The Liquid-Metal Fast Neutron Reactor Has a Long History

In the U.S., several fast neutron reactors have been designed, and five of them have achieved operation (Figure 2). There has also been one U.S. Navy application of a liquid-metal reactor.

2. Evolution of the PRISM reactor. Source: GE Hitachi Nuclear Energy

Experimental Breeder Reactor-1 (EBR-I, 1949–1964). As part of the National Reactor Testing Station (now known as the Idaho National Laboratory), construction of EBR-I started in late 1949 in the desert, about 18 miles southeast of Arco, Idaho. In 1951, it became the world’s first electricity-generating nuclear power plant when it produced sufficient electricity to illuminate four 200-watt lightbulbs, and subsequently generated enough electricity to power its own building. However, the actual design purpose of EBR-I was not focused on electricity production but rather on validating the breeder reactor concept. In 1953, experiments revealed the reactor was producing additional fuel during fission, as designed. However, on Nov. 29, 1955, EBR-I suffered a partial meltdown during a coolant flow test. After being repaired, the EBR-1 continued to operate until it was deactivated in 1964 and replaced with the EBR-II. The EBR-I was declared a National Historic Landmark in 1965.

EBR-II (1963–1994). The EBR-II was a 19-MWe (62.5-MWth) demonstration reactor, providing heat and power to the Idaho facility from 1963 through 1994. The EBR-II demonstrated a complete sodium-cooled breeder reactor power plant with on-site reprocessing of metallic fuel between 1964 and 1969. The emphasis then shifted to testing materials and fuels (metal and ceramic oxides, carbides and nitrides of uranium and plutonium) for larger fast reactors.
The EBR-II became the basis of the U.S. Integral Fast Reactor (IFR) program. The plan was to develop a fully integrated system with electrometallurgical “pyroprocessing,” fuel fabrication, and a fast reactor in the same complex. The reactor could be operated as a breeder reactor, or not. About $46 million of IFR funding was provided by a Japanese utility consortium. The IFR program goals demonstrated the inherent safety concepts of the EBR-II apart from engineered controls in April 1986. The program was terminated by the Clinton administration in 1994.

USS Seawolf (1957–1987). USS Seawolf (SSN-575) was the only U.S. submarine built with a sodium-cooled nuclear reactor. The submarine was launched on July 21, 1955, and commissioned on March 30, 1957. Although the sodium-cooled reactor reduced the size of machinery spaces by nearly 40% and was more efficient than a water-cooled reactor, concerns posed by the liquid sodium coolant led to the selection of the pressurized water reactor (PWR) as the Navy’s standard. The USS Seawolf was converted to a PWR and returned to service in 1960. The submarine was decommissioned on Mar. 30, 1987, after 30 years of service.

Fermi 1 (1957–1972). The 94-MWe prototype, located in Frenchtown Charter Township, Mich., was first U.S. commercial fast breeder reactor. Construction started in 1957, but it operated for only three years before a coolant problem caused overheating and partial damage to the fuel on Oct. 5, 1966. Following an extended shutdown that involved fuel replacement, repairs to the vessel, and cleanup, Fermi 1 was restarted in 1970 and continued to operate intermittently until Sept. 22, 1972. Fermi 1’s license was not renewed, and it was officially decommissioned Dec. 31, 1975.

The Southeast Experimental Fast Oxide Reactor (SEFOR) (1965–1972). The deactivated 20-MWth SEFOR reactor is located in Cove Creek Township, near Fayetteville, Ark. The reactor was built in 1965 and was used to confirm the inherent safety features of the oxide fuel/sodium-cooling configuration. The fuel and irradiated sodium coolant were removed and taken offsite in 1972, and the facility was placed in safe storage. The reactor was acquired by the University of Arkansas in 1975. SEFOR was designated a Nuclear Historic Landmark site in October 1986.
Clinch River Breeder Reactor (CRBR)  Project (1970–1983). Congress authorized the CRBR program in 1970 as a cooperative effort between industry and the U.S. government to build a demonstration-scale sodium-cooled reactor. The plant was to be located within Tennessee Valley Authority’s system at a site on the Clinch River just west of Oak Ridge, Tenn. The CRBR was designed to produce plutonium from the abundant uranium-238 isotope (hence the term “breeder”). The plutonium would be recovered from the reactor fuel and then used in water-cooled reactors as a constituent of a mixed oxide of uranium and plutonium.
Licensing began in 1973, and the project environmental impact statement was submitted on Dec. 31, 1975. The plant design was reported as 90% complete, and $500 million of reactor components were on order by Sept. 30, 1981. The Reagan administration made the CRBR project a funding priority in fiscal year 1982 and said it “should be constructed in a timely and expeditious manner.” However, on Oct. 26, 1983, the U.S. Senate terminated funding for the project.

Fast Flux Test Facility (FFTF, 1978–1993, 1997–2001). Construction of the 400-MWth FFTF in Hanford, Wash., was completed in 1978; initial operation followed in 1980. From April 1982 to April 1992, it operated as a national research facility to test various aspects of commercial reactor design and operation, especially relating to breeder reactors. The FFTF is not a breeder reactor itself, but rather a sodium-cooled fast neutron reactor. By December 1993, the number of uses for the reactor was diminishing, so the decision was made to deactivate it. In January 1997, the DOE ordered that the reactor be maintained in a standby condition, pending a decision to incorporate it into the U.S. Government’s tritium production program for both medical and fusion research. In December 2001, deactivation continued after it was determined that the FFTF was not needed for tritium production. In May 2005, the core support basket was drilled to drain the remaining sodium coolant, effectively making the reactor unusable. In April 2006, the FFTF was honored by the American Nuclear Society as a National Nuclear Historic Landmark.

Recent Advanced Reactor and Nuclear Fuel Cycle Programs (1999–Present). The U.S. slowly restarted its advanced reactor and nuclear fuel cycle programs via the Generation IV Nuclear Energy Systems program, the Generation IV International Forum, Advanced Fuel Cycle Initiative, and the Global Nuclear Energy Partnership (GNEP). (See “Developing the Next Generation of Reactors,” April 2008 in the POWER archives at www.powermag.com.) In April 2009, the DOE announced the cancellation of the U.S. domestic component of GNEP, and in June 2009 it announced that it is no longer pursuing domestic commercial reprocessing of nuclear fuel. The program is now referred to as the International Framework for Nuclear Energy Cooperation.