Remembering Charlie McMillan

Former Los Alamos National Laboratory Director Charlie McMillan was on vacation in Belize when he received a phone call from current Laboratory Director Thom Mason. Mason was calling to see if McMillan might be interested in leading a Department of Energy–wide effort to streamline and execute various projects involving artificial intelligence (AI).

“I called him on a Saturday, and he explained that he was snorkeling,” Mason remembers. “And I thought, this is not going to go well. Here I am trying to convince him that he ought to take on this challenge, and he is enjoying the life of a retiree, looking at beautiful tropical fish on reconstructed coral reefs.”

But, as Janet McMillan notes, her husband was actually not very good at retirement. “I used to tease him that he was failing retirement because he joined the boards of two startup companies, and he continued to work with colleagues at the Lab,” she says. So, she was not surprised when, after giving it some thought, McMillan accepted Mason’s offer.

For the next year, McMillan worked part time on the new AI initiative. “But I would say part-time of Charlie is worth more than time-and-a-half of most people,” Mason says. “He really jumped into it and made a huge, huge difference.”

That work came to an abrupt and tragic end when McMillan died in a traffic collision on September 6, 2024.

In the months after the accident, as the impact of McMillan’s career and character continue to be shared and understood, “there’s much to recognize and much to celebrate,” Mason says. “Charlie’s contributions will be with us for a long, long time.”

Early days

McMillan was born on October 25, 1954, in Fayetteville, Arkansas, where his father, a physicist, was taking graduate classes at the University of Arkansas. When his father got a job at Fort Belvoir, a U.S. Army garrison in northern Virginia, the family moved north, settling in Virginia and then in Maryland, where his mother worked as an elementary school math teacher.

When he was four years old, McMillan asked his mother if she could teach him to read words, but she instead taught him to read music, sparking what would become a lifelong passion. By 14, McMillan had learned not only to play piano but also to tune pianos. According to his younger sister, “he often took his tuning forks and tuning kit on family vacations in case of a piano-tuning emergency.” 

At Columbia Union College (now Washington Adventist University), McMillan became particularly proficient at playing the organ, so much so that his organ teacher encouraged him to add a music major to his curriculum. “He took lots of organ and lots of music classes and of course shined in them because he invested in anything that he was interested in,” Janet says. “When he became passionate about something, he would learn everything possible about it.”

In the end, McMillan decided to major in only two areas: math and physics, the latter of which he studied as a doctoral student at the Massachusetts Institute of Technology (MIT)—but not before marrying Janet and teaching English and science in Zambia for a year.

Janet says that whether her husband was attending school or teaching school, “Charlie’s motto was always: do your best in whatever things you do. If you’re going to do it, don't bother doing it halfway. That outlook is what drove him to success in everything he did.”

A career in service begins

At the recommendation of a former MIT officemate, McMillan applied to be an experimental physicist at California’s Lawrence Livermore National Laboratory, one of three national laboratories responsible for maintaining the United States’ nuclear weapons (Los Alamos and Sandia are the others). When the job offer came through, the McMillans flew cross-country, and McMillan began work in the Advanced Experiments Group in January 1983.

Physicist Mike Anastasio recalls getting to know McMillan at Livermore. “I’d been there a few years when Charlie showed up. We got together to explore ways to understand and measure the ejecta from shocked metals. And Charlie’s creativity showed through at the very beginning. He immediately came up with several different experimental techniques, and his excitement and aptitude for learning were manifest from the very beginning of our relationship.”

McMillan’s “first love was being an experimentalist—doing things, seeing things, and watching things happen that he designed,” according to Janet. Moving beyond that environment into management was not an obvious or easy choice.

Yet, Anastasio, who was a few years senior to McMillan, saw McMillan’s promise as a leader from the beginning. “The first time Mike asked Charlie to apply for a position outside of the experiments group, Charlie thought, why does he want me to apply for that? It’s not my forte. It’s not where I’m really good,” Janet remembers. “But Mike said to him, I want you to practice applying for an upper-level job because I think you’re going to grow into that. Mike saw the potential.”

