Advanced High-Temperature Reactor
The MSRE Intermediate Heat Transfer Loop used clean salt. Molten Salt Coolants provide good heat transfer, low pressure operation, and in-service inspection.
Oak Ridge National Laboratory, Sandia National Laboratories, and the University of California–Berkeley are developing a new reactor concept for hydrogen and electricity production: the Advanced High-Temperature Reactor (AHTR). The AHTR is a type of Very High-Temperature Reactor (VHTR). The goal is to develop a large economic reactor with passive safety systems that delivers high-temperature heat with the coolant exit temperature (depending upon the specific objectives) between 750 and 1000EC. The passive safety systems require no operator actions or moving parts to assure safety. The safety goal is to equal to or exceed that of a modular high-temperature gas (helium)-cooled reactor (MHTGR). The unique characteristic of this reactor is the combination of high-temperature, passive safety, and large size. This combination may offer major economic advantages.
The AHTR fuel is a graphite-matrix coated-particle fuel, the type used in MHTGRs. The coolant is a molten fluoride salt with a boiling point near 1400EC. Because of this low-pressure liquid coolant, the type of passive safety systems proposed for liquid-metal reactors (such as the General Electric S-PRISM) can be used. Electricity is produced using a multi-reheat helium or nitrogen Brayton cycle. Depending upon design details, the power output for this passively safe reactor will be between 1000 and 1500 MW(e), with the longer-term potential for higher power outputs. When coupled to a thermochemical cycle for hydrogen production, 300 million cubic feet of hydrogen would be produced per day. In a thermochemical cycle, water plus high-temperature heat yields hydrogen and oxygen. This hydrogen output is equal to the largest hydrogen production plant now under construction that will use natural gas for hydrogen production.
Above: Schematic of the AHTR for electricity production
The AHTR concept was developed as part of the Department of Energy, Office of Nuclear Energy Generation IV program. The Generation IV program was an international effort to identify advanced nuclear electrical power generating options for the future. Ten countries (including the United States) examined over 100 reactor concepts. Of the 19 concept sets identified as potentially viable, one new reactor concept was identified—the Advanced High-Temperature Reactor (AHTR). This reactor uses a new combination of existing fuel and coolant technologies that creates the potential for major reductions in electricity production costs and the economic production of hydrogen (H2) by thermochemical cycles.
Below: Conceptual AHTR vessel
The key technologies include:
- High-temperature, low-pressure molten-fluoride-salt reactor coolants developed during the U.S. aircraft nuclear propulsion program of the 1950s and the molten salt breeder reactor program of the 1960s
- Coated-particle graphite-matrix fuel developed for high-temperature gas-cooled reactors
- Passive safety systems from the proposed modular gas-cooled and liquid-metal-cooled reactors
- High-efficiency Brayton power cycles
Research Contact:
- David Holcomb, Advanced Reactor Systems and Safety
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