Table of Contents

• Introduction
• History
• Iran’s Nuclear Infrastructure
• Weaponization Efforts and Undeclared Sites
• Key Institutions and Personnel
• Foreign Assistance
• Sanctions and Export Control Measures
• The Role of Export Control
• Key Sources

Introduction

Iran is a nuclear threshold state. Although it is not known to possess nuclear weapons, it possesses the technologies needed to build nuclear warheads, had a well-coordinated effort to develop these in the past, and has accumulated a stockpile of highly enriched uranium large enough to fuel multiple weapons with minimal further enrichment. Iran has long maintained that its nuclear program is benign and authorized by its membership as a non-nuclear weapon state in the nuclear Non-Proliferation Treaty (NPT), which guarantees its members the right "to develop nuclear energy for peaceful purposes." However, Iran has undertaken decades of nuclear work in secret, in violation of its NPT obligations.

These clandestine activities date back to the late 1980s, when Iran began a secret uranium enrichment program, importing key equipment and material from Pakistan and China. In the late 1990s and early 2000s, Iran ran a covert project to develop and test nuclear weapons called the Amad Plan. Since this work was discovered, Iran has not been fully transparent about it with the International Atomic Energy Agency (IAEA), the United Nations body tasked with monitoring compliance with the NPT. 

Beginning in 2002, revelations related to these projects spurred years of diplomacy and pressure aimed at curbing the nuclear program while Iran openly accumulated large stockpiles of enriched uranium. These diplomatic and sanctions efforts culminated in 2015, when Iran and six world powers concluded the Joint Comprehensive Plan of Action (JCPOA). The purpose of the agreement was both to limit Iran’s nuclear activities and to increase transparency surrounding those activities by expanding the scope of monitoring by the IAEA. In 2018, however, the United States withdrew from the deal, and, a year later, Iran began decreasing its compliance. By 2020, Iran announced it would no longer observe any limit set by the agreement. Progress since then has brought Iran to the nuclear threshold status where it stands today.

History

Beginnings (1970s through the Iran-Iraq War)

Under the Shah, Iran launched a series of ambitious nuclear projects that relied on assistance from the United States and Europe. According to Akbar Etemad, the President of the Atomic Energy Organization of Iran (AEOI) from 1974 through 1978, Iran was already carrying out nuclear research and education at the University of Tehran when the NPT—of which Iran was one of the original 62 signatories—entered into force on March 5, 1970. The work centered on a five-megawatt research reactor supplied by the United States, which began operation in 1967.

By the mid-1970s, according to Etemad, Iran had launched an extensive nuclear energy program. In 1974, the Shah set the goal of producing roughly 23,000 megawatts of electrical power from a series of nuclear power stations within 20 years. A host of contracts between Iran and nuclear suppliers in Europe and the United States followed: Iran struck a deal with Kraftwerk Union (KWU, a Siemens subsidiary) of then-West Germany to build two 1,200 megawatt reactors at Bushehr and negotiated with the French company Framatome for two additional 900-megawatt reactors. In 1974, Iran reportedly invested $1 billion in a French uranium enrichment plant owned by Eurodif, a European consortium. Etemad also described Iran's indigenous work on the nuclear fuel cycle in the 1970s, including plans for a new nuclear research center at Isfahan and the exploration of uranium mining and ore processing.

The 1979 Iranian revolution halted this work for a number of years. The war with Iraq, which began in 1980, consumed resources and damaged Iran's existing nuclear infrastructure. The two power reactors under construction at Bushehr were bombed several times, after which Siemens abandoned the project.

Clandestine Nuclear Development (late 1980s to early 2000s)

By the early 1990s, as Iran recovered from the war with Iraq, its nuclear program was once again moving forward, based on assistance from Russia, China, and Pakistan. With China, Iran signed two nuclear cooperation protocols, in 1985 and again in 1990. And in 1995, Iran concluded a protocol of cooperation with Russia to complete the construction of the reactor at Bushehr and possibly supply a uranium enrichment plant. Some of the items originally contemplated in these deals, like the enrichment plant, were never delivered as a result of pressure from the United States. Others, like Bushehr, served as a justification for Iran’s acquisition of sensitive equipment that would not be sold on its own because of its bomb-making potential. Throughout the 1990s, entities in Russia and China continued to help Iran, despite occasional pledges from their governments to curtail nuclear assistance. Iran is also believed to have received uranium enrichment technology through the black-market network run by Pakistani scientist A. Q. Khan during this period.

In the late 1990s, senior Iranian officials approved a plan, called the Amad Plan, to build an arsenal of five nuclear weapons by 2004. The project, which proceeded in secret and was led by Mohsen Fakhrizadeh, made considerable progress in just a few short years. Under the Amad Plan, Iran acquired several foreign weapon designs and refined them to develop its own; conducted conventional explosives testing; carried out casting and machining experiments with surrogate materials; and studied how to integrate the warhead with a Shahab-3 missile. The main element that Iran lacked during this program was the weapons-grade uranium or plutonium to fuel the bombs.

In the summer of 2002, the National Council of Resistance of Iran, an umbrella organization made up of several Iranian dissident groups, revealed the existence of two Iranian nuclear sites: a uranium enrichment facility at Natanz and a heavy-water production facility at Arak. Because of their dual-use nature, the facilities could be useful for a civilian nuclear program, but they could also be used for making bombs: Natanz could provide Iran with weapons-grade uranium, while Arak could help it obtain weapons-grade plutonium. The fact that Iran had hidden the facilities from the IAEA immediately raised international suspicions as to their intended purpose.

