Idaho's 52 Reactors
Since 1949, 52 reactors have been built and operated on INL’s 890-square-mile site.
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Nuclear Heritage
On Feb. 18, 1949, the recently formed Atomic Energy Commission (predecessor to today’s U.S. Department of Energy) selected a Naval Proving Ground in Idaho as the site of a planned National Reactor Testing Station. Within just a few years, the site was home to numerous milestones that paved the way for the peaceful use of nuclear energy to generate safe, emission-free electricity.
Although names at the site changed over the years, nearly every operating reactor in the world has technological roots in Idaho. That proud tradition continues today at what is now Idaho National Laboratory, the nation’s leading center for nuclear energy research and development.
52 Reactors
Browse the cards below to find out more information about the 52 reactors that have been built and operated on INL’s 890-square-mile site since 1949.
Advanced Reactivity Measurement Facility No. 1
Advanced Reactivity Measurement Facility No. 1 (1960-1974)
ARMF-I was used to characterize reactor fuels and materials for testing in the Materials Test Reactor, to improve core component performance and reliability.
Advanced Reactivity Measurement Facility No. 2
Advanced Reactivity Measurement Facility No. 2 (1962-1968)
A refinement on ARMF-I, ARMF-II had a “readout” system that automatically recorded measurements on IBM data cards, speeding up data processing.
Advanced Test Reactor
Advanced Test Reactor
(1967-present)
The world’s largest test reactor, ATR simulates the environment within a power reactor for studying the effect of radiation on steel, zirconium and other materials.
Advanced Test Reactor Critical Facility
Advanced Test Reactor Critical Facility
(1964-present)
ATRC is used for preliminary low-power testing of materials before they go into ATR, and also to verify experiment safety.
Argonne Fast Source Reactor
Argonne Fast Source Reactor
(1959-late ‘70s)
Operating at 1 kilowatt, AFSR was used to calibrate instruments and study fast reactor physics. It contributed to better measurement techniques with experimental data instruments.
Boiling Water Reactor Experiment No. 1
Boiling Water Reactor Experiment No. 1 (1953-1954)
BORAX-I was designed to test boiling water as a reactor moderator and coolant. It was deliberately blown up in 1954 to learn more about its operating limits.
Boiling Water Reactor Experiment No. 2
Boiling Water Reactor Experiment No. 2
(1954-1955)
BORAX-II continued testing boiling water reactors, this time at a power level capacity of 6 megawatts. Tests used fuels with varying enrichments of uranium-235.
Boiling Water Reactor Experiment No. 3
Boiling Water Reactor Experiment No. 3
(1955-1956)
BORAX-III was 15 megawatts and connected to a 2,000-kw turbine/generator. The night of July 17, 1955, it produced sufficient power to momentarily light the city of Arco, Idaho.
Boiling Water Reactor Experiment No. 4
Boiling Water Reactor Experiment No. 4
(1956-1958)
BORAX-IV, at 20 megawatts, tested fuel elements made from mixed oxides (ceramics) of uranium and thorium. These materials could operate longer in a reactor’s extreme heat before they failed.
Boiling Water Reactor Experiment No. 5
Boiling Water Reactor Experiment No. 5
(1962-1964)
BORAX-V tested the feasibility of an integral, nuclear superheat system, producing superheated or dry steam entirely by nuclear means for the first time.
Cavity Reactor Critical Experiment
Cavity Reactor Critical Experiment
(1967-early ‘70s)
CRCE came from a NASA program to investigate nuclear propulsion in space. The concept called for uranium in a gaseous state in the reactor cavity with hydrogen propellant flowing around it.
Coupled Fast Reactivity Measurement Facility
Coupled Fast Reactivity Measurement Facility
(1968-1991)
Advanced Reactivity Measurement Facility No. 2 was modified in 1968 and renamed CFRMF. A section of the core was modified to provide data on unmoderated neutrons, contributing to the development of fast neutron reactors.
“I reached over across the front seat of the car and with my finger drew four circles for test loops, and then a snakelike fuel line partially around each loop… The more we looked at that strange arrangement, the better it looked.”
