Sodium Reactor Experiment (SRE)


The SRE was a complex of buildings used to support the earliest nuclear research in commercialized nuclear power in Area IV. The buildings presented here represent the key operations involving nuclear materials at the SRE complex.

Available in the Library section of this website are a number of historical documents related to the Sodium Reactor Experiment (SRE), including information on the design, construction, and operation of the SRE, the SRE accident of 1959, and subsequent decommissioning and closure activities. These documents may be found here.

Also available are materials and video associated with an August 2009 public workshop focused on the SRE accident of 1959. The workshop materials may be found here.

Building 4143 Operations

In the late 1950s, Atomics International was exploring ways to harness atomic energy to produce electricity for homes.

A nuclear reactor cooled by sodium was designed and constructed. Sodium was chosen because it carries heat from the reactor better than other coolants and operates under low pressures. The Sodium Reactor Experiment (SRE), located in building 4143, was the first commercial nuclear power plant to provide electricity to the public by powering the near-by city of Moorpark in 1957. It was the highest power research reactor at Santa Susana at 20 megawatts thermal (or less than 1% of the power of commercial power plants). The Sodium Reactor Experiment operated from 1957 until 1964.

The reactor was supported by numerous auxiliary buildings including the turbine generator and fuel fabrication which are shown in the picture above.

In 1959, the SRE experienced a core damage accident as a result of coolant flow blockage within the reactor. See SRE Accident for more information.

Building 4143 Cleanup

In 1964 the mission of the SRE was completed and the reactor was permanently shut down. Over the next few years the nuclear fuel and associated reactor equipment were removed and sent to other DOE facilities. Decontamination and Decommissioning of the SRE began in 1974 and continued through 1983. This activity included the removal of the reactor and surrounding soil and concrete, as well as underground structures.

Following D&D, a series of final radiological surveys were conducted: Building 4143, Building 4041, Building 4163, Region I, Region II, Region III, Region IV, Region V, Region VI, Region VII, Region VIII, Region IX, and Region X.

An Environmental Evaluation of the SRE was conducted by DOE in 1983 and found that Building 4143 was acceptably free of contamination and recommended that the facility be released for unrestricted use.

Argonne National Laboratory (ANL) performed an independent verification survey in 1984. The survey found that Building 4143 and its surrounding area was decontaminated to below the limits specified in the draft ANSI Standard N13.12 dated 1982. These levels also met the soil cleanup standards at the time.

DOE released the facility and surrounding soil for unrestricted use in September 1985. This survey included all the buildings and land within the SRE complex. The SRE structure was torn down in 1999.

In the summer and fall of 2000, the SRE septic tank, leachfield and associated drainage pipes were excavated. Radiological sampling was performed. All radiological measurements of the SRE septic tank, leachfield and surrounds displayed either background levels of radioactivity or levels that were well below the DOE and DHS approved soil cleanup standards.

In 2001, soil sampling was conducted at SRE for areas that were being planned for excavation as part of the RCRA (chemical cleanup) corrective action effort. No elevated radioactivity levels were found in the area proposed for excavation, but elevated levels were found in two distinct locations in a drainage ditch north and west of the former location of Building 4143. The areas were remediated and resurveyed and shown to be below cleanup standards.

In 2001, the California Department of Health Services (DHS) conducted soil sampling at the location of elevated soil mercury levels east of the prior SRE location. All radionuclide concentrations met the site-wide release criteria.

Historical Site Assessment - SRE

Building 4003 Operations


From 1957 through 1964, Building 4003 was used to assemble fuel for the Sodium Reactor Experiment (SRE). In Building 4003, uranium and thorium metal slugs were loaded into metal tubes, the remaining tube space was filled with sodium, and the tubes were then sealed.

Later activities involved research into the reprocessing of used (or irradiated) fuel assemblies. A process was developed to make a partial separation of used fuel, removing part of the fission products so that the material could be used again as reactor fuel. These bench scale tests were done in a well-shielded 'Hot Cave' located at Building 4003. This research was not developed into a full scale process.

Building 4003 Cleanup

D&D of 4003, including the Hot Cave, was completed in 1975. Some traces of radioactivity were later found in the drain line from this building, and was subsequently removed. Other contaminated facilities removed from Building 4003 included: fume hoods, radioactive waste sinks, drain lines, holding tanks and the facility exhaust system.

A final decommissioning report was prepared in 1982.  Following a final survey performed by the Energy Systems Group (ESG) in 1983, verification surveys (interim and post) were performed by the Argonne National Laboratory (ANL).   The facility was subsequently released for unrestricted use by the DOE in 1985 and was demolished in 1999.

Historical Site Assessment - 4003

Building 4654 Operations

The Interim Storage Facility (Building 4654) was built in 1958 to store SRE fuel elements in 10 below grade storage tubes. It was subsequently used for storage of fuel shipping casks for other reactors. It was taken out of service in 1964.

Building 4654 Cleanup

The facility was decontaminated and decommissioned in 1984. The excavation was backfilled with clean concrete rubble and clean soil. The backfill was sampled to ensure that no contaminated material was used for backfill. The area was then surveyed to verify that no residual contamination remained.

In 1995, the Oak Ridge Institute of Science and Education (ORISE) reviewed Rockwell D&D and characterization survey data from 1985 and suggested that additional sampling was required to adequately demonstrate that the facility could be released. Accordingly, in 1997 Rocketdyne arranged for subsurface core samples of the area be taken at ORISE's direction and then provided the samples to ORISE for analysis. At the same time, Rocketdyne took an additional ~100 surface soil samples. ORISE documented their verification survey in1997 and Rocketdyne documented their final survey in 1999.

A final decommissioning report and certification docket was submitted to DOE in May 1999. On February 1, 2005 DOE provided a letter to Boeing declaring that Boeing and ORISE surveys had confirmed that DOE and DHS approved soil cleanup limits had been met, and that the 4654 site was suitable for release for unrestricted use.


Historical Site Assessment - 4654