Dr. Siegfried Hecker is an American nuclear scientist and the former Director of the Los Alamos National Laboratory, a role he held from 1986 to 1997. Born in Europe during World War II, he emigrated to the United States in 1956. He earned his PhD in metallurgical engineering from Case Western Reserve University in 1968, after which he joined Los Alamos as a postdoctoral fellow.
Following the collapse of the Soviet Union, Hecker assumed a leadership role in post-Soviet lab-to-lab cooperation between the US and Russia. In the chaos of the 1990s, the security of the Soviet nuclear arsenal was dangerously uncertain. It is a notable achievement that the vast arsenal of the former USSR, with its 40,000 nuclear weapons and 1 million nuclear personnel, did not find its way into the hands of international terrorists. Hecker documents this period in the book Doomed to Cooperate, which features the perspectives of over 100 Russian and American nuclear scientists.
Between 2004 and 2010, Hecker was given access to North Korea’s nuclear weapons facilities in order to confirm the viability of the program. Among other things, he confirmed that North Korea had mastered plutonium production when Dr. Ri Hong Sop, the head of North Korea’s nuclear program, presented him with physical samples.
I sat down with Dr. Hecker to discuss the North Korean nuclear program, the challenge of proliferation, and the evolution of nuclear energy. What follows is a transcript of our conversation.
CB: When I read about your life, it's very clear that one central moment was the Second World War — this terrible disaster that befell Europe and drove you to the United States as a boy, and that also extinguished those little pockets of the German nation throughout Eastern Europe that your family comes from. Do you often reflect on this history?
SH: It certainly shaped my life. I was born during the Second World War, in 1943, while my father was stationed with the German Army in what is now Ukraine. I wound up being born in Poland. Then, of course, for the Germans and German-speaking people, everything went pretty poorly from 1944 on, so my mother had the job of getting our family to someplace where we could live and be reasonably safe. Eventually she took us from Poland through Croatia and Slovenia, back to Austria proper, where I grew up until I was 13. Both the war and the fact that my father never returned from the Russian front — and then growing up without a father, in barracks in Austria with no running water and no central heat the entire time I lived there — certainly shaped the rest of my life.
CB: What do you recall about the deprivations of the postwar era?
SH: Actually, I didn't know that people lived very differently than we were living. We were in this little town of 4,800 people in the Austrian Alps called Rottenmann — the town of the Red Man — and most of the people around us, particularly the ones who lived in the barracks, were just as poor. So I didn't realize that I was deprived. You just deal with it. I played soccer, I skied on what were essentially wooden boards, and when I look back on those 13 years, I'd say I had a pretty happy childhood.
CB: What was your journey to the United States like? Did you travel by train, by airplane, by boat?
SH: Not by airplane. This was 1956; I had just turned 13. From Rottenmann we took the train up to Bremerhaven, the port in Germany, and from there we went on an old US naval ship called the USS General Langfitt. Oh God, that was a miserable, miserable trip. But after five days or so, we survived and arrived in New York Harbor. We had uncles in the United States, and my older brother had gone ahead of us — specifically to Cleveland, Ohio. So we took the train from New York City to Cleveland, where my brother, who was five years older than I was — he was a little over 18 by then — was waiting with my uncle to pick us up.
CB: Your career spans 75 to 80 percent of the atomic age. What were your impressions of those early years of the nuclear era?
SH: In Austria, I never thought much about this. When you live the sort of life we did, what you care most about is how you make it to the next day and how you can go out and play with your friends. So for those 13 years, I never thought much about the nuclear era. Of course, I'd heard that the Americans had dropped these atomic bombs and that it ended the war. And when I came to Cleveland at the age of 13, I must say I also didn't think all that much about the postwar atomic era we were in.
The first time it really came to my mind was the Cuban Missile Crisis. I still remember being at Case Tech — the Case Institute of Technology, as it was called — when we heard about the Cuban Missile Crisis. From then on, it started to stick more in my mind. But it still wasn't central to my thinking and my concerns about the future. That didn't happen until I came to Los Alamos as a summer student, after finishing my undergraduate degree at Case Tech. At that time it was called the Los Alamos Scientific Laboratory.
I didn't come to Los Alamos because of the bomb, or because of its fame from the Manhattan Project. I came for two reasons. One was that the brochure that attracted me showed there was skiing at Los Alamos. Let me just say there was not much skiing in Cleveland, Ohio, so from age 13 until then, when I was 21, I hadn't skied much, and the thought of going to a place with mountains was very attractive. The other was simply the fame of Los Alamos as one of the best scientific laboratories in the world. I wasn't thinking bombs; I was thinking science.
