Newly minted PhD. Isabella Karle's first job at the Project's University of Chicago Met Lab was purifying "crude plutonium dioxide in the form of greasy yellow flakes... from Oak Ridge." Close to her laboratory door was a Coca Cola machine ,of the sort that dispensed Coke syrup and carbonated water into wax paper cups.
"The man who came to service the machine at our lunch hour forgot to bring his hose for filling the syrup reservoir. He walked into a neighboring laboratory and borrowed a rubber hose from an aspirator, filled the the reservoir with syrup , returned the hose and left."
The transfer of plutonium to the coke machine was detected hours later by a thirsty technician who happened to be carrying a geiger counter. How many paused to refresh themselves before him remains a mystery of the atomic age.