Lake Karachay, Mayak, and Chelyabinsk-40: A Look at the Most Contaminated Place on Earth

Imagine a lake so polluted and contaminated that spending just an hour on its shores would result in certain death, and the only way seen fit to deal with it is to fill the entire water body with concrete blocks to keep the toxic soil underneath from moving onshore. That lake is Lake Karachay in Russia’s Chelyabinsk Oblast, and it is considered by many to be the most polluted place on the planet.

View Larger Map

From above, Lake Karachay looks somewhat innocuous.  Zoom out, however, and its surroundings reveal the lake’s true situation:


Lake Karachay lies within the Mayak Production Association, one of Russia’s largest and oldest nuclear facilities and a major source of plutonium during the Soviet era.  The Chelyabinsk region as a whole has for many decades been one of Russia’s major industrial centres.  Built immediately following World War II, Mayak has been the site of numerous nuclear-related accidents throughout its history, some approaching the size of the Chernobyl meltdown but far more concentrated.  Both the Mayak site and the city built to service it (originally called Chelyabinsk-40, later Chelyabinsk-65, and now Ozyorsk) were kept officially hidden by Soviet officials with no acknowledgement of their existence until 1992.  Karachay, the small, dried-up lake to the south of the nuclear plant, spent a quarter-century receiving Mayak’s waste. 

Right from the beginning, the Mayak complex was an environmental disaster in progress.  Right from the time of the nuclear plant coming online in 1948, liquid waste from Mayak was being dumped into the shallow Techa River via the adjacent Kyzyltash Lake.  Between 1949 and 1956, the estimated discharge into the Techa was 76 million m3 (2.68 billion cu ft).  A 1951 survey revealed rather than a typical background gamma radiation measurement of 0.21 Röntgens per year, the Techa was giving off 5 Röntgens per hour.  Even today, water from the upper Techa cannot be consumed.

Statistics uncovered by the producers of the 1994 documentary Chelyabinsk: the Most Contaminated Spot on the Planet revealed that by the 1990s, there had been a 21% increase in the incidences of cancer, a 25% increase in birth defects, a 41% increase in leukaemia, and a rendering of 50% of the population of child bearing age sterile in the Mayak region.  Of the 40 villages on the river downstream from Mayak, 24 relied upon it for water; 23 of those villages had to be evacuated.  28 000 people living along the Techa were seriously irradiated, and another 100 000 experienced some of irradiation.  One village, Metlino, was found to have 65% of residents suffering from chronic radiation sickness, and workers at the plutonium plant reported the same.  Due to the fact that attending doctors were not allowed by the military to mention ‘chronic radiation sickness’ in their diagnoses for fear it would reveal the nature of the facility, patients were simply told they had ‘astheno-vegetative syndrome’ and medical records simply recorded vague terms such as ‘special disease’.   66 people would ultimately succumb to the sickness, plus another 49 to 55 to radiation-induced cancer.  Although cofferdams have now been erected alongside the lagoons now used to treat nuclear waste, leakage into the Techa continues.  Downstream water is now nearly free of radioactive caesium, but the sediments and riverbankswill contain caesium and strontium for a few hundred years more.

Realising that discharging watered-down radioactive material into the Techa was a bad idea, Soviet officials turned to a small, swampy lake on the south edge of Mayak for their next solution.  Waste would now be put into storage tanks made of steel and concrete for a year at a time to release some of the radioactivity of the material before being pumped into the now-infamous Lake Karachay (lesser-grade was pumped into nearby Lake Staroye Boloto).  Just three meters (ten feet) deep and 45 ha (110 acres) in area, the sediments underlying Lake Karachay became filled with radioactive material.

