Date: 26 May 1971
Location: Kurtchatov, Russia, USSR
Type of event: criticality accident with uranium in water
Experiments were being conducted to determine the number of uranium fuel rods (90% U-235) required to produce a critical configuration. Rods were placed in various geometries within a Plexiglas tank which was filled with water, with additional rods added a few at a time. Insufficient calculations had been performed regarding such an apparatus. At the completion of one experiment, the water was being rapidly drained, causing the rods to slump into a supercritical configuration. The excursion ejected water and fuel rod fragments from the tank. One technician received about 6,000 rem and died 5 days later; a supervisor received 2,000 rem and died 15 days later. Two others in the room received doses of 700-800 rem and suffered acute radiation sickness; they survived with long term health effects.
Consequences: 2 fatalities (6,000 and 2,000 rem), 2 injuries (700-800 rem).
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Last modified 14 September 2005.
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