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      Helping the cause of environmental resilience

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      Haruko Wainwright, the Norman C. Rasmussen Career Development Professor in Nuclear Science and Engineering (NSE) and assistant professor in civil and environmental engineering at MIT, grew up in rural Japan, where many nuclear facilities are located. She remembers worrying about the facilities as a child. Wainwright was only 6 at the time of the Chernobyl accident in 1986, but still recollects it vividly.

      Those early memories have contributed to Wainwright’s determination to research how technologies can mold environmental resilience — the capability of mitigating the consequences of accidents and recovering from contamination.

      Wainwright believes that environmental monitoring can help improve resilience. She co-leads the U.S. Department of Energy (DOE)’s Advanced Long-term Environmental Monitoring Systems (ALTEMIS) project, which integrates technologies such as in situ sensors, geophysics, remote sensing, simulations, and artificial intelligence to establish new paradigms for monitoring. The project focuses on soil and groundwater contamination at more than 100 U.S. sites that were used for nuclear weapons production.

      As part of this research, which was featured last year in Environmental Science & Technology Journal, Wainwright is working on a machine learning framework for improving environmental monitoring strategies. She hopes the ALTEMIS project will enable the rapid detection of anomalies while ensuring the stability of residual contamination and waste disposal facilities.

      Childhood in rural Japan

      Even as a child, Wainwright was interested in physics, history, and a variety of other subjects.

      But growing up in a rural area was not ideal for someone interested in STEM. There were no engineers or scientists in the community and no science museums, either. “It was not so cool to be interested in science, and I never talked about my interest with anyone,” Wainwright recalls.

      Television and books were the only door to the world of science. “I did not study English until middle school and I had never been on a plane until college. I sometimes find it miraculous that I am now working in the U.S. and teaching at MIT,” she says.

      As she grew a little older, Wainwright heard a lot of discussions about nuclear facilities in the region and many stories about Hiroshima and Nagasaki.

      At the same time, giants like Marie Curie inspired her to pursue science. Nuclear physics was particularly fascinating. “At some point during high school, I started wondering ‘what are radiations, what is radioactivity, what is light,’” she recalls. Reading Richard Feynman’s books and trying to understand quantum mechanics made her want to study physics in college.

      Pursuing research in the United States

      Wainwright pursued an undergraduate degree in engineering physics at Kyoto University. After two research internships in the United States, Wainwright was impressed by the dynamic and fast-paced research environment in the country.

      And compared to Japan, there were “more women in science and engineering,” Wainwright says. She enrolled at the University of California at Berkeley in 2005, where she completed her doctorate in nuclear engineering with minors in statistics and civil and environmental engineering.

      Before moving to MIT NSE in 2022, Wainwright was a staff scientist in the Earth and Environmental Area at Lawrence Berkeley National Laboratory (LBNL). She worked on a variety of topics, including radioactive contamination, climate science, CO2 sequestration, precision agriculture, and watershed science. Her time at LBNL helped Wainwright build a solid foundation about a variety of environmental sensors and monitoring and simulation methods across different earth science disciplines.   

      Empowering communities through monitoring

      One of the most compelling takeaways from Wainwright’s early research: People trust actual measurements and data as facts, even though they are skeptical about models and predictions. “I talked with many people living in Fukushima prefecture. Many of them have dosimeters and measure radiation levels on their own. They might not trust the government, but they trust their own data and are then convinced that it is safe to live there and to eat local food,” Wainwright says.

      She has been impressed that area citizens have gained significant knowledge about radiation and radioactivity through these efforts. “But they are often frustrated that people living far away, in cities like Tokyo, still avoid agricultural products from Fukushima,” Wainwright says.

      Wainwright thinks that data derived from environmental monitoring — through proper visualization and communication — can address misconceptions and fake news that often hurt people near contaminated sites.

      Wainwright is now interested in how these technologies — tested with real data at contaminated sites — can be proactively used for existing and future nuclear facilities “before contamination happens,” as she explored for Nuclear News. “I don’t think it is a good idea to simply dismiss someone’s concern as irrational. Showing credible data has been much more effective to provide assurance. Or a proper monitoring network would enable us to minimize contamination or support emergency responses when accidents happen,” she says.

      Educating communities and students

      Part of empowering communities involves improving their ability to process science-based information. “Potentially hazardous facilities always end up in rural regions; minorities’ concerns are often ignored. The problem is that these regions don’t produce so many scientists or policymakers; they don’t have a voice,” Wainwright says, “I am determined to dedicate my time to improve STEM education in rural regions and to increase the voice in these regions.”

      In a project funded by DOE, she collaborates with the team of researchers at the University of Alaska — the Alaska Center for Energy and Power and Teaching Through Technology program — aiming to improve STEM education for rural and indigenous communities. “Alaska is an important place for energy transition and environmental justice,” Wainwright says. Micro-nuclear reactors can potentially improve the life of rural communities who bear the brunt of the high cost of fuel and transportation. However, there is a distrust of nuclear technologies, stemming from past nuclear weapon testing. At the same time, Alaska has vast metal mining resources for renewable energy and batteries. And there are concerns about environmental contamination from mining and various sources. The teams’ vision is much broader, she points out. “The focus is on broader environmental monitoring technologies and relevant STEM education, addressing general water and air qualities,” Wainwright says.