The revelations, coupled with the U.S. invasion of Iraq in 2003 over American suspicions about Iraq’s weapons of mass destruction (WMD) programs, may have contributed to Iranian leaders’ decision to formally halt the Amad Plan in late 2003. However, the end of the Amad Plan did not spell the end of Iran’s nuclear weapon development activities. Rather, Iranian leaders decided to divide the nuclear program into overt and covert streams. The overt stream included facilities and activities that had a plausible civilian rationale, including the Natanz enrichment facility and the Arak heavy water production plant. Iran declared both to the IAEA in 2003.

The covert stream, smaller in scale than before but still constituting a coordinated effort, involved sensitive research and development work aimed at filling in technical gaps related to weapon development and preserving the knowledge gained under the Amad Plan. According to the IAEA, activities such as computer modeling of implosion, compression, and nuclear yield continued until 2009.

This work, still led by Fakhrizadeh, was initially organized under a Ministry of Defense and Armed Forces Logistics (MODAFL) subsidiary called the Section for Advanced Development Applications and Technologies (SADAT), but around 2011 was moved under the Organization of Defensive Innovation and Research (SPND). Israeli officials have estimated that about 70 percent of the staff who once worked on the Amad Plan were transferred to work under SPND.

Iranian leaders also decided to keep some of the facilities associated with the Amad Plan a secret, including the Fordow enrichment facility, which was still under construction at the time.

Early Diplomacy and International Pressure (early 2000s to 2010s)

The public revelations about Arak and Natanz kicked off an intense diplomatic effort to halt Iran’s uranium enrichment program. In October 2003, Iran struck a deal with three European countries, agreeing to suspend its enrichment activities and ratify an Additional Protocol to its safeguards agreement. This followed a resolution by the IAEA Board of Governors a month earlier demanding Iran’s cooperation. By the end of the year, IAEA verification efforts had begun and Iran had signed an Additional Protocol with the Agency.

But Iran did not follow through on these commitments. Its declarations to the IAEA in 2004 and 2005 were incomplete and at times inconsistent, preventing the Agency from developing a full picture of the nuclear program and Iran’s past activities. Iran also resumed or continued activities that the IAEA considered to be related to enrichment. These issues led to a June 2004 rebuke and a September 2005 finding of non-compliance by the IAEA Board of Governors, opening the door to a U.N. Security Council referral. Iran responded by ceasing its implementation of the Additional Protocol and restarting previously suspended enrichment activities. By April 2006, the country had announced that it had enriched uranium to the level of 3.6 percent.

Two months later, China, France, Germany, Russia, the United Kingdom, and the United States (dubbed the P5+1) proposed another framework agreement offering incentives if Iran suspended its enrichment program. Almost concurrently, the U.N. Security Council adopted resolution 1696, the first legally binding exhortation for Iran to do so. Over the subsequent years, the Security Council adopted a series of increasingly severe resolutions imposing international sanctions on Iran’s nuclear program. All the while, a rotating constellation of Western officials met with Iranian officials to discuss diplomatic proposals aimed at stopping Iran’s uranium enrichment activities.

Diplomatic efforts reached a new level of urgency in September 2009, when U.S. President Barack Obama, French President Nicolas Sarkozy, and British Prime Minister Gordon Brown revealed the existence of a second covert uranium enrichment plant near Qom, later called the Fordow Fuel Enrichment Plant (FFEP), which had been under construction for years. According to its safeguards commitments, Iran should have informed the IAEA of the facility’s existence as soon as the decision to build it was taken.

Diplomatic exchanges continued into the early 2010s, even as Iran began enriching uranium to 20 percent purity, the U.N. Security Council adopted resolution 1929 drastically expanded sanctions against Iran, and the Stuxnet computer virus – widely considered to have been developed by the United States and Israel – targeted Iran’s uranium enrichment infrastructure.

Nevertheless, Iran’s nuclear enrichment program continued apace. By the summer of 2013, Iran had installed more than 18,000 of its first-generation IR-1 centrifuges and 1,300 more advanced centrifuges, mostly of the IR-2m model, across its enrichment sites. It had also amassed a stockpile of about 9,700 kg of uranium enriched up to 5 percent and 370 kg enriched up to 20 percent. According to the U.S. government in 2016, this amount would yield enough weapons-grade fissile material for a nuclear weapon, with further enrichment, within two or three months.

JPOA and JCPOA (2013 to 2018)

Secret “back channel” talks between Iranian and American officials began in Oman in 2012, and the inauguration in June 2013 of Iranian President Hassan Rouhani – who had campaigned on a platform of pragmatic engagement with the P5+1 over the nuclear program – further improved the diplomatic outlook. Iran and the P5+1 resumed serious negotiations in October 2013, and by November the sides had reached a preliminary agreement, the Joint Plan of Action (JPOA).

The JPOA called for specific steps to be implemented between January and July 2014, with the possibility to extend the six-month period if all parties agreed. Iran’s commitments under the deal included halting the production of uranium enriched to 20 percent, diluting its existing stockpile of 20 percent enriched uranium, and allowing increased IAEA monitoring and access at its nuclear sites. In return, the P5+1 granted Iran limited sanctions relief, agreed not to impose new sanctions while the agreement was in force, and unfroze approximately $4.2 billion worth of Iranian funds held abroad. More importantly, the JPOA laid out a framework for negotiations toward a more comprehensive agreement.