— Deslonde deBoisblanc, on the inspiration for ATR’s core configuration striking him while driving home from the Site.
Critical Experiment Tank
Critical Experiment Tank
(1958-1961)
The low-power CET reactor was part of the Aircraft Nuclear Propulsion program. It produced neutrons used to calibrate various types of neutron sensors and chambers.
Engineering Test Reactor
Engineering Test Reactor
(1957-1981)
ETR evaluated fuel, coolant and moderator materials in conditions similar to power reactors. Over 24 years, it was modified for test programs related to breeder reactors.
Engineering Test Reactor Critical Facility
Engineering Test Reactor Critical Facility
(1957-1982)
ETRC was a full-scale, low-power nuclear facsimile of the ETR, used to test the characteristics of experiments planned for ETR, saving time and money.
Experimental Beryllium Oxide Reactor
Experimental Beryllium Oxide Reactor
EBOR’s purpose was to develop beryllium oxide as a neutron moderator in high-temperature gas-cooled reactors. The project was canceled in 1966 as graphite gained favor as a moderator.
Experimental Breeder Reactor I
Experimental Breeder Reactor I
(1951-1963)
EBR-I produced the world’s first usable electricity from nuclear energy. It used unmoderated enriched uranium for fuel and sodium-potassium alloy (NaK) as coolant. It was designated a National Historic Landmark in 1966 and remains open for visits and tours.
Experimental Breeder Reactor II
Experimental Breeder Reactor II
(1962-1994)
EBR-II was built to demonstrate on-site fuel reprocessing as an add-on to a liquid-metal-cooled, fast-breeder-reactor power plant. The reactor operated submerged in a tank of liquid sodium coolant.
Experimental Organic Cooled Reactor
Experimental Organic Cooled Reactor
(never operated)
EOCR was intended to build on research from OMRE but was placed on standby in 1962 when Atomic Energy Commission leadership decided the concept would not meaningfully improve nuclear power plant performance.
Fast Spectrum Refractory Metals Reactor
Fast Spectrum Refractory Metals Reactor
(1962-1968)
This low-power critical facility collected data for the 710 Reactor, a fast-spectrum refractory-metal reactor concept considered for generating power in space.
Gas Cooled Reactor Experiment
Gas Cooled Reactor Experiment
(1960-1961)
GCRE generated heat but no electricity for the U.S. Army, which wanted to develop mobile nuclear power plants. GCRE provided engineering data for improved components, as well as training.
Heat Transfer Experiment No. 1
Heat Transfer Experiment No. 1
(1955-1956)
During the 1950s, the U.S. Air Force sought to build a nuclear-powered jet airplane using direct-cycle heat transfer engineering. HTRE-I produced 20 megawatts of heat energy on a test stand using enriched uranium fuel clad in nickel-chromium.
Heat Transfer Experiment No. 2
Heat Transfer Experiment No. 2
(1957-1961)
To irradiate fuel elements too large to fit in the MTR, the Aircraft Nuclear Propulsion program drilled a hole in the center of HTRE-I and converted it to a materials test reactor, advancing the technology of high-heat ceramic reactor fuels.
Heat Transfer Experiment No. 3
Heat Transfer Experiment No. 3
(1958-1960)
Anticipating use in an airframe, HTRE-I’s reactor, engine, shielding and heat transfer systems were arranged in a horizontal configuration. President John F. Kennedy canceled the Aircraft Nuclear Propulsion program in March 1961, and the reactors are now on display at EBR-I.
“Electricity flows from atomic energy. Rough estimate indicates 45 kw.”
— Walter Zinn’s entry in the EBR-I logbook at 1:23 p.m. on Dec. 20, 1951.
High Temperature Marine Propulsion Reactor
High Temperature Marine Propulsion Reactor
(1962-1964)
A low-power critical experiment operated at Test Area North to explore the feasibility of an air-cooled, water-moderated system for nuclear-powered merchant ships. This project was discontinued in December 1964.