      The issues also weave into the courses Wainwright teaches at MIT. “I think it is important for engineering students to be aware of environmental justice related to energy waste and mining as well as past contamination events and their recovery,” she says. “It is not OK just to send waste to, or develop mines in, rural regions, which could be a special place for some people. We need to make sure that these developments will not harm the environment and health of local communities.” Wainwright also hopes that this knowledge will ultimately encourage students to think creatively about engineering designs that minimize waste or recycle material.

      The last question of the final quiz of one of her recent courses was: Assume that you store high-level radioactive waste in your “backyard.” What technical strategies would make you and your family feel safe? “All students thought about this question seriously and many suggested excellent points, including those addressing environmental monitoring,” Wainwright says, “that made me hopeful about the future.” More

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      Working to make nuclear energy more competitive

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      Assil Halimi has loved science since he was a child, but it was a singular experience at a college internship that stoked his interest in nuclear engineering. As part of work on a conceptual design for an aircraft electric propulsion system, Halimi had to read a chart that compared the energy density of various fuel sources. He was floored to see that the value for uranium was orders of magnitude higher than the rest. “Just a fuel pellet the size of my fingertip can generate as much energy as a ton of coal or 150 gallons of oil,” Halimi points out.

      Having grown up in Algeria, in an economy dominated by oil and gas, Halimi was always aware of energy’s role in fueling growth. But here was a source that showed enormous potential. “The more I read about nuclear, the more I saw its direct relationship with climate change and how nuclear energy can potentially replace the carbonized economy,” Halimi says. “The problem we’re dealing with right now is that the source of energy is not clean. Nuclear [presented itself] as an answer, or at least as a promise that you can dig into,” he says. “I was also seeing the electrification of systems and the economy evolving.”

      A tectonic shift was brewing, and Halimi wanted in.

      Then an electrical engineering major at the Institut National des Sciences Appliquées de Lyon (INSA Lyon), Halimi added nuclear engineering as a second major. Today, the second-year doctoral student at MIT’s Department of Nuclear Science and Engineering (NSE) has expanded on his early curiosity in the field and researches methods of improving the design of small modular reactors. Under Professor Koroush Shirvan’s advisement, Halimi also studies high burnup fuel so we can extract more energy from the same amount of material.

      A foot in two worlds

      The son of a computer engineer father and a mother who works as a judge, Halimi was born in Algiers and grew up in Cherchell, a small town near the capital. His interest in science grew sharper in middle school; Halimi remembers being a member of the astronomy club. As a middle and high schooler, Halimi traveled to areas with low light pollution to observe the night skies.

      As a teenager, Halimi set his goals high, enrolling in high school in both Algeria and France. Taking classes in Arabic and French, he found a fair amount of overlap between the two curricula. The divergence in the nonscientific classes gave Halimi a better understanding of the cultural perspectives. After studying the French curriculum remotely, Halimi graduated with two diplomas. He remembers having to take two baccalaureate exams, which didn’t bother him much, but he did have to miss viewing parts of the 2014 World Cup soccer tournament.

      A multidisciplinary approach to engineering

      After high school, Halimi moved to France to study engineering at INSA Lyon. He elected for a major in electrical engineering and, ever the pragmatist, also signed up for a bachelor’s degree in math and economics. “You can build a lot of amazing things, but you have to take costs into account to make sure you’re proposing something feasible that can make it in the real world,” Halimi says, explaining his motivation to study economics.

      Wrapping up his bachelor’s in math and economics in two short years, Halimi decided to pursue a double curriculum in electrical and nuclear engineering during his final year of engineering studies. Since his school in Lyon did not offer the double curriculum, Halimi had to move to Paris to study at The French Alternative Energies and Atomic Energy Commission (CEA), part of the University of Paris-Saclay. The summer before he started, he traveled to Japan and toured the Fukushima nuclear power plant.

      Halimi first conducted research at MIT NSE as part of an internship in nuclear engineering when he was still a student in France. He remembers wanting to explore work on reactor design, when an advisor at CEA recommended interning with Shirvan.

      Pragmatism in nuclear energy adoption

      Halimi’s work at MIT NSE focuses on high burnup fuel assessment and small modular reactor (SMR) design.

      Existing nuclear plants have faced stiff competition during the last decade. Improving the fuel efficiency (high burnup) is a potential way of improving the economic competitiveness of the existing reactor fleet. One challenge is that materials degrade when you keep them longer in the reactor. Halimi evaluates fuel performance and safety features of more efficient fuel operation using advanced computer simulation tools. At the 2022 TopFuel Light Water Reactor Fuel Performance Conference, Halimi presented a paper describing strategies to achieve higher burnups. He is now working on journal paper about this work.

      Halimi’s research on SMR design is motivated by the industry’s move to smaller plants that take less time to construct. The challenge, he says, is that if you simply make the reactors smaller, you lose the advantages of economies of scale and might end up with a more expensive economic proposal. Halimi’s goal is to analyze how smaller reactors can compensate for economies of scale by improving their technical design. Other advantages stacked in favor of smaller reactors is that they can be constructed faster and in series.

