System for Nuclear Auxiliary Power (SNAP)

For a historical overview of the SNAP program, please click here.

The SNAP Environmental Test Facility (SETF) 4024


The SNAP Environmental Test Facility, also known as Building 24, was constructed in 1960 for the testing of SNAP nuclear reactors in a simulated space environment. The facility features two large underground test cells which were lined with aluminum to maintain a vacuum and thick walls to provide shielding from the radiation produced by the reactor. A high bay structure above the test cells housed two cranes. A control room was located on one side of the high bay while an vacuum equipment room was placed on the opposite side.

The SETF was used for the testing of three different SNAP nuclear reactors and one critical assembly over a ten year period. From January 1965 to March 1966, a SNAP-10 reactor was tested at a relatively low power (40 kwt) for 10,000 hours. Overall, the facility was used for roughly 20,000 hours of testing.

The operation of the nuclear reactors caused the concrete to become radioactive through a process called activation. Although the last reactor operated in 1971, the activation products remain within the concrete walls today. Samples of walls show the activated concrete extends some fifteen inches into the test cell walls. Samples from other parts of the building indicate no activation or radioactive contamination exists within other parts of the building.


During 2004 and 2005, Boeing surveyed the office areas and equipment rooms and the upper portion of the high bay, down to the basement. Equipment was removed and surveyed, and the stack was removed and surveyed. Survey results confirmed the absence of contamination. Results were sent to California Department of Health Services (DHS) for review, and DHS conducted verification surveys to confirm Boeing data. Subsequently the office and equipment rooms were demolished, and following three DHS approval letters (Letter One, Letter Two, Letter Three), the material was shipped to Kettleman Hills, a Class 1 hazardous waste landfill, in compliance with the 2002 Governor's Moratorium. The building has been proposed to be demolished in a "Non-Time Critical Removal Action" under the DOE's CERCLA authority. Further information can be found in the Engineering Evaluation / Cost Analysis (EE/CA) prepared for building 4024.

The decommissioning and demolition of building 4024 is on hold pending completion of the EIS.

In October 2007, AREVA completed a field sampling plan for the 4024 final status survey.

In January 2008, AREVA completed a characterization survey report for buuilding 4024.

DOE has proposed to remove Building 4024 as part of the ongoing Decommissioning & Decontamination (D&D) of ETEC. The D&D involves the complete removal and off-site disposal of all above and below ground structural components and any radiologically impacted soil that may exist within the facility’s footprint.

Historical Site Assessment - 4024

Building 4010 Operations


The SNAP Experimental Reactor (SER) was a prototype reactor, operated during 1959-1960 at a power level of 50 kWt, for power demonstration and endurance tests. Follow test completion the SER was removed.

The next major program to be conducted in Building 4010 was the SNAP 8 Experimental Reactor (S8ER). The S8ER was the first in a series of reactor tests to be performed to develop a flight-qualified SNAP 8 reactor. The S8ER was a compact, 600-kWt reactor and operated during 1963-1965.

During operation of the S8ER some cracks developed in the tubing (cladding) which served to separate the zirconium-uranium alloy fuel from the liquid metal coolant. The cracks were later determined to be a  result of fuel swelling (resulting from thermal cycling) which in turn stretched the cladding beyond its ductility limit. Some fission products diffused out of the fuel and found their way into the liquid metal flowing through the cracks in the cladding. There was no melting of the fuel or cladding and all of the fission products were contained within the reactor system.

Building 4010 Cleanup

The facility was decommissioned and decontaminated in 1978 and subsequently underwent a final survey.

A verification survey was then performed by Argonne National Laboratory (ANL) in October 1981 and DOE released the building for unrestricted use in December 1982. The building was subsequently demolished.

During recent installation of groundwater wells, tritium was identified in the vicinity of the Building 4010.


Historical Site Assessment - 4010

Building 4012 Operations


Building 4012 was constructed in 1961 to support the continued criticality testing of SNAP reactors. Three SNAP reactor critical assemblies (SCA-4A, SCA-4B, and SCA-5) were tested here for the AEC between 1961 and 1967, and additional criticality tests of space reactor configurations were done here for NASA through 1971.

In 1969 and 1970, the critical assembly machine was modified for use in the Heavy Metal Reflected Fast Spectrum Reactor (HMRFSR) project and operated for the HMRFSR project from 1970 to 1972.

All reactors tested in this facility were called Critical Assemblies which operated at very low powers without the need for any cooling systems.

Building 4012 Cleanup

In 1985, a comprehensive radiological survey of Building 4012 and surrounding areas was performed. Final decontamination and decommissioning (D&D) of the remaining portion of Building 4012 was performed in 1995.

Following D&D efforts, Rocketdyne completed a final radiological survey. The results of the final survey indicated that the facility was suitable for release without radiological restrictions.

A verification survey was conducted by the Oak Ridge Institute of Science and Education (ORISE) in October 1996. ORISE concluded that Building 4012 met DOE guidelines for unrestricted release.

The DHS performed a confirmation survey of Building 4012 on July 31, 1996.

After publication of a Certification Docket, and publication in the Federal Register, DOE released the facility for unrestricted use in October 1997.  DHS concurred with this release in November 1997.  EPA performed a validation survey and document review in January 2000. EPA field measurements confirmed the conclusions reached by both Rocketdyne and ORISE.

Immediately following building demolition in 2003, 24 soil samples were taken in a MARSSIM grid pattern over the original building footprint. Gamma spectroscopy did not detect any man-made gamma emitting radionuclides. Subsequent analysis by an outside laboratory did not detect any man-made radionuclides.


