Worst nuclear waste accident

The worst nuclear-waste accident in history is the "Kyshtym Disaster", which occurred at the Mayak Production Association, a nuclear facility in Chelyabinsk Oblast, Russia, in 1957. A some point in the preceding months a cooling system on a tank of radioactive waste had failed, and the temperature inside had been steadily climbing, eventually reaching around 350°C (660°F). This increase in heat and pressure eventually reached a critical point, and at 4:20 p.m. local time on 29 September the tank exploded, releasing around 740 petaBecquerels (20,000,000 curies) of radiation.

Most of the radioactive material contained in the tank settled in the immediate area of the Mayak plant and was relatively easy to contain. Witnesses describe a thick layer of red dust settling on everything, and almost immediately causing the leaves of plants to wither and fall off. Roughly 10 percent of the released radioactivity (74 PBq), however, was contained in a cloud of fine dust that was dispersed by the wind across the countryside to the north-east of the plant.

The 1,100 residents of the towns of Berdyanish, Satlykovo, and Galikaeva were evacuated within around a week of the accident. The contamination of these towns was so severe that the clothes and personal effects of the evacuees had to be destroyed. Over the next few weeks many more settlements were evacuated. In 1958, after food products from the Techa river valley were found to be severely contaminated, the area downwind of the Mayak plant was withdrawn from economic use and human habitation, creating the 590 km2 (227 sq mi) East Ural Reserve, which still exists to this day.

Despite the magnitude of the event (it was retroactively rated as an level 6 incident on the International Nuclear Event Scale, the second highest category behind level 7 incidents like Chernobyl and Fukushima), studies have no found any statistically significant changes in health outcomes for people living in the area around the plant.

Rumours of a catastrophic nuclear accident on the other side of the Iron Curtain reached the West in spring of 1958. A few stories were published in European newspapers in April of that year, but none contained anything more than the vaguest details, and the severity of the incident was greatly exaggerated. The event didn't come to be widely known in the West until 1977, when London-based Soviet defector Zhores Medvedev published a book on nuclear safety in the Soviet Union.

It is during this period that the accident gained the name by which it is widely known today, the "Kyshtym Disaster". This name reflects the dense veil of secrecy that surrounded the Soviet Nuclear program – the town of Kyshtym, located about 10 km (6.2 miles) from the Mayak Production Association, was connected to the disaster because it was the closest known settlement to the apparent source of the radiation plume. The existence of the Mayak Production Association and its factory town of Ozyorsk (then called "Chelyabinsk-40") was a closely guarded state secret.