      Halimi analyzes the fuel performance, core design, thermal hydraulics, and safety of these small reactors. “One efficient way that I particularly assess to improve their economics is high power density operation,” he says. In late 2021 Halimi published a paper on the relationship between cost and reactor power density in Nuclear Engineering and Design Journal. The research has been featured in other conference papers.

      When he’s not working, Halimi makes time to play soccer and hopes to get back into astronomy. “I sold all my gear when I moved from Europe so I need to buy new ones at some point,” he says.

      Halimi is convinced that nuclear power will be a serious contender in the energy landscape. “You have to propose something that will make everyone happy,” Halimi laughs when he describes work in nuclear science and engineering.

      The work ahead is daunting — “Nuclear power is safe, sustainable, and reliable; now we need to be on time and on budget [to achieve] climate goals” he says — but Halimi is ready. By addressing both the competitiveness of the existing reactors through high burnup fuels and designing the next generation of nuclear plants, he is adopting a dual-pronged approach to make nuclear energy an economical and viable alternative to carbon-based fuels. More

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      Preparing students for the new nuclear

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      As nuclear power has gained greater recognition as a zero-emission energy source, the MIT Leaders for Global Operations (LGO) program has taken notice.

      Two years ago, LGO began a collaboration with MIT’s Department of Nuclear Science and Engineering (NSE) as a way to showcase the vital contribution of both business savvy and scientific rigor that LGO’s dual-degree graduates can offer this growing field.

      “We saw that the future of fission and fusion required business acumen and management acumen,” says Professor Anne White, NSE department head. “People who are going to be leaders in our discipline, and leaders in the nuclear enterprise, are going to need all of the technical pieces of the puzzle that our engineering department can provide in terms of education and training. But they’re also going to need a much broader perspective on how the technology connects with society through the lens of business.”

      The resulting response has been positive: “Companies are seeing the value of nuclear technology for their operations,” White says, and this often happens in unexpected ways.

      For example, graduate student Santiago Andrade recently completed a research project at Caterpillar Inc., a preeminent manufacturer of mining and construction equipment. Caterpillar is one of more than 20 major companies that partner with the LGO program, offering six-month internships to each student. On the surface, it seemed like an improbable pairing; what could Andrade, who was pursuing his master’s in nuclear science and engineering, do for a manufacturing company? However, Caterpillar wanted to understand the technical and commercial feasibility of using nuclear energy to power mining sites and data centers when wind and solar weren’t viable.

      “They are leaving no stone unturned in the search of financially smart solutions that can support the transition to a clean energy dependency,” Andrade says. “My project, along with many others’, is part of this effort.”

      “The research done through the LGO program with Santiago is enabling Caterpillar to understand how alternative technologies, like the nuclear microreactor, could participate in these markets in the future,” says Brian George, product manager for large electric power solutions at Caterpillar. “Our ability to connect our customers with the research will provide for a more accurate understanding of the potential opportunity, and helps provide exposure for our customers to emerging technologies.”

      With looming threats of climate change, White says, “We’re going to require more opportunities for nuclear technologies to step in and be part of those solutions. A cohort of LGO graduates will come through this program with technical expertise — a master’s degree in nuclear engineering — and an MBA. There’s going to be a tremendous talent pool out there to help companies and governments.”

      Andrade, who completed an undergraduate degree in chemical engineering and had a strong background in thermodynamics, applied to LGO unsure of which track to choose, but he knew he wanted to confront the world’s energy challenge. When MIT Admissions suggested that he join LGO’s new nuclear track, he was intrigued by how it could further his career.

      “Since the NSE department offers opportunities ranging from energy to health care and from quantum engineering to regulatory policy, the possibilities of career tracks after graduation are countless,” he says.

      He was also inspired by the fact that, as he says, “Nuclear is one of the less-popular solutions in terms of our energy transition journey. One of the things that attracted me is that it’s not one of the most popular, but it’s one of the most useful.”

      In addition to his work at Caterpillar, Andrade connected deeply with professors. He worked closely with professors Jacopo Buongiorno and John Parsons as a research assistant, helping them develop a business model to successfully support the deployment of nuclear microreactors. After graduation, he plans to work in the clean energy sector with an eye to innovations in the nuclear energy technology space.

      His LGO classmate, Lindsey Kennington, a control systems engineer, echoes his sentiments: This is a revolutionary time for nuclear technology.

      “Before MIT, I worked on a lot of nuclear waste or nuclear weapons-related projects. All of them were fission-related. I got disillusioned because of all the bureaucracy and the regulation,” Kennington says. “However, now there are a lot of new nuclear technologies coming straight out of MIT. Commonwealth Fusion Systems, a fusion startup, represents a prime example of MIT’s close relationship to new nuclear tech. Small modular reactors are another emerging technology being developed by MIT. Exposure to these cutting-edge technologies was the main sell factor for me.”

      Kennington conducted an internship with National Grid, where she used her expertise to evaluate how existing nuclear power plants could generate hydrogen. At MIT, she studied nuclear and energy policy, which offered her additional perspective that traditional engineering classes might not have provided. Because nuclear power has long been a hot-button issue, Kennington was able to gain nuanced insight about the pathways and roadblocks to its implementation.

      “I don’t think that other engineering departments emphasize that focus on policy quite as much. [Those classes] have been one of the most enriching parts of being in the nuclear department,” she says.

