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Behind the bamboo curtain

Only two U.S. nuclear weapons experts have officially seen the Chinese nuclear test site at Lop Nur. They were from Los Alamos.
July 6, 2020
A man stands to the right of a screen showing an image of a mushroom cloud.

During a 2007 exhibition at a military museum in Beijing, a security guard stands beside a screen showing a video about China’s nuclear weapons research. Between 1964 and 1996, the Chinese tested 45 nuclear devices at their test site at Lop Nur.CREDIT: China Photos/Getty Images


“More Americans have walked on the moon than have visited Lop Nur!”- John Hopkins

By Clay Dillingham

Located in hot and arid northwest China, Lop Nur was once the country’s largest inland lake. As the water dried up over the first half of the 20th century, it left behind a salt-covered, windswept, largely uninhabitable landscape. In other words, a landscape ideal for testing nuclear weapons.

China established the Lop Nur Nuclear Test Base on October 16, 1959. The first Chinese nuclear bomb was detonated there exactly five years later, on October 16, 1964, making China the world’s fifth nuclear power. Between 1964 and 1996, 45 nuclear tests (atmospheric and underground) were conducted at Lop Nur, including China’s first hydrogen bomb test in June 1967. China issued a formal moratorium on nuclear testing in 1996, but low-level testing may still be conducted there today.

An aerial view of Lop Nur.

A recent satellite image shows activity at Lop Nur. Photo: Satellite image ©2020 Maxar Technologies.

Only two U.S. nuclear weapons experts have ever officially visited Lop Nur. They were both from Los Alamos National Laboratory. The first was former Lab director Harold Agnew, who visited in 1982 when he was working as the chief executive officer of General Atomics. Then, in June 1990, weapons physicist John Hopkins traveled to China. He was joined by his wife, Adele (a plutonium chemist), Terry Hawkins (then a Laboratory intelligence analyst), Danny Stillman (then the head of Laboratory intelligence), and Bob Daniels (then head of intelligence at the Department of Energy [DOE]).

“When we went into the town near the test site, the children wanted to touch my face, feel my skin, look into my round eyes,” Hawkins remembers. “They’d never seen a person who looked like me.”

Hopkins agrees. “More Americans have walked on the moon than have visited Lop Nur!”

In this interview, Hopkins and Hawkins—both now in their 80s (and the only two of the six Americans who officially visited Lop Nur who are still living)—share their memories of what it was like peering behind the bamboo curtain and seeing the secret China protected the most—its nuclear weapons program.

Lop Nur's location within China.

American visitors have accessed the Lop Nur test site by flying into Ürümqi, China. Ürümqi (population 3.5 million) claims to be the most remote big city from any sea in the world.

China has always been secretive about its nuclear weapons programs. Why were you invited to Lop Nur?

Hopkins: In 1989, Yang Fuchai, who was the head of physics at Fudon University in Shanghai, met with Jay Keyworth at the Lab. Jay was the head of the Lab’s Physics Division. [Keyworth later became President Reagan’s scientific advisor.] The physics program at Fudon University was a major source of physicists for the Chinese nuclear weapons program. Yang was very closely associated with China’s nuclear weapons program. I met Yang when he met with Jay, and Yang invited me to visit Fudon, but the trip didn’t happen due to the Tiananmen Square massacre [when the Chinese government forcibly shut down a series of pro-democracy protests in Tiananmen Square in Beijing].

So, the next year, Yang invited me again. Sig Hecker was the Laboratory director at that point. I talked to Sig about this invitation, and I said that I thought someone from the Lab’s intelligence group ought to go. That’s how Danny Stillman made the list, and he brought Terry along. I also thought getting permission to go from the DOE would be easier if someone from DOE intelligence could go with us, and that’s how Bob Daniels joined us.

When it came to working out the trip’s itinerary, the Chinese said they were going to take us out to their nuclear test site at Lop Nur. They told me to “tell your wife she won’t want to come because it’s very primitive out there.” But she said, “Absolutely no! I want to go, and I’m going.” So, that was that. Adele was the first, maybe the last, non-Chinese woman to visit the Lop Nur test site.

