SL-1 Accident

Three military technicians were killed during maintenance of the SL-1 experimental nuclear reactor in Butte County, Idaho, in January of 1961. A control rod was withdrawn too quickly, causing the reactor to undergo a “prompt critical” reaction. The sudden power-surge instantaneously vaporized a large amount of coolant-water, creating a pressure-wave that caused the entire 26,000 lb. vessel to jump nine feet into the air and a water-hammer event that launched debris and steam into the surrounding area. Army Specialists John A. Byrnes, age 27, and Richard Leroy McKinley, age 22, were killed by the resulting spray of scalding, radioactive steam. Navy Construction Electrician Richard C. Legg, age 26, who was standing on top of the vessel at the time, was impaled through the groin and out of the shoulder by one of the shield-plugs, with his body left pinned to the ceiling. This event resulted in the design of future nuclear reactors being greatly altered for improved safety.

Submission by Logan Agle. Thank you.