On September 29, 1957, an explosion in a steel storage tank containing liquid nuclear waste led to the release of a massive 2 MCi of radioactive material. It measured as a Level 6 disaster on the International Nuclear Event Scale, making it the third most serious nuclear accident ever recorded, behind the Fukushima Daiichi nuclear disaster and the Chernobyl disaster (both Level 7 on the INES).
Known as the Kyshtym Disaster, the incident occurred at Mayak, a nuclear fuel reprocessing plant sequestered in the closed city of Ozyorsk, near the town of Kyshtym. Spent nuclear waste generates heat, the tank cooling systems failed and containment of the material also failed leading to a non-nuclear explosion on the order of 70-100 tons of TNT.
Within ten hours of the release, the radioactive cloud travelled 300-350 kilometres in a northeast direction. Fallout contaminated an area of approximately 800 square kilometres later called the East-Ural Radioactive Trace (EURT). Secrecy surrounding Mayak and its operations led to the suppression of information about the danger to the local population; it was a full week before people began to be evacuated, without explanation.
According to an article in Critical Mass Journal by Richard Pollock, people “grew hysterical with fear with the incidence of unknown ‘mysterious’ diseases breaking out. Victims were seen with skin ‘sloughing off’ their faces, hands, and other exposed parts of their bodies”.
Knowledge about the event could only be gathered indirectly. An estimated 200 people died from cancer as a direct result of the explosion and release; massive amounts of contaminated soil apparently were excavated and stockpiled; and an off-limits “nature reserve” was created in the EURT to isolate the affected region.
Nuclear Waste and Safety Measures
At the time, the Soviets were hurrying to catch up with American nuclear weapons researchers. In their desire to produce sufficient quantities of weapons-grade uranium and plutonium, they proceeded without full understanding of the safety measures necessary to protect citizens and the environment.
All six reactors were on Lake Kyzyltash and used an open cycle cooling system, discharging contaminated water directly back into the lake. Initially Mayak was dumping high-level radioactive waste into a nearby river, which was taking waste to the river Ob, flowing further down to the Arctic Ocean.
A storage facility for liquid nuclear waste was added to the pant around 1953. It consisted of steel tanks mounted in a concrete base, 8.2 meters underground.
Because of the high level of radioactivity, the waste was heating itself through decay heat (though a chain reaction was not possible). For that reason, a cooler was built around each bank containing 20 tanks. Facilities for monitoring operation of the coolers and the content of the tanks were inadequate however.
On 29 September 1957, the cooling system in one of the tanks containing about 70–80 tons of liquid radioactive waste failed and was not repaired. The temperature in it started to rise, resulting in evaporation and a chemical explosion of the dried waste, consisting mainly of ammonium nitrate and acetates (see ammonium nitrate bomb).
There were no immediate casualties as a result of the explosion, but it released an estimated 20 MCi (800 PBq) of radioactivity. Most of this contamination settled out near the site of the accident and contributed to the pollution of the Techa River, but a plume containing 2 MCi (80 PBq) of radionuclide spread out over hundreds of kilometres.
Aftermath & Cover Up
Because of the secrecy surrounding Mayak, the populations of affected areas were not initially informed of the accident. A week later (on 6 October) an operation for evacuating 10,000 people from the affected area started, still without giving an explanation of the reasons for evacuation.
Although vague reports of a “catastrophic accident” causing “radioactive fallout over the Soviet and many neighbouring states” began appearing in the western press between 13 and 14 April 1958, it was only in 1976 that Zhores Medvedev made the nature and extent of the disaster known to the world.
The true number of fatalities remains uncertain because radiation-induced cancer is clinically indistinguishable from any other cancer, and its incidence rate can only be measured through epidemiological studies.
To reduce the spread of radioactive contamination after the accident, contaminated soil was excavated and stockpiled in fenced enclosures that were called “graveyards of the earth”. The Soviet government in 1968 disguised the EURT area by creating the East-Ural Nature Reserve, which prohibited any unauthorised access to the affected area.
According to Gyorgy, who invoked the Freedom of Information Act to gain access to the relevant Central Intelligence Agency (CIA) files, the CIA knew of the 1957 Mayak accident since 1959, but kept it secret to prevent adverse consequences for the fledgling American nuclear industry.
If details of the incident had been wider known, it would have provided extra momentum to the anti-nuclear cause, and may have resulted in significant budget cuts and regulatory changes that would have directly impeded the U.S in its nuclear arms race against the Soviets.