ORNL to lead, partner on FIRE Collaboratives in critical fusion energy technologies

The Department of Energy's Oak Ridge National Laboratory has been selected to lead two new research collaborations and partner on two others under the Fusion Innovation Research Engine, or FIRE, Collaboratives program. These projects aim to close critical gaps in fusion materials, blanket and coolant technology, liquid metal components and reactor modeling and simulation.

Administered by DOE's Fusion Energy Sciences program, the FIRE Collaboratives connect FES's basic fusion research with the practical needs of the fusion energy industry through coordinated, multi-institutional teams focused on delivering innovative solutions to real-world fusion challenges. The $128 million in funding was awarded to seven teams that are focused on creating a fusion energy science and technology innovation ecosystem, according to the official DOE announcement.

"The new FIRE collaborations give ORNL an opportunity to apply its cutting-edge fusion research to advance practical, mature technologies that can pave the way toward a fusion pilot plant and beyond," said Troy Carter, director of ORNL's Fusion Energy Division. "These projects reflect both the depth of the lab's fusion energy program and the strong partnerships we have built across national labs, universities and private industry."

The FIRE collaboratives ORNL is leading or partnering on are:

SWIFT-PFCs: Accelerating the deployment of next-generation plasma-facing components

Components exposed to the plasma within a fusion device must withstand extreme conditions, and currently, no existing material or combination of materials can provide the sustained performance necessary to make fusion energy a reality.

The Solution-Oriented Workflow for Integrated Fusion Technology in Plasma-Facing Components, or SWIFT-PFCs, FIRE collaborative will combine ORNL's materials expertise and advanced modeling capabilities to close this fusion materials gap and design the next generation of materials for plasma-facing components, or PFCs.

Over the next four years, the SWIFT-PFCs project will create an integrated design and evaluation workflow to develop, test, model and iterate upon PFC material systems for use in technology demonstration facilities and fusion pilot plants, or FPPs. The materials developed in this project will be characterized under fusion-relevant conditions and used to validate and improve fusion simulation codes, which will, in turn, be used to model virtual component designs and predict material performance and lifespan. This data will be used to inform the development of the next generation of materials that address and overcome the main limitations in today's candidates.

"This project is focused on creating well-vetted fusion material systems on an accelerated timescale. We've assembled a stellar team of experts who are keen on developing new materials while remaining open to the new discoveries and research pathways we could expect, but not necessarily predict, as the work progresses," said Zeke Unterberg, principal investigator and fusion materials R&D lead in ORNL's Materials Science and Technology Division. "Our team's moonshot goal is to develop a new paradigm for fusion PFCs to 'swiftly' deliver plasma-facing materials ready for an FPP on the timescale desired by industry but are also ultimately needed for any fusion reactor we build on Earth."

SWIFT-PFCs is a complementary project to another FIRE collaborative announced earlier this year called the Integrated Materials Program to Accelerate Chamber Technologies, or IMPACT, led by UT-ORNL Governor's Chair for Nuclear Materials Steve Zinkle at the University of Tennessee. IMPACT and SWIFT-PFCs were developed collaboratively by the national community of fusion materials experts to pool resources and share knowledge between projects. Just as SWIFT-PFCs will develop a workflow to design and test materials for plasma-facing components, IMPACT will do the same for fusion structural materials, which must be radiation resistant, maintain strength at extremely high temperatures, and not become brittle when exposed to the helium generated from a fusion reaction. The materials under investigation are an advanced vanadium alloy and a class of advanced ferritic/martensitic steels called Castable Nanostructured Alloys, both developed at ORNL, that display superior mechanical properties at high temperatures and are resistant to both radiation and helium-induced embrittlement. The ORNL principal investigator for IMPACT is Ying Yang from the Materials Science and Technology Division.

SWIFT-PFCs is led by ORNL, with coinvestigators from University of Tennessee - Knoxville, Northwestern University, General Atomics, State University of New York at Stony Brook, University of Texas at San Antonio, University of California - San Diego, and Sandia, Ames, Pacific Northwest, Idaho, Los Alamos and Savannah River national laboratories.

Building a better blanket with HASTE

The first wall and blanket are critical components of a fusion device. They face the super-hot plasma and absorb the heat and high-energy neutrons emitted by it, protecting the other components and structural elements of the device from damage. The coolant system in the blanket extracts the heat and uses it to generate electricity, and another system known as a breeder captures the neutrons and uses them to turn lithium into tritium, a form of hydrogen used as fusion fuel.

The coolant and breeder materials flowing through the first wall and blanket vary by reactor design, but the top candidates are helium, a liquid metal alloy of lead-lithium, and a molten salt known as FLiBe. To date, no facility exists that can test these coolant and breeder prototypes in an integrated environment that closely simulates the operating conditions of a fusion reactor.

