A Review of Criticality Accidents A Review of Criticality Accidents
A Review of Criticality Accidents A Review of Criticality Accidents A Review of Criticality Accidents A Review of Criticality Accidents
82 Figure 49. Lady Godiva after the excursion of 3 February 1954.
Figure 50. Burst rod and several sections of Lady Godiva showing oxidation and warpage that accompanied the second accident, 12 February 1957. 8. Los Alamos Scientific Laboratory, 17 June 1960 235 U metal, graphite reflected, assembly; single excursion; insignificant exposures. The critical parameters of highly enriched (93% 235 U) uranium metal cylinders in thick graphite (about 9 inches) and near infinite water reflectors were being investigated. In the experiment of interest, an approximate 48 kg uranium annulus was built up on a cylinder of graphite that, in turn, rested on a hydraulic lift device. This annulus was raised by remote control into a reflector of graphite resting on a stationary steel platform. The system became critical before complete assembly and was scrammed both manually and automatically at about 1 inch from closure. Following the scram signal, the lift dropped rapidly and the system became subcritical, but about one–third of the metal mass stuck in the graphite reflector for a few seconds before falling to the floor. The yield was 6 × 10 16 fissions; there was no contamination or damage to the fissile metal. Personnel radiation doses were immeasurably small. This accident was, in many respects, similar to that of Jemima (II-B.4). The reactivity sensitivity of this particular experiment was not measured after the power transient but, when investigators examined similar systems, the reactivity insertion rate probably did not exceed a few dollars per second and the initial spike could have included 10 15 fissions. The fission yield was very close to that of the first Godiva accident (3 February 1954, 5.6 × 10 16 fissions), and the two masses are quite comparable. In the earlier case, all of the energy release took place during the power spike and some warping of pieces and damage to supports was seen. In this transient, the metal was undamaged, thus supporting the assertion that the initial power spike was small compared to the total yield. 83
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- Page 125 and 126: References 1. Stratton, W. R. A Rev
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82<br />
Figure 49. Lady Godiva after the excursion <strong>of</strong> 3 February 1954.
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