The SL-1 Reactor: America's Only Fatal Nuclear Accident

At nine oh one on the night of January third, nineteen sixty-one, a radiation alarm went off at the National Reactor Testing Station in the Idaho desert, eighteen miles from Arco. Emergency teams drove out to a small building called S-L-One, a stationary low-power reactor used to test military power systems. When the first team reached the building, their dosimeters pegged at the maximum reading before they could get through the door. They could not go in.

S-L-One was a compact experimental reactor, the kind the Army intended to use at remote military bases. On that night, three men were performing routine maintenance: John Byrnes, twenty-two years old; Richard Legg, twenty-six; and Richard McKinley, twenty-seven. Their job that evening required manually reinserting a control rod that had been left slightly withdrawn. Somewhere in the sequence of work, the central control rod was pulled out to about twenty inches, roughly sixteen inches farther than the four inches the procedure called for. The withdrawal took less than a second. In four milliseconds, the reactor went prompt critical.

The steam explosion that followed drove a control rod upward through the reactor vessel with enough force to pin one of the men to the ceiling. All three were dead within hours. Two died almost immediately from the blast and radiation exposure; the third survived briefly before dying of his injuries.

What followed was unlike any accident response in American history. The men's bodies were so heavily contaminated with radioactive material that they could not be recovered immediately. When they were finally removed, workers could spend only seconds near them before reaching their radiation exposure limits. The personal effects found at the site were classified as low-level nuclear waste and buried accordingly. The men were interred in lead-lined coffins in a national cemetery, with special authorization from the Atomic Energy Commission.

S-L-One remains the only nuclear reactor accident in American history to cause immediate radiation fatalities. The site is open to visitors. Almost nobody comes.