Fusion and Fission Energy and Science

We are working to extend the life of nuclear reactors, investigate economical advanced reactor systems, make fusion energy viable, enable peaceful use of nuclear technologies, and produce isotopes for medicine, space exploration, element discovery, and national security.

About the Fusion and Fission Energy and Science Directorate

The Fusion and Fission Energy and Science Directorate (FFESD) addresses compelling challenges in fission and fusion energy systems, enabling Oak Ridge National Laboratory to pursue national priorities in current and advanced nuclear research, development, and deployment.

FFESD traces its roots to the X-10 Graphite Reactor, the world’s first continuously operated nuclear reactor. The directorate is focusing on fission and fusion technologies; advancing modeling and simulation; and managing the US ITER project.

The directorate’s unique facilities, capabilities, and talented scientists and engineers are currently tackling such challenges as extended operations of the current US nuclear reactor fleet; investigating economical and flexible advanced reactor systems; and making fusion energy a viable power source. The directorate leverages synergies between fusion and fission across domestic and international programs. 

FFESD leads US ITER, which has the responsibility of designing, fabricating, and delivering hardware for the international ITER fusion project. The directorate also leads the Transformational Challenge Reactor demonstration program, an effort to build the world’s first additively manufactured reactor, and the Material Plasma Exposure eXperiment (MPEX), a future world-leading capability that will produce the extreme plasma environments to test materials for use in fusion energy devices.


Launched in 2019, the Transformational Challenge Reactor (TCR) demonstration program is led by FFESD researchers and leverages capabilities and expertise from across ORNL. The program is harnessing the latest advances in science and manufacturing to build a microreactor using 3D printing and operate it by 2023. TCR will demonstrate a faster, more affordable path to deploying new nuclear energy systems and lay the groundwork for the nuclear industry to quickly adopt the technology.

The research portfolio for the Fusion and Fission Energy and Science Directorate spans two divisions and the US ITER Project. The directorate advances key science, technology, and engineering capabilities while building a competitive world-class workforce to meet our future mission needs.

Fusion Energy Division experts are developing the understanding required for the deployment of practical fusion energy systems. This includes realizing next-generation fusion materials, achieving a sustainable fuel cycle, ensuring adequate power exhaust in high-confinement systems, and maintaining long-term control of the plasma. Researchers are building a foundation for sustaining burning plasma and using theory and modeling to resolve critical issues and to come up with workable designs for future fusion devices. The division is also identifying and developing remote-monitoring technologies for harsh environments, including fusion devices.

The Nuclear Energy and Fuel Cycle Division provides science and technology breakthroughs to extend the lives of current nuclear plants, to accelerate the deployment of new, advanced nuclear-power technologies, to further the state of the art in modeling and simulation capabilities for nuclear application, to deliver new insights into nuclear fuel performance at all stages of the fuel cycle, and to provide innovations for nuclear fuel systems. The division is leading the Transformational Challenge Reactor demonstration program and also developing other advanced reactor concepts; assessing and improving effective, cost-efficient nuclear systems; and developing and testing molten-salt components and other energy conversion methods.

The US ITER project is working with industry, universities, and national laboratories to deliver 12 hardware systems for the ITER fusion research facility under construction France. The ITER tokamak will enable the study and control of burning plasmas, an essential step in fusion energy development.

Delivering Nuclear Energy Innovation

Established in 2020 as part of Reimagining ORNL, FFESD is aligning the Lab’s nuclear science and engineering capabilities for maximum impact on the future of nuclear energy. Having built and operated 13 nuclear reactors in its history, ORNL is fertile ground for nuclear innovation. In the past decade, the Lab has led the Consortium for Advanced Simulation of Light Water Reactors, DOE’s first energy innovation hub; developed a new accident tolerant fuel cladding and handed it to industry for testing; and managed the fabrication of the 60-foot-tall central solenoid magnet for ITER. Each of these milestones represents the unique impact of ORNL and how it will shape the coming decade of fission and fusion energy research and development.


Over the next decade, we will produce world-leading impacts in nuclear science and engineering, helping produce clean, economical nuclear energy, a viable path for fusion energy, and oversee the nation’s contributions to ITER.

Our vision enables us to:

  • Establish ORNL as the nation’s fusion energy laboratory by delivering the technology to enable fusion energy systems, delivering essential systems for ITER research operations, fully leveraging MPEX, establishing new research and development capabilities, and growing our public-private partnerships.
  • Advance the path to fusion energy and burning plasma research with initial operations of the ITER tokamak.
  • Demonstrate successful engineering of high-performance fusion technologies for a reactor-scale fusion environment.
  • Operate ORNL’s 14th reactor—the Transformational Challenge Reactor—and showcase the rapid deployment of advanced reactor technologies unlike anything the world has seen.
  • Accelerate reactor deployment through partnerships with the reactor community, the development of new fission technologies, and by helping industry adopt our world-leading modeling and simulation tools.
  • Further our leadership in nuclear fuels and fuel cycle technology, from exploring new types of promising fuels to improving confidence in the management of used fuel.