The Chinese must have been aware of your positions in the national security world. What do you think they knew about you?

Hawkins: As an analyst, I had been studying the Chinese nuclear test program before I came to Los Alamos. I knew what they were doing, and I knew that the Chinese knew me.

Hopkins: Yes, the Chinese knew an enormous amount about us. Our Chinese hosts liked to tease poor Bob Daniels. When they were having dinner with us, our Chinese hosts would sometimes ask, “Oh, Mr. Daniels, we don’t understand what you do. Could you please tell us what you do?” Well, they knew he was head of DOE intelligence. They didn’t tease us this way, but they did tease Daniels. These guys knew everything about what we did—probably what dry cleaners we used.

Hawkins: Daniels thought he knew how to impress people. He presented the Chinese with little gifts: pens with Department of Energy logos. He gave five or six to some very senior Chinese people. But the next day, they came in, and they had big blue spots on their shirts. These pens that he’d given them had leaked like sieves!

Hopkins: One evening at dinner they asked my wife about a paper she had written 20 years before. I’d forgotten that she’d even written it. They were just telling us that they knew all about us. The Chinese knew everything there was to know about us from the open literature. They’d done their homework.

But why would they want you to know they’d done the homework?

Hopkins: I think they wanted to show us how good they were, how smart they were. Our trip was made during the summer, in June. It was very hot, dry, and dusty at the Chinese site. The first day, when we got back to the hotel, my wife said, “I wish I could have a glass of ice water.” Well, two minutes later, there was a knock on the door, and a guy with a tray said, “We thought you might like a glass of ice water.” Well, that immediately tipped us off that our room was bugged.

Not long after that, one afternoon after we got back to the hotel, I made use of our discovery. I said to my wife, “Gosh, I wish we could eat a dinner at a Chinese restaurant.” You see, each night for dinner, the Chinese had been feeding our little group of five at a table right in the middle of a big, empty ballroom. Well, no surprise, about an hour or so later, when we went downstairs for dinner, the host said, “We thought maybe tonight you’d like to eat at a Chinese restaurant!”

But we managed to surprise them, too. They’d asked me to give a talk about Los Alamos testing while we were out at their test site, and I did. At the end of my talk one of the Chinese guys asked a question, in English, but I didn’t understand exactly what he was getting at. So, they began animatedly chatting amongst themselves, in Chinese, how to better explain the question to this American. But then Adele, who apparently was much more perceptive than I was, said, “I think what they’re interested in is blah, blah, blah.”

Suddenly, they all stopped talking. You could hear a pin drop. They were absolutely thunderstruck. The Chinese looked at each other, then they looked at her, and one of them said, “Oh, you understand Chinese.”

Well, she didn’t. But it was clear they were convinced she’d been listening to their conversation and understood everything they said. They were shocked that she knew Chinese, and, in addition, were embarrassed they hadn’t found this incredibly important fact about her during their research.

As we were leaving, I said to her, “Don’t admit a thing.” And she didn’t. For years afterwards, we got Christmas cards from them. And, each one had a little paragraph in Chinese, just for her. It might say, “We hope your family is well…” or something similar.

Talk about your journey to the test site.

Hawkins: We flew into Ürümqi, the capital of the Xinjiang region and the city that is farthest away from any sea in the world. It’s a huge city. It’s also in the news frequently because it’s in the center of the disputes between the ethnic Han Chinese and Muslim Uyghurs. Currently, the ruling Chinese Communist Party is putting tens of thousands of the Uyghurs into huge detention and concentration camps.

