The SL-One Reactor Accident

On the evening of January third, nineteen sixty-one, just a few miles from where EBR-One had produced history's first nuclear electricity nine years earlier, a very different chapter was being written. Three Army soldiers were performing routine maintenance on a small experimental reactor called Stationary Low-Power Reactor Number One, or SL-One. The reactor had been shut down for the holidays. The men were reassembling the control rod mechanism when something went catastrophically wrong.

At nine zero one PM, the central control rod was withdrawn far too fast, by how much and why has never been conclusively established. The reactor went prompt critical in a fraction of a second. An enormous steam explosion, powered by superheated water flashing to vapor, drove the entire reactor vessel upward nine feet, pinning one of the three men to the ceiling on a control rod. All three soldiers died: Richard Legg, John Byrnes, and Richard McKinley. The accident killed them almost instantly.

The rescue and recovery operation that followed was harrowing. Radiation levels in the building were so high that teams could only enter for a few minutes at a time. Recovering the bodies took days. All three men were buried in lead-lined caskets because their remains were too radioactive for standard burial. Two are interred at Arlington National Cemetery.

SL-One remains the only fatal nuclear reactor accident in United States history. It reshaped reactor safety protocols worldwide, leading to new requirements for interlocking control rod systems that make a single-operator withdrawal physically impossible. The accident site was decommissioned and buried in place. A historical marker on the Idaho National Laboratory site today acknowledges the three men who died there. Their names are not widely known, but the safety systems protecting every nuclear plant on earth carry the shadow of what happened here on that January night.