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

Arzamas-16 criticality accident, 1997

compiled by Wm. Robert Johnston
last modified 14 September 2005

Date: 17 June 1997

Location: Russian Federal Nuclear Center (Arzamas-16), Sarov, Russia

Type of event: criticality accident with uranium metal assembly


A criticality accident occurred at the Russian Federal Nuclear Center, formerly Arzamas-16. An experimenter was attempting to replicate a successful 1972 experiment involving a sphere of highly enriched uranium (90%) surrounded by a spherical copper reflector. However, he had incorrectly recorded the outside reflector dimensions and as a result used a much larger reflector; further, he had failed to complete appropriate paperwork on the experiment and was working alone. He had assembled the uranium sphere within a hemisphere of the copper reflector in an experimental cell. While adding the first layer of the second copper hemisphere, it dropped onto the assembly and produced a supercritical assembly at 10:40 AM. A flash of light resulted, after which the experimenter left the cell. The uranium core reached a calculated peak temperature of 865° C before power output declined to a steady 480 W. The assembly remained in this state until 12:45 AM on 24 June 1997 when it was remotely disassembled. The experimenter received a dose of 4850 rem, from which he died the morning of 20 June, 66 hours after the accident.

Consequences: 1 fatality (4850 rem).


© 2004, 2005 by Wm. Robert Johnston.
Last modified 14 September 2005.
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