The advanced high-temperature reactor is a new reactor concept that combines four technologies in a new way: coated-particle nuclear fuels traditionally used for helium-cooled reactors, Brayton power cycles, passive safety systems and plant designs from liquid-cooled fast reactors, and low-pressure liquid-salt coolants. The new combination of technologies may enable the development of a large high-efficiency, lower-cost high-temperature (700 to 1,000 degrees C) reactor for electricity and hydrogen production. As the peak reactor coolant temperatures approach 700 degrees C, several technologies (Brayton cycles, passive reactor safety systems, available materials, etc.) work together to improve total system performance while significantly reducing costs relative to those for other reactors. A window of performance and lower capital costs exists between these temperatures and the practical temperature limits of materials. The higher temperatures and efficiency of the Brayton power cycle greatly reduce the total heat rejection compared with that achieved in current light-water reactors and may allow economic heat rejection with dry cooling towers, thus radically reducing the water consumption used in energy production. The option for dry cooling is facilitated by the characteristics of Brayton cycles, which reject heat over a temperature range of 40 to 50 degrees C and thus match the requirements of dry cooling systems.