CB: How does the American national laboratory system work?
SH: It was all set up because of the Manhattan Project. As the film Oppenheimer showed, General Groves wanted the scientists to wear uniforms, and Oppenheimer was more or less resigned to that. But his super scientists said, "There's no way we're going to wear Army uniforms." So Oppenheimer and his colleagues managed to get the University of California to operate the laboratory, and that really developed the blueprint for the national laboratory system. At that time there was also Argonne, outside of Chicago, and Oak Ridge — they weren't called national laboratories then — and Los Alamos. Those three contributed in a major way not only to the Manhattan Project but to the future of science and the way one runs science. The University of California continued to run Los Alamos from 1943 until 2005. A number of other laboratories were created, and the whole system now comprises 17 laboratories managed under the Department of Energy.
The key aspects were looking for the best possible science, having a university connection, which always brings in new blood and new thinking, and tackling something of critical importance to the nation. For the Manhattan Project, that was clearly the bomb, and afterward it was nuclear weapons and deterrence. But it was also nuclear energy and so many other things critical to the nation's future. That's what the national laboratory system turned out to be. It's changed some, of course, over the last 10 or 20 years, but that was the design.
CB: When did you first witness a nuclear test?
SH: I've actually never witnessed a nuclear test, if by "witnessed" you mean seeing something like an atmospheric test. The United States signed the Partial, or Limited, Test Ban Treaty in 1963 with the Soviets and the British, agreeing not to test anywhere except underground, and that was before I came to Los Alamos. So I never saw an atmospheric test. Later, as director of Los Alamos, I of course participated in some of the underground nuclear tests, which by then we conducted at the Nevada Test Site.
CB: Would you like to lay eyes on an atmospheric test? Is that something you regret?
SH: No.
CB: No? Why not?
SH: Because putting all that radioactive material up in the atmosphere just doesn't sound like a good idea. Under the circumstances of the Second World War and the Manhattan Project, and then the Cold War with the Soviet Union and the race to stay ahead, as I look back, it was all understandable. This country wanted to make sure that it stayed ahead, and nuclear testing was an absolutely essential part of that. The easiest way to test was in the atmosphere, and it's also where you learn the most, because you can make all kinds of measurements that tell you a lot about how a bomb worked. So I can understand why it was done. But it was a very good thing that at least those three big nations decided to stop atmospheric testing.
CB: During that period there was an enormous push to reduce the risk of nuclear weapons, and yet since then we've had proliferation in India, Pakistan, North Korea, and supposedly Israel. How do you explain the thinking of the cohort of scientists that were pushing test bans when you began your career? Why were they so concerned?
SH: Of course I can't speak for what the key people were thinking at the time. But as one looks back, and from what I've read, the Soviet Union and the United States were racing against each other to make sure neither fell behind, yet they realized that unless there were some restraints, this race would endanger the whole world. The Cuban Missile Crisis scared not only John F. Kennedy but also Nikita Khrushchev. From that experience, and from the realization that they now had hydrogen bombs — what we call two-stage thermonuclear weapons, a thousand times more destructive than the atomic bombs used at Hiroshima and Nagasaki — they were concerned that we might put an end to the world as we know it. So they realized there had to be restraints, and that's how the test ban treaty came about: restraints in terms of shaping the arsenals, but particularly because of fallout and global health concerns.
If you look at how the arsenals grew in the '50s, '60s, and into the '70s, they still grew quite substantially. Nevertheless, the two sides talked about, and eventually signed, treaties to limit nuclear arms. What also struck them was that it's really important not to get too many fingers on the nuclear trigger, and that's where the idea of nonproliferation came from. They said: look, we stand at this precipice against each other, and if we now get five or 10 — or, as John F. Kennedy said in the early 1960s, 20 or 25 — nuclear powers, that's simply not a situation you want in this world. That's what made them want to take part in limiting nuclear weapons around the world.
What's fascinating is that the initial drive to stop the spread of nuclear weapons actually came from non-nuclear-weapon states. Ireland, of all places, began through the United Nations to say, "Look, it's to the benefit of all of us non-nuclear countries that others not develop nuclear weapons." So, more or less, we had a consensus that more nuclear weapon states are bad news.
