|Fig. 1: Mountains surrounding Kyshtym. (Source: Wikimedia Commons)|
The Kyshtym nuclear disaster was a Level 6 Disaster on the International Nuclear Event scale that occurred in Ozyork, Chelyabink in the Soviet Union. It is named for Kyshtym, the nearest known town that was marked on maps. The disaster occurred at the Mayak plant, a nuclear weapons production site and nuclear fuel reprocessing plant.  The Mayak Production Association was a primary site for the Soviet nuclear program after World War II. From the years following World War II, the facility produced weapons-grade plutonium for Soviet nuclear weapons. The high-level radioactive waste was originally discharged into a nearby body of water, and then eventually stored in cooling composite steel-concrete tanks underground. 
Because of its sensitive political nature, media reporting was sparse, only occasionally appearing after 1958. However, when literature appeared in 1976 by Dr. Zhores Medvedev, an exiled Soviet geneticist, alleging thousands of casualties and long-term radioactive contamination, the Kyshtym disaster garnered worldwide attention. 
On 29 September 1957, a 70 to 80 ton waste capacity storage tank's cooling systems failed, causing the internal temperature to increase and the cooling liquid to evaporate. This resulted in a chemical explosion that ejected radioactive material into the surrounding environment.  About 90% of the 740 PBq of mixed fission products landed within 5 km of the tank, and the rest was deposited as dry fallout north of the facility. 
Around 15,000 to 20,000 square kilometers measured contamination levels above 3.7 kBq/square meters of 90Sr, below the established intervention level for population evacuation of 74 kBq/square meters of 90Sr. An area of some 1000 square kilometers became recognized as the East Urals Radioactive Trace (EURT), where levels of radioactivity quickly declined due to the decay of short-lived isotopes.  Even still, there were significant consequences for both the environment and the population. From 1957 to 1959, more than 10,000 tons of agricultural products were destroyed after declared unfit for human consumption.  More than 6000 hectares of agricultural land underwent deep ploughing decontamination to reduce uptake via root systems.  From 1958- 1959, more than 20,000 hectares of the EURT was subjected to ploughing to reduce gamma radiation exposure. 
Because of the accident, food intervention limits regarding the content of radionuclides in food was implemented to protect the public from dangerous radiation exposure.  Milk existed as a primary source of contamination of the human diet, comprising up to 50% of ingested radioactivity. 
The nuclear incident at Kyshtym was the third worst nuclear accident recorded, behind Fukushima Daiichi and Chernobyl.  Various methods were developed to decrease the risk of contamination. Deep ploughing, removing contaminated soil layers, adding fertilizers and ameliorants that were developed to slow the uptake of contaminants, and utilizing crops with low uptake of contaminants, were some of the measures taken to ensure low assimilation of contaminants into body tissues. 
© Samantha Chang. The author grants permission to copy, distribute and display this work in unaltered form, with attribution to the author, for noncommercial purposes only. All other rights, including commercial rights, are reserved to the author.
 "USSR: Nuclear Accident Near Kyshtym in 1957-58" U.S. National Foreign Assessment Center, SW 81-10102, October 1981.
 "The Kyshtym Accident, 29th September 1957," Norwegian Radiation Protection Agency, August 2007.
 D. M. Soran and D. B. Stillman, "An Analysis of the Alleged Kyshtym Disaster," Los Alamos National Laboratory, LA-9217-MS, January 1962.