The Sodium Reactor Experiment was a pioneering nuclear power plant built by Atomics International at the Santa Susana Field Laboratory near Simi Valley, California. The reactor operated from 1957 to 1964. On July 12, 1957 the Sodium Reactor Experiment became the first nuclear reactor in California to produce electrical power for a commercial power grid by powering the nearby city of Moorpark. In July 1959, the reactor experienced a partial meltdown when 13 of the reactor's 43 fuel elements partially melted, and radioactive gas was released into the atmosphere. The reactor was repaired and restarted in September 1960. In February 1964, the Sodium Reactor Experiment was in operation for the last time. Removal of the deactivated reactor was completed in 1981. Technical analyses of the 1959 incident have produced contrasting conclusions regarding the types and quantities of radioactive materials released. Members of the neighboring communities have expressed concerns about the possible impacts on their health and environment from the incident. In August 2009 the Department of Energy hosted a community workshop to discuss the 1959 incident.
Location The Sodium Reactor Experiment facility was situated in a northwestern administrative section (known as Area IV) on a mountaintop known as The Hill of the Santa Susana Field Laboratory, about 30 miles (48 km) northwest of downtown Los Angeles in Simi Valley. When the Sodium Reactor Experiment was active, the Santa Susana Field Laboratory was operated by two business divisions of the North American Aviation company. The Rocketdyne division conducted liquid-propellant rocket engine testing and development at the site, while the Atomics International division focused on the development of commercial nuclear reactors and compact nuclear reactors for outer-space applications.
History In 1954, the United States Atomic Energy Commission announced plans to test the basic nuclear reactor designs then under study by building five experimental reactors in five years. The Sodium Reactor Experiment, designed by Atomics International, was one of the chosen reactors. Design of the Sodium Reactor Experiment began in June 1954, and construction was underway in April 1955. A local utility company, Southern California Edison, installed and operated a 6.5 MW electric-power generating system. Controlled nuclear fission began on April 25, 1957.
The Los Angeles Times published a front-page story when Moorpark was supplied with nuclear-generated electricity. Edward R. Murrow’s television program See It Now featured the event as a special news report, broadcast on November 24, 1957. In July 1958, Atomics International produced a film describing the construction of the Sodium Reactor Experiment facility. The Sodium Reactor Experiment used sodium as a coolant. Heat generated in the reactor was transported by liquid sodium through the reactor facility piping system. The pumps used to move the sodium were hot-oil centrifugal pumps modified for use in a sodium system. A support system used tetralin (an oil-like fluid) to cool the pump seals, which prevented leakage of hot sodium at the pump shaft. In July 1959, tetralin seeped into the primary coolant system through a pump seal and was decomposed by the high-temperature sodium. The decomposed tetralin clogged several narrow cooling channels used by the sodium system to remove heat from the reactor fuel elements. As the tetralin residues clogged the reactor's internal cooling channels, 13 of the reactor's 43 fuel elements overheated and were damaged. The exact date of the fuel damage is unknown, but is believed to have occurred between July 12 and 26. At the time, operators were aware of unusual reactor behavior but were unaware of the damage. They continued operations for several days before shutting down the reactor for examination. When the operators attempted to remove the fuel elements from the reactor, most elements were removed normally but some were found to be jammed. Pieces of the damaged fuel elements fell to the bottom of the reactor. During the following months, Atomics International personnel removed all the jammed fuel elements, retrieved the pieces of dropped fuel elements, cleaned the sodium system and installed a new reactor core. The Sodium Reactor Experiment was restarted on September 7, 1960, nearly fourteen months after the accident. In 1961, Atomics International produced another movie explaining the accident and the recovery operation. The Sodium Reactor Experiment operated until February 15, 1964.
In 1964, several modifications were made to the reactor. These modifications were completed in May 1965, but the Atomic Energy Agency and Atomics International decided to close the reactor rather than restart it. The facility decommissioning began in 1976 with the removal of the reactor core, support systems and contaminated soil under the structure. The source of the contaminated soil underneath the building does not appear related to the 1959 reactor incident. Decommissioning was completed in 1981. In 1982, Atomics International produced a film on the decommissioning and decontamination of the Sodium Reactor Experiment. A group of certified health physicists from the Argonne National Laboratory conducted independent sampling to determine if the then-current minimum cleanup standards for radioactive residue were met. In 1985, the United States Department of Energy completed its evaluation of the survey reports and certified “…that there is no evidence the facilities pose a radiological threat to either personnel or the environment”. In 1999, the remaining structures were demolished and removed from the site.
Principles
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