3. High-temperature (HTR) or very-high-temperature (VHTR) reactors

3.1 Description – Current state of development and outlook

HTRs or VHTRs (high temperature reactor or very high temperature reactor), grouped together under the abbreviation V/HTR, are nuclear reactors with a thermal neutron spectrum cooled by pressurized helium circulation (50 to 90 bar). Graphite serves as both moderator and neutron reflector. V/HTRs are characterized by high helium heating in the core (around 500°C) and average core exit temperatures of 750 to 850 ^° C for HTRs, and over 900°C in the future for VHTRs. These characteristics mean that thermodynamic efficiencies of at least 50% can be envisaged, compared with 30 to 35% for current pressurized water reactors and 40% for SFRs, as well as coupling to industrial facilities...