Reference concepts for geologic disposal of used nuclear fuel and high-level radioactive waste in
the U.S. are developed, including geologic settings and engineered barriers. Repository thermal
analysis is demonstrated for a range of waste types from projected future, advanced nuclear fuel
cycles. The results show significant differences among geologic media considered (clay/shale,
crystalline rock, salt), and also that waste package size and waste loading must be limited to meet
targeted maximum temperature values.