Hot Critical Experiment
Hot Critical Experiment
(1958-1961)
HOTCE was designed to obtain information on measurement techniques for high-temperature reactors. Part of the Aircraft Nuclear Propulsion program, it operated in the Critical Experiment cell of the Low Power Test Facility at TAN.
Large Ship
Reactor A
Large Ship Reactor A
(1958-1994)
The A1W-A plant was one of a pair of prototype reactors (A1W A and B) for the USS Enterprise, the U.S. Navy's first nuclear-powered aircraft carrier. Located at the Naval Reactors Facility, the pair of reactors simulated one of four pairs that would power the Enterprise (CVN-65).
Large Ship
Reactor B
Large Ship Reactor B
(1959-1987)
A1W-B was the second of a pair of prototype
reactors for the USS Enterprise (CVN-65) . The
A1W A and B plants were the first in which
two reactors powered one ship propeller shaft. Enterprise had four pairs of reactors driving the ship to record setting speeds.
Loss of Fluid Test Facility
Loss of Fluid Test Facility
(1973-1985)
LOFT was a scale-model version of a commercial pressurized water plant built chiefly to explore the effects of loss-of-coolant accidents. 38 nuclear power tests were conducted in this reactor.
Materials Testing Reactor
Materials Testing Reactor
(1952-1970)
MTR’s high-flux radiation fields made it possible to accelerate the screening of potential reactor materials. In 1958, it became the first reactor to operate using plutonium-239 as fuel. Its materials testing was supplanted in the late ‘60s by the Advanced Test Reactor.
Mobile Low-Power Reactor No. 1
Mobile Low-Power Reactor No. 1
(1961-1964)
ML-1 was a mobile, low-power nuclear plant for the U.S. Army designed to be transported either by standard cargo plane or standard Army low-bed trailers. The Army phased out its reactor development program around 1965.
Natural Circulation Reactor
Natural Circulation Reactor
(1965-1995)
The S5G was the prototype of a pressurized-water reactor for USS Narwhal, capable of operating in either a forced or natural circulation flow mode. To prove that the design concept would work at sea, the prototype was built in a submarine hull section capable of simulating a ship’s rolling motion.
Neutron Radiography Facility
Neutron Radiography Facility
(1977-present)
Using two neutron beams from a 250-kilowatt reactor, NRAD produces neutron radiographs showing the internal condition of highly irradiated test specimens without physically cutting into the specimen.
Nuclear Effects Reactor
Nuclear Effects Reactor
(1968-1970)
FRAN was a small-pulsed reactor used to test the performance of new detection instruments being developed for reactor control purposes. It was moved back to DOE’s Lawrence Livermore National Laboratory in 1970.
Organic Moderated Reactor Experiment
Organic Moderated Reactor Experiment
(1957-1963)
OMRE demonstrated the feasibility of using a liquid hydrocarbon as both coolant and moderator. The waxy coolant was considered promising because it liquified at high temperatures but didn’t corrode metal.
Power Burst Facility
Power Burst Facility (1972-1985)
PBF’s purpose was to test light water reactor fuel rods under representative accident conditions. Data from these tests were used to develop and validate fuel behavior computer codes for the Nuclear Regulatory Commission.
“Well, we’ve got us a reactor.”
— Leonard “Bill” Johnston, manager of the AEC’s Idaho Field Office, when MTR went critical for the first time.
Reactivity Measurement Facility
Reactivity Measurement Facility
(1954-1962)
RMF was a detector reactor that measured reactivity changes in materials irradiated in the MTR or ETR. It was used to assay new and spent fuel elements and to assist in experiment scheduling.
Shield Test Pool Facility
Shield Test Pool Facility
(1961-1964)
Situated in a water-filled pool at Test Area North, the SUSIE reactor was used for bulk shielding experiments. After the Aircraft Nuclear Propulsion program was discontinued, SUSIE continued to be used by other National Reactor Testing Station programs.
Special Power Excursion Reactor Test No. I
Special Power Excursion Reactor Test No. I
(1955-1964)
SPERT-I was the first in a series of four safety-testing reactors designed to study the behavior of reactors when their power level changed rapidly. The tests demonstrated the damage-resistant capabilities of low-enrichment uranium-oxide fuel pins.
