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Nuclear Science and Engineering Division

Argonne’s Major Nuclear Energy Milestones

Argonne’s Nuclear Science and Technology Legacy

Nuclear energy is the largest generator of carbon-free electricity in use today, and it will play an increasing role in worldwide power generation as advanced reactor designs and improved fuel-cycle technologies are brought into commercial application. 

Nearly every commercial reactor in operation today was developed from Argonne research. Building on this heritage, we are supporting the reliable, safe and secure use of nuclear power worldwide – and fostering its increased use in the future by incorporating science and engineering breakthroughs in the design of advanced nuclear energy systems. We capitalize on Argonne’s role as a national center of scientific research and high-performance computing to achieve transformational advances in the performance, safety and economics of nuclear energy systems. Our researchers are developing advanced reactors and fuel-cycle technologies that promise to improve the affordability of nuclear power, enhance the assurance of safety and security, and minimize the discharge of radioactive waste. View more information on Argonne’s current nuclear programs here.


December 2, 1942: Enrico Fermi’s team produces the world’s first sustained and human-controlled nuclear chain reaction at Chicago Pile 1 (CP-1).

March 20, 1943: Chicago Pile 2 (CP-2) achieves criticality. It was CP-1 dismantled and reassembled at the Argonne Forest site in the Cook Country Forest Preserve.

May 15, 1944: Walter Zinn starts Chicago Pile 3, the world’s first heavy-water-moderated nuclear reactor, at Site A.

January 31, 1947: Argonne begins design of a thermal, water-cooled submarine reactor. This work created the design for the Nautilus submarine reactor.

December 20, 1951: Experimental Breeder Reactor 1 (EBR-I) produces the world’s first usable amount of electricity from nuclear energy, lighting four electric light bulbs. EBR-I was originally referred to as CP-4 or ZIP,” short for Zinn’s Infernal Pile.”

June 4, 1953: The Atomic Energy Commission (AEC) announces that EBR-I has achieved the first demonstration of the breeding principle in a nuclear reactor.

February 10, 1954: Chicago Pile 5 (CP-5) goes critical for the first time. This was a heavy water cooled reactor that served as a source of neutrons for research.

March 14, 1955: Thirty-nine students from 19 foreign nations and the United States begin Argonne’s first International School of Nuclear Science and Engineering. The school was organized to carry out the Atoms-for-Peace program.

July 17, 1955: Arco, Idaho, population 1,200, becomes the world’s first community to have all its electrical power provided by nuclear energy. The power was generated by Argonne’s BORAX III reactor.

December 1956:  Achieved first criticality of the Experimental Boiling Water Reactor (EBWR), designed and built by Argonne as the first-ever prototype for a boiling water reactor power plant.  EBWR operation demonstrated safety and dynamic stability of directly employing the core’s water coolant for conversion of fission heat to electricity.

September 1, 1958: Argonne’s Argonaut training reactor arrives in Geneva, Switzerland, after being disassembled at Argonne and shipped to Geneva, then is reassembled at the Second International Conference on Peaceful Uses of Atomic Energy and brought to criticality September 6.  During the final days of the conference, the reactor is dismantled and then shipped back to Argonne and reassembled.

May 14, 1959: The Fuel Fabrication Facility is dedicated in Building 350 in Illinois. It was the nation’s first large-scale plant for making nuclear reactor fuel elements from plutonium. Today, the building has been repurposed for other uses.

November 27, 1962: EBR-I becomes the world’s first reactor to produce electricity with a plutonium core.

August 14, 1964: EBR-II produces 8,000 kilowatts of electricity, its first electricity and the first significant nuclear power for use at the National Reactor Testing Station.

April 18, 1969: The Zero Power Plutonium Reactor (later renamed the Zero Power Physics Reactor) goes critical for the first time and is put into operation at Argonne-West.

November 9, 1978: The first International Meeting on Reduced Enrichment for Research and Test Reactors convened at Argonne.  The RERTR program was formed to convert research reactors and Mo-99 medical isotope production from the use of High Enriched Uranium (HEU) to Low Enriched Uranium (LEU).  The conversions reduce the risks of nuclear proliferation while ensuring that vital peaceful uses of nuclear science can continue.

April 3, 1986: Two tests at EBR-II demonstrate the inherent safety of the Integral Fast Reactor concept, a reactor fueled by metal alloy and cooled by liquid sodium.

July 1988: The US Nuclear Regulatory Commission releases NUREG-1313, qualifying Low Enriched Uranium (LEU) Uranium Silicide Aluminum Dispersion fuel for use in research reactors.  The new fuel developed by Argonne and collaborators would allow many conversions from High Enriched Uranium (HEU) to LEU and became the standard fuel for new Western research reactors deployed.

June 21, 1996: At 11:01 a.m. Idaho time, the electrorefiner at Argonne-West’s Fuel Conditioning Facility began operations when Argonne Director Alan Schriesheim pressed a touch-sensitive computer screen to insert chopped EBR-II fuel.

January 29, 2001: The Argonne News reports that all the sodium coolant has been drained from Experimental Breeder Reactor-II at Argonne-West, marking a major milestone in demonstrating safe decommissioning of a sodium-cooled nuclear reactor.

2009: The internationally sponsored Melt Coolability and Concrete Interaction (MCCI) programs were completed. This series of experiments performed at Argonne provided reactor material data on the nature and extent of core debris cooling during an ex-vessel severe accident in a light water reactor. 

June and August, 2017:  The RERTR Program achieved the 100th conversion metric upon conversion of the GHARR-1 Miniature Neutron Source Reactor in Ghana and verified shutdown of the Alberta Slowpoke in Canada.   Since the program began in 1978, the Argonne and global collaborators converted 70 reactors, confirmed that an additional 28 reactors using HEU shutdown rather than converting, and converted two Mo-99 medical isotope production facilities.  The 100 projects were completed in 33 distinct nations (including the US).