Organic Moderated Reactor and the Sodium Graphite Reactor
Both the Organic Moderated Reactor and the Sodium Graphite Reactor were low-power critical experiment facilities. Building 4009 was originally constructed in 1958 to house both critical facilities. Although both the OMR and SGR operated from 1958 to 1967, they were used for different purposes.
The Organic Moderated Reactor (OMR) Critical Facility was used for testing uranium fueled reactors moderated and cooled by organic liquids. Various types and configurations of fuel elements and core geometries were tested. The OMR was a pilot plant to test the possibility of developing a larger nuclear power plant that would provide commercial electricity.
The Sodium Graphite Reactor (SGR) Critical Facility was used to determine the operating characteristics of reactors with cores cooled by sodium and moderated with graphite. The basic critical assembly consisted of graphite cylinders into which various amounts and configurations of fuel and sodium could be inserted. The building 4009 SGR was a pilot plant to test the possibility of developing larger nuclear power plant that would provide commercial electricity.
In 1967, all equipment associated with the OMR and SGR was removed. The building continued to be used for storage and testing . In the late 1980s, the west high bay was used for high-energy rate forging (HERF) that utilized depleted uranium.
A radiation survey of the OMR high bay and supporting rooms was performed in 1988. The grounds and drainlines were sampled in 1989. The SGR high bay and roof were surveyed in 1995. The California Depatment of Health Services (DHS) performed verification surveys of the OMR high bay in 1995 and the whole building in 1998. Based on the results of these surveys, the DHS released Building 4009 for unrestricted use in January 1999.
In December 2002, EPA published a document review of prior surveys, confirming their results.