Nuclear Science


Advanced Reactor Concepts

Liquid salt test loop

FHR Liquid Salt Test Loop

Nuclear Science research supports the Department of Energy (DOE) in conducting R&D on advanced reactor concepts focusing on the conceptual design, operation, control, and safety of nuclear systems for the development of next generation reactors for terrestrial and space power applications. ORNL also identifies the requisite technologies requiring further R&D to evolve these advanced concept employing capabilities that include both analysis and modeling of reactor power systems combined with technology development and validation of such systems through unique experimental facilities.

Through DOE’s Office of Nuclear Energy (NE), ORNL is developing an advanced high-temperature reactor concept that integrates technologies from several other thermal power plant designs. This new class of reactors, known as Fluoride salt-cooled High-temperature Reactors (FHRs), features low-pressure liquid fluoride salt cooling, coated-particle fuel, a high-temperature power cycle, and fully passive decay heat rejection. While FHRs represent a distinct reactor class, they inherit desirable attributes from other thermal power plants whose characteristics provide general guidance on plant configuration, anticipated performance, and costs. As high-temperature plants operating at 700°C, FHRs can support either high-efficiency electricity generation or process heat production. FHR’s combination of liquid cooling and a high output temperature makes FHRs well suited for coupling to hydrogen production facilities and thereby to liquid hydrocarbon fuel production.

ORNL is performing R&D on advanced salt compatible alloys, ceramic composite materials, TRISO fuel fabrication, economic model development, licensing and safety evaluation, FHR system modeling tools development, high temperature instruments, and liquid salt compatible component development, as well as creating a roadmap for the overall FHR program. As part of the technology development for FHRs, ORNL has designed and constructed a liquid salt component test facility for establishing baseline operations with the coolant salts at temperature with materials and in developing appropriate components suitable for salt operations.

Sectional view of AHTR concept.

ORNL also leads the concept development and evaluation efforts for two FHR design concepts. The Advanced High Temperature Reactor (AHTR) is a design concept for a central station type (1500 MWe) FHR plant. ORNL has produced a preconceptual design report on the AHTR. The Small-modular Advanced High Temperature Reactor (SmAHTR) is a design concept for a 125 MWth FHR plant. ORNL is leveraging other FHR R&D initiatives supported by DOE NE that include university R&D projects at the Massachusetts Institute of Technology, University of California at Berkeley, University of Wisconsin, The Ohio State University, and the Georgia Institute of Technology. Internationally, ORNL is cooperating with China on its FHR reactor development program and the Czech Republic where testing of a fluoride salt is underway at the Nuclear Research Institute at Řež. Finally, ORNL staff is a part of DOE’s Generation IV International Forum (GEN-IV) activities collaborating with other countries who have interests and efforts underway on FHRs and other molten-salt reactor concepts.

In addition to supporting DOE in developing reactor concepts and advanced reactor technologies, ORNL staff assists DOE NE in supporting the National Aeronautics and Space Administration (NASA) in developing nuclear power systems for exploration of the outer planets and surface power applications. ORNL collaborates with several of the NASA centers and other DOE labs in developing and evaluating both reactor concepts and power conversion technologies.

For More Information, Contact:

Group Leader, Advanced Reactor Systems and Safety
Gary Mays

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