      Most of all, she says, it’s a pivotal time to be part of a new, blossoming program at the forefront of clean energy, especially as fusion research grows more prevalent.

      “We’re at an inflection point,” she says. “Whether or not we figure out fusion in the next five, 10, or 20 years, people are going to be working on it — and it’s a really exciting time to not only work on the science but to actually help the funding and business side grow.”

      White puts it simply.

      “This is not your parents’ nuclear,” she says. “It’s something totally different. Our discipline is evolving so rapidly that people who have technical expertise in nuclear will have a huge advantage in this next generation.” More

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      A new way to assess radiation damage in reactors

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      A new method could greatly reduce the time and expense needed for certain important safety checks in nuclear power reactors. The approach could save money and increase total power output in the short run, and it might increase plants’ safe operating lifetimes in the long run.

      One of the most effective ways to control greenhouse gas emissions, many analysts argue, is to prolong the lifetimes of existing nuclear power plants. But extending these plants beyond their originally permitted operating lifetimes requires monitoring the condition of many of their critical components to ensure that damage from heat and radiation has not led, and will not lead, to unsafe cracking or embrittlement.

      Today, testing of a reactor’s stainless steel components — which make up much of the plumbing systems that prevent heat buildup, as well as many other parts — requires removing test pieces, known as coupons, of the same kind of steel that are left adjacent to the actual components so they experience the same conditions. Or, it requires the removal of a tiny piece of the actual operating component. Both approaches are done during costly shutdowns of the reactor, prolonging these scheduled outages and costing millions of dollars per day.

      Now, researchers at MIT and elsewhere have come up with a new, inexpensive, hands-off test that can produce similar information about the condition of these reactor components, with far less time required during a shutdown. The findings are reported today in the journal Acta Materiala in a paper by MIT professor of nuclear science and engineering Michael Short; Saleem Al Dajani ’19 SM ’20, who did his master’s work at MIT on this project and is now a doctoral student at the King Abdullah University of Science and Technology (KAUST) in Saudi Arabia; and 13 others at MIT and other institutions.

      The test involves aiming laser beams at the stainless steel material, which generates surface acoustic waves (SAWs) on the surface. Another set of laser beams is then used to detect and measure the frequencies of these SAWs. Tests on material aged identically to nuclear power plants showed that the waves produced a distinctive double-peaked spectral signature when the material was degraded.

      Short and Al Dajani embarked on the process in 2018, looking for a more rapid way to detect a specific kind of degradation, called spinodal decomposition, that can take place in austenitic stainless steel, which is used for components such as the 2- to 3-foot wide pipes that carry coolant water to and from the reactor core. This process can lead to embrittlement, cracking, and potential failure in the event of an emergency.

      While spinodal decomposition is not the only type of degradation that can occur in reactor components, it is a primary concern for the lifetime and sustainability of nuclear reactors, Short says.

      “We were looking for a signal that can link material embrittlement with properties we can measure, that can be used to estimate lifetimes of structural materials,” Al Dajani says.

      They decided to try a technique Short and his students and collaborators had expanded upon, called transient grating spectroscopy, or TGS, on samples of reactor materials known to have experienced spinodal decomposition as a result of their reactor-like thermal aging history. The method uses laser beams to stimulate, and then measure, SAWs on a material. The idea was that the decomposition should slow down the rate of heat flow through the material, that slowdown would be detectable by the TGS method.

      However, it turns out there was no such slowdown. “We went in with a hypothesis about what we would see, and we were wrong,” Short says.

      That’s often the way things work out in science, he says. “You go in guns blazing, looking for a certain thing, for a great reason, and you turn out to be wrong. But if you look carefully, you find other patterns in the data that reveal what nature actually has to say.”

      Instead, what showed up in the data was that, while a material would usually produce a single frequency peak for the material’s SAWs, in the degraded samples there was a splitting into two peaks.

      “It was a very clear pattern in the data,” Short recalls. “We just didn’t expect it, but it was right there screaming at us in the measurements.”

      Cast austenitic stainless steels like those used in reactor components are what’s known as duplex steels, actually a mixture of two different crystal structures in the same material by design. But while one of the two types is quite impervious to spinodal decomposition, the other is quite vulnerable to it. When the material starts to degrade, the difference shows up in the different frequency responses of the material, which is what the team found in their data.

      That finding was a total surprise, though. “Some of my current and former students didn’t believe it was happening,” Short says. “We were unable to convince our own team this was happening, with the initial statistics we had.” So, they went back and carried out further tests, which continued to strengthen the significance of the results. They reached a point where the confidence level was 99.9 percent that spinodal decomposition was indeed coincident with the wave peak separation.

      “Our discussions with those who opposed our initial hypotheses ended up taking our work to the next level,” Al Dajani says.

      The tests they did used large lab-based lasers and optical systems, so the next step, which the researchers are hard at work on, is miniaturizing the whole system into something that can be an easily portable test kit to use to check reactor components on-site, reducing the length of shutdowns. “We’re making great strides, but we still have some way to go,” he says.

      But when they achieve that next step, he says, it could make a significant difference. “Every day that your nuclear plant goes down, for a typical gigawatt-scale reactor, you lose about $2 million a day in lost electricity,” Al Dajani says, “so shortening outages is a huge thing in the industry right now.”

