August 2013 Plutonium Mountain Inside the 17-year mission to secure a dangerous legacy of Soviet nuclear testing By Eben Harrell & David E. Hoffman Project on Managing the Atom

Belfer Center for Science and International Affairs  |  

Harvard Kennedy School

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United States, Nazarbayev agreed after the Soveit collapse to return the nuclear-armed ballistic 

missiles and all nuclear weapons in Kazakhstan to Russia. However, the last weapons did not 

leave until 1995, creating a four-year period after the Soviet collapse when Russians remained at 

some nuclear facilities in Kazakhstan, although most people at the test site had left. 

During this period, Degelen Mountain itself received an upgrade: in 1993, the United States 

began a $6 million program that by 1997 had begun closing the portals to the nuclear-testing 

tunnels, a project intended to destroy the infrastructure of nuclear testing so it could never be 

resumed at the site. In total, 181 tunnels and 13 test shafts were sealed. Many U.S. officials felt 

the danger of nuclear material from Kazakhstan falling into the wrong hands was largely fixed by 

this tunnel-closing effort, and the United States had the problem under control. 

But the tunnel sealing had not dealt with the fissile materials the Soviets had left behind—some 

of which were readily accessible if anyone got inside the tunnels, and some of which were in 

containers outside the tunnels. In the tunnel-sealing effort, U.S. officials were required to fol-

low strict limits about how far into the shafts they could explore, according to a senior official.

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Indeed, the full scope of the Soviet nuclear weapons archipelago—as well as the chemical and 

biological weapons research and development facilities—had yet to be discovered by the West. 

     

Source: U.S. Department of Defense

External and internal views of a tunnel used for nuclear testing, from 1997.

‘Project Amber’ 

When Hecker considered the potentially overlooked nuclear dangers, the test site at Semipala-

tinsk came to mind right away. Hecker concluded that, if there was unguarded fissile material, it 

would probably be there. “I knew that if I wanted to find vulnerable nuclear material I’d look at 

their test site,” Hecker later recalled, “because I mirror-imaged what we did in the U.S.” 

While still Los Alamos director, Hecker had encouraged Danny Stillman, at the time head of the 

Technical Intelligence Division at Los Alamos National Laboratory, to explore Semipalatinsk. 

Stillman had spent years studying Soviet and Chinese nuclear testing programs. (He had also 

visited Arzamas-16 in the run-up to Hecker’s visit in 1992.) In addition, Stillman was involved in 

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   Interview with Andrew C. Weber, assistant secretary of defense for nuclear, chemical and biological defense programs, June 

18, 2012, Washington. Weber said the limit was 50 meters into the tunnel.

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Plutonium Mountain: Inside the 17-year mission to secure a dangerous legacy of Soviet nuclear testing

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the U.S. hydronuclear experiments and had for years studied the mysterious activities recorded 

by satellites at the Semipalatinsk test site. He visited the area in early 1995, and from that and 

other sources, the details of the Soviet hydronuclear and safety tests were confirmed. The infor-

mation suggested a “large number” of tests between 1967 and 1976 at the Semipalatinsk site. 

In November, 1995, Stillman and colleagues at Los Alamos wrote a memo to Hecker about the 

potential for another nightmare scenario – that plutonium might be buried in the tunnels of De-

gelen Mountain or elsewhere around Semipalatinsk in forms that thieves could extract. They pro-

posed a rapid effort to carry out an on-site assessment, and then develop a plan for cleaning the 

site up. Stillman titled his memo, “Project Amber: Elimination of a Potential Source of Special 

Nuclear Materials.”

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The memo recounted that Kadyrzhanov and other Kazakh scientists had told Stillman of their 

concern that plutonium remained in a remote area unprotected by fences or guard posts. A sum-

mary of the information suggested that “problem will not go away,” and added that there was 

more than 150 kilograms (330 pounds) of “special nuclear material” at the location (a term of art 

for material that can be used to fuel nuclear bombs), available for “collection without detection.” 

There was no security, nomads and herdsmen roamed at will, and there had been “discovery of 

surface gold on site.”

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Stillman wrote in the “Project Amber” memo:

If the tests were similar to tests conducted in the US (in particular at TA-49 in Los Alamos), 

we would expect the material deposited in the trenches to contain several hundred … 

kilograms of weapons grade special nuclear materials (Pu, and possibly highly-enriched 

uranium)…. Because this site is so remote from the main test site, the presence of this 

significant amount of plutonium poses a serious threat to the proliferation goals of both the 

US and Kazakhstan. Deposits of gold have recently been discovered in the immediate area 

surrounding this site, thereby increasing the potential of increased access by the general 

public.  This  site  provides  a  potential  ‘Pu  mine’  for  a  potential  proliferator  unless  it  is 

contained or cleaned up in the near future.

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Stillman and his colleagues laid out a plan for dealing with what they called “a potential and ac-

cessible source of weapons-grade nuclear material.” At the time, the main proliferation concern 

was Iran, which was thought to be hunting in the former Soviet Union for weapons-grade nuclear 

materials. Stillman estimated that containment and remediation of the materials at the site might 

cost up to $1 million.

Nothing happened immediately. But within weeks of Hecker’s retirement in late 1997, he began 

to focus on the problem outlined in the Project Amber memo. One of the side benefits of the 

1994 HEU removal from Kazakhstan was that the U.S. provided funds, through the International 

Science and Technology Center, to Kazakh nuclear institutes.

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 This, in turn, promoted closer 

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   The 1995 Degelen Mountain visit is reported in Hecker, “Dealing with Kazakhstan’s Nuclear Legacy.” 

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   Los Alamos National Laboratory memorandum, written by staff scientists for Siegfried S. Hecker, “Nuclear Proliferation 

Problem.” The paper was probably written about the time of the Project Amber memo or shortly thereafter.

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   “Project Amber: Elimination of a Potential Source of Special Nuclear Materials.” November 30, 1995. Pu is the chemical 

symbol for plutonium.

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   The International Science and Technology Center was established in 1992 by the United States, European nations, and Japan 

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