As you indicate, some other countries still developed nuclear weapons. But to me, one of the most important achievements of the Non-Proliferation Treaty and the movement behind it is that today we have fewer than 10 countries in the world with nuclear weapons. There are what we call the P5: the United States, Russia, China, France, and the United Kingdom. Then the two that declared themselves nuclear powers are India and Pakistan — and I've spent a lot of time working with India and Pakistan, because at one time I considered that the most dangerous nuclear region in the world. Then North Korea declared itself a nuclear power with a nuclear test. So those are the eight. And then there's the one we don't know about — at least the US government says we don't know — which is Israel. A lot of people in the world think Israel has nuclear weapons — certainly the Iranians do — but the US government, for various reasons, says we don't know whether Israel has them or not.
And over the years there have probably been some 15 to 20 other countries that at one time or another explored getting their own nuclear weapons. Believe it or not, that started with countries like Switzerland and Sweden, right after the Manhattan Project, around the 1950s. Then they decided this was really not a good idea, and of course they backed off.
CB: Do you have any particular insight into the South African nuclear program, the only former nuclear power?
SH: South Africa is a really peculiar case. The answer is no, I've never had any firsthand connection with South Africa. I think the main reason is that by the time I became really interested in the rest of the nuclear world, with the dissolution of the Soviet Union, South Africa was giving up its nuclear weapons program, including dismantling the five or six nuclear devices it had built. I've studied their program a lot, both technologically — the path they chose to nuclear weapons, which was highly enriched uranium — and politically, in terms of why in the world South Africa would want nuclear weapons. There are some very good books on that subject. But I haven't been personally involved.
CB: If you look at the actual science of the bomb, why are uranium and plutonium the only elements that have been used to construct a nuclear weapon? In your book Hinge Points, you mention there's a theoretical case for other elements sustaining a nuclear reaction.
SH: Yes, there are some others. These elements are in what we call the actinide series of the periodic table, and uranium and plutonium are the two most practical fissile materials — or at least some of their isotopes are. Others, like americium or curium, are such low probability that we haven't worried too much about them. So the focus has been on uranium — specifically the uranium-235 isotope. That's what enriching uranium means: Mother Nature gives you only 0.7 percent of the 235 isotope; the rest is primarily uranium-238. So you have to throw away most of the 238 and concentrate the 235. Uranium-235 was the Hiroshima bomb, so you can make a bomb with it. Plutonium-239 is the primary weapons isotope.
And by the way, even though you can use both, it turns out plutonium is a much, much better element for a bomb — if there's such a thing as a good bomb. Plutonium is by far the most potent, and therefore, if you want to build a bomb, the most desirable. You can certainly use uranium-235, as Hiroshima showed, but if you want to make a small, potent bomb, plutonium would be the first choice.
CB: And plutonium is not naturally occurring, right?
SH: Actually, it is. It was created in the Big Bang, through what's called the r-process, as all the other heavy elements were. But because it's radioactive, it transmutes into other elements. Plutonium-239 has a half-life of 24,100 years, meaning half of it transmutes into something else in 24,100 years. Some other isotopes, like plutonium-242 and plutonium-244, have much longer half-lives. So while plutonium was created in the r-process, it fades away over a billion or two billion years, and only minute traces of plutonium-244 might be found in nature. So one typically says plutonium is man-made — and the material we use for bombs or in reactors is man-made.
CB: With regard to the enrichment process, where does one acquire centrifuges and how do they work?
SH: The idea with the uranium you put into a centrifuge is to separate the heavy isotope from the light one. As I mentioned, 238 is the prevalent isotope, and it's heavier. We want to separate it from uranium-235, the lighter isotope, which is fissile — in other words, it works for bombs. First you turn the uranium into a gas by combining it with fluorine, which gives you uranium hexafluoride: six fluorine atoms along with one uranium atom. You put that gas in a centrifuge that spins very, very rapidly. The heavy material goes to the outside, the light material stays toward the center, and then you siphon off the light material. You have to do this over and over again to get from 0.7 percent up to, say, 80 or 90 percent.
These machines spin at enormously fast rates, and uranium hexafluoride is a pretty corrosive substance. So you need centrifuges that are fast-spinning, high-strength, and corrosion-resistant, and all of that makes centrifuge technology quite complicated. There was a man named Gernot Zippe, one of the German scientists taken to Russia after the Second World War, who helped the Russians develop these centrifuges. Eventually they let him go, and he also brought that capability to the United States. It's much more difficult for, say, the Iranians or the Pakistanis to learn it — but they did learn it. Those capabilities can be learned, and centrifuges can be built. Iran and North Korea have demonstrated that, even though people think of them as technologically unadvanced countries — which isn't true of either one. I've been to North Korea, and let me tell you, they're not technologically backward. They've demonstrated they can make centrifuges.