And so McMillan was promoted to a leadership role in Livermore’s B Division in 1992, a pivotal time for the country’s nuclear weapons laboratories, which had for decades conducted full-scale detonation tests on nuclear devices to both understand them and certify the safety and reliability of weapons in the U.S. nuclear stockpile. In September of that year, the United States not only placed a moratorium on nuclear testing but also decided not to introduce any new weapons into the stockpile. Ensuring the existing, aging weapons would work now required a different type of scientific understanding. Legacy testing data was combined with newer data from nonnuclear and subcritical experiments and then modeled and simulated using supercomputers. Nuclear testing had gone digital, so to speak, and key to the success of this new way forward were computer codes, which essentially told the computers what to do.

As the head of B Division’s weapons code development group, McMillan helped produce the first 3D parallel simulations of a primary (fission) explosion, which allowed weapons designers to “see” the early phases of a weapon detonating—without actually detonating it.

“He really pushed our code teams to be ambitious in the goals that they set,” says Kim Budil, who joined B Division in 1999 and is now the director of Livermore. “We were writing all new high-performance simulation codes, and he really brought a physicist’s mindset to that work: How can we advance the state of the art? How can we advance our knowledge and capabilities? How can we build better models? How can we build more modern tools for our weapons design community to use?”

Budil notes that some weapons designers are slow to adapt to change. “So, in some cases, it takes a special person to bring that community along to adopt a new approach. I think Charlie was identified as someone who was willing to take on whatever the new emerging challenge was in the division, whether it was something he’d done before or not. He learned a great deal about whatever it was he was taking on so that he could be very credible in that role, and I think people trusted that. He was not just managing a project or trying to promote a new way of doing things for no reason; he had good scientific motivations, and he spent time working with people.”

McMillan’s can-do attitude and willingness to tackle big challenges was perhaps why, in 1999, he was hired to lead the team that, at the direction of the Department of Energy, transferred responsibility for the W80, a thermonuclear warhead designed for cruise missiles, from Los Alamos to Livermore. The transfer was significant because of the longtime rivalry between the laboratories and also because Livermore, in close partnership with Sandia National Laboratories, would begin a life extension program for the W80.

But McMillan, with his thoughtful and collaborative approach to tough scientific and people challenges, was just the man for the job. “This is a collaborative effort that will require the labs to work closely together and will tap the scientific capabilities and unique research facilities at all three laboratories,” McMillan is quoted in a 2001 Livermore news release. In a nod to Los Alamos, he added: “We’re fortunate that some of the scientists who originally designed and developed the W80 are still around to serve as a resource. They’re an invaluable asset to this effort.”

By 2001, McMillan had been promoted to B Division leader, responsible for all aspects of primary design for Livermore weapons systems in the stockpile, at that time the B83 gravity bomb and the W80 and W87 warheads.

The move to Los Alamos

In recounting his relationship with McMillan, Anastasio, who became the director of Livermore in 2002, described “the fateful brown bag lunch in the park at Livermore” in early 2005. Anastasio recalls sitting at a picnic table and probing McMillan’s interest in joining a bid team to take over management at Los Alamos. As the potential new director of Los Alamos, Anastasio wanted to see if McMillan had interest in being an associate director, in charge of Weapons Physics. “To the surprise of many,” Anastasio says, “we actually won the government’s contract competition, which was a major change in both of our lives.”

Janet, however, was not surprised. “When I heard he was on the team, I said, Charlie, your team is going to win. He said, nobody thinks we’re going to win, but this is a fun exercise. I said, oh no, you’re going to win. This is a stellar team. I knew the guys, they were A-plus guys. I had no doubt they were going to win.”

Budil imagines that “it must have been an extraordinary experience to come from Livermore to Los Alamos in a leadership position. Charlie embraced Los Alamos and learned to be a part of this culture while still respecting and appreciating and celebrating the things that he’d done in the time he’d spent at Livermore,” she says. “The two labs are very different. The joke always went that during the Cold War, the Soviet Union was the adversary, and Livermore was the enemy for Los Alamos, so it’s hard to overstate how strange that transition must have felt. But he became such a beloved member of this community, I think because of that genuine, earnest commitment to the work, to the people, to being part of the community here. He really gave himself over to New Mexico.”