      He adds that the team’s goal was to find ways to enable existing plants to operate longer: “Let them be down for less time and be as safe or safer than they are right now — not cutting corners, but using smart science to get us the same information with far less effort.” And that’s what this new technique seems to offer.

      Short hopes that this could help to enable the extension of power plant operating licenses for some additional decades without compromising safety, by enabling frequent, simple and inexpensive testing of the key components. Existing, large-scale plants “generate just shy of a billion dollars in carbon-free electricity per plant each year,” he says, whereas bringing a new plant online can take more than a decade. “To bridge that gap, keeping our current nukes online is the single biggest thing we can do to fight climate change.”

      The team included researchers at MIT, Idaho National Laboratory, Manchester University and Imperial College London in the UK, Oak Ridge National Laboratory, the Electric Power Research Institute, Northeastern University, the University of California at Berkeley, and KAUST. The work was supported by the International Design Center at MIT and the Singapore University of Technology and Design, the U.S. Nuclear Regulatory Commission, and the U.S. National Science Foundation. More

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      Ian Hutchinson: A lifetime probing plasma, on Earth and in space

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      Ordinary folks gazing at the night sky can readily spot Earth’s close neighbors and the light of distant stars. But when Ian Hutchinson scans the cosmos, he takes in a great deal more. There is, for instance, the constant rush of plasma — highly charged ionized gases — from the sun. As this plasma flows by solid bodies such as the moon, it interacts with them electromagnetically, sometimes generating a phenomenon called an electron hole — a perturbation in the gaseous solar tide that forms a solitary, long-lived wave. Hutchinson, a professor in the MIT Department of Nuclear Science and Engineering (NSE), knows they exist because he found a way to measure them.

      “When I look up at the moon with my sweetheart, my wife of 48 years, I imagine that streaming from its dark side are electron holes that my students and I predicted, and that we then discovered,” he says. “It’s quite sentimental to me.”

      Hutchinson’s studies of these wave phenomena, summed up in a paper, “Electron holes in phase space: What they are and why they matter,” recently earned the 2022 Ronald C. Davidson Award for Plasma Physics presented by the American Physical Society’s Division of Plasma Physics.

      Measuring perturbations in plasma

      Hutchinson’s exploration of electron holes was sparked by his work over many decades in fusion energy, another branch of plasma physics. He has made many contributions to the design, operation, and experimental investigation of tokamaks — a toroidal magnetic confinement device — intended to replicate and harness the fiery thermonuclear reactions in the plasma of stars for carbon-free energy on Earth. Hutchinson took a particular interest in how to measure the plasma, notably the flow at the edges of tokamaks.

      Heat generated from fusion reactions may escape magnetic confinement and build up along these edges, leading to potential temperature spikes that impact the performance of the confinement device. Hutchinson discovered how to interpret signals from small probes to measure and track plasma velocity at the tokamak’s edge.

      “My theoretical work also showed that these probes quite likely induce electron holes,” he says. But proving this contention required experiments at resolutions in time and space beyond what tokamaks allow. That’s when Hutchinson had an important insight.

      “I realized that the phenomena we were trying to investigate can actually be measured with exquisite accuracy by satellites that travel through plasma surrounding Earth and other solid bodies,” he says. Although plasmas in space are at a much larger scale than the plasmas generated in the laboratory, measurements of these gases by a satellite is analogous “to a situation where we fly a tiny micron-sized spacecraft through the wakes of probes at the edge of tokamaks,” says Hutchinson.

      Using satellite data provided by NASA, Hutchinson set about analyzing solar plasma as it whips by the moon. “We predicted instabilities and the generation of electron holes,” he recounts. “Our theory passed with flying colors: We saw lots of holes in the wake of the moon, and few elsewhere.”

      Developing tokamaks

      Hutchinson grew up in the English midlands and attended Cambridge University, where he became “intrigued by plasma physics in a course taught by an entertaining and effective teacher,” he says.

      Hutchinson headed for doctoral studies at Australian National University on fellowship. The experience afforded him his first opportunity for research on plasma confinement. “There I was at the ends of the Earth, and I was one of very few scientists worldwide with a tokamak almost to myself,” he says. “It was a device that had risen to the top of everyone’s agenda in fusion research as something we really needed to understand.”

      His dissertation, which examined instabilities in plasma, and his hands-on experience with the device, brought him to the attention of Ronald Parker SM ’63, PhD ’67, now emeritus professor of nuclear science and engineering and electrical engineering and computer science, who was building MIT’s Alcator tokamak program.

      In 1976, Hutchinson joined this group, spending three years as a research scientist. After an interval in Britain, he returned to MIT with a faculty position in NSE, and soon, a leadership role in developing the next phase of the Institute’s fusion experiment, the Alcator-C Mod tokamak.

      “This was a major development of the high-magnetic field approach to fusion,” says Hutchinson. Powerful magnets are essential for containing the superhot plasma; the MIT group developed an experiment with a magnetic field more than 150,000 times the strength of the Earth’s magnetic field. “We were in the business of determining whether tokamaks had sufficiently good confinement to function as fusion reactors,” he says.