Hopkins: One of the more surreal images I recall was at one of their truck stops along the major highway (really just a dirt road) to the test site. It was late at night when we pulled in, and very hot. We drove up to a simple, small, cinderblock building painted blue. I could see inside. There was a single, naked light bulb hanging down, revealing these Chinese truck drivers sitting around a color TV … and they were intently watching an episode of Little House on the Prairie that was dubbed into Chinese. I couldn’t imagine how Communist Chinese TV got a hold of it or what was going through the minds of those tough-looking truck drivers as they watched a show about life in 1870s Minnesota.

What is the Lop Nur test site like?

Hopkins: The morning we arrived, the buildings smelled like fresh paint. They’d been busy into the night painting the walls and installing new carpeting.

Hawkins: It’s an enormous area—nearly 39,000 square miles [for comparison, America’s Nevada National Security Site, formerly the Nevada Test Site, is 1,351 square miles]. They showed us a series of vertical shafts for testing nuclear devices, similar to the ones we used in Nevada.

Hopkins: I asked their designers if they needed to test nuclear weapons. And they told me, “As long as we need nuclear weapons, we need to test them.”

I counted the diagnostic cables coming out of one or two of their shafts. Their cabling was about the same number as ours. And they appeared to be high-quality fiber optic cables.

They had much harder rock than we have in Nevada. Everything for them seemed to be harder. It took them about a year to drill a shaft. It took us a month or so, maybe a few months, depending on the depth of it. They just had less equipment. If the scientists out at the Nevada Test Site wanted three bulldozers at ground zero tomorrow at 8 o’clock, three bulldozers would be there at 8 o’clock. I didn’t think the Chinese could do that.

In Nevada, we were shooting in rock that was like Styrofoam. They had granite. Also, their water table was about 12 or 15 feet down. So, they had to either pump out the hole or make waterproof canisters to contain their nuclear explosions. Mostly, they did the latter. We were always fortunate in that, in Nevada, we had a deep water table.

Hawkins: They were very concerned about their tests breaching. Before they moved into testing in granite, they had one shot in dolomite, which is a carbonaceous material. It generated so much carbon dioxide when the test went off that the detonation blew the shaft apart, spreading contamination all over. That was a major surprise for them and a big disaster.

Picutres of the Nevada Test Site and the Nevada Test Site's location within the United States.

The Lop Nur test site is the equivalent of the Nevada National Security Site (formerly the Nevada Test Site) north of Las Vegas, Nevada. Between 1951 and 1992, the U.S. tested 928 nuclear devices at Nevada using more advanced and efficient techniques and equipment (shown here) than the Chinese.

So, they were concerned about the environment?

Hawkins: No, I think it was a programmatic concern. When you blow out a shaft like that, it contaminates your whole testing area, which ruins it. The mistake is costly and puts your testing program behind.

Did you see the inside of their testing tunnels? [Testing in horizontal tunnels is often done to investigate weapons effects on items placed inside the tunnel.]

Hawkins: Yes. And although I tried to be careful, the general who was escorting me noticed I was pacing off the distance from the entrance. He smiled and said, “You don’t have to do that. I’ll tell you how many meters it is.”

Hopkins: It turns out, without coordinating, both Danny and I were also pacing it. It is interesting to finally see the things that you’ve been studying the satellite photographs of for years.

Hawkins: It’s really incredible that they actually let us go inside and told us the length. We went all the way up to the shot point, the detonation point. That was significant. The distance from there to the tunnel entrance relates to a weapon’s yield. So they were, in effect, letting us know about their yields.

It also gave us an idea of their mining prowess, and, along with other insights, it told us how they went about engineering their tunnels for nuclear tests.

Hopkins: They mined their tunnels with a sort of 1920s technology. When we drilled a tunnel in Nevada, we had a huge powered cylindrical drill bit, 15 feet across, that drilled into the tunnel.

Hawkins: Our tunnels looked like beautifully engineered, large, smooth highway road tunnels. Their tunnels looked more like railroad tunnels, as if a group of Chinese miners with picks and shovels dug them out, leaving rough unfinished walls.

Hopkins: Anything that required specialized equipment, like our drills, well, they were never as far along as we were.