Physicist Charlie Nakhleh, who is currently the head of Weapons Physics at Los Alamos, notes that Los Alamos employees were not only getting new managers with Anastasio and McMillan’s bid team, but also a new management company. Instead of being run solely by the University of California (UC), the Lab was now operated by Los Alamos National Security, a private limited liability company formed by UC together with three other entities. “Many of us who had only known the University of California and who were proud of being UC employees were less than excited about the transition to an unknown ‘corporate’ ownership,” Nakhleh says. But McMillan’s steady hand helped alleviate any concerns. “I found myself working with Charlie—for Charlie—and was struck anew by his personal and leadership skills in this new role,” Nakhleh says. “He had a remarkable ability to be both firm in direction and kind in manner all at the same time.” 

As the head of Weapons Physics, McMillan’s accomplishments included leading integrated experiments and advancing computer modeling and simulations to evaluate the health and extend the lifetimes of America’s nuclear weapons. Essential to this work were the $400-million Dual-Axis Radiographic Hydrodynamic Test facility and the world’s first petascale computer, Roadrunner—both acquired under McMillan’s watch.

From 2007 to 2011, Los Alamos made plutonium pits—the cores of nuclear weapons—to replace pits in some W88 warheads. This work took place in the Lab’s Plutonium Facility, and Kane Fisher, who at that time was the deputy in charge of pit engineering, recalls that he started giving McMillan tours of PF-4 right away. “Charlie wanted to visit and he wanted to learn and he wanted to see—he was extremely present,” says Fisher, who estimates that over the next 18 years, he toured McMillan around PF-4 at least 30 times.

In 2009, McMillan was promoted to the Lab’s principal associate director for the Weapons Program—the person in charge of everything weapons-related at Los Alamos, not just physics but also engineering and production. The work occurred primarily in New Mexico but often took him farther afield. Subcritical experiments, which use nuclear material but do not result in a nuclear reaction, were executed at an underground laboratory at the Nevada National Security Sites. The innovative subcritical plutonium experiments during this time “helped to usher in an experimental ‘golden age,’” McMillan wrote on his LinkedIn profile.

Despite moving up the org chart, Fisher notes that McMillan was always grounded, personable, and interested. “He wasn’t a person who cared about status,” Fisher says. “If I had something to say, he would listen—even back when I was a little peon.”

Becoming director

In January 2011, Anastasio announced his retirement as Los Alamos director. Although McMillan was an obvious candidate to succeed Anastasio, “Charlie had to apply just like everyone else,” Janet remembers. She also notes that “Charlie didn’t have this big plan laid out of becoming the director of the Lab one day. He never thought that. His move into higher-level positions came as a result of his dedication to always doing a good job at whatever he was doing.”

Fisher says McMillan was the rare combination of a talented physicist and a talented leader. “He could see problems faster and easier than other people,” Fisher explains. “And he had the power to solve them—and not just technical problems. He had the whole enchilada.”

The board members of Los Alamos National Security must have agreed because they hired McMillan to be the Los Alamos director and CEO, effective June 1, 2011. During an all-employee meeting on his first day, McMillan summarized his management style with a quote from Lives of a Cell, an essay by Lewis Thomas: “What [research] needs is for the air to be made right. If you want a bee to make honey, you do not issue protocols on solar navigation or carbohydrate chemistry, you put him together with other bees . . . and you do what you can to arrange the general environment around the hive. If the air is right, the science will come in its own season, like pure honey.”

Among McMillan’s priorities as director was helping people do their best work. “It brought him great satisfaction to be able to say, I helped create the environment where these guys do amazing things,” Janet says. “His joy was to go out to the different areas and talk to people. He was very engaged. He would ask intelligent questions, listen to their responses, and ask more questions.”

In addition to technical questions, McMillan asked personal questions. “One of his rules was family first,” Fisher says. “So he would ask me how my boys are doing. He was caring, he was compassionate. He was smart as hell. His recollection was off the charts. And he was open. He was just a remarkable human being.”

Liana Lovato, who served as McMillan’s executive assistant for more than a decade, agrees. “He took his time to know each of us, really know us and our families. He celebrated with us during weddings, births, graduations, and he supported us through hard times,” she said at McMillan’s memorial service. “Charlie and Janet welcomed us into their home, hosting dinners and holiday parties and student gatherings. They shared their lives with us and we felt like part of the family.”