      Hutchinson oversaw the nearly six-year construction of the device, which was funded by the U.S. Department of Energy. He then led its operation starting in 1993, creating a national facility for experiments that drew scientists and students from around the world. At the time, it was the largest research group on campus at MIT.

      In their studies, scientists employed novel heating and sustainment techniques using radio waves and microwaves. They also discovered new methods for performing diagnostics inside the tokamak. “Alcator C-Mod demonstrated excellent confinement in a more compact and cost-effective device,” says Hutchinson. “It was unique in the world.”

      Hutchinson is proud of Alcator C-Mod’s technological achievements, including its record for highest plasma pressure for a magnetic confinement device. But this large-scale project holds even greater significance for him. “Alcator C-Mod helped beat a new path in fusion research, and has become the basis for the SPARC tokamak now under construction,” he says.

      SPARC is a compact, high-magnetic field fusion energy device under development through a collaboration between MIT’s Plasma Science and Fusion Center and startup Commonwealth Fusions Systems. Its goal is to demonstrate net energy gain from fusion, prove the viability of fusion as a source of carbon-free energy, and tip the scales in the race against climate change. A number of SPARC’s leaders are students Hutchinson taught. “This is a source of considerable satisfaction,” he says. “Some of their down-to-Earth realism comes from me, and perhaps some of their aspirations have been molded by their work with me.” 

      A new phase

      After leading Alcator C-Mod for 15 years and generating hundreds of journal articles, Hutchinson served as NSE’s department head from 2003 to 2009. He wrote the standard textbook on measuring plasmas, and has more recently written “A Student’s Guide to Numerical Methods” (2015), which evolved from a course he taught to introduce graduate students to computational problem-solving in physics and engineering.

      After this, his 40th year on the MIT faculty, Hutchinson will be stepping back from teaching. “It’s important for new generations of students to be taught by people at the pinnacle of their mental and intellectual capacity, and when you reach my age, you’re aware of the fact that you’re slowing down,” he says.

      Hutchinson’s at no loss for ways to spend his time. As a devout Christian, he speaks and writes about the relationship between religion and science, trying to help skeptics on both sides find common ground. He sings in two choral groups, and is very busy grandparenting four grandsons. For a complete change of pace, Hutchinson goes fly fishing.

      But he still has plans to explore new frontiers in plasma physics. “I’m gratified to say I still do important research,” he says. “I’ve solved most of the problems in electron holes, and now I need to say something about ion holes!” More

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      MIT scientists contribute to National Ignition Facility fusion milestone

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      On Monday, Dec. 5, at around 1 a.m., a tiny sphere of deuterium-tritium fuel surrounded by a cylindrical can of gold called a hohlraum was targeted by 192 lasers at the National Ignition Facility (NIF) at Lawrence Livermore National Laboratory (LLNL) in California. Over the course of billionths of a second, the lasers fired, generating X-rays inside the gold can, and imploding the sphere of fuel.

      On that morning, for the first time ever, the lasers delivered 2.1 megajoules of energy and yielded 3.15 megajoules in return, achieving a historic fusion energy gain well above 1 — a result verified by diagnostic tools developed by the MIT Plasma Science and Fusion Center (PSFC). The use of these tools and their importance was referenced by Arthur Pak, a LLNL staff scientist who spoke at a U.S. Department of Energy press event on Dec. 13 announcing the NIF’s success.

      Johan Frenje, head of the PSFC High-Energy-Density Physics division, notes that this milestone “will have profound implications for laboratory fusion research in general.”

      Since the late 1950s, researchers worldwide have pursued fusion ignition and energy gain in a laboratory, considering it one of the grand challenges of the 21st century. Ignition can only be reached when the internal fusion heating power is high enough to overcome the physical processes that cool the fusion plasma, creating a positive thermodynamic feedback loop that very rapidly increases the plasma temperature. In the case of inertial confinement fusion, the method used at the NIF, ignition can initiate a “fuel burn propagation” into the surrounding dense and cold fuel, and when done correctly, enable fusion-energy gain.

      Frenje and his PSFC division initially designed dozens of diagnostic systems that were implemented at the NIF, including the vitally important magnetic recoil neutron spectrometer (MRS), which measures the neutron energy spectrum, the data from which fusion yield, plasma ion temperature, and spherical fuel pellet compression (“fuel areal density”) can be determined. Overseen by PSFC Research Scientist Maria Gatu Johnson since 2013, the MRS is one of two systems at the NIF relied upon to measure the absolute neutron yield from the Dec. 5 experiment because of its unique ability to accurately interpret an implosion’s neutron signals.

      “Before the announcement of this historic achievement could be made, the LLNL team wanted to wait until Maria had analyzed the MRS data to an adequate level for a fusion yield to be determined,” says Frenje.

      Response around MIT to NIF’s announcement has been enthusiastic and hopeful. “This is the kind of breakthrough that ignites the imagination,” says Vice President for Research Maria Zuber, “reminding us of the wonder of discovery and the possibilities of human ingenuity. Although we have a long, hard path ahead of us before fusion can deliver clean energy to the electrical grid, we should find much reason for optimism in today’s announcement. Innovation in science and technology holds great power and promise to address some of the world’s biggest challenges, including climate change.”

