy intended to protect the uranium dioxide pellets, which are the nuclear fuel, from direct contact with reactor coolants or neutron moderators and dissolution by exposure to high temperature water under operating conditions in a reactor. Colloid: As applied to radionuclide migration, a colloidal system is a group of large molecules or small particles having at least one dimension with the size range of 10 to 10 m [3.9 × 10 to 3.9 × 10 in] that are suspended in a solvent. Colloids that are transported in groundwater can be filtered out of the water in small pore spaces or very narrow fractures because of the large size of the colloids. Conceptual Model: A set of descriptive features used to characterize a system or subsystem for a given purpose in a model. These features are compatible with one another and fit the existing data within the context of the given purpose of the model. Corrosion: The deterioration of a material, usually a metal, as a result of a chemical or electrochemical reaction with its environment. Criticality: The condition in which a fissile material sustains a chain reaction. It occurs when the number of neutrons present in one generation cycle equals the number generated in the previous cycle. The state is considered critical when a self-sustaining nuclear chain reaction is ongoing.