The 'plume' of salts, irradiated by decades of top secret Soviet era nuclear waste dumping at Lake Karachai in the southern Urals, is creeping its way through rock and soil at a speed of 80 metres a year.
Fed by a lake as radioactive as the cloud of debris that shadowed Europe after the Chernobyl disaster of 1986, if the plume reaches the River Techa and the Arctic, the effect on the precious eco- systems of Western Siberia and further afield could be devastating.
Yuri Vishnevsky, head of Russia's nuclear inspectorate, Gosatomnadzor, warns that the build-up of radioactive waste under the lake threatens ''nuclear catastrophe on a global scale''.
He estimates that the five million cubic metre plume, 100 metres under the lakebed, also threatens the Siberian Tobol, Irtysh and Ob river systems.
''If the plume reaches this system, Western Siberia and the Arctic Ocean will be polluted with radioactive waste, triggering a global disaster within ten years, where international intervention may be required,'' Vishnevsky says. ''No technology is available now to keep the plume in place.''
Lake Karachai was constructed in the late 1950 inside the grounds of the Mayak Chemical Combine, Russia's main nuclear reprocessing plant and formerly a major nuclear weapons production site. It was created to hold liquid nuclear wastes previously dumped in the River Techa.
But these discharges had to stop when the river, which eventually flows into the Arctic Sea, became highly contaminated and forced the evacuation of the villages along its banks.
It is estimated that Lake Karachai contains 120 million curies (Ci) of radioactivity, similar to the total amount released by the 1986 Chernobyl accident. Put another way, the total amount of radioactive discharges from the Russian Navy's fleets adds up to only 0.5 per cent of the radioactivity in Lake Karachai.
In 1991, U.S. experts measured a dose rate of 300 to 600 millirems per hour near the shores of the lake, which is three to six times maximum U.S. safety levels. It was estimated that just one minute standing on its shore without full protection would mean certain death.
Over the years contamination from Karachai has spread throughout the region. In 1967, during a particularly hot summer, the lake dried up and winds carried radioactive dust over a large area, forcing more evacuations. On another occasion, radioactive contamination found at a children's summer camp was traced to bats who live and breed near the lake.
Efforts have been made to fill in the lake with large rocks and concrete, but have only contributed to the problem. Vishnevsky says this is partly responsible for the groundwater contamination as filling that lake has only forced the poisonous waters down through the seabed.
Just over a third of the project to 'close' Lake Karachai has been completed. The containment plan involves covering the area with u-shaped blocks to keep radioactive silts at the bottom of the lake, and filling in the water with gravel. The project has received only meagre funding each year, and does not yet include any measures to prevent downward contamination.
But Karachai is only one of many sources of radioactive contamination within the Mayak site. From 1949 to 1951 Mayak discharged about 2.76 million Ci of liquid radioactive wastes into the River Techa.
Plutonium levels in the river bed remain high. When the Techa river was dammed in 1956 and 1963, releases of irradiated waters were reduced. However, the series of pools and marches created by the dams continue to be a source of pollution. The Assanov Marshes, which cover a 30 square kilometre area below dam number 11 contains about 6,000 Ci of strontium-90 and cesium-137, and this is still seeping into the Techa river system.
Karachai is not the only ''storage'' lake inside Mayak. Another, called Staroye boloto, contains about 200,000 Ci of radioactive waste. In addition, large quantities of solid wastes, measured at around two million Ci is buried on site. Radioactive sediments removed from liquid waste, and liquid wastes itself, measured at about 150 million and 976 million Ci respectively, are kept in special storage tanks on site.
In 1957 one of liquid waste containers exploded, spreading irradiation over an estimated 23,000 square kilometres, much of which is still a restricted area.
Then there are the routine atmospheric discharges arising from day-to-day operation of the facility. In all, a total area 26,700 square kilometres are affected by surface contamination.
Mayak is estimated to be responsible for producing a billion Ci of wastes, all of which poses a major threat to the region's water supply. Already, 437,000 people have been exposed to increased levels of radioactivity as a result.
If the underground reservoir beneath Karachai reaches the Irtysh River system, the radioactive contamination could eventually reach the Arctic Ocean.
Even if only a small percentage of the total radiation in the lake were to travel into international waters, the threat would easily exceed any posed by Russia's nuclear submarines, which are currently the main focus of international attention.
Increased technical and financial assistance to, as well as political pressure on, the Russian government to provide containment of the radioactivity at Lake Karachai would therefore seem to be in the long-term interest of many neighbouring countries, especially those in the north. (END/IPS/AI/JMP/RJ/98)