Database of radiological incidents and related events--Johnston's Archive

Mayak Enterprise criticality accident, 1958

compiled by Wm. Robert Johnston
last modified 21 September 2007

Date: 2 January 1958

Location: Mayak Enterprise, Russia, USSR

Type of event: criticality accident with uranium solution


Following the criticality accident at the same facility in 1957, an apparatus had been constructed to test criticality phenomena in fissile solutions. A 400-liter tank on a platform was used for measurements involving solutions; after each experiment, the tank was drained into individual 6-liter containers of favorable geometry. On this occasion, the tank contained uranyl nitrate solution (90% U-235) and was being drained for another experiment. After filling several 6-liter containers, operators decided to circumvent the standard procedure to save time. Three operators unbolted the tank and lifted it to pour directly into containers. The presence of the operators provided sufficient neutron reflection to cause a criticality excursion, producing a flash of light and ejecting solution as high as the ceiling, 5 meters above the tank. The operators dropped the tank and, along with a fourth operator in the room, left the area for decontamination and transport to the hospital within 2 hours of the accident, having already exhibited symptoms of acute radiation syndrome. The three operators who lifted the tank (all men) incurred fatal doses of radiation, with respective doses of 7,000-12,500 rad (died on day 6), 7,600-13,100 rad (died on day 7), and 3,000-4,800 rad (died on day 10). The fourth operator, a woman, sustained a dose of 700-1,200 rad but recovered from radiation sickness. She suffered chronic health problems afterwards, developing cataracts in both eyes and becoming blind years later, eventually dying of lung cancer in 1982.

Consequences: 3 fatalities, 1 injury.


© 2004-2005, 2007 by Wm. Robert Johnston.
Last modified 21 September 2007.
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