According to Fred deSousa, who supported communications in the director’s office, key to McMillan’s personable nature was that “he understood that it’s not only about being right from a factual or logical standpoint. He understood that things like credibility and trust and reassurance are really difficult to measure empirically. Without those things, it doesn't matter if you’re right. If you disregard the emotional side of certain interactions, your message will be lost.”

Although qualities like kindness and compassion came naturally to McMillan, others he had to work on. “He was, especially as a youth, a very shy person,” Janet says. To improve as a public speaker, McMillan hired a speech coach who snapped his fingers every time McMillan said ah, or like, or uh. “That coaches you very quickly,” says Fisher, who was later snapped at by McMillan during a mentoring session.

McMillan also leveraged decades of music recitals and theater performances to feel more comfortable in front of large audiences. (“When you dance on stage in tights, it just takes away different inhibitions,” says Janet, noting that for years both she and her husband performed in the California Revels Christmas productions.) McMillan often used a music stand to hold his notes instead of a traditional podium. “He was a musician, and his approach to life was that he was far more comfortable behind a music stand than a podium,” says Anne Menefee, formerly of the Lab’s Protocol office.

Often, from behind that music stand, McMillan would begin a talk by stating three things he wanted to speak about. “For most speeches or written pieces, three topics is the magic number,” deSousa explains. “Less than that and you’re not specific enough, more than that and you’re too far in the weeds, and people are going to lose you. So he literally would say to his audiences, from members of Congress to regulators to high school students, I’m going to talk about three things. And then he’d list them and proceed in that order.”

Lovato, whose work often involved helping her boss prep for those talks, says that “Charlie’s leadership guided this Lab through good times and hard times. And he did it all with grace, dignity, and unshakable integrity. He was admired by so many, not just for his intelligence, but for the way he made every challenge seem surmountable with his steady hand.”

Jill Hruby, until recently the head of the National Nuclear Security Administration, was the director of Sandia when McMillan was the director of Los Alamos. “Being a lab director is a hard job,” she says. “Nobody would do the job of a lab director if they didn’t believe deeply in the mission. I know Charlie did.” Hruby recalls McMillan saying to her once that he could have a thought standing in his closet in the morning and that by the time he got to work, everyone was talking about it. “It does feel like that,” Hruby says. “It feels like your thoughts are being sought, your ideas are being scrutinized at all times, but Charlie, he knew that was part of the job, and he handled it remarkably well.”

From integrating with local, state, and federal officials during the 2011 Las Conchas wildfire that threatened the Laboratory just 26 days after he became director to securing $3 million for local nonprofits in his last few months on the job, McMillan was always on the go. “Charlie was passionate about expanding Los Alamos’ capabilities beyond Weapons,” explains Los Alamos Deputy Director for Weapons Bob Webster. “While he recognized that Weapons was our foundation, he knew that we could and should excel in other technical fields as well. His leadership led to key investments and advancements that have strengthened the Lab’s legacy of innovation and world-class science.” McMillan was a major proponent of cutting-edge research in areas such as advanced manufacturing, vaccine development, Earth-system modeling, and Mars exploration.

Only seven years after acquiring Roadrunner, McMillan was instrumental in acquiring the Trinity supercomputer—the sixth-fastest supercomputer in the world at the time of its activation in 2015. Trinity played a major role in ensuring the safety and reliability of the nation’s nuclear weapons.

As part of ensuring the soundness of the nuclear stockpile, McMillan also wrote and signed eight annual assessment letters, which inform the secretary of energy, the secretary of defense, and the chair of the Nuclear Weapons Council of the Lab’s confidence that the stockpile remains safe, secure, and effective now and into the future because of the Lab’s dedicated sustainment and modernization efforts.

The annual assessment letters are also platforms for Lab directors to raise concerns, and in the 2016 letter, McMillan voiced his opinion that the U.S. government was not producing enough tritium—a radioactive isotope of hydrogen that is a key ingredient in nuclear weapons—at its Tennessee Valley Authority (TVA) Watts Bar Nuclear Plant. “Under the current set of stockpile planning assumptions, one reactor is not adequate to provide the tritium necessary to fuel the future stockpile,” McMillan wrote. 

