Commenter is probably referring to this incident[1] where a sodium-cooled nuclear reactor on a Soviet satellite ended up spraying a bunch of small beads of sodi

Commenter is probably referring to this incident[1] where a sodium-cooled nuclear reactor on a Soviet satellite ended up spraying a bunch of small beads of sodium into Earth orbit. The number and density of the beads makes them a long-lived hazard. [1] - https://en.wikipedia.org/wiki/Kosmos_954 https://en.wikipedia.org/wiki/Kosmos_954