VIENNA, Austria — More than two tons of radioactive material stored in a rundown research facility in Serbia offer an easy target for terrorists seeking to build a “dirty bomb,” according to the United Nations’ nuclear watchdog.
Nuclear inspectors have branded the lightly guarded storage facility at a communist-era reactor, which closed 22 years ago, the world’s most dangerous disused nuclear site — because of the potency of the material and the risk of leakage.
The outdated facility is on a 48-acre site at the Institute of Nuclear Sciences in Vinca, 10 miles outside the capital, Belgrade, surrounded by a rusty barbed wire fence and secured only by a small number of armed guards.
Michael Durst, the special program manager at the Vienna-based International Atomic Energy Agency (IAEA), said the Vinca site topped the global priority list of unsecured uranium sources because it combined the threats of nuclear proliferation and environmental disaster.
“Vinca is unique in the amount of uranium stored within its facility — at least 2.5 tons — and the fact that about 30 percent of it is leaking. It would be easily accessible to an organized group,” he said.
“There are other sites in Bulgaria, Romania and Hungary, as well as elsewhere in the world, but the amount of nuclear material, the accessibility and the leakage makes Vinca the most dangerous. It requires immediate action.”
In 1992, more than 100 pounds of highly enriched uranium fuel — which can be used to make an atomic bomb — was removed from Vinca by the IAEA and the American, Russian and Serbian governments. It was transported to a disposal facility near Dimitrovgrad, in Russia.
The IAEA fears that the remaining nuclear material could be packaged with conventional explosives to spread radioactive material over a large area — a so-called dirty bomb.
Officials said much of the uranium is stored in a 75-foot-deep pool, filled with murky water, in the institute’s reactor building. Other nuclear material stored at the site includes plutonium and highly radioactive spent-fuel byproducts.
This week, the IAEA will appeal to international donors for funds to pay for decommissioning the site and shipping the most dangerous material to Russia for disposal.
A joint project by the IAEA, the Vinca institute and the Serbian authorities to secure the material has stalled for lack of funds.
“The Vinca staff are highly professional and very cooperative,” Mr. Durst said. “But the budgets of the institute, and of the whole country, are very limited. They are keeping the whole thing together with gum and tape.”
The institute was founded in what was communist Yugoslavia in 1948 with the help of Soviet scientists. Its nuclear reactor was shut down in 1984, but there are still more than 800 workers at the site, 400 of them scientific staff.