      Frenje also credits the rest of the team at the PSFC’s High-Energy-Density Physics division, the Laboratory for Laser Energetics at the University of Rochester, LLNL, and other collaborators for their support and involvement in this research, as well as the National Nuclear Security Administration of the Department of Energy, which has funded much of their work since the early 1990s. He is also proud of the number of MIT PhDs that have been generated by the High-Energy-Density Physics Division and subsequently hired by LLNL, including the experimental lead for this experiment, Alex Zylstra PhD ’15.

      “This is really a team effort,” says Frenje. “Without the scientific dialogue and the extensive know-how at the HEDP Division, the critical contributions made by the MRS system would not have happened.” More

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      in Energy

      Pursuing a practical approach to research

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      Koroush Shirvan, the John Clark Hardwick Career Development Professor in the Department of Nuclear Science and Engineering (NSE), knows that the nuclear industry has traditionally been wary of innovations until they are shown to have proven utility. As a result, he has relentlessly focused on practical applications in his research, work that has netted him the 2022 Reactor Technology Award from the American Nuclear Society. “The award has usually recognized practical contributions to the field of reactor design and has not often gone to academia,” Shirvan says.

      One of these “practical contributions” is in the field of accident-tolerant fuels, a program launched by the U.S. Nuclear Regulatory Commission in the wake of the 2011 Fukushima Daiichi incident. The goal within this program, says Shirvan, is to develop new forms of nuclear fuels that can tolerate heat. His team, with students from over 16 countries, is working on numerous possibilities that range in composition and method of production.

      Another aspect of Shirvan’s research focuses on how radiation impacts heat transfer mechanisms in the reactor. The team found fuel corrosion to be the driving force. “[The research] informs how nuclear fuels perform in the reactor, from a practical point of view,” Shirvan says.

      Optimizing nuclear reactor design

      A summer internship when Shirvan was an undergraduate at the University of Florida at Gainesville seeded his drive to focus on practical applications in his studies. A nearby nuclear utility was losing millions because of crud accumulating on fuel rods. Over time, the company was solving the problem by using more fuel, before it had extracted all the life from earlier batches.

      Placement of fuel rods in nuclear reactors is a complex problem with many factors — the life of the fuel, location of hot spots — affecting outcomes. Nuclear reactors change their configuration of fuel rods every 18-24 months to optimize close to 15-20 constraints, leading to roughly 200-800 assemblies. The mind-boggling nature of the problem means that plants have to rely on experienced engineers.

      During his internship, Shirvan optimized the program used to place fuel rods in the reactor. He found that certain rods in assemblies were more prone to the crud deposits, and reworked their configurations, optimizing for these rods’ performance instead of adding assemblies.

      In recent years, Shirvan has applied a branch of artificial intelligence — reinforcement learning — to the configuration problem and created a software program used by the largest U.S. nuclear utility. “This program gives even a layperson the ability to reconfigure the fuels and the reactor without having expert knowledge,” Shirvan says.

      From advanced math to counting jelly beans

      Shirvan’s own expertise in nuclear science and engineering developed quite organically. He grew up in Tehran, Iran, and when he was 14 the family moved to Gainesville, where Shirvan’s aunt and family live. He remembers an awkward couple of years at the new high school where he was grouped in with newly arrived international students, and placed in entry-level classes. “I went from doing advanced mathematics in Iran to counting jelly beans,” he laughs.

      Shirvan applied to the University of Florida for his undergraduate studies since it made economic sense; the school gave full scholarships to Floridian students who received a certain minimum SAT score. Shirvan qualified. His uncle, who was a professor in the nuclear engineering department then, encouraged Shirvan to take classes in the department. Under his uncle’s mentorship, the courses Shirvan took, and his internship, cemented his love of the interdisciplinary approach that the field demanded.

      Having always known that he wanted to teach — he remembers finishing his math tests early in Tehran so he could earn the reward of being class monitor — Shirvan knew graduate school was next. His uncle encouraged him to apply to MIT and to the University of Michigan, home to reputable programs in the field. Shirvan chose MIT because “only at MIT was there a program on nuclear design. There were faculty dedicated to designing new reactors, looking at multiple disciplines, and putting all of that together.” He went on to pursue his master’s and doctoral studies at NSE under the supervision of Professor Mujid Kazimi, focusing on compact pressurized and boiling water reactor designs. When Kazimi passed away suddenly in 2015, Shirvan was a research scientist, and switched to tenure track to guide the professor’s team.

      Another project that Shirvan took in 2015: leadership of MIT’s course on nuclear reactor technology for utility executives. Offered only by the Institute, the program is an introduction to nuclear engineering and safety for personnel who might not have much background in the area. “It’s a great course because you get to see what the real problems are in the energy sector … like grid stability,” Shirvan says.

      A multipronged approach to savings

      Another very real problem nuclear utilities face is cost. Contrary to what one hears on the news, one of the biggest stumbling blocks to building new nuclear facilities in the United States is cost, which today can be up to three times that of renewables, Shirvan says. While many approaches such as advanced manufacturing have been tried, Shirvan believes that the solution to decrease expenditures lies in designing more compact reactors.

      His team has developed an open-source advanced nuclear cost tool and has focused on two different designs: a small water reactor using compact steam technology and a horizontal gas reactor. Compactness also means making fuels more efficient, as Shirvan’s work does, and in improving the heat exchange device. It’s all back to the basics and bringing “commercial viable arguments in with your research,” Shirvan explains.

