Local environmentalists in western Siberia have filed a lawsuit against the authorities in an attempt to revoke a dumping permit at Tomsk-7, which produced plutonium and uranium for the Kremlin's nuclear weapons during the Cold War.
The radioactivity of the waste dumped there over the last 35 years is about 1,200m curies - utterly dwarfing the 50m curies released when the 1986 Chernobyl disaster sent a cloud of radioactivity across the northern hemisphere.
"It is a unique case," said Thomas Nielsen, of the Bellona Foundation, an Oslo-based environmental research organisation which monitors the Russian nuclear industry. "This is the first time that an independent local group has tried to take on the authorities in the Russian courts in this way."
Government officials admit that the Siberian Chemical Combine at Tomsk- 7 - for years a closed city known only by its postcode and ringed by miles of barbed wire - injects highly radioactive liquid waste underground.
This is held in what they call "deep wells", 300m- to 400m-deep water- carrying layerssealed by deposits of clay. But they say the waste is safe.
"It is absolutely meaningless to compare this with Chernobyl, as it makes no impact whatever on the environment," Yevgeny Kudryavtsev, head of the nuclear chemical division of Russia's Ministry of Atomic Energy, told The Independent yesterday. But the ministry's opponents, including Bellona, point to the fact that the underground dumps are only a few miles from wells that supply drinking water to the 500,000 residents of the city of Tomsk. They fear a leak, warning that it could one day cause a catastrophe by flooding the food chain with radioactivity.
"This is the biggest dumping ground for such waste in the entire world," said Mr Nielsen. "This also happens to be a few miles from the Tom River, a tributary of the Ob River which flows into the Arctic and the Barents Sea, the fishing ground for the whole of Europe."
Over the years, he said, at least 10kg of plutonium - which will threaten the environment for centuries - has been dumped underground at Tomsk-7, mixed with other liquid waste. There is no known way of extracting and disposing of it.
Bellona believes the law suit, bought by local groups - including a regional organisation called Green World - will be a critical test of the 1993 Russian constitution. This grants the "right to a favourable environment, reliable information on the state of the environment and compensation for damage caused to health and property by violations of environmental laws".
However, the ministry's Mr Kudryavtsev was yesterday bullishly confident about the plant - scene of a serious nuclear accident in 1993, in which a 45-mile surrounding zone was contaminated.
He says the underground dumps are sealed by deposits of clay the "width of a 10-storey building" providing a barrier would last "thousands and thousands" of years. Asked if he could be certain that the waste would not one day escape, he replied: "Are you sure that there won't be a nuclear accident in Britain in the next few days? Can you ever be absolutely sure? It is a meaningless question."