SEMEY, Kazakhstan -- The nuclear testing ground of the former Soviet Union is a vast, barren area close to the size of Lake Ontario that continues to hold some amount of security risk.
During the Cold War, hundreds of atmospheric and underground atomic weapons tests were conducted here at the Semipalatinsk Test Site in northeastern Kazakhstan, near the Russian border.
Nuclear explosions decades ago at the test site left behind considerable sensitive material that Kazakhstan, Russia and the United States have worked together for years to secure.
Last fall, the three nations completed activity on a joint project that sealed a number of tunnels in Degelen Mountain at the southern end of the experimental range, where Soviet underground nuclear weapons tests were conducted during the Cold War.
Despite the success of that project, a real likelihood exists that more nuclear material remains out there, buried beneath the soil of the Semipalatinsk steppe, unsecured and potentially vulnerable to theft, according to Sergey Lukashenko, director of the Institute of Radiation Safety and Ecology at Kazakhstan’s National Nuclear Center.
It is not clear whether authorities know exactly where the substances are located and in what amounts and conditions.
Kazakhstani government officials and issue experts say that any material still left unaccounted likely stops far short of posing the kind of nuclear terrorism risk that the plutonium, left behind in the tunnels of Degelen Mountain, did.
Still, Sergei Berezin, the deputy director general of the National Nuclear Center, which manages Semipalatinsk, last week told a group of visiting U.S. journalists “it is possible” that there might still be sensitive nuclear material at the former test site.
The Kazakhstani government in Astana is discussing with Moscow what it knows about any nuclear experiments that might have been conducted by the Soviet Union at various points around Semipalatinsk, an area of roughly 7,000 square miles.
“We’ve been holding consultations with the Russian government. It’s an ongoing negotiation,” Berezin said through a translator.
“The problem is even Russians, they don’t have very exact information about events that happened in the 1950s,” Lukashenko said.
Lukashenko is leading a team of scientists that spends stretches of time living in camps at Semipalatinsk -- also known as “the Polygon,” due to its shape -- while they conduct research into the lingering environmental impacts of radiation produced by the nuclear tests and search for areas of unusually high radioactivity that can signal the presence of unaccounted nuclear material.
Under the Soviet Union, details about individual weapons tests -- as well as atomic energy safety experiments that employed nuclear materials -- were kept secret by different ministries, according to Lukashenko.
“One department didn’t know what the other department [was] doing and only a few people who planned [the] experiment, who invented [the] experiment, knew everything,” he told U.S. reporters, whose travel to Kazakhstan was organized by the International Reporting Project.
The Soviets were understood to have spotty record-keeping, making it possible that there is yet more sensitive material to be found at the test site. There is little indication that Russia has withheld relevant information, but rather Moscow could simply lack reliable data that might be passed along to Washington or Astana.
The National Nuclear Center has begun a comprehensive survey of the Semipalatinsk Experimental Field, the area where most of the atmospheric tests took place.
Based on concerns that bad actors might seek to gather up large amounts of contaminated dirt in order to extract the plutonium contained within it and use it to build a weapon, the center is documenting levels of the chemical element in the soil over an area about 125 square miles.
“There are some places with high concentrations of plutonium,” Lukashenko said.
Still, he thinks it would be very difficult for the plutonium to be fashioned into a nuclear bomb.
“To extract a significant amount of plutonium, you have to treat tons of soil, hundreds of tons,” Lukashenko said.
One would also need access to specialized equipment and knowledge of specific chemical processes for removing the plutonium from the soil, “but it’s possible in principle” to extract the fissile material, he said.
Less technically arduous would be using the soil to construct a radiological “dirty bomb.” Kazakhstan and the United States previously worked together to pave over a different section of Semipalatinsk containing a large amount of plutonium-filled soil that was judged to pose a dirty-bomb threat.
Lukashenko said he supports carting away all of the heavily contaminated soil at the Experimental Field, which he estimated might contain enough plutonium to produce one or perhaps even two bombs.
Presently, the U.S. and Kazakhstani governments are discussing the parameters of a project that would gather up all of the highly contaminated soil and transfer it to a tunnel in Degelen Mountain that would then be sealed. Washington is understood to be willing to fund the work.
Both governments declined to discuss specifics about the consultations, including when the project might get under way, due to the sensitive nature of the work.
While Degelen Mountain is kept under surveillance by Kazakhstani troops -- as well as by sensors and drones provided by the United States -- the rest of Semipalatinsk is left fairly unprotected, according to Dmitriy Kalmykov, director of the Eco-Museum in the city of Karaganda, south of Astana.
Kalmykov’s organization estimates that a few thousand people actually live on the Polygon. Cattle are free to graze on the land and cars come and go.
Prior to the start of the Experimental Field survey, Russia indicated it did not expect the study would turn up anything unusual, Lukashenko said.
“When we start this very detailed survey of [the] Experimental Field, Russia changes their opinion. Before they said ‘No, it’s nothing interesting for us.’ Now, they change a little bit,” the radiation institute director said with a chuckle. “They said, ‘We are afraid you will find something.’”
He added: “They are just afraid that maybe somebody from their organization made something” in the early 1950s that “nobody knows [about] and if we try to dig up something, we will find [it].”
Just within the past year, Lukashenko’s team found a fragment of a special alloy that contains a very unique composition of enriched uranium, nickel and iron. The alloy was found buried about three feet deep in the Experimental Field.
“I don’t understand for what they produced this material,” Lukashenko said, adding that much nuclear research performed at Semipalatinsk six decades ago went beyond just weapons testing. “Nobody knows for what they produced this alloy.”
It’s discoveries like these that Lukashenko said led former Los Alamos National Laboratory Director Siegfried Hecker to dub him and his team “nuclear archeologists.”