Fusion and Fission Energy and Science Divisions, Sections and Groups

Fusion Energy Division

Fusion Energy Division experts are developing the understanding required for the deployment of practical fusion energy systems. This includes realizing next-generation fusion materials, achieving a sustainable fuel cycle, ensuring adequate power exhaust in high-confinement systems, and maintaining long-term control of the plasma.

Burning Plasma Foundations Section

Provide the technical basis and resolve key challenges in achieving and sustaining high performance burning plasmas in fusion devices.

  1. Plasma Theory and Modeling Group — Deliver the theoretical foundation and state-of-the-art simulation/modeling capabilities to resolve critical issues and inform design/operation of ITER and future fusion devices.
  2. Diagnostics and Control Group — Develop and validate innovative measurement and control capabilities needed to understand and control important physics phenomena in present devices and maintain robust control in the fusion nuclear environment of future fusion devices.
  3. Advanced Tokamak Physics Group — Establish high confidence, embodied in a validated modeling suite, in achieving high performance, steady-state tokamak regimes in ITER and future fusion devices.
  4. Power Exhaust and Particle Control Group — Deliver power exhaust/particle control solutions and accompanying physics basis required for compact fusion devices.

Fusion Nuclear Science, Technology, and Engineering Section

Establish the technical basis and provide cost-attractive solutions for fusion subsystems needed to turn a burning plasma into a viable commercial power plant.

  1. Blanket and Fuel Cycle Group — Provide the technical basis and solutions for closing the tritium fuel cycle and efficient power extraction in future fusion systems.
  2. Fusion Technology Group — Develop innovative technology approaches for heating, fueling, and controlling plasmas required for efficient operation of future fusion systems.
  3. Fusion Engineering Group — Develop advanced designs and engineering solutions
    for both individual components and integrated systems for future US and international fusion systems.
  4. Remote Systems Group — Provide creative solutions for remote monitoring and manipulation in extreme environments.

Nuclear Energy and Fuel Cycle Division

ORNL is a world-leader in innovation for nuclear energy and is working to accelerate the deployment of economical technologies from concept through industry and regulatory adoption. The Nuclear Energy and Fuel Cycle Division provides science and technology breakthroughs to extend the lives of current nuclear plants, to accelerate the deployment of new, advanced nuclear-power technologies, to further the state-of-the-art in modeling and simulation capabilities for nuclear application, to deliver new insights into nuclear fuel performance at all stages of the fuel cycle, and provide new innovations for nuclear fuel systems.

Advanced Reactor Engineering and Development Section

World-class capabilities for design and performance analysis of advanced reactor concepts and development of advanced technologies for cost-competitive nuclear energy.

  1. Advanced Reactor Systems Group — System analysis for advanced reactor concepts: Provides assessment of reactor performance and impact of modern technologies on cost- competitiveness for nuclear energy.
  2. Energy Systems Development Group — Component testing and integration: Provides technology development and testing for molten-salt components and advanced energy conversion systems.
  3. Advanced Nuclear System Safety and Licensing Group — Siting, safety, and systems analysis for advanced reactor systems: Provides support for deployment of advanced reactors, microreactors, and space reactor systems. Provides reactor expertise for safeguard and security activities.
  4. Thermal Hydraulics Group — Computational fluid-dynamics and experimental testing: Provides performance analysis of thermal hydraulics in advanced reactor concepts, detailed computational and experimental analysis of components.
  5. Nuclear Structures and Construction Group — Expertise in civil engineering and concrete performance for nuclear structures: Provides characterization and predictive analysis of concrete performance under time, stress, and irradiation. Development of new construction architectures.
  6. Modern Nuclear I&C Group — Development of instrumentation and control systems for nuclear applications: Provides development of new measurement approaches, analytics of data for nuclear components, and artificial intelligence for automated control systems.

Nuclear Modeling & Simulation Development and Deployment Section

Leads application-driven development of innovative and validated computational tools and analysis methods to efficiently model fission energy systems, nuclide transmutation, and nuclear fuel cycles.

