Q&A with ORNL’s Michael Loughlin on bridging decades of fission experience to advance fusion energy
Decades of nuclear fission research are providing critical insights to help scientists design the next generation of fusion systems, and few understand that connection better than ORNL’s Michael Loughlin.
A distinguished R&D scientist in the Radiation Transport and HPC Methods Group at the Department of Energy’s Oak Ridge National Laboratory, Loughlin has devoted more than 35 years to advancing fusion neutronics, nuclear integration and diagnostics on the world’s largest experiments, including the Joint European Torus, the Tokamak Fusion Test Reactor, the Mega Amp Spherical Tokamak, and the International Thermonuclear Experimental Reactor (ITER). From helping achieve record-breaking fusion power production to coordinating nuclear analysis and shielding for ITER, his career reflects both the curiosity that drives new questions and the expertise to deliver meaningful answers.
Q: How are fission and fusion similar, and how are they different?
A: Both fusion and fission are similar in that they both produce neutrons in nuclear reactions. The key difference is in the energy of those neutrons: in fusion, they carry much more energy — about 14 million electron volts — meaning they travel faster than 115 million miles per hour. However, both types of reactions involve similar issues, including radiation shielding, radiation damage to materials, induced radioactivity and radioactive waste, and the need for remote handling. Fusion faces challenges that fission doesn’t, including the need to create its own fuel, tritium, to keep the reaction going. Fusion systems also operate under extreme conditions, requiring powerful vacuum environments and super-cold or cryogenic components.
Q: What lessons from decades of nuclear fission science and engineering can inform us of the way we design fusion systems?
A: Most fusion experiments have been focused on heating and confining the fuel — deuterium and tritium — to a degree to generate sufficient reactions. The first fusion-based power plant will produce more neutrons in its first few seconds of operation than the neutrons produced in all controlled fusion experiments to date. Therefore, fusion engineers and operators must look to the decades of experience available in fission systems, like nuclear engineering, civil engineering, radiation damage, energy conversion, materials research, nuclear data, radio-active waste disposal, safety and licensing among others. There are a few important lessons to be learnt, for example the use of heavy concrete to shield against neutrons while taking up as little space as possible and the development of special (so-called reduced activation) steel alloys that avoid the generation of long-lived radio-active waste that can be a burden on future generations.
Q: How does your research connect insights from fission to the challenges of fusion?
A: I research how all the systems in a fusion plant interact with the radiation and how to maintain the operability and safety of the plant. While nuclear fission power plants require a certain degree of shielding around the core because of radiation produced by nuclear reactions, fusion power plants are more complex; they need external heating, and monitoring and control systems. In a fusion reactor, we have to estimate the impact of the nuclear radiation on all the components, not just a few core areas. We do this by creating computer models that describe all the sources of radiation as well as the geometry of the power plants before simulating how the radiation behaves as it interacts with all the materials. This requires unprecedentedly large models on some of the world’s most powerful computers and the development of new methodologies for the simulation of the complex sources and geometries.
Q: What role could fusion play alongside fission in the future?
A: The current understanding of the economics of fusion power plants indicates their suitability for base-load electricity supply, or the constant energy provided to the electric grid, 24/7. Fusion energy would complement nuclear’s status as a baseload generator, in addition to supporting other intermittent forms of energy. Fusion devices are being considered for spent nuclear fuel processing that would help resolve the challenge of long-term radioactive waste produced by fission reactors.
Q: How can collaboration between fission and fusion researchers speed up progress in both areas?
A: Both areas stand to benefit from collaborations to enhance our understanding of the interaction of radiation with matter — for example, studying how advanced materials perform under high neutron flux. Both fusion and fission depend on advances in nuclear data, diagnostic instrumentation, radiation transport simulation, shielding, minimization of radioactive waste and the reduction of the dose to workers and the environment ORNL is advancing collaborative research through materials testing and characterization at the High Flux Isotope Reactor, which enables us studying how materials behave under intense neutron irradiation and generate critical data that can support fusion materials and ongoing reactor development.
UT-Battelle manages ORNL for DOE’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.