      Shirvan is excited about the future of the U.S. nuclear industry, and that the 2022 Inflation Reduction Act grants the same subsidies to nuclear as it does for renewables. In this new level playing field, advanced nuclear still has a long way to go in terms of affordability, he admits. “It’s time to push forward with cost-effective design,” Shirvan says, “I look forward to supporting this by continuing to guide these efforts with research from my team.” More

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      in Energy

      Finding community in high-energy-density physics

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      Skylar Dannhoff knew one thing: She did not want to be working alone.

      As an undergraduate at Case Western Reserve University, she had committed to a senior project that often felt like solitary lab work, a feeling heightened by the pandemic. Though it was an enriching experience, she was determined to find a graduate school environment that would foster community, one “with lots of people, lots of collaboration; where it’s impossible to work until 3 a.m. without anyone noticing.” A unique group at the Plasma Science and Fusion Center (PSFC) looked promising: the High-Energy-Density Physics (HEDP) division, a lead partner in the National Nuclear Security Administration’s Center for Excellence at MIT.

      “It was a shot in the dark, just more of a whim than anything,” she says of her request to join HEDP on her application to MIT’s Department of Physics. “And then, somehow, they reached out to me. I told them I’m willing to learn about plasma. I didn’t know anything about it.”

      What she did know was that the HEDP group collaborates with other U.S. laboratories on an approach to creating fusion energy known as inertial confinement fusion (ICF). One version of the technique, known as direct-drive ICF, aims multiple laser beams symmetrically onto a spherical capsule filled with nuclear fuel. The other, indirect-drive ICF, instead aims multiple lasers beams into a gold cylindrical cavity called a hohlraum, within which the spherical fuel capsule is positioned. The laser beams are configured to hit the inner hohlraum wall, generating a “bath” of X-rays, which in turn compress the fuel capsule.

      Imploding the capsule generates intense fusion energy within a tiny fraction of a second (an order of tens of picoseconds). In August 2021, the National Ignition Facility (NIF) at Lawrence Livermore National Laboratory (LLNL) used this method to produce an historic fusion yield of 1.3 megajoules, putting researchers within reach of “ignition,” the point where the self-sustained fusion burn spreads into the surrounding fuel, leading to a high fusion-energy gain.  

      Joining the group just a month before this long-sought success, Dannhoff was impressed more with the response of her new teammates and the ICF community than with the scientific milestone. “I got a better appreciation for people who had spent their entire careers working on this project, just chugging along doing their best, ignoring the naysayers. I was excited for the people.”

      Dannhoff is now working toward extending the success of NIF and other ICF experiments, like the OMEGA laser at the University of Rochester’s Laboratory for Laser Energetics. Under the supervision of Senior Research Scientist Chikang Li, she is studying what happens to the flow of plasma within the hohlraum cavity during indirect ICF experiments, particularly for hohlraums with inner-wall aerogel foam linings. Experiments, over the last decade, have shown just how excruciatingly precise the symmetry in ICF targets must be. The more symmetric the X-ray drive, the more effective the implosion, and it is possible that these foam linings will improve the X-ray symmetry and drive efficiency.

      Dannhoff is specifically interested in studying the behavior of silicon and tantalum-based foam liners. She is as concerned with the challenges of the people at General Atomics (GA) and LLNL who are creating these targets as she is with the scientific outcome.

      “I just had a meeting with GA yesterday,” she notes. “And it’s a really tricky process. It’s kind of pushing the boundaries of what is doable at the moment. I got a much better sense of how demanding this project is for them, how much we’re asking of them.”

      What excites Dannhoff is the teamwork she observes, both at MIT and between ICF institutions around the United States. With roughly 10 graduate students and postdocs down the hall, each with an assigned lead role in lab management, she knows she can consult an expert on almost any question. And collaborators across the country are just an email away. “Any information that people can give you, they will give you, and usually very freely,” she notes. “Everyone just wants to see this work.”

      That Dannhoff is a natural team player is also evidenced in her hobbies. A hockey goalie, she prioritizes playing with MIT’s intramural teams, “because goalies are a little hard to come by. I just play with whoever needs a goalie on that night, and it’s a lot of fun.”

      She is also a member of the radio community, a fellowship she first embraced at Case Western — a moment she describes as a turning point in her life. “I literally don’t know who I would be today if I hadn’t figured out radio is something I’m interested in,” she admits. The MIT Radio Society provided the perfect landing pad for her arrival in Cambridge, full of the kinds of supportive, interesting, knowledgeable students she had befriended as an undergraduate. She credits radio with helping her realize that she could make her greatest contributions to science by focusing on engineering.

      Danhoff gets philosophical as she marvels at the invisible waves that surround us.

      “Not just radio waves: every wave,” she asserts. “The voice is the everywhere. Music, signal, space phenomena: it’s always around. And all we have to do is make the right little device and have the right circuit elements put in the right order to unmix and mix the signals and amplify them. And bada-bing, bada-boom, we’re talking with the universe.”

      “Maybe that epitomizes physics to me,” she adds. “We’re trying to listen to the universe, and it’s talking to us. We just have to come up with the right tools and hear what it’s trying to say.” More