Nuclear Accident at Military Reactor SL-1


On January 3, 1961 a fatal nuclear reactor accident took place in Idaho. The reactor was an Army SL-1 model. The SL-1 designation stood for Stationary Low-power 1. The Army designed the reactor to supply power to remote bases. A similar reactor did provide power in Antarctica for many years. The reactor in Idaho had operated safely for two and a half years, until the evening of January 3.

First Indication of a Problem

The reactor had undergone maintenance during the preceding holidays. On January 3, three military service members prepared the reactor for startup. The first indication of a problem occurred in the central test facility security complex. A fire alarm registered at SL-1 and a fire crew consisting of six firefighters responded.

The firefighters had received many false alarms from the SL-1 facility and were not expecting the conditions they encountered. Upon arriving at the facility, they proceeded to enter the building when they noticed a high radiation detector light was on. They quickly perused the control room and left.

Health Physics Personnel Arrive On Scene

Within minutes, a health physicist arrived with a radiation detector. The health physicist and a fire fighter donned positive pressure respirators and entered the building. The detector the health physicist was carrying read 25 R/hr and the men decided to leave the building and wait for more support. Although not a lethal dose for a short period, the reading was sufficient to indicate to the men that a major accident was in progress.

About an hour later, a team of health physicists arrived with gear enabling them safe entry into the complex. They found two of the men and brought them out. One of the men was still alive but died shortly thereafter. The team removed the injured man’s clothing and his body remained so contaminated that a person standing next to the injured man would receive a lethal dose of radiation within an hour.

Third Service Member Found

An entire day passed before a team of volunteers entered the building to look for the third service member. Even so, it took a few days before they encountered a gruesome scene. They found the third man pinned to the ceiling of the reactor room. The man was pinned by one of the control rods and it took days to remove him because of the high radiation dose. Federal regulations limited the amount of radiation dose that workers could receive and therefore workers could only enter for sixty-five seconds to try to free the man.

Because of the high radioactive contamination levels on the men, the government buried them in lead lined caskets enclosed by concrete vaults. The military buried one of the service members in Arlington National Park and the others in their hometowns in New York and Michigan.

Cause of the Disaster Determined

An investigation concluded that a steam explosion occurred when a service member pulled out a control rod too quickly. The SL-1 was a primitive design and the control rods required manual retraction. The service member, for a reason that remains unknown, removed the control rod too quickly. The quick removal caused a rapid increase in temperature that heated the water to steam almost instantaneously. The steam blew the control rod out and propelled the service member to the ceiling. The reactor then blew apart because of the steam explosion. There never was a nuclear explosion, but the components that held the radioactive fuel blew apart allowing contamination to escape and fill the building. The military dismantled SL-1 and buried the remains in the Idaho desert where they remain to this day.