High Temperature Gas cooled Reactors (HTGRs)distinguished from other gas-cooled reactors by the higher temperatures attained within the reactor. Such higher temperatures might permit the reactor to be used as an industrial heat source in addition to generating electricity.

Among the future uses for which HTGRs are being considered is the commercial generation of hydrogen from water. In some cases, HTGR turbines run directly by the gas that is used as a coolant. In other cases, steam or alternative hot gases such as nitrogen are produced in a heat exchanger to run the power generators. Recent proposals have favored helium as the gas used as an HTGR coolant.

The most famous U.S. HTGR example was the Fort Saint Vrain reactor that operated between 1974 and 1989. Other HTGRs have operated elsewhere, notably in Germany. Small research HTGR prototypes presently exist in Japan and China. Commercial HTGR designs are now promoted in China, South Africa, the United States, the Netherlands, and France though none of these is yet commercially marketed.

The proposed Next Generation Nuclear Plant (NGNP) in the U.S. will most likely be a helium-based HTGR, if it is funded to completion.