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1 [1] (April 9, 2026)

handle is hein.crs/goveubv0001 and id is 1 raw text is: Iran and Nuclear Weapons Production Updated April 9, 2026 Background Iran's nuclear program has for decades generated widespread concern that Tehran is pursuing nuclear weapons. According to past U.S. intelligence assessments, Tehran has the capacity to produce nuclear weapons at some point but has halted its nuclear weapons program and has not mastered all of the necessary technologies for building such weapons. The extent to which June 2025 and February 2026 Israeli and U.S. airstrikes affected Iran's ability to produce nuclear weapons is unclear. Since the early 2000s, Tehran's construction of gas centrifuge uranium enrichment facilities has been the main source of proliferation concern. Gas centrifuges enrich uranium by spinning uranium hexafluoride (UF6) gas at high speeds to increase the concentration of the uranium- 235 (u-235) isotope. Such centrifuges can produce both low-enriched uranium (LEU), which can be used in nuclear power reactors, and highly enriched uranium (HEU), which is one of the two types of fissile material used in nuclear weapons. Tehran has asserted that its enrichment program is only meant to produce fuel for peaceful nuclear reactors. The 2015 Joint Comprehensive Plan of Action (JCPOA) requires Iran to implement various restrictions on its nuclear program, as well as to accept specific monitoring and reporting requirements. Then-President Donald Trump announced in May 2018 that the United States was ending U.S. participation in the JCPOA. Over time, Iran subsequently stopped implementing many of its JCPOA obligations and also scaled back JCPOA-required International Atomic Energy Agency (IAEA) monitoring. Beginning in July 2019, the IAEA verified that some of Iran's nuclear activities were exceeding JCPOA-mandated limits. Tehran's subsequent expansion of the country's enrichment program has decreased the amount of time needed for Iran to produce enough weapons-grade HEU for a nuclear weapon-an action frequently termed breakout. According to official U.S. assessments, Iran halted its nuclear weapons program in late 2003. This program's goal, according to U.S. officials and the IAEA, was to develop an implosion-style nuclear weapon for Iran's Shahab-3 ballistic missile. A 2025 public U.S. intelligence assessment stated that Iran is not building a nuclear weapon and that the now-former Supreme Leader had not reauthorized the nuclear weapons program he suspended in 2003. IAEA Director General Rafael Grossi stated on March 4, 2026, that the agency never had information indicating that there was a structured systematic [Iranian] program to build or to construct a nuclear weapon. The U.S. government assessed prior to the JCPOA that Iran had not mastered all of the necessary technologies for building a nuclear weapon. However, Tehran may now be conducting work on such technologies. The 2024 U.S. Intelligence Community Annual Threat Assessment published by the Office of the Director of National Intelligence (ODNI) observed that Iran is not currently undertaking the key nuclear weapons-development activities necessary to produce a testable nuclear device. But this phrase is absent from 2024 and 2025 ODNI assessments of Tehran's nuclear program. The JCPOA-mandated restrictions on Iran's nuclear program, as well as the agreement's Iran-specific monitoring and reporting requirements, both supplement Tehran's obligations pursuant to the government's comprehensive IAEA safeguards agreement. Such agreements empower the agency to detect the diversion of nuclear material from peaceful purposes, as well as to detect undeclared nuclear activities and material. These agreements also require governments to declare their entire inventory of certain nuclear materials, as well as related facilities. Safeguards include agency inspections and monitoring of declared nuclear facilities. Prior and subsequent to the JCPOA's January 2016 implementation, IAEA and U.S. officials expressed confidence in the ability of both the IAEA and the U.S. intelligence community to detect an Iranian breakout attempt using either Tehran's IAEA-monitored facilities or clandestine facilities. More recently, an ODNI spokesperson indicated that the U.S. intelligence community is capable of detecting Iranian efforts to build a nuclear weapon, according to an August 9, 2024, press report. Estmated Nudear ea ons Development T melnes U.S. estimates concerning Iranian nuclear weapon development account for the time necessary to produce a sufficient amount of weapons-grade HEU and also complete the remaining steps necessary for an implosion- style nuclear device suitable for explosive testing. Such a device, according to the Office of Technology Assessment, uses a shell of chemical high-explosive surrounding the nuclear material ... to rapidly and uniformly compress the nuclear material to form a supercritical mass necessary for a sustained nuclear chain reaction. Fissile Material Production The time needed to produce enough weapons-grade HEU for a nuclear weapon is a function of a nuclear program's enrichment capacity, as well as the mass and u-235 content of the UF6 stockpile fed into the enrichment process. LEU used in nuclear power reactors typically contains less than 5% u-235; research reactor fuel can be made using enriched uranium containing 20% u-235; HEU used in nuclear weapons typically contains about 90% u-235. The JCPOA mandates restrictions on Iran's declared enrichment capacity and requires that Iran's enriched uranium stockpile must not exceed 300 kilograms (kg) of