This afternoon in 1957, at the closed city of Chelyabinsk-65 near Kyshtym in the Southern Urals, a stainless steel tank holding 70-80 tons of highly-radioactive waste left over from processing plutonium for nuclear weapons exploded, releasing 20 million curies of radioactivity.
While the explosion was chemical in nature (much of the liquid waste evaporated over time, leaving behind a volatile dry mixture of sodium nitrate and sodium acetate), a brief nuclear criticality may have initiated it. The explosion's size has been estimated at 5-100 tons of TNT.
The explosion completely destroyed the tank and damaged two adjacent ones. About 90 percent of the radioactive waste fell to the ground in the immediate vicinity of the tank, while about 10 percent was lofted by the wind in a plume up to 1 kilometer high and 300 kilometers long.
The most significant radioactivity came from strontium-90, cerium-144, and zirconium-95. Some 15,000-23,000 square kilometers were contaminated with at least 0.1 curies of Sr-90/sq. km, about 2X greater than fallout from nuclear testing; 1,000 sq. km were 20X more contaminated.
The Soviet Union kept this nuclear accident secret until June 1989. Some 270,000 people are estimated to have lived in the most heavily contaminated 15,000-kilometer zone, but only 10,180 were evacuated, and then only in phases over about two years. They were never told why.
About 59,000 hectares of contaminated agricultural land were removed from production and contaminated food disposed of. In 1961, some agriculture in the zone resumed, but it wasn't until 1978 that 40,000 hectares were returned to cultivation (the rest was still too dangerous).
1,300 tons of grain, 240 tons of potatoes, 61 tons of vegetables, 100,000 kg of meat, and 67,000 kg of milk were disposed of. Nevertheless, doses in the most contaminated zone were estimated to average a whole body equivalent of 52 rems and 150 rems to the gastrointestinal tract.
Although the Soviets did not disclose the accident's location, severity, or cause, the CIA soon discovered the truth. However, it did not use this information against the Soviet Union. Some details only became public in the West in 1977 via a Freedom of Information Act request.
To date, this nuclear accident ranks as the third worst in world history, after Fukushima in 2011 and Chernobyl in 1986.
Share this Scrolly Tale with your friends.
A Scrolly Tale is a new way to read Twitter threads with a more visually immersive experience.
Discover more beautiful Scrolly Tales like this.