  1. Power Reactor Modeling — Power reactor R&D focuses on commercial nuclear power systems including tool development and analysis expertise to support nuclear industry and NRC customers.
  2. Depletion Modeling — Depletion modeling R&D at ORNL focuses on method development and analysis applied for nuclear fuel cycle assessments, radionuclide inventories, source terms, and decay heat.
  3. Research and Test Reactor Modeling — Research reactor R&D focuses on non-commercial nuclear power systems including tool development and analysis expertise to support key national user facilities such as HFIR and VTR as well as first-of-a-kind systems such as TCR.
  4. Nuclear Code Integration — Support for code development, revision, and upgrades: Provides an essential capability in deployment of modeling and simulation packages by providing technical support for code quality, debugging, as well as customer support.
  5. HPC Methods for Nuclear Applications — Extends modeling and simulation tools for nuclear to high performance computing: Most mod-sim tools for nuclear applications are not compatible with modern computational tools. This requires a multi-disciplined approach, bridging both exascale computing and nuclear engineering.

Nuclear Criticality, Radiation Transport and Safety Section

Provide integrated nuclear data, modeling & simulation, nuclear criticality safety and radiation transport analysis capabilities to enable innovative technical solutions for nuclear technology applications.

  1. Nuclear Criticality Group — Modeling and simulation and nuclear criticality safety analysis: Possesses a broad range of physics and nuclear engineering expertise that is used to provide technical support to nuclear criticality safety licensing submittals and other issues associated with storage and handling of nuclear fuel at power plants and in storage and transportation systems.
  2. Nuclear Data Group — Improved measurement of nuclear data and new measurement techniques: Provides high-quality nuclear data with covariances, which are required for the design and analysis of nuclear systems. The group develops new methods for measurement in partnership with leading facilities around the world.
  3. Radiation Transport Group —Leading analysis of radiation transport and shielding: Develops, applies and deploys state-of-the-art modeling and simulation capabilities along with extensive expertise to solve challenging radiation transport problems across a wide range of applications, including shielding for ITER and other facilities, as well as spent nuclear fuel.

Fuel Development Section

World-leading expertise in the fundamental science and characterization of fuel cladding and fuel performance, the development of advanced fuel systems, and unique experience in design and implementation of in-reactor testing.

  1. Advanced Fuel Forms Development Group —Innovation in development of new, high-performance fuel forms: Applies modern materials science to design, develop, optimize, and test prototypical advanced nuclear fuels that will accelerate the deployment of higher performance nuclear energy systems.
  2. Nuclear Cladding Development and Characterization Group — Characterization and development of nuclear fuel cladding for existing and advanced reactors: Provides advanced materials characterization and modeling of cladding materials. The use of advanced and additive manufacturing technologies provides innovative performance solutions to cladding systems.
  3. Particle Fuel Forms Group — International leadership in development of coated particle fuel forms (TRISO): Delivers new fuel particle innovations and designs, supports industry partners in production and processing, leading capability in post-irradiation examination and long-term performance of fuel particles.
  4. Irradiation Testing Design and Fabrication Group — Experimental design and analysis for complex experiments and testing for reactor service: Combines leading edge thermal, fluid, and structural analysis methods with sophisticated experimental techniques to develop effective solutions for testing.
  5. Nuclear Experiments Group — Fabrication and qualification of experiments for reactor components and systems: Group expertise is applied to solve the most challenging thermal hydraulic problems and complex experimental designs such as coolant loops and instrumentation.

Integrated Fuel Cycle Section

World-leading fission fuel cycle capabilities that underpin reactor deployment and operation.

  1. Fuel Cycle Chemistry Research Group — Performs applied research on chemical reactions (conversions) and separations chemistry associated with the production of nuclear materials. Activities are of a more fundamental nature that will be incorporated into technologies developed and assessed by the FRT group.
  2. Fuel Reprocessing Technology Group — Performs applied R&D with emphasis on technology and process development for nuclear materials, processing irradiated materials, and immobilizing wastes. This also includes systems analysis and experimentation for determination and characterization of facility source terms.
  3. Uranium Process Chemistry Group — Research on the handling, behavior, environmental fate, and detection of materials associated with gas phase U enrichment processes. This includes development of methods and devices for determining U assay and processing history.
  4. Extended Burn-Up and Increased Enrichment Fuel Group — Characterization and performance of extended burnup fuel and cladding: Delivers fuel characterization of used fuel using advanced modeling and simulation capabilities, and insights from characterization supporting industry and regulator decisions. Analysis of increased enrichment forms and performance is a priority.
  5. Packaging Systems and Logistics Group — Characterization of packaging containers and logistics: Supports implementation and planning for storage and maintaining a database of the nation’s used fuel inventory, as well as safeguarding of spent nuclear fuel and high-level waste. Spent fuel package testing, development of standards and transportation methods, and logistics are key capabilities.
  6. Used Fuel Disposition Group — Implementation of disposition of used fuel: Leads activities associated with disposal of spent fuel, development of standards and transportation methods, and analysis of disposition scenarios.