On July 14, 2015, Iran and the P5+1 announced the broader agreement, the Joint Comprehensive Plan of Action, or JCPOA. Under the deal, Iran’s commitments included:

• Operating no more than 5,060 IR-1 centrifuges for a period of 10 years
• Enrichment to no higher than 3.67 percent for a period of 15 years
• A stockpile of no more than 300 kilograms of enriched uranium for a period of 15 years
• No uranium enrichment at Fordow for a period of 15 years
• A re-design of the Arak Heavy Water Reactor to make it more proliferation-resistant
• Additional transparency measures including the eventual ratification of an Additional Protocol to its safeguards agreement

The P5+1 commitments included:

• The removal of almost all U.N. Security Council sanctions against Iran
• The suspension and eventual removal of most EU sanctions against Iran and a pledge to refrain from re-introducing sanctions suspended under the JCPOA.
• The suspension of some U.S. sanctions, including those against Iran’s energy and banking sectors.

The JCPOA was accompanied by the adoption of U.N. Security Council resolution 2231, which suspended previous U.N. sanctions resolutions while continuing an arms embargo against Iran for five years and restrictions on Iran’s missile program for eight years. Resolution 2231 also provided for the “snap back” of U.N. sanctions against Iran in the event of significant non-compliance by one or more parties to the JCPOA.

Post-JCPOA (2018 onward)

After a little over two years of implementation, President Donald Trump withdrew the United States from the JCPOA on May 8, 2018, citing Iran’s lack of transparency about its past nuclear weapons work and faulting the agreement for not curbing Iran’s missile program or Iran’s funding of militant groups. After Washington reimposed sanctions and took steps to curb Iran’s oil sales, Iran announced in May 2019 that it would begin reducing its compliance with the deal. In January 2020, Iran announced that it had abandoned all JCPOA limits on its uranium enrichment program.

Iran’s nuclear activities accelerated following the assassination of Mohsen Fakhrizadeh, widely regarded as the father of Iran’s nuclear program, on November 27, 2020. In December, the Iranian parliament passed a law mandating the resumption of 20 percent enrichment, the installation and operation of more advanced centrifuges, and the production of uranium metal.

U.S. President Joe Biden, who had pledged to return the United States to the deal, took office in January 2021. By April, diplomats from Iran and the P5+1 were meeting in Vienna to negotiate a restoration of the deal. Although the sides appeared to be nearing an agreement by June, the negotiations slowed during the summer and the deal was not finalized. Iran continued to demand greater reassurances that the United States would not withdraw from the deal a second time and the closure of an IAEA probe into manmade uranium particles found at several undeclared sites across the country. Moreover, Iran’s violent crackdown against protestors in the fall of 2022 and its support for Russia’s war against Ukraine reduced Western leaders’ appetite for engagement with Iran.

In the meantime, Iran continued to expand its nuclear activities. It amassed a stockpile of uranium enriched to 60 percent sufficient to fuel several nuclear weapons if enriched further; installed several thousand advanced centrifuges, predominantly of the IR-2m, IR-4, and IR-6 models; and experimented with producing uranium metal enriched to 20 percent.

Iran’s Nuclear Infrastructure

Nuclear Fuel Cycle Overview

The nuclear fuel cycle is the progression of nuclear fuel through different stages, from creation to eventual disposal. It is usually divided in two: The “front end” of the fuel cycle includes all the steps that prepare the fuel for use in a reactor, while the “back end” involves the management of “spent” nuclear fuel that has been removed from a reactor. It is described as a cycle because spent fuel can in principle be reprocessed and used again to generate nuclear power.

Steps in the front end include the mining and milling of natural uranium; the conversion of uranium ore concentrate to uranium hexafluoride (UF6), a gas; enrichment of UF6 in centrifuges to increase the ratio of uranium-235, which is a fissile isotope and so can sustain a nuclear reaction, relative to the non-fissile isotope uranium-238; and fuel fabrication, which involves converting the UF6 gas into a solid form.

Steps in the back end include removing the spent fuel from the reactor; storing it in a spent fuel pond to further cool the assemblies and block the release of radiation; placing it in on-site dry casks for interim storage; and, eventually, either reprocessing or final disposition in an underground repository.

Both the front and back end of the nuclear fuel cycle pose proliferation challenges, as they respectively enable the two pathways toward acquiring fissile material for a nuclear weapon. The uranium enrichment process used to produce enriched uranium fuel for a nuclear power reactor could also be used to make weapons-grade uranium for a bomb. Similarly, the reprocessing of spent nuclear fuel from reactors can reclaim fissile material in order to reuse it for energy production, but it is also a method for extracting weapons-grade plutonium. Because plutonium exists naturally only in trace amounts but is produced as a by-product of nuclear reactions, reprocessing spent fuel is the only way to obtain a quantity sufficient for a nuclear weapon. Iran has built dual-use infrastructure that enables both the uranium and plutonium pathways to a weapon.

Iran’s Nuclear Infrastructure

Some of Iran’s nuclear infrastructure, including the Tehran Research Reactor and the nuclear power station at Bushehr, dates to before the 1979 revolution and has been declared to the IAEA and under Agency safeguards. But in the 1980s, under the Islamic Republic, Iran began building the infrastructure for an indigenous fuel cycle—work that was hidden from the IAEA until the public revelations about Natanz and Arak in 2002. Any and all of Iran’s activities involving fissile material that were not declared to the IAEA were violations of its 1974 safeguards agreement with the Agency.