Historical Site Assessment - 4012

Building 4019 Operations


The SNAP Flight System Critical Facility was also called the Acceptance Test Facility. This facility was built in 1962 to do criticality acceptance tests of SNAP reactors before they were to be delivered to the AEC for launch as space power systems. The criticality tests of the S10FS3 reactor were done here, in 1963, before it was operated in the SNAP Environmental Test Facility (Building 4024).

Criticality tests of other flight-qualified SNAP 10 reactors were performed including SNAP 10A which was launched in April 1965.

Three reactors (FS-1, FS-4 and FS-5) were assembled and tested from 1964 to 1965. In 1965, all nuclear materials were removed from Building 4019 when the last SNAP reactor was removed.

All reactors tested in this facility operated at very low powers and brief durations in order to ensure the reactor was able to achieve criticality.

Building 4019 Cleanup

The last SNAP reactor was removed in 1965. In 1988, a radiological survey of the building was performed by Rocketdyne. Later, in 1996, ORISE surveyed the high bay and found a small 3 ft x 3 ft area with fixed contamination, slightly above release limits. In 1998, this area was decontaminated and the entire building, including high-bay test vault, associated rooms and offices were surveyed to verify that they met cleanup standards.

Also in September/October 1998, ORISE and the State DHS performed verification surveys of Building 4019. ORISE issued their verification survey report in February 1999. DHS was asked for concurrence for release for unrestricted use in July 1999. A final D&D report and Certification Docket were prepared for DOE in September 1999.

In October 2001, EPA performed a validation survey and document review of Building 4019. They issued their report in January 2003, demonstrating that federal cleanup standards had been met.

The results of these three surveys demonstrated that the building is suitable for release for unrestricted use. In January 2005, the DOE declared the facility suitable for release for unrestricted use.


Historical Site Assessment - 4019

Building 4059 Operations


Construction of Building 4059 was completed in 1963 including a vacuum system intended to simulate outer space conditions. The reactor and vacuum system were located three floors below ground level. The power level of the reactor was 600 kWt.

Testing of the S8DR began in 1968 and continued through 1969 when the program was terminated. After termination, the reactor core and support systems were removed.

Building 4059 Cleanup

At the end of the nuclear test operations, the reactor core and control system were removed, sent to the Hot Lab for inspection, and then shipped off-site for disposal. At this time, sufficient D&D work was done to make a portion of the facility available for other use. The reactor cell was then sealed up, and the vacuum system prepared for storage. Further D&D of the facility (except for the reactor cell and vacuum system) was then done between June and September, 1978.

D&D of the below-grade part of the facility was initiated in 1987. Between 1987 and 1989, the vacuum system suction pipe and its sand shielding were removed. The next phase involved removing the vacuum chamber and the concrete test cell walls (which contained activation products).

DOE and DHS approved the demolition of 4059 in two Phases: Phase I would be release and demolition of the clean portions of the building and Phase II would be the removal and disposal of the remaining activated concrete in the vaults, pipe chase room and vacuum equipment room. The above grade portion of Building 4059 and the underground non-activated portions of the basement was cleaned, and a final survey was completed in June 1999. In October 1999, Phase I demolition was subjected to verification surveys by the Oak Ridge Institute of Science and Education (ORISE) and the California Department of Health Services (DHS). In October 2000, the EPA and Tetra-Tech performed a document review and validation survey on Phase I.  Since all four surveys confirmed that Phase I was suitable for unrectricted use, DOE gave approval to demolish Phase I of the building. Building demolition occurred in 2003-2004. Removal of the remaining activated concrete occurred in the summer of 2004.

Following removal of the radioactive waste, the soil in the building footprint was sampled by Rocketdyne as part of a final status survey in September 2004; and ORISE and DHS then performed verification soil sampling in October 2004. All soil results indicated the land was suitable for release for unrestricted use. The excavation was backfilled and Boeing performed a MARSSIM final status survey of the backfilled area. Boeing's final status survey was documented in May 2006. DHS performed a verification survey in October 2006.

The final demolition, excavation and sampling of 4059 was featured in the December 2004 public meeting, the March 2005 public meeting, and the June 2005 Health Physics Society Conference in Spokane, Washington.

In February 2008, ORISE performed a verification survey of the building footprint confirming that release limits had been satisfied. Once the area was cleared of radiological controls, DTSC and Rocketdyne conducted characterization sampling for RCRA chemical contaminants at the bottom of the excavation. The excavation was backfilled and a MARSSIM final status survey of the backfilled area was performed. ORISE and DHS performed a verification survey in 2006.

A near-surface groundwater report completed in 2002 identified contamination with organic chemicals.  Additional sampling will be completed at the site of the former Building 4059 as part of the RCRA Corrective Action program.


Historical Site Assessment - 4059

Building 4373 Operations

Building 4373 was used for some of the earliest tests of the SNAP reactor.  These tests observed the nature of critical (i.e., non-sustaining) nuclear tests of the SNAP reactor prototype.

In 1962 the SNAP critical tests concluded, and the facility was modified to include a NaK test loop to support the SNAP Experimental Reactor. Additional liquid metal test loop programs carried out here involved rubidium, mercury test loops and potassium.

Building 4373 Cleanup

Following the end of testing, radiation surveys confirmed the building to be free of contamination. No decontamination was necessary. Following an extended period of inactivity, the facility was subjected to a final survey in 1987. The California Department of Health Services released the facility for unrestricted use in May, 1995. The building was demolished in 1999.

Historical Site Assessment - 4373