LegiStorm

Summary:

Iran’s nuclear program has generated widespread concern that Tehran is pursuing nuclear weapons. According to 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. (For additional information, see CRS Report RL34544, Iran’s Nuclear Program: Status, by Paul K. Kerr.) 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 uranium235 (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 asserts 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. (For more information, see CRS Report R40094, Iran’s Nuclear Program: Tehran’s Compliance with International Obligations, by Paul K. Kerr.) 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 much of this agreement, as well as JCPOArequired International Atomic Energy Agency (IAEA) monitoring. Beginning in July 2019, the IAEA verified that some of Iran’s nuclear activities were exceeding JCPOAmandated 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 and has not resumed it. 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. Iran has not made a decision to develop nuclear weapons, according to several 2024 public U.S. intelligence assessments. 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) observes 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 July and November 2024 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 (see CRS Report R40094). More recently, an ODNI spokesperson indicated that the U.S. intelligence community is capable of detecting Iranian efforts to build a nuclear weapon, the Wall Street Journal reported on August 9, 2024.