Special Power Excursion Reactor Test No. II
Special Power Excursion Reactor Test No. II
(1960-1964)
SPERT-II was a closed pressurized water reactor with coolant flow systems designed for light or heavy water.
Special Power Excursion Reactor Test No. III
Special Power Excursion Reactor Test No. III
(1958-1968)
SPERT-III was developed to study nuclear reactors’ inherent safety characteristics, providing the widest practical range of control over three variables: temperature, pressure and coolant flow.
Special Power Excursion Reactor Test No. IV
Special Power Excursion Reactor Test No. IV
(1962-1970)
SPERT-IV was an open-tank, twin-pool facility that permitted detailed studies of reactor stability as affected by hydrodynamic effects such as forced coolant flow.
Spherical Cavity Reactor Critical Experiment
Spherical Cavity Reactor Critical Experiment
(1972-1973)
SCRCE was the final experiment for NASA to determine the feasibility of a reactor going critical with a gaseous core of uranium. The spherical shape was considered a more likely geometry for application in a rocket.
Stationary Low-Power Reactor
Stationary Low-Power Reactor
(1958-1961)
The SL-1 reactor was designed for the U.S. Army as a prototype of a low-power, boiling-water reactor plant to be used in geographically remote locations. It malfunctioned in January 1961, killing three men.
“What happened here merely raised the curtain on a promising drama in our long journey to a better life.”
— President Lyndon B. Johnson during the dedication of Experimental Breeder Reactor-I as a National Historic Landmark in 1966.
Submarine Thermal Reactor
Submarine Thermal Reactor
(1953-1989)
The S1W was installed inside two submarine hull sections matching the size and specifications of the USS Nautilus. After startup, S1W accomplished a simulated 96-hour voyage nonstop from Newfoundland to Ireland, proving the feasibility of atomic ship propulsion long before Nautilus went to sea. It was later used to test advanced equipment and provide training for Navy personnel.
Systems for Nuclear Auxiliary Power 10A Transient No. 1
Systems for Nuclear Auxiliary Power 10A Transient No. 1
(Early 1960s)
The SNAPTRAN program at Test Area North involved three test series and three reactors investigating the behavior of fuels under large-transient, power-excursion conditions.
Systems for Nuclear Auxiliary Power 10A Transient No. 2
Systems for Nuclear Auxiliary Power 10A Transient No. 2
(1965)
This test version of the small space reactor, SNAP 10A/2, was intentionally destroyed to provide information on the dynamic response, fuel behavior and inherent shutdown mechanisms of these reactors in an open-air environment.
Systems for Nuclear Auxiliary Power 10A Transient No. 3
Systems for Nuclear Auxiliary Power 10A Transient No. 3
(1964)
SNAPTRAN-3 simulated the accidental fall of a space reactor into water or wet earth. It demonstrated that the reactor would destroy itself immediately instead of building up a high inventory of radioactive fission products.
Thermal Reactor Idaho Test Station
Thermal Reactor Idaho Test Station
(1964)
Located at Test Area North, THRITS’ nuclear core was arranged in two halves, in a vertical honeycomb matrix. The two halves could be brought together to form a critical fuel mass, allowing operators to obtain basic physics and design data.
Transient Reactor
Test Facility
Transient Reactor Test Facility
(1959-1994, 2017-present)
TREAT is a uranium-oxide-fueled, graphite-moderated, air-cooled reactor designed to produce short, controlled bursts of nuclear energy to simulate accident conditions leading to fuel damage. The data helps refine computer simulations of reactor accidents, leading to better, safer reactors and fuels.
Zero Power Physics Reactor
Zero Power Physics Reactor
(1969-1992)
A low-power critical facility, ZPPR provided reactor physics data for fast neutron spectrum reactors, from tiny space-power reactors to large commercial breeder reactors.
Zero Power Reactor No. 3
Zero Power Reactor No. 3
(1955-1970)
ZPR-III was a low-power, split-table reactor that achieved criticality by bringing two halves of a fuel configuration together. Experimental critical assembly results in this field were almost completely lacking before this reactor started up.
