What about Yugoslavia’s Nuclear Explosive Material?

by David Albright, President

April 21, 1999

ISIS Policy Paper

Note: The following article was written to promote IAEA inspections in Yugoslavia during the NATO bombing campaign. That effort succeeded and the IAEA did an inspection at Vinca on 3-4 June 1999. For further information on the effort to get inspections see the New York Times (19 April 1999 and 5 May 1999) and the Reuters (4 June 1999).

We will continue to follow and encourage monthly inspections of the Vinca site.


Should we worry about 60 kilograms of 80 percent highly enriched uranium at the Vinca Institute of Nuclear Science outside Belgrade being turned into nuclear weapons by a desperate Yugoslav government? What if Yugoslavia becomes unstable or physical protection becomes weakened, leaving the highly enriched uranium vulnerable to theft by a criminal group or a country such as Iraq, which has had a long and often secret relationship with Yugoslavia? What if President Slobodan Milosevic or another senior official decides to trade the material for military or political assistance? There is enough material to make two nuclear weapons of the implosion-type design, or one of the simpler-to-make gun-type design.

Worries are greater because the International Atomic Energy Agency (IAEA) has not inspected the highly enriched uranium since late January. It was scheduled to conduct monthly inspections of the fuel, but did not obtain visas to go to Yugoslavia in February or March because the Yugoslavian government said that it could not guarantee the safety of the inspectors. With war breaking out, the United Nations issued an advisory on March 23, 1999 to its employees not to travel on official business to Yugoslavia without special permission (unless they are humanitarian relief workers or security personnel for UN staff and even then this travel be must approved on a case-by-case basis).

In a meeting on April 7 in Vienna, senior IAEA officials decided not to ask Yugoslavia for permission to go to Vinca. However, the IAEA wrote Yugoslavia on April 9 that it is ready to send an inspection mission as soon as circumstances will allow. In the letter, the IAEA stressed that Yugoslavia was responsible to maintain adequate physical protection of its highly enriched uranium and to leave the material in place.

The IAEA was responding to a letter from the Yugoslavian ambassador in Vienna, who raised the potential danger of attacking the nuclear site. The ambassador asked the IAEA to raise the issue with NATO and the United Nations, asking in the course of the letter for help in ending the bombing. The letter did not contain any veiled threats about the fate of the highly enriched uranium.

US officials have said that the site is not a target of NATO bombs or missiles. Attacking the site would violate a U.S. policy (albeit reversed in the case of Iraq and never publicly stated) not to bomb sites inspected by the IAEA. A bombing raid would also give Yugoslavia a legitimate reason to secrete away the highly enriched uranium under the pretense of protecting it. Such an attack could also spread radioactive contamination into the surrounding area. Making matters worse, the site is no longer isolated and housing developments have been built around the site.

Nonetheless, the lack of IAEA inspections can fuel suspicions about Yugoslavia’s intentions with this nuclear explosive material or its ability to protect it adequately. In a worst- case, these suspicions could cause NATO or its members to distort or miscalculate the situation. On the other hand, IAEA inspections could help deter Yugoslavia from diverting the highly enriched uranium and encourage it to protect the material better.

Past Nuclear Efforts

Although Yugoslavia is reported to have had a nuclear weapons program several decades ago, it did not progress very far before it abandoned the program. (1) Based on an extensive survey of public Yugoslavian scientific and technical documents, Mark Gorwitz, an independent researcher, concluded that “nuclear research has declined since the 1970s at Vinca.” (2)

The Soviet Union provided 80 percent highly enriched uranium fuel for a large research reactor and for a small zero-power reactor. The highly enriched uranium and Yugoslavia’s reactors are under IAEA safeguards to ensure their peaceful use. The large reactor has been shut down for years, but the highly enriched uranium fuel remains. Some of this fuel has also been used in the zero-power reactor, which has been used for civil research.

About 50 kilograms of the material is in fresh or unirradiated fuel, and another ten kilograms is in only slightly irradiated fuel. Enrichment of the 60 kilograms of highly enriched uranium remains at 80 percent.

Additional Soviet-supplied highly enriched uranium is contained in spent fuel. This fuel was irradiated in the large civil research reactor prior to its shutdown.

