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Tehran Research Reactor (TRR)

  • Location
    Tehran Nuclear Research Center
  • Type
    Nuclear-Research Reactors
  • Facility Status

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The Tehran Research Reactor (TRR) is a 5MWt pool-type light water research reactor. The United States supplied the reactor to Iran in 1967, together with hot cells for the production of medical isotopes and 5.58kg of highly enriched uranium (HEU) fuel. 1 The reactor is housed at the Tehran Nuclear Research Center and is capable of producing up to 600 grams of plutonium annually. 2 In 1987, Argentina’s Applied Research Institute converted the reactor to run on low enriched uranium (LEU) instead of HEU, and Argentina subsequently supplied Iran with 115.8kg of safeguarded LEU. 3 Between 1988 and 1992, Iran conducted undeclared reprocessing experiments with fuel pellets irradiated in the TRR. 4

In 2009 the TRR was expected to run out of fuel within the following few years. 5 After the failure of the proposed LEU-fuel exchange deal between Iran on the one hand, and Russia and France on the other, Iran declared it had started enriching uranium to up to 20% in order to manufacture fuel pellets for the TRR. 6 In February 2012, Iran loaded the first batch of indigenously-produced fuel rods into the Tehran research reactor. 7

In early 2013, the TRR began testing prototype natural uranium fuel assemblies for eventual use in the IR-40 heavy water reactor. 8

In July 2021, Iran announced that it would begin producing uranium silicide fuel for the TRR to produce medical isotopes.9


Light-water reactor
Light-water reactor: A term used to describe reactors using ordinary water, where the hydrogen is hydrogen-1, as a coolant and moderator, including boiling water reactors (BWRs) and pressurized water reactors (PWRs), the most common types used in the United States.
Research reactor
Research reactor: Small fission reactors designed to produce neutrons for a variety of purposes, including scientific research, training, and medical isotope production. Unlike commercial power reactors, they are not designed to generate power.
Medical isotopes
See entry for Radioisotopes.
Highly enriched uranium (HEU)
Highly enriched uranium (HEU): Refers to uranium with a concentration of more than 20% of the isotope U-235. Achieved via the process of enrichment. See entry for enriched uranium.
Plutonium (Pu)
Plutonium (Pu): A transuranic element with atomic number 94, produced when uranium is irradiated in a reactor. It is used primarily in nuclear weapons and, along with uranium, in mixed-oxide (MOX) fuel. Plutonium-239, a fissile isotope, is the most suitable isotope for use in nuclear weapons.
Low enriched uranium (LEU)
Low enriched uranium (LEU): Refers to uranium with a concentration of the isotope U-235 that is higher than that found in natural uranium but lower than 20% LEU (usually 3 to 5%). LEU is used as fuel for many nuclear reactor designs.
Safeguards: A system of accounting, containment, surveillance, and inspections aimed at verifying that states are in compliance with their treaty obligations concerning the supply, manufacture, and use of civil nuclear materials. The term frequently refers to the safeguards systems maintained by the International Atomic Energy Agency (IAEA) in all nuclear facilities in non-nuclear weapon state parties to the NPT. IAEA safeguards aim to detect the diversion of a significant quantity of nuclear material in a timely manner. However, the term can also refer to, for example, a bilateral agreement between a supplier state and an importer state on the use of a certain nuclear technology.

See entries for Full-scope safeguards, information-driven safeguards, Information Circular 66, and Information Circular 153.
Reprocessing: The chemical treatment of spent nuclear fuel to separate the remaining usable plutonium and uranium for re-fabrication into fuel, or alternatively, to extract the plutonium for use in nuclear weapons.
Irradiate: To expose to some form of radiation.
Enriched uranium
Enriched uranium: Uranium with an increased concentration of the isotope U-235, relative to natural uranium. Natural uranium contains 0.7 percent U-235, whereas nuclear weapons typically require uranium enriched to very high levels (see the definitions for “highly enriched uranium” and “weapons-grade”). Nuclear power plant fuel typically uses uranium enriched to 3 to 5 percent U-235, material that is not sufficiently enriched to be used for nuclear weapons.


  1. Yossi Melman and Meir Javedanfar, The Nuclear Sphinx of Tehran (New York: Basic Books, 2008), p. 84.
  2. “Nuclear, Iran, Production Capability,” Jane’s CBRN Assessments, 28 May 2010, www.janes.com.
  3. Christina Walrond, “Timeline 1967-1993: Argentine Low-Enriched Uranium At Tehran Research Reactor,” Institute for Science and International Security, 7 October 2009, www.isisnucleariran.org.
  4. “Implementation of the NPT Safeguards Agreement in the Islamic Republic of Iran,” International Atomic Energy Agency (IAEA), 10 November 2003, www.iaea.org.
  5. David Albright, “Technical Note: Annual Future Low-Enriched Uranium Fuel Requirements for the Tehran Research Reactor,” Institute for Science and International Security, 7 October 2009, www.isisnucleariran.org.
  6. David Albright, Paul Brannan, and Andrea Stricker, “Has Iran Initiated a Slow Motion Breakout to a Nuclear Weapon?” Institute for Science and International Security, 12 July 2010, www.isisnucleariran.org.
  7. “Iran to Install New Core in Tehran Research Reactor,” Fars News Agency, 20 February 2012.
  8. David Albright and Christina Walrond, “Update on the Arak Reactor,” Institute for Science and International Security, 15 July 2013, www.isis-online.org.
  9. Richard Stone, “Iran’s plans for research reactor fuel imperil revival of nuclear deal,” Science, 15 July 2021, www.science.org.


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