In this historical photo from the U.S. space agency, Bill Fecych shut down the reactor for the last time on 5 January 1973, as Dale McCutheon, Dan Gardner, George Gowan, and others looked on.
Employees had gathered in the Plum Brook auditorium for an announcement by Lewis Center Director Bruce Lundin, little expecting to hear the news that Plum Brook would be closed. Two hours later, stunned employees crowded into the reactor control room and just after 2 p.m., witnessed the final shutdown of the Plum Brook reactor.
For more information browse the Plum Brook Facility Page.
Each weekday, SPACE.com looks back at the history of spaceflight through photos (archive).