On Oct 24, 1996 a clogged line caused the lab's miniature plutonium and uranium extraction (PUREX) system to overflow. The system was outputting to an unsafe cylinder configuration and the resulting mass of enriched uranium hexafluoride solution became critical. It is estimated that 1.5 x 1017 fission events occurred. The integral shielding of the cubicle walls absorbed most of the gamma rays, limiting exposure to under 500 mrem for all lab personnel. This image was captured 400 msec into the criticality incident, and the blue Cerenkov glow is clearly visible.
This image was taken with the now-long-defunct PDL webcam. Since then, in part due to increased DOE interest in our activities, the lab has abandoned its nascent nuclear program; we are currently focusing our energies on a more straightforward plan to take over the world.