The Guardian reports:

A nuclear waste dump in the Russian Arctic may be in danger of exploding because of corrosion caused by salt water in enormous storage tanks, a Norwegian environmental group warned Friday.

The three tanks are used to store spent nuclear fuel rods at Andreeva Bay, on the Kola Peninsula of northwestern Russia, just 28 miles from the Norwegian border, the Oslo-based Bellona said in a statement. "We discover now that we are sitting on a powder keg, with a fuse that is burning, but we don't know how long that fuse is,'' said Alexander Nikitin, a former Russian navy officer who is now one of Bellona's nuclear experts. The group cited a report from Rosatom, the Russian nuclear authority, describing the danger. Bellona said the storage tanks were long believed to be dry inside, but that recent studies show corrosive salt water is inside the tanks. "Ongoing degradation is causing fuel to split into small granules. Calculations show that the creation of a homogenous mixture of these particles with water can cause an uncontrolled chain reaction,'' said the group's Norwegian translation of the report.

Russian and Norwegian nuclear officials downplayed the danger. The Norwegian Nuclear Protection Authority said in a statement that while a chain reaction was possible, the likelihood was "extremely small.'' Russia's Federal Nuclear Power Agency said there was no danger, and that steps were being taken to improve the storage tanks. Norwegian Foreign Minister Jonas Gahr Stoere said the government was aware of the problem and was working with the Russians to find a solution. Bellona has long been involved in probes of the nuclear risks in Russia, especially on the Kola Peninsula. Its 1996 report on conditions there were a reference work even for Russian officials. Experts have said the Kola Peninsula has the world's greatest concentration of nuclear materials, with aging nuclear power plants, rusting hulks of Russian Northern Fleet atomic submarines and waste dumps. Bellona said it first reported on the storage tanks in 1993 but the risk of explosion was a new development. "It has been 14 years since Bellona offered information about Andreeva Bay. But our analysis shows that nothing has happened since then,'' Nikitin, who is based in Russia, said in the news release. Nikitin was detained by Russian authorities in 1996 on charges of espionage for his contribution to Bellona's report on nuclear safety within the Russian Northern Fleet. He was finally acquitted by the Supreme Court in 2000. In an interview published Friday by the Oslo newspaper Aftenposten, Nikitin said the storage tanks contain 21,000 spent nuclear fuel rods. He said the tanks are near the sea and salt water is corroding metal piping, breaking down fuel rods and releasing small uranium particles. The tanks were put into service as temporary storage for spent fuel in 1982 and 1983, because radiation had begun to leak from used fuel rods that had been store in warehouses at the Russian nuclear submarine base at Andreeva Bay.