Mines, Mills, and Conversion. Iran announced plans to extract uranium from a mine at Saghand in Yazd province as early as 2003. However, it was not until 2013 that this mine became fully operational. China is believed to have been the source of the Saghand mining technology. Iran has admitted that Chinese experts participated in detailed exploration work for the mine. Experts from China's Beijing Research Institute of Uranium Geology have conducted scientific exchanges with Iranian nuclear scientists and have explored in Iran in the past.

Similarly, Iran’s Atomic Energy Organization approved the construction of a yellowcake production plant at Ardakan in 1994 and contracted with an Iranian company to build the plant in 1999. In 2003, Iranian authorities admitted to producing yellowcake at the facility.

Another mine at Gachine (Gchine), located in the south of Iran near Bandar Abbas, came online in 2004, and its co-located milling facility became operational in 2006. The facilities reportedly closed in 2016. Subsequent reporting suggests that Gachine was originally conceived as part of Iran’s covert nuclear weapons program.

In February 2023, Iran announced the start-up of a third uranium mine at Narigan in Yazd province. It is expected that ore from this mine will be milled at the Ardakan yellowcake facility nearby.

To convert the yellowcake into UF6, Iran has relied on a facility located at the Isfahan Nuclear Technology Center called the Uranium Conversion Facility. Iran provided the IAEA with preliminary design information for this facility in July 2000, updated design information in April 2003, and began conducting hot tests in May and June 2004. As of 2015, Iran had produced 550 tons of natural UF6 at the facility, of which about one third had been transferred to Natanz for enrichment.

China is widely acknowledged to be the source of information for the conversion plant. As part of a 1997 agreement with the United States to prevent new cooperation and to halt all existing projects with Iran in the nuclear field, China pledged to cancel a project to help Iran build a conversion plant. Despite this promise, however, China appears to have provided Iran with a blueprint for the plant. Iran admits that the conversion plant is based on a design provided by a foreign supplier in the mid-1990s. China is also believed to have given Iran design information and test reports for equipment.

In addition, China supplied uranium compounds in 1991, which Iran did not declare to the IAEA and which allowed Iran to conduct laboratory tests of the processes to be used in the conversion plant. These compounds included 1,000 kg of UF6, 400 kg of UF4, and about 400 kg of natural UO2.

Uranium enrichment. For enrichment, Iran has focused on gas centrifuge enrichment but has also experimented with laser isotopic separation. Uranium enrichment involves raising the concentration of the fissile isotope U-235 in a given quantity of uranium relative to the non-fissile isotope U-238. Uranium found in nature contains only about 0.7 percent U-235, with more than 99 percent being U-238. For use in a typical light water reactor, that concentration must be raised to between 3 and 5 percent fissile purity. Highly enriched uranium (HEU), defined as uranium enriched to greater than 20 percent of the U-235 isotope, is sometimes used in research reactors or in reactors to power ships and submarines. Weapon-grade uranium is usually defined as uranium enriched above 90 percent, although a working atomic bomb could contain uranium enriched to lower levels. Due to the way uranium enrichment works, converting natural uranium to 20 percent HEU requires more time and effort than converting 20 percent HEU to weapon-grade uranium.

Laser isotopic separation. Because isotopes of different masses absorb different wavelengths of light, uranium isotopes can be separated by lasers precisely tuned to excite or ionize only U-235. The U-235 is then separated out from the rest of the uranium by using a chemical reaction or magnetic forces that attract the excited atoms and leave behind the neutral ones.

Iran's laser uranium enrichment program began before the 1979 revolution and relied on assistance from at least four foreign sources, according to the IAEA. By 2000, Iran had established several laboratories for laser separation at the Tehran Nuclear Research Center. Around the same time, it also began working to establish a pilot laser enrichment plant at Lashkar Abad. Iran carried out some experiments at the laboratories in Tehran before moving them to Laskhar Abad in 2002. Laser enrichment work never progressed beyond the laboratory scale, however, and Iran eventually dismantled its laser-enrichment equipment and moved it to a storage facility at Karaj.

Gas centrifuges. Iran's centrifuge program was launched in 1985 at facilities controlled by the AEOI in Tehran. In 1987, the A.Q. Khan network offered Iran a list of items that it was willing to sell, including a disassembled P-1 centrifuge, drawings and specifications for a complete centrifuge plant, and materials for 2,000 centrifuge machines. According to the IAEA, Iran stated that it purchased one or two disassembled centrifuges along with supporting drawings and specifications from the Khan network and acquired some of the other equipment directly from other suppliers. A second deal with the Khan network materialized in the mid-1990s. Between 1994 and 1995, Iran received some 500 disassembled P-1 centrifuge machines as well as drawings for the P-2 model. According to the IAEA, Iran admitted to receiving a total of about 2,000 centrifuge components and some subassemblies from foreign sources between 1985 and 1997.

In 1997, Iran moved its centrifuge development effort to the Kalaye Electric Company in Tehran. According to Iranian authorities, from 1997 through 2002, Kalaye was used to test and assemble centrifuges for uranium enrichment. The IAEA first visited Kalaye’s operations in March 2003, and Agency inspectors were allowed to take environmental samples at the site during a follow-up visit in August.

Beginning in 2002, Iran's centrifuge program was moved to Natanz, which houses both a 1,000-centrifuge pilot fuel enrichment plant (PFEP) and a commercial-scale fuel enrichment plant (FEP) intended to house over 50,000 centrifuges. The Natanz site was revealed publicly in August 2002 by the NCRI and first visited by the IAEA in February 2003. Centrifuge testing with nuclear material began a few months later. By August 2013, Iran had installed about 15,400 first generation (IR-1) centrifuges, of which about 9,100 were operational at the larger facility. It had also installed about 1,000 IR-2m centrifuges there, although none of these had been fed with uranium gas at that time.

