http://www.lutins.org/nukes.html
24 July 1964
Robert Peabody, 37, died at the United Nuclear Corp. fuel facility in Charlestown, Rhode Island, when liquid uranium he was pouring went critical, starting a reaction that exposed him to a lethal dose of radiation.
Sounds vaguely familiar. The guy poured a solution of a uranium compound from a flat tray into a round vessel. It was fine in the tray, but in the round vessel it achieved criticality. I don't think he died on the spot, but rather it was a horrible lingering death.