SL-1

SL-1, first known as the Argonne Low Power Reactor, was a small experimental nuclear reactor built in eastern Idaho for the U.S. Army to test whether compact, transportable plants could provide heat and electricity at remote military sites. Designed by Argonne National Laboratory, it began operating in 1958 as part of the Army Nuclear Power Program. Its compact core had a dangerous vulnerability: the center control rod exerted unusual influence over reactivity. On January 3, 1961, during restart after a holiday shutdown, that rod was withdrawn too far, causing a violent steam explosion that killed three operators. The accident reshaped U.S. reactor safety and ended the reactor’s service.

Idaho · United States