SL-One: America's Only Fatal Reactor Accident
Idaho
About forty miles west of Idaho Falls, in the same high-desert testing ground that gave the world its first nuclear electricity, something went catastrophically wrong on the night of January third, nineteen sixty-one. What happened there remains the only fatal nuclear reactor accident in United States history.
The reactor was called Stationary Low-Power Reactor Number One, SL-One for short. It was a small Army experimental unit, designed to test the concept of portable nuclear power plants that could be shipped to remote military outposts in pieces and assembled on site. Three operators were on duty that evening, conducting routine maintenance after an eleven-day shutdown. The main task was simple: manually withdraw the central control rod a few inches to prepare the reactor for restart.
At nine oh one in the evening, the central control rod was withdrawn not four inches but approximately twenty inches, nearly to the top of the core. Within four milliseconds, the reactor went prompt critical. The power level spiked to roughly twenty billion watts. A steam explosion tore through the reactor building.
All three men died. Richard Legg, the twenty-six-year-old shift supervisor, was found impaled on the ceiling of the building, driven there by the force of the control rod's ejection. The bodies were so contaminated that conventional burial was not possible. All three men were interred in lead-lined coffins, with portions of their remains buried as low-level radioactive waste at a separate facility.
Investigators never definitively established why the rod was withdrawn so far. The most widely accepted theories involve either a deliberate act or a catastrophic accident during the operation. The remote desert location prevented any off-site radioactive contamination.
The investigation led directly to new international safety standards for reactor design, requiring physical interlocks that make it impossible for a single control rod to be withdrawn so far. No American reactor has experienced a fatal accident since.