Just to give you another case, since you mentioned South Africa: when South Africa was doing this in the 1970s and 1980s, it decided it didn't have the technologies it needed, so it developed its enrichment capability in a different way.
CB: Let's go back earlier in your career. You trained as a metallurgist. Tell me about that part of your education and how it applied to your early nuclear career.
SH: Metallurgy is what I chose at Case Tech, where I went to school. I started in nuclear physics, but I was from a very poor immigrant family. After a couple of years in nuclear physics, I said to myself, "My God, I'm not learning anything that will get me a job, and I'm going to have to get a job after four years. My parents can't afford to send me to graduate school." One of my colleagues said, "Hey, Sig, we could go into metallurgy, because in metallurgy you can actually get a job after four years." So I switched to metallurgy and finished my four years.
Then came a really defining moment in my life. First of all, I got married after undergraduate school. And by that time I had decided I didn't just want to get a job — I wanted to go to graduate school — and that I would get a summer job at Los Alamos. So 1965 held two defining moments: I married my wife, Nina, who had once been the Polish girl next door, and I went to Los Alamos, where I got my introduction to the laboratory.
The connection to metallurgy was really fascinating. That's when I was introduced to the most complex and enigmatic metal of all: plutonium. I joined a part of Los Alamos that was essentially a materials science and technology organization, and within a couple of weeks of arriving I was doing experiments on plutonium in glove boxes. That started my affair with plutonium 61 years ago. The metallurgy has really paid off, because plutonium is still a very complex metal that we don't fully understand, and it's the key, central part of nuclear weapons — whether you can reproduce them or extend their lifetimes. Even today I still go to Los Alamos occasionally as an unpaid guest scientist to help with understanding plutonium and how we deal with the primary issue of today from the American standpoint: How do we extend the lifetime of our nuclear weapons, or how do we remanufacture them? The key to that is plutonium.
CB: What are the “known unknowns” when it comes to plutonium?
SH: The most complicated part, related to what I just said, is the aging of plutonium. Consider what we typically think of as aging. If you take a hunk of iron, it ages from the outside in — it rusts, or oxidizes. Plutonium also oxidizes, much, much faster than iron, so it has a very reactive surface. That's a major challenge. But plutonium doesn't just age from the outside in; it also changes from the inside out, because it's constantly bombarding itself. Because it's radioactive, it's transmuting into other elements like americium and neptunium, and into isotopes of uranium, and it generates helium through this radioactive process. What that aging process does to the structure of the plutonium, and how it affects plutonium's nuclear performance — we'd really like to be able to find that out, but we can't without nuclear testing. So understanding that is today's primary challenge in the nuclear weapons business.
CB: You took some time away from nuclear to work in the auto industry, right?
SH: After I finished my PhD at Case, which I went back for, in 1968, I returned to Los Alamos as a postdoc. After finishing the postdoc, in 1970 I went to the General Motors Research Laboratories just outside Detroit, Michigan, and worked in the auto industry.
I was at General Motors for three years, and I had a great time. They gave me everything I wanted. I could do fundamental work and sheet metal stamping work. But my wife didn't like Detroit. And the General Motors people — I was about 28 years old — wanted to put me on a management track. They said, "Siggy, you would make a really good manager here at General Motors." I said, "I'm a research guy. I don't want to do management. There's no way." With Los Alamos calling every six months asking, "Are you ready to come back?" I finally said in '73, "I'm ready to come back."
I slowly moved up in the leadership at Los Alamos and eventually became leader of one of the big divisions, Materials Science and Technology. Then I said, "I don't want to do this. I'm really a researcher." So I gave up the division leadership — it was a division of 715 people — and we helped found the Center for Materials Science, to get back to the science. That was in July 1985. And then, lo and behold, somehow I wound up being chosen by December 1985 as the fifth director of the Los Alamos National Laboratory — something I had never thought of doing and never wanted to do. But it happened, and that's how I became director of Los Alamos.
CB: When you became director of the Los Alamos National Laboratory, what was your primary mission?
SH: This was January 1986, and we were still in the Cold War, so the primary mission was still the US nuclear arsenal — making sure it was safe, reliable, and effective. What I also thought was really important is that we never know what another country can do technologically. From the beginning of the Manhattan Project, and from the association with all those great scientists and with the University of California, I believed it was crucial for the laboratory to guard against technological surprise. In other words, always keep looking: What else is out there? What's new in the scientific world, and could there be defense-related applications, vulnerabilities for the United States, or advantages for the United States? So in 1986, what was on my mind was taking care of the US nuclear arsenal and continuing to explore the frontiers of science in every possible way. But then the world changed.
