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Experimental Breeder Reactor I

Coordinates: 43°30′41″N 113°00′23″W / 43.51132°N 113.0064°W / 43.51132; -113.0064
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Experimental Breeder Reactor No. 1
Experimental Breeder Reactor Number 1 in Idaho, the first power reactor
Experimental Breeder Reactor I is located in Idaho
Experimental Breeder Reactor I
Experimental Breeder Reactor I is located in the United States
Experimental Breeder Reactor I
LocationButte County, Idaho, US
Nearest cityArco, Idaho
Coordinates43°30′41″N 113°00′23″W / 43.51132°N 113.0064°W / 43.51132; -113.0064
ArchitectAtomic Energy Commission
NRHP reference No.66000307
Significant dates
Added to NRHPOctober 15, 1966[1]
Designated NHLDecember 21, 1965[2]

Experimental Breeder Reactor I (EBR-I) is a decommissioned research reactor and U.S. National Historic Landmark located in the desert about 18 miles (29 km) southeast of Arco, Idaho. It was the world's first breeder reactor.[3] At 1:50 p.m. on December 20, 1951, it became one of the world's first electricity-generating nuclear power plants when it produced sufficient electricity to illuminate four 200-watt light bulbs.[4][5] EBR-I subsequently generated sufficient electricity to power its building, and continued to be used for experimental purposes until it was decommissioned in 1964. The museum is open for visitors from late May until early September.[citation needed]


As part of the National Reactor Testing Station (since 2005 Idaho National Laboratory), EBR-I's construction started in late 1949. The reactor was designed and constructed by a team led by Walter Zinn at the Argonne National Laboratory[6] Idaho site, known as Argonne-West. In its early stages, the reactor plant was referred to as Chicago Pile 4 (CP-4) and Zinn's Infernal Pile.[7] Installation of the reactor at EBR-I took place in early 1951 (the first reactor in Idaho) and it began power operation on August 24, 1951. On December 20 of that year, EBR-I produced electricity for its first time. The following day, the reactor produced enough power to light the whole building. The EBR-I produced 200 kW of electricity out of 1.4 MW of heat generated by the reactor.[8]

The production of electricity at EBR-I is the first time that a reactor created in-house available electricity, and it is sometimes misreferred to as the first time that a nuclear reactor has ever created electricity. However, the world's first electricity produced by a nuclear reactor occurred during an experiment 3 years earlier in September 1948 at the X-10 Graphite Reactor at the Oak Ridge National Lab in Tennessee.[9] Later in 1955, another nuclear milestone was reached when an experimental boiling water reactor plant called BORAX-III (also designed, built, and operated by Argonne National Laboratory) was connected to external loads, powering the nearby city of Arco, Idaho, the first time a city had been powered solely by nuclear power.[10]

Part of the core after the 1955 partial meltdown

The design purpose of EBR-I was not to produce electricity but instead to validate nuclear physics theory that suggested that a breeder reactor should be possible. In 1953, experiments revealed the reactor was producing additional fuel during fission, thus confirming the hypothesis. On November 29, 1955, the reactor at EBR-I suffered a partial meltdown during a coolant flow test. The flow test was trying to determine the cause of unexpected reactor responses to changes in coolant flow. It was subsequently repaired for further experiments, which determined that thermal expansion of the fuel rods and the thick plates supporting the fuel rods was the cause of the unexpected reactor response.[11]

Besides being one of the world's first to generate electricity from atomic energy, EBR-I was also the world's first breeder reactor and the first to use plutonium fuel to generate electricity (see also the Clementine nuclear reactor). EBR-I's initial purpose was to prove Enrico Fermi's fuel breeding principle, a principle that a nuclear reactor can produce more fuel atoms than it consumes. EBR-I proved this principle.[12]


EBR-I used uranium metal fuel and NaK primary coolant.[13] It was in this identical to the initial configuration of the later Dounreay Fast Reactor which first went critical in 1959.

The primary liquid metal coolant flows by gravity from the supply tank through the reactor core, where it absorbs heat. Then, the coolant flows to heat the exchanger, where it gives up this heat to the secondary coolant, another liquid metal. The primary coolant is returned to the supply tank by an electromagnetic pump. The secondary coolant is pumped to the boiler, where it gives up its heat to water, generating steam. This steam passes to the turbine, which is how electricity is produced. This steam then condenses and returned to the boiler by a water pump.[14]

Decommission and legacy[edit]

EBR-I was deactivated by Argonne in 1964 and replaced with a new reactor, Experimental Breeder Reactor II.

It was declared a National Historic Landmark in 1965[2][15] with its dedication ceremony held on August 25, 1966, led by President Lyndon Johnson and Glenn T. Seaborg.[16] It was also declared an IEEE Milestone in 2004.[17]


See also[edit]


  1. ^ "Experimental Breeder Reactor No. 1". NPGallery. National Park Service. Retrieved October 27, 2018.
  2. ^ a b "Experimental Breeder Reactor No. 1". National Historic Landmark summary listing. National Park Service. Archived from the original on January 10, 2008. Retrieved February 6, 2008.
  3. ^ Breeder reactor. Retrieved December 31, 2017. {{cite encyclopedia}}: |website= ignored (help)
  4. ^ "EBR-I (Experimental Breeder Reactor-I)". Argonne National Laboratory.
  5. ^ Rick Michal (November 2001). "Fifty years ago in December: Atomic reactor EBR-I produced first electricity" (PDF). Nuclear News. American Nuclear Society.
  6. ^ "Nuclear Reactors Built, Being Built, or Planned in the United States as of June 30, 1970". U.S. Department of Energy, Office of Scientific and Technical Information. October 31, 1970. doi:10.2172/4115425. {{cite journal}}: Cite journal requires |journal= (help)
  7. ^ Argonne’s Nuclear Science and Technology Legacy: Chicago Pile reactors create enduring research legacy part of the Argonne National Laboratory Highlights in the period 1942–1949
  8. ^ "Nuclear energy for peace: the birth of nuclear energetics". Archived from the original on July 26, 2011. Retrieved July 21, 2009.
  9. ^ Garceau, Gil. "World's First Nuclear Power Generated Electricity from Jensen #50 on the X 10 Graphite Reactor 1948". YouTube. Retrieved April 4, 2022.
  10. ^ "AEC Press release for BORAX-III lighting Arco, Idaho". U.S. Department of Energy, Argonne National Laboratory. 1999. Retrieved July 26, 2012.
  11. ^ The Story of the Borax Nuclear Reactor and the EBR-I Meltdown — Ray Haroldsen ISBN 978-1-56684-706-3
  12. ^ "Experimental Breeder Reactor I". ASME. Retrieved December 18, 2017.
  13. ^ "Experimental Breeder Reactor I" (PDF). ASME. Retrieved October 28, 2019.
  14. ^ "EBR-1 in Photos". www.ans.org. Retrieved January 13, 2024.
  15. ^ Blanche Higgins Schroer (June 12, 1976). "Experimental Breeder Reactor #1" (PDF). National Register of Historic Places Inventory Nomination Form. National Park Service. Retrieved June 22, 2009. and Accompanying 4 photos, from 1975. (1.43 MB)
  16. ^ "EBR-I now open to the public for tours". Idaho National Laboratory. May 26, 2016. Retrieved December 18, 2017.
  17. ^ "Milestones:Experimental Breeder Reactor I, 1951". IEEE Global History Network. IEEE. Retrieved August 3, 2011.

External links[edit]