In 1957, the year after Lake Karachay became a receptacle for radioactive waste, one of those storage tanks used to let waste cool down before it entered the lake exploded following a cooling system failure.  The tanks were submerged in concrete canal with water constantly running over them to carry away heat.  The hot isotopes in this waste water create evaporation within the tanks, which not only eventually compromised the tanks’ seals due to the upward-moving air but also left behind a volatile mix of nitrate and acetate.  By 29 September, the cooling fluid in one of the tanks had evaporated and the temperature within the tank began rising as a result, heating up to 350 °C (660 °F) before the nitrate-acetate mix in the bottom of the tank detonated with the force of 75 tons of TNT, setting off a chain reaction of explosions amongst the nearby tanks and blowing several tons of radioactive material into the atmosphere.

The East Ural Radioactive Trace (EURT), the area contaminated in the Kyshtym disaster.  Source: J. Rieke,  Licensed under the Creative Commons Attribution-Share Alike 3.0 Unported licence.

As Chelyabinsk-40 was not officially acknowledged or shown on maps (the only designation for the complex was its postal code), the explosion and resulting fallout would come to be known as the Kyshtym disaster after the nearest known city to the west.  23 000 km2 (8 880 sq mi) of land was tainted, 10 700 people were evacuated, and 270 000 people were affected as far away as Tyumen, 330 km (207 mi) to the northeast, thanks to a radioactive cloud 8 km (5 mi) wide.  All pines within 18 km (12 mi) of the complex were killed within two years, and tales of villagers vomiting blood and losing skin on exposed body parts were not uncommon.  The resulting contaminated area is known as the East Ural Radioactive Trace (EURT), as shown in the above image.

Back at Lake Karachay, the next Chelyabinsk-40 disaster would occur there in 1967.  That year’s abnormally warm summer saw the shallow lake begin to dry up to about half its original size, exposing the contaminated lake sediment, which promptly blew away into the atmosphere, spreading the strontium contained within over an area approximately 1 800 km2 (695 sq mi) with a population of 400 000.  Only 180 000 of these irradiated people, many of whom had already suffered through the Kyshtym disaster a decade earlier, were evacuated.  Interestingly, though the Central Intelligence Agency was aware of the incident, it did not release its knowledge of it to the public for fear that it may discourage the nuclear energy program back in the US.  It was after this event that Soviet officials devised the plan to cover the lakebed with concrete blocks to prevent contaminated sediments from blowing away in the future.  Between 1978 and 1986, 10 000 such blocks were laid down.  The lake has continued to shrink slowly over the years.

Weapons-grade plutonium ceased being produced at the complex after two of the five reactors were shut down in 1987.  In total, over 500 000 people have been irradiated by the various disasters at Mayak, with the total levels of radiation emitted being higher than those of Chernobyl.  Between 1948 and the closure of the last reactor in 1990, 26 700 km(10 040 sq mi) of territory was irradiated.  In addition to the above-ground toll the pollution took on people and vegetation, around 1 billion gallons (3.8 billion litres) of groundwater were ruined.  Only after the end of the Soviet period were residents of the region told about the true extent of the damage caused at the Mayak complex.  Even in recent years there have been incidents, including a 1994 fire that caused 4% of the annual allowable radioactive gas release to be discharged at once and a 2003 revocation of the plant’s operating license for discharging waste into open water.

Further Reading

Bellows, A. (2008).  In Soviet Russia, Lake Contaminates You.  Damn Interesting, 17 October 2008.  Available at  Accessed 2 October 2012.

Burmistrov, D., et al. (2000).  Radioactive Contamination of the Techa River and its Effects.  Technology 7:553-575.  Available at  Accessed 2 October 2012.

Goulet, M. (1997).  Ural Mountains Radioactivity and Health.  TED Case Studies7(1):392.  Available at  Accessed 2 October 2012.

Grunberg, S. (1997). Chelyabinsk: The Most Contaminated Spot on the Planet.  Available at  Accessed 2 October 2012.

Pike, J. (2011).  Chelyabinsk-65/Ozersk ., 24 July 2011.  Available at  Accessed 2 October 2012.

4 thoughts on “Lake Karachay, Mayak, and Chelyabinsk-40: A Look at the Most Contaminated Place on Earth

Comments are closed.