Hawkins: And their process for loading vertical shafts? They always used the Livermore way of doing things, not the Los Alamos way.

Hopkins: Yes, I asked one of them, “How do you put your bombs down the hole?"

“We put them down with a drill pipe like Livermore does, not on a cable harness like you do.” Again, just to show us that they were paying attention. How they knew the details of how the different labs tested underground is anybody’s guess. But they knew it.

Besides being remote, what were advantages to Lop Nur’s location?

Hawkins: The Chinese were really frightened by the Soviets possibly taking out their facilities. So, to avoid a total wipeout from a single attack, they dispersed their facilities across very great distances. It would be like having a computer division here and a physics division miles away over there, not buildings next door to one another the way they are at Los Alamos.

Hopkins: So many of their experimental areas were spread to the four winds that it took a long time to get from one place to another. This meant they couldn’t easily meet up with their colleagues to share information or ask questions. They stationed facilities of 60 to 100 people all over the place. We also learned about some facilities that our intelligence folks were totally unaware of. For example, they took us to a small hydrodynamic testing facility, like the Lab’s, only in miniature. They wanted us to know they were pursuing everything we would pursue in weapons science, but they didn’t have the huge facilities or equipment we had.

Hawkins: They were also trying to emulate what Livermore was doing at its National Ignition Facility, researching the use of laser beams to ignite fusion. But theirs was basically half the size of Livermore’s design. I asked the head of their program, “Why are you so small in comparison to Livermore in fusion research?” He replied, “We don’t have the money. But we’ll do all the same research. And in the end, we’ll not have achieved ignition—and neither will Livermore. Yet, we will have done it for half the price.” I thought that was very insightful, powerful.

Hopkins: The Chinese can afford to do anything. But they can’t afford to do everything. So, they had to pick and choose across the engineering and scientific horizon whether they wanted to support this or that. Higher-priority things were in defense: rocket research, ballistic missiles, etc. These had much higher priority, for example, than an apartment building for workers. The accommodations for their workers were really primitive by our standards.

We saw a lot of their equipment, and it looked sort of like miniatures of ours. That is, where we would have a box of electronics the size of a big table, they would have one about one-quarter the size. Generally, their hardware looked much more primitive than ours. It looked like it was made by a college student.

Hawkins: That extreme separation of staff and facilities was one of the major impediments to the advancement of the Chinese weapons program. They told me they understood that was the problem. Sure enough, after the fall of the Soviet Union, they began to consolidate their facilities.

People walk around a large missile in a museum.

At a military museum in Beijing, visitors walk past China’s Dongfeng 1 nuclear missile. Limited numbers of the DF-1 were produced in the 1960s and have since been retired. Photo: TEH ENG KOON/AFP via Getty Images

What was your impression of the people you met at the test site?

Hawkins: During the trip we took to some of their more remote places, one of the things they said was, “We have to apologize for some of the people you meet.” They said, “They are some of the most brilliant people in China when it comes to physics and chemistry. They are the smartest people you will possibly meet in the world. But because of the way they’re dressed, their language, their awareness of international affairs, you will go away with the idea that these are peasants.” And I thought, You should see and meet some of our folks who work at Los Alamos!

Hopkins: The Chinese had lots and lots and lots of very smart people. Their theoretical design capability was larger than Livermore’s plus Los Alamos’—about 600 people. One of their guys told me, “Well, you know why we’re so much better than you are is that we don’t have the big computers; we really have to do this on the back of an envelope. We try harder.” And I was, indeed, very impressed with the quality of their scientists and engineers.

They wanted to show us what they were doing. In fact, if we didn’t ask the right questions, they’d give us hints about what we should ask. That’s a key part of deterrence: letting the other person know what you’ve got and just how dangerous you are.

Hawkins: That’s the message they wanted us to bring back.

People walk past a missile on display outside of a museum.

China's Dongfeng-2 (DF-2) nuclear missile was first tested at Lop Nur in the 1960s and was an active part of the Chinese stockpile until the 1980s. Pictured in 2007, this one is on display at a military museum in Beijing. Photo: TEH ENG KOON/AFP via Getty Images

Was the whole point of your visit to intimidate you?