Iran used the pilot plant to enrich uranium to 20 percent purity beginning in 2010, justifying this action by claiming that the higher enrichment was necessary to fuel the Tehran Research Reactor. As Iran’s enrichment program has matured, the plant has been used to test the performance of advanced centrifuges.

Following the unravelling of the JCPOA, Iran has not only restored the enrichment capacity that it achieved prior to the agreement but has exceeded it. It has done so with a greater reliance on advanced centrifuges relative to the first-generation IR-1. As of November 2023, Iran was enriching uranium up to 5 percent at the Natanz FEP using about 6,200 IR-1, 1,500 IR-2m, 500 IR-4, and 500 IR-6 models. At the pilot plant, Iran was operating several hundred each of IR-4 and IR-6 centrifuges to accumulate uranium enriched up to 60 percent.

Iran began construction on a third enrichment facility, the Fordow Fuel Enrichment Plant (FFEP) near Qom, sometime in 2006 or 2007. The plant was built secretly and is situated under a mountain and fortified against air attack. It consists of two enrichment halls with a potential capacity of about 3,000 centrifuges. Fordow’s existence was revealed publicly by the leaders of France, the United Kingdom, and the United States in a joint statement in September 2009. According to the IAEA Director General at the time, Iran’s delay in notifying the Agency was a violation of its safeguards agreement; according to the Agency, Iran should have declared the facility no later than 2007, when Iran claimed the decision was made to construct it.

The FFEP’s covert nature, its fortified location, and its size—the facility would be too small to produce enough enriched uranium to meet Iran’s energy needs—generated concern that it was built for a military purpose. These concerns were substantiated by Iranian documents uncovered in 2018 demonstrating that the Fordow facility, code-named the Al Ghadir project, was planned as the site for enriching weapons-grade uranium under the Amad Plan.

Fordow became operational in 2011. By August 2013, it held nearly 3,000 IR-1 centrifuges arranged into 16 cascades, of which four were enriching uranium up to 5 percent. While Iran agreed under the JCPOA to convert Fordow into a research facility for stable isotope production, it resumed its enrichment activities there in November 2019. As of November 2023, Iran was using about 1,000 IR-1 centrifuges and 300 IR-6 centrifuges to enrich uranium up to 60% purity there.

Tehran Research Reactor. In the late 1960s, the United States supplied to Iran the Tehran Nuclear Research Center (TNRC) with a five-megawatt research reactor, hot cells, and 93% enriched uranium reactor fuel. The United States stopped the fuel supply after the 1979 revolution. In the late 1980s, Argentina reportedly helped Iran reconfigure the reactor's core and in 1992 provided about 115 kg of uranium enriched to 20% U-235.

In October 2003, Iran acknowledged that between 1988 and 1992 it had irradiated depleted uranium dioxide targets (UO2) in the reactor and then conducted plutonium separation experiments in hot cells in a nearby building. According to Iran, seven kilograms of UO2 were irradiated, three kilograms of which were processed into separated plutonium. The separated plutonium was presented to inspectors from the IAEA in November 2003 at the Jabr Ibn Hayan Laboratories, located at the TNRC. Iran estimated that it had produced 200 micrograms. However, the inspectors concluded that Iran understated the amount of plutonium and that the age of the plutonium was less than the 12–16 years Iran declared.

This history highlights the dual-use nature of the Tehran Research Reactor and its role in opening Iran’s path to a plutonium-fueled bomb. The research reactor has also served as a justification for Iran to enrich uranium to higher levels, since it operates on fuel enriched to almost 20 percent.

Heavy water technology. Iran’s heavy-water infrastructure also supports the plutonium path. Iran decided to develop a heavy water production plant and a heavy water research reactor at Arak near Khondab. The project remained secret until August 2002, when it was publicly revealed by the NCRI. The heavy water plant was inaugurated in August 2006. Although it is not under safeguards, the IAEA has been able to partially monitor its activities via satellite imagery. Iran informed the IAEA that the two heavy water production lines at Arak would produce about 16 tons of heavy water annually.

In May 2003, Iran announced its plans to build a heavy water research reactor with a 40-megawatt thermal capacity, now called the Khondab Heavy Water Research Reactor (IR-40), at the same site. Fueled by natural uranium, the Arak reactor was designed to use heavy water as both coolant and moderator. Iran has admitted that it received some foreign assistance for the design of the reactor; the United States suspects that Russia provided the help.

IAEA inspectors visited the site in November 2010 and confirmed that civil construction was “almost complete” and that some major equipment, including the pressurizer for the reactor cooling system and the main crane in the reactor building, had been installed. In June 2013, Iran installed the main reactor vessel.

Although Iran has always claimed that the IR-40 is intended for civilian research, it was a proliferation concern under its original design because its spent fuel would have contained plutonium better suited for nuclear weapons. Most states that have built this type of reactor, which is widely considered larger than necessary for research, have used it to produce bombs. Well-known precedents include Israel's Dimona reactor, supplied by France and Norway, and India's CIRUS reactor, supplied by Canada and the United States.

Iran began producing fuel for the original IR-40 reactor at the Fuel Manufacturing Plant at Isfahan before the reactor construction had been completed. On May 23, 2009, IAEA inspectors were able to visit the plant and verified the production of natural uranium pellets to fuel the heavy water reactor. Iran ceased the production of fuel assemblies for the Arak reactor after the implementation of the JPOA in January 2014. All previously produced fuel assemblies remained at the Fuel Manufacturing Plant.

