ABSTRACT
The high-temperature gas-cooled reactors (HTGRs) concept evolved from early air-cooled and CO2-cooled reactors. The use of helium in lieu of air or CO2 as the coolant, in combination with a graphite moderator, offered enhanced neutronic and thermal efficiencies. The combination of helium cooling and graphite moderator makes possible production of high-temperature nuclear heat, and hence the name HTGR.