To advance fusion blanket R&D and fulfill a key need in the national fusion program, the Blanket Collaborative on Test Facilities project plans to build and operate the Helium and Salt Technology Experiment, or HASTE. The HASTE facility will be able to replicate the pressures, temperatures, flow rates and magnetic fields inside a fusion blanket to study the flow physics of different systems, improve blanket simulation codes and test tritium breeding and extraction technologies. It will also provide a testbed for subsystems and components for both magnetic and inertial fusion systems.

The project will also work with collaborators in the United Kingdom and Japan, where the UK Atomic Energy Authority and Kyoto Fusioneering operate the CHIMERA and UNITY-1 facilities, respectively. These facilities are capable of testing large-scale liquid lead-lithium systems under fusion-relevant conditions and will complement the work done at HASTE.

These integral systems will also allow researchers to assess material compatibility and test corrosion effects of different breeders, especially molten salts, on blanket components.

"This collaborative effort will allow us to test blanket concepts faster and more effectively, at significantly reduced cost," said Paul Humrickhouse, principal investigator and leader of ORNL's Blanket and Fuel Cycle Group. "By leveraging investments made in international facilities and building new capabilities here at ORNL, this project can accelerate the pace of fusion blanket and materials innovation and bring them to a higher technological readiness level."

The BCTF project is led by ORNL, with coinvestigators from the UK Atomic Energy Authority, Kyoto Fusioneering, Savannah River National Laboratory, Idaho National Laboratory, the Massachusetts Institute of Technology, Columbia University, the University of Michigan, Texas A&M University, the University of Massachusetts Lowell, and the University of Tennessee - Knoxville.

Flowing forward with FILMS

ORNL is also partnered on the FIRE collaborative Advancing the maturity of liquid metal plasma-facing materials and first wall concepts, led by Princeton Plasma Physics Laboratory.

Liquid metal technologies, especially liquid lithium, are promising candidates for plasma-facing materials in the first wall and blanket of future fusion reactors, but critical scientific and engineering questions remain before they can be deployed in next-step integrated fusion facilities. This collaboration will address these challenges by testing and analyzing plasma-facing components, characterizing material properties, developing novel liquid metal alloys and validating models of liquid metal flows in strong magnetic fields.

For its part, ORNL will design a Fully Integrated Liquid Metal breeding/cooling System, or FILMS. FILMS will combine three major components into a single continuous system: a liquid metal first wall, a liquid metal breeding blanket, and a liquid metal open-surface divertor, the system that acts like the exhaust pipe of a fusion device, removing excess heat and waste gases, and is exposed to extreme heat and particle bombardment. The liquid lithium first wall flows downward through the reactor chamber over the solid first wall and is split into two streams. The first stream feeds the liquid metal breeding blanket, where it would generate tritium fuel in a working reactor, while the second stream enters the divertor at the bottom of the reactor to remove some of the intense heat load. The system will use both external mechanical pumps and internal electromagnetic pumps to circulate the liquid lithium through the system. ORNL will also analyze how the metal flow is affected by high magnetic fields, the open-surface flow behavior of the first wall and divertor, and the heat transfer capabilities of the components.

The liquid metal FIRE collaborative is led by PPPL, with coinvestigators from ORNL, University of Illinois Urbana-Champaign, ExoFusion, Lawrence Livermore National Laboratory, Massachusetts Institute of Technology, Penn State University, Princeton University, and Virginia Commonwealth University. The ORNL principal investigator is Sergey Smolentsev.

An engineering MiRACL

ORNL's fourth FIRE collaboration, also led by Princeton Plasma Physics Laboratory, is called Mitigating Risks from Abrupt Confinement Loss, or MiRACL.

Reactor-scale magnetic confinement fusion facilities will have massive amounts of thermal energy and magnetic current stored in the plasma, and if a disruption causes a sudden loss of confinement, that free energy is directed at the walls, potentially causing significant thermal, electrical and mechanical damage to the reactor components. The MiRACL project will quantify the risks to plasma-facing components and surrounding structures from an abrupt confinement loss, evaluate technologies for avoiding and mitigating such incidents, and deploy modeling tools to optimize the robustness of fusion facility designs.

ORNL will leverage its state-of-the-art simulation tools for evaluating energetic particle transport and connect them to models of the first wall and structural components of a reactor, using machine learning methods to accelerate the process. By coupling validated physics tools and engineering models, researchers can quickly and accurately assess disruption mitigation and avoidance techniques and inform the risks and operational limits of actual fusion facility designs.

ORNL is partnered on MiRACL with project lead PPPL and researchers from Columbia University, Fiat Lux, General Atomics, the KTH Royal Institute of Technology in Sweden, Massachusetts Institute of Technology, Rensselaer Polytechnic Institute, University of Illinois Urbana-Champaign, University of Texas - Austin, and University of Wisconsin - Madison. The ORNL principal investigator for MiRACL is Yashika Ghai.

The full list of FIRE collaboratives and partner institutions can be found on the DOE Office of Science website.

UT-Battelle manages ORNL for the Department of Energy's Office of Science, the single largest supporter of basic research in the physical sciences in the United States. The Office of Science is working to address some of the most pressing challenges of our time. For more information, please visit energy.gov/science. - Sean Simoneau