Hawkins: They were looking for opportunities to collaborate with us. We were so far ahead of them, back then, that any kind of collaboration would have been much more to their benefit than to ours.

Hopkins: We weren’t interested in any collaboration with the Chinese. But they would have welcomed it. For instance, among the things they told us is that they had done some experiments on the electromagnetic pulse from nuclear explosions. And, if we were interested in that, maybe together we could pursue researching it. We weren’t, so we didn’t. But it was clear to me that collaboration was something they really wanted us to do.

What were some of the key takeaways from your trip, the points the Chinese wanted to make sure you took back home?

Hawkins: This was their visit. They were going to exploit it to the fullest to serve their purposes, not ours. One of their purposes was to convince us how well they knew nuclear weapons technology.

Hopkins: And they surprised us every once in a while; some details of their nuclear weapons program really astounded us. I think they pretty well gave us an idea of everything they were working on.

Hawkins: I think so, too.

Hopkins: It was essentially everything that we were working on. It was clear that their physics of nuclear weapons was not all that far behind us. Their engineering was not so far along. In trying to make the nuclear weapons in the smallest size with the largest yield, using the smallest amount of materials—these were very difficult things that often took the best numerically controlled machines. The Chinese, in the 1990s, couldn’t do it. Today they can.

Hawkins: When they stopped atmospheric tests in 1980, where we could see what they were doing, and went underground, it became necessary to invite us to see what they were doing underground.

Hopkins: Certainly, that was their agenda, to let us report back that we were looking at a competent adversary who was developing weapons very similar to what we were doing. That was their agenda. They accomplished it.

Hawkins: Since our visit, one of the things that they’ve done—that we haven’t done—is build modern production facilities. We know from things like satellite imagery that their plutonium pit production facilities are incredibly modern. They still want us to know, at least generally, how far along they are.

So, they were happy to let you go home?

Hawkins: When we were at the airport getting ready to leave, gathering our belongings to board the plane, we suddenly noticed our plane, a big commercial jet, had moved out onto the runway and was taxiing away. This was not good. The person at the desk said that, unfortunately, we’d have to wait, maybe three or four days, because they didn’t have another plane.

General Chen—he was a major general who ran the nuclear weapons program for China—he saw the plane leaving, too. General Chen pulled a little red card from his jacket, held it up, and barked some order in Chinese. I don’t know what he said, but the result was like a break in billiards: uniformed Chinese sprinted off in all directions. Suddenly, we saw the plane stop on the runway. It stopped so fast that it rocked. Then, a half a dozen Chinese suddenly got off the plane … and the half a dozen of us got on.

Before we climbed aboard, General Chen asked, “Is there anything else I can do for you?”

I said, “Yes sir!”


“Can you get me one of those little red cards you showed these guys?”

His eyes twinkled, and he said, “I won’t be able to do that.”

Two men and a woman stand together.

From left: John Hopkins, the director of the Lop Nur test site, and Adele Hopkins in 1990. Photo: courtesy Terry Hawkins

About John Hopkins

John Hopkins was the Laboratory’s nuclear test division leader and later the Laboratory’s associate director for the Nuclear Weapons Program. He participated in five atmospheric nuclear tests in the Pacific and some 170 tests at the Nevada Test Site. He has worked with the nuclear weapons programs of Britain, France, China, and Russia.

Three men stand together with trees and other plants in the background.

From left: Danny Stillman, the director of the Chinese Academy of Engineering Physics, and Terry Hawkins in 1990. Photo: courtesy Terry Hawkins

About Terry Hawkins

Houston T. “Terry” Hawkins is a retired Air Force colonel and a Los Alamos National Laboratory Senior Fellow currently assigned to the Associate Laboratory Directorate for Global Security. He is an internationally recognized intelligence expert on Chinese and Russian nuclear programs.