After the JCPOA was concluded, Iran removed the calandria from the reactor and agreed not to pursue its construction based on its original design. Instead, with the assistance of an international consortium, Iran began redesigning and rebuilding the reactor to minimize its production of plutonium (a by-product of the reactor’s operation). This project is ongoing as of late 2023.

Bushehr Light Water Reactor. In 1974, Iran contracted the German company Siemens (then KraftWerk) to build two reactors at the Bushehr site. The Iranian Revolution and the Iran-Iraq war caused construction to be halted, and Siemens subsequently abandoned the project.

Russia took over the project in 1995, agreeing to incorporate its own light-water reactor technology into the existing infrastructure. After years of delay, the billion-dollar reactor was connected to the grid in September 2011, and Iran took control of the Bushehr reactor from Russia in September 2013. In November 2014, the two countries signed an agreement to build two more reactors at the site, with initial planned completion dates of 2024 and 2026, although both are behind schedule. In 2016, AEOI spokesman Behrouz Kamalvandi stated that the single reactor was contributing about four percent of Iran's total electricity output to the national power grid.

In principle, Bushehr’s single reactor is capable of providing Iran with enough weapon-grade plutonium to construct approximately 35 nuclear weapons annually. This assessment is based on an estimate of the plutonium output from a typical 1,000-megawatt pressurized light-water power reactor. To use the plutonium from Bushehr in a nuclear weapon, however, Iran would have to keep the spent reactor fuel and construct a plant to extract plutonium from it, neither of which it has done.

Russia has agreed to provide Iran low-enriched uranium fuel and to take back the spent fuel under agreements dating back to 2005, before the reactor was in operation. Since then, Russia has made good on its commitments, supplying about 38 tons of uranium enriched to 4.5 percent every year for the reactor. But Iran remains intent on manufacturing the fuel for the Bushehr reactor domestically. According to remarks by Kamalvandi in January 2021, Iran and Russia signed a roadmap around 2016 that envisioned Iran becoming a supplier of fuel for the Bushehr reactor within 10 years.

Weaponization Efforts and Undeclared Sites

In 2002, the IAEA became concerned about the possible existence of undisclosed nuclear-related activities involving military-linked organizations in Iran. Around 2005, as it was developing a more complete picture, the Agency became aware of alleged studies related to the conversion of uranium dioxide into UF4 (the so-called “Green Salt Project”), as well as tests related to high explosives and a missile re-entry vehicle. The Agency stated that these activities could have a “military nuclear dimension,” and sought clarification from Iran on them.

For years, however, Iran refused to answer the Agency’s increasingly detailed questions and insisted that the allegations were false. In 2011, the IAEA attempted to resolve all of its outstanding questions about Iran’s alleged efforts to pursue nuclear weaponization research, or the “possible military dimensions to Iran’s nuclear program.” In November of that year, it published its findings based on information it had received from IAEA member states, information provided by Iran, and its own investigative efforts. The IAEA judged the allegations of work on nuclear weapons “to be, overall, credible” and “consistent in terms of technical content, individuals and organizations involved, and time frames.”

The 2011 report contained detailed information about Iran’s effort to develop a nuclear weapon, including:

• computer modeling of implosion, compression, and nuclear yield, as recently as 2009;

• high explosive tests simulating a nuclear explosion but using non-nuclear material in order to see whether an implosion device would work;

• the construction of at least one containment vessel at a military site, in which to conduct such high explosive tests;

• studies on detonation of high explosive charges, in order to ensure uniform compression in an implosion device, including at least one large scale experiment in 2003, and experimental research after 2003;

• support from a foreign expert, reportedly a former Soviet weapon scientist named Vyacheslav Danilenko, in developing a detonation system suitable for nuclear weapons and a diagnostic system needed to monitor the detonation experiments;

• manufacture of a neutron initiator, which is placed in the core of an implosion device and, when compressed, generates neutrons to start a nuclear chain reaction, along with validation studies on the initiator design from 2006 onward;

• the development of exploding bridgewire detonators (EBWs) used in simultaneous detonation, which are needed to initiate an implosive shock wave in fission bombs;

• the development of high voltage firing equipment that would enable detonation in the air, above a target, in a fashion only making sense for a nuclear payload;

• testing of high voltage firing equipment to ensure that it could fire EBWs over the long distance needed for nuclear weapon testing, when a device might be located down a deep shaft;

• a program to integrate a new spherical payload onto Iran’s Shahab-3 missile, enabling the missile to accommodate the detonation package described above.

But the report did not resolve all of the IAEA’s concerns. Between 2011 and 2015, it regularly reported that Iran was evading questions related to the Agency’s investigation of the alleged weaponization efforts. 

When the JCPOA was agreed in July 2015, Iran and the IAEA signed a “roadmap” agreement intended again to resolve all of the IAEA’s outstanding questions related to this investigation. In December 2015, the IAEA issued its “Final Assessment,” concluding that Iran had a coordinated nuclear weapon-related program until 2003, and that some weapon-related activities continued through 2009. The report disclosed that Iran did not provide meaningful additional information for most of the 12 outstanding issues in the IAEA’s investigation. To many of the Agency’s questions, Iran offered no new information, made denials without explanation, or gave explanations contradicted by other information. Nonetheless, the IAEA Board of Governors voted unanimously to close the Agency’s investigation.

