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

Argonne criticality accident, 1952

compiled by Wm. Robert Johnston
last modified 14 September 2005

Date: 2 June 1952

Location: Argonne National Laboratory, Illinois, USA

Type of event: criticality accident with uranium particles in plastic


A criticality excursion occurred in an experimental apparatus using uranium-235 oxide. The uranium oxide was in small particles (most 10 microns in diameter, some 40 microns in diameter) embedded in polystyrene plastic; a total of 6.8 kg of U-235 was involved. These fuel strips were combined with zirconium strips in a water-containing tank. Contrary to operating procedures, a control rod was being replaced while the tank was filled to the normal level with water. A criticality excursion occurred, heating the fuel sufficiently to cause bubble formation near the larger uranium oxide particles. This bubble formation forced most of the water out of the core, terminating the excursion within 0.6 seconds. Most of the 3 megajoule energy release occurred in a period of about 0.02 seconds. Doses to four individuals were 136, 127, 60, and 9 rad.

Consequences: 2 injuries? (136, 127 rad).


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