The words had their intended effect, and “in large part due to Charlie, two reactors are now operational at TVA for tritium production to meet the stockpile demand,” explains Los Alamos engineer Brad Meyer, who worked closely with McMillan on the tritium issue.

Each annual assessment letter ends with “final thoughts” that summarize the year’s challenges in maintaining the four Los Alamos weapons systems—the B61 gravity bomb and the W76, W78, and W88 warheads.

In his 2017 letter—his final letter—McMillan notes that despite a suite of challenges ranging from aging weapons components to inadequate infrastructure to production hiccups, the Laboratory was effective in executing its mission. “This year marks the 22nd anniversary of the Stockpile Stewardship Program,” he wrote. “By most measures, it has been impressively successful. As intended by its creators, the development and application of powerful, modern assessment tools provide the technical basis for the moratorium on nuclear testing and have led to a deeper understanding of the science associated with nuclear weapons.”

He concluded the letter by asking for collaboration—and funding:

“A proper balance among fundamental nuclear weapons science, robust nuclear weapons facilities, and stockpile modernization is important, but strategy must drive budget. Nuclear security enterprise stakeholders must work together to develop and execute a long-term strategic plan with a rational and sustainable budgetary structure for the nuclear deterrent.”

Retirement

When McMillan was applying for the Los Alamos directorship, Anastasio told his longtime friend and colleague, “you may think you know what this job is about, but it is bigger than you imagine.”

“And that was true,” Janet says. “Charlie got a lot more gray hairs those six years.” He announced his retirement in September 2017, telling employees that “it has truly been an honor and a privilege to serve as your director these past six years. Every day, I have been in awe of the people of this great Laboratory and what we have been able to contribute to this nation’s security.” His last day on the job was December 31.

But retirement for McMillan didn’t involve games of horseshoes or relaxing in front of the television (“He didn’t watch TV sitcoms or follow popular culture at all, really,” explains deSousa, who notes that McMillan once sat beside Ashton Kutcher at a dinner party and didn’t know who the actor was). Instead, McMillan remained active in national security work, including coordinating efforts in artificial intelligence and facilitating discussions about the importance of artificial intelligence oversight and its potential geopolitical implications.

But perhaps McMillan’s most meaningful work in retirement was mentoring—everyone from students to upper-level managers. When the Laboratory launched an Executive Leadership Development Program in 2023, McMillan mentored five senior employees.

“He was delighted to serve as a mentor,” Mason says. “And I know that the people he worked with really valued his input and his thoughtfulness. He made a big contribution to cultivating the next set of leaders for the Lab, and that’s something that will pay dividends for a long time to come.”

Fisher, who was among those mentored by McMillan, agrees. “Charlie was our guy; he spent 2 to 4 hours a week with us for a year,” Fisher says. “He was so invested in us, and he said one of his crowning achievements was passing on his leadership knowledge to the next generation.”

Fisher was also fortunate to interact with McMillan during the 2024 Oppenheimer Science and Energy Leadership Program, an annual program in which fellows from the 17 Department of Energy laboratories come together to explore the broader scientific, policy, and energy ecosystem within which the labs operate.

Three months after McMillan’s death, Fisher was the final speaker at an event in Washington, D.C.—the last gathering of the 2024 Oppenheimer fellows. Fisher ended his remarks with a dedication to McMillan, whom he described as his mentor, hero, and a champion of the program. “The dedication included a rule that Charlie taught us,” Fisher explains. “That if you care for and love someone, anyone, including coworkers, you have to tell them. So I told the Oppenheimer fellows that I cared for and loved them. Not many dry eyes after that.”

The rule Fisher shared was one of three that McMillan lived by. In fact, they were printed on the back of the program for his memorial service, which was held October 10 at Ashley Pond in Los Alamos. They are

• Always do your best. Most things are difficult before they get easier.
• Always remember to work as a team. We can accomplish more and better together than alone.
• Tell those whom you love that you love them every day. Never assume that they know, and don’t take those opportunities for granted.

“Internalize these rules and don’t forget them,” Janet says. “They make your life good.” ★

Read more: Past and present Los Alamos colleagues pay their respects to Charlie McMillan.