Over time, the IAEA’s investigation focused on several sites not declared by Iran to be connected to the nuclear program. One of the first was Lavisan-Shian, where, according to Iran, a military institute called the Physics Research Center had been established in 1989. However, by the time the Agency became aware of Lavisan-Shian and its possible nuclear-related activities in 2004, Iran had razed the site, complicating the investigation.

Another location of interest was Parchin, a sprawling military complex located east of Tehran. Although Iran allowed inspectors to visit the complex in January 2005, they were severely limited in which areas and buildings they could enter. Although environmental samples taken during that visit did not indicate the presence of nuclear material, the Agency’s interest in Parchin turned out to be well-founded. In 2018, Israeli agents conducted a raid inside Iran and seized a trove of tens of thousands of documents relating to Iran’s past nuclear weapon effort, the so-called “Atomic Archive.” The Atomic Archive revealed Iran’s efforts to build nuclear weapons in much greater detail than was previously known (the Amad Plan). It also revealed the existence of a several sites connected to Iran’s nuclear weapon development effort. In particular, Parchin was home to high explosive test chambers and an underground tunnel site whose purpose might have been the production of uranium metal components for nuclear weapons.

Based on the new information it received in 2018, the IAEA took a renewed interest in Lavisan-Shian, as well as three additional sites where nuclear-related activities might have occurred in the past but that were never declared to the Agency: Turquzabad, Varamin, and Marivan. In subsequent visits to the latter three sites, the agency took environmental samples that revealed the presence of uranium particles of “anthropogenic origin.” Marivan in particular may have been associated with Iran’s past nuclear weapon development efforts. In 2022, the IAEA stated that the information it had collected about Marivan was consistent with Iran having used the site to conduct “explosive testing with protective shielding in preparation for the use of neutron detectors.”

The IAEA closed its investigations into Lavisan-Shian and Marivan in 2022 and 2023, respectively, after determining, effectively, that it would not be able to verify any more information about the presence of uranium particles at those two sites. It concluded that Iran had violated its safeguards agreement by not declaring work done on a uranium metal disc at Lavisan-Shian in 2003. In regard to Marivan, the Agency accepted a “possible” Iranian explanation attributing the presence of manmade uranium particles there to a pre-1979 mine in the same location, while upholding its assessment that Iran conducted explosive testing at the site in the early 2000s. The Agency has not resolved outstanding issues related to Turquzabad and Varamin, due to a lack of cooperation from Iran.

Analysts reviewing documents from the Atomic Archive have also alleged that Iran worked on a key nuclear weapon subcomponent called a shock-wave generator at the Research Center for Explosion and Impact (METFAZ) at Sanjarian.

Key Institutions and Personnel

AEOI and TESA

The Atomic Energy Organization of Iran (AEOI) is the central entity in Iran’s publicly-disclosed nuclear program. It oversees key sites such as the uranium enrichment plants at Natanz and Fordow, a nuclear technology center at Isfahan, the Bushehr and Arak reactors, and the Tehran Research Reactor. A network of contractors, subsidiaries, and affiliates has assisted and supplied AEOI, including Mesbah Energy Company, Novin Energy Company, and Kalaye Electric Company.

The Iran Centrifuge Technology Company (TESA) has played a crucial role in Iran’s uranium enrichment program by manufacturing centrifuges for the AEOI. According to the European Union, TESA took over the activities of Farayand Technique, which itself was a subsidiary of Kalaye Electric Company.

SPND and MODAFL

The military dimension of Iran’s nuclear program centers on the Organization for Defensive Innovation and Research (SPND), an institute subordinate to the Ministry of Defense and Armed Forces Logistics (MODAFL) and formerly led by Mohsen Fakhrizadeh, who directed Iran’s Amad Plan effort to develop nuclear weapons. The SPND has its roots in the Physics Research Center, a military-related institute established at Lavisan-Shian in 1989 that was involved in efforts to acquire dual use materials and equipment that could be used in uranium enrichment and conversion activities.

Universities

Iranian universities and nuclear scientists are one of the links between the civilian and military sides of the nuclear program. Shahid Beheshti University has collaborated with both MODAFL and AEOI, and the MODAFL-subordinate Malek Ashtar University of Technology has been sanctioned by the United Nations for having contributed to Iran’s research on nuclear weapons. Prominent nuclear scientists including Fakhrizadeh (before his assassination in 2020), Mohammad Mehdi Tehranchi, and former AEOI head Fereidoun Abbasi-Davani have maintained links to those and other universities.

Foreign Assistance

In 1985, Iran secretly launched a domestic centrifuge enrichment program that would receive a substantial boost from illicit foreign assistance. The illicit assistance was set in motion by an attempt at civil nuclear cooperation through official channels, however. In 1987, Iran approached the government of Pakistan seeking help on its nuclear program, and the two countries signed a formal agreement that year that included training for at least six Iranian scientists at the Pakistan Institute of Nuclear Science and Technology.

Yet the deal yielded little else for Iran, prompting it to look for other means by which to access Pakistani nuclear technology. These efforts led to its contacts with the black-market network led by A. Q. Khan. Khan had reportedly traveled to Iran in 1986 to visit the Bushehr reactor and inspect the damage done to it by Iraqi bombing during the war.

At a meeting in 1987, the Khan network made an offer in the form of a one-page, handwritten letter to the Iranians. The offer contained a menu of items such as a disassembled P-1 centrifuge, drawings and specifications for a complete centrifuge plant, and materials for 2,000 centrifuge machines. Iran did not purchase everything on the list but did buy one or two disassembled centrifuges along with supporting drawings and specifications. Iran also admitted to using the menu as a shopping list to purchase other items from different suppliers.

