One of the most overlooked but the single most fatal (in terms of direct casualties) nuclear incident on American soil is the SL-1 disaster. Occuring at the height of the Atoms For Peace phase in 1961 in a remote part of Idaho, it’s understandable that it wasn’t as publicized. But it is an ‘incredible’ story, one that seems to combine the worst parts of Chernobyl and the Byford Dolphin.

The US army was experimenting with small reactors. One such reactor was the SL-1. On January 3, 1961, three men were performing maintenance on the ‘shut down’ reactor. John Byrnes moved a control rod too far, causing the reactor to go prompt critical and immediately explode in a blast of radioactive steam. Byrnes and fellow technicians Richard Legg and Richard McKinley were killed.

That Byrnes’ moving the control rod caused the disaster was well established. But since all with possible knowledge of why he did that died in the explosion, that part remains mysterious. The most likely explanation is simply that the ill-built reactor had a rod get stuck, and while Byrnes pulled he moved it too far. Other theories range from a distraught Byrnes over a failing marriage not paying attention, Legg pulling a prank that caused Byrnes to get startled and yank on the rod, and most infamously the theory that a love triangle involving Byrnes, Legg, and their spouses led him to intentionally cause a murder-suicide.

We will never know the why.