Until recently, the Vinca site was transparent to a large number of IAEA inspectors and safety and physical protection experts. A couple of years ago, the site upgraded physical security over the highly enriched uranium with the help of the IAEA and the United States. Safety experts from the IAEA, Russia, and western countries have helped the site operators store irradiated fuel more safely. The most serious remaining safety problem involves about 5,000 low enriched uranium and highly enriched uranium spent fuel elements from the large reactor stored in 30 aluminum casks in a murky water pool. (3) These casks require careful treatment to prevent an accidental leak of radioactive material. As of mid-April, IAEA safety officials had been unable to reach anyone at the Vinca site for two weeks. Western experts have not been there for weeks, although a few Russian experts may still be there. Nucleonics Week reported on April 1 that the head of the Vinca site had been “suddenly sacked for political reasons in recent weeks.” The significance, if any, of his termination is unknown.


Despite the site’s increasing international isolation, most officials interviewed in the course of preparing this paper believe that Yugoslavia would not divert the highly enriched uranium and, in fact, would have a hard time producing a nuclear weapon. Why would President Slobodan Milosevic risk alienating his Russian allies, his most important friends right now? Even though Russia strongly opposes the NATO strikes against its Slavic cousin, it is unlikely to tolerate a decision by Yugoslavia to arm itself with nuclear weapons, or for that matter, to accept deteriorating physical protection arrangements over the Russian-supplied highly enriched uranium.

No evidence of any current weapons work exists. IAEA and U.S. officials have given no indication that Yugoslavia could produce a nuclear explosive quickly, i.e. within weeks or a few months, or that it has any intentions to do so. However, information that allows an independent judgement of Yugoslavia’s intentions or current technical capability is limited. If the Yugoslavian government decided to make a nuclear explosive, it may be able to do so, although probably not quickly.


A more pressing concern is that the physical security of the highly enriched uranium may become compromised. Yugoslavia’s security forces are focused elsewhere. The current situation may make the highly enriched uranium more vulnerable to theft in the coming weeks. Several countries, including Iraq, may be tempted to take advantage of the current situation. Criminal elements likewise may also be tempted.

If the position of the Milosevic government becomes more desperate, it may be tempted to use the highly enriched uranium as a bargaining chip to acquire assistance from other states. Senior officials may be tempted to sell the material themselves for personal gain, if the regime is collapsing.

Getting the IAEA Back into Yugoslavia

The IAEA needs to resume its regular inspections of Vinca’s nuclear activities, in particular to verify as soon as possible that the highly enriched uranium remains in storage at the Vinca site and is adequately protected. It should also try to satisfy itself anew that Yugoslavia does not have a nuclear weapons program. The latter determination is important, because Yugoslavia could build the infrastructure to make nuclear weapons in secret and divert the highly enriched uranium between inspections.

How to get the IAEA into Yugoslavia? Russia could play a constructive role by asking the Yugoslavian government to invite inspectors. Whatever its differences with NATO and the United States in particular, Russia is unlikely to want Yugoslavia to give any impression, inadvertent or deliberate, that it may divert this material, or that it has lost control over the highly enriched uranium. Russia might also be willing to help in the longer-term by taking Yugoslavia’s highly enriched uranium fuel back home, as it did with the Soviet- and French- supplied Iraqi highly enriched uranium fuel.

It is in Yugoslavia’s interest to invite the IAEA to inspect the fuel. Yugoslavia has not sent any signals to the IAEA or others that it would not allow inspections, only that it is unable to guarantee the safety of the inspectors.

The safety of the inspectors is paramount, however. According to a western ambassador in Geneva who is handling refugee issues for his country, UN personnel remain at serious risk in all Serb-controlled territories. As a result, the Yugoslavian government would need to provide adequate assurances to the inspectors that it would protect them. NATO would need to signal that it would not bomb the Vinca site. The IAEA would require special permission from the United Nations as long as the UN security advisory remains in effect.

Inspectors could also be asked to volunteer for this IAEA mission. The IAEA has many inspectors who have worked in risky situations in Iraq and elsewhere.

It is vital to verify that the risk of theft of the highly enriched uranium is minimized More importantly, the specter of nuclear weapons is a wild card that no one should play.

1 See for example, Andrew Koch, “Yugoslavia’s Nuclear Legacy: Should We Worry?” The Nonproliferation Review, Spring/Summer 1997, pp. 123-128.

2 Telephone interview, April 15, 1999.

3 Mark Hibbs, “Crisis, Air War, Hold Up Cleanup of Vinca Spent Fuel,” Nucleonics Week, April 1, 1999.

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