A second deal with the Khan network materialized in the mid-1990s. Between 1994 and 1995, Iran received some 500 disassembled P-1 centrifuge machines as well as drawings for the P-2 model. Iran told the IAEA in 2003 that these were domestically produced, but trace particles of highly enriched uranium on the machines allowed the IAEA to forensically connect them to the Pakistani program, and Iran later acknowledged their foreign origin. But the Khan network was not Iran’s only source. According to the IAEA, Iran admitted to receiving a total of about 2,000 centrifuge components and some subassemblies from foreign sources between 1985 and 1997.

Also around 1987, the Khan network provided a 15-page document describing procedures for the conversion of uranium hexafluoride into metal and the casting of the metal into hemispheres. Such activities, according to the IAEA, were “related to the fabrication of nuclear weapon components.” Iran showed the 15-page document to the IAEA in 2005, although the IAEA was not given sufficient access or evidence to confirm the veracity of Iran’s claims regarding the document’s origin.

In addition to assistance from the Khan network, Iran is also believed to have received help from China as well. For example, China is widely acknowledged to be the source of information for Iran’s uranium conversion plant at Isfahan. It also supplied Iran with uranium compounds in 1991 that Iran did not declare to the IAEA, including 1,000 kg of UF6, 400 kg of UF4, and about 400 kg of natural UO2.

Iran may have received considerable help from foreign experts in its crash nuclear weapon development program as well. For example, the Atomic Archive indicates that Iran acquired several designs for nuclear weapons from abroad, including one obtained via the Khan network in the early 1990s. Further, according to the IAEA, Iran could have benefited in its effort to develop an explosives technology known as multipoint initiation from a certain “foreign expert.” This expert is  identified elsewhere as Vyacheslav Danilenko, who was present in Iran in the period from 1996 to 2001. Both Iran and Danilenko have denied that he contributed to the nuclear program, claiming instead that his work was related to the production of nanodiamonds. But the Atomic Archive reveals that Danilenko was not the only one—well over a dozen foreign scientists may have assisted Iran in its nuclear weapons development program.

Iran has also attempted to illicitly procure dual use items for its nuclear program from unwitting foreign firms over the years. For example, a 2013 report by a U.N. Panel of Experts highlighted one case in which Iran attempted to import high-quality valves, which have a variety of industrial applications, from Germany and Sweden. To acquire the valves, Iran used false shipping documents and other suspicious methods, and the panel was subsequently able to establish that they were intended for use in the Arak heavy-water reactor. Other dual use goods that Iran has sought to illicitly procure include vacuum pumps, high-frequency converters, heat exchangers, nuclear-grade graphite, high-strength aluminum, and carbon fiber. To advance these efforts, Iran has made use of front companies, concealed the true end user, and falsified documentation in order to deceive suppliers and evade sanctions and export controls.

Iran has also received official foreign assistance for its nuclear program as well. During the Shah’s rule, the United States built a five-megawatt research reactor at the University of Tehran, which began operation in 1967 and remains in use as of 2023. The Shah also pursued deals with European suppliers, signing a contract with Kraftwerk Union (later Siemens) to build two 1,200 megawatt reactors at Bushehr and negotiating with the French company Framatome for two additional 900-megawatt reactors.

Under the Islamic Republic, in the 1990s, Iran turned to Russia and China for cooperation on its nuclear program. In particular, in 1995, it concluded an agreement with Russia to complete the construction of the reactor at Bushehr and possibly supply a uranium enrichment plant. Russia’s state nuclear company Rosatom finished the Bushehr reactor in 2011 and continues to supply the low-enriched uranium fuel for it, returning the spent fuel to Russia. The uranium enrichment plant was never delivered.

The JCPOA also contained provisions for international nuclear cooperation with Iran. As a result of the multilateral accord, in 2017 Iran concluded an agreement with China’s state-owned nuclear corporation to re-design and rebuild the heavy-water reactor at Arak.

Sanctions and Export Control Measures

United Nations

U.N. Security Council resolution 2231 is the primary legal basis for U.N. sanctions on Iran. This resolution endorses the Joint Comprehensive Plan of Action (JCPOA) and supersedes earlier resolutions, thereby lifting most U.N. sanctions on Iran. Until 2025, the resolution limits Iran’s ability to import nuclear-related items without case-by-case approval from the Security Council. This list of restricted items is based on the list established by the Nuclear Suppliers Group (NSG), a multilateral export control regime of 48 countries that have agreed to a set of guidelines about which nuclear technologies they will export, and under what conditions.

Previously, resolution 2231 had also restricted Iran’s imports of items usable in nuclear weapon delivery systems (namely missiles), called upon Tehran to suspend tests of ballistic missiles designed to carry a nuclear warhead, and imposed targeted sanctions on entities that had contributed to unsafeguarded nuclear activities or ballistic missile testing. Those provisions expired in mid-October 2023. Resolution 2231 also included limitations on Iran’s arms transfers, which expired in 2020.

In the event of “significant non-performance” of Iran's commitments under the JCPOA, resolution 2231 includes a mechanism that would allow for the reimposition, or “snapback,” of U.N. sanctions in place before the accord. Snapback would restore the provisions of previous Security Council resolutions, notably transfers to Iran of most nuclear and missile-related items. This mechanism, along with the remaining provisions of resolution 2231, expires in 2025.

European Union

Most nuclear-related EU sanctions were also lifted after the Joint Comprehensive Plan of Action (JCPOA) went into effect in 2016, but some restrictions remain. These are authorized by EU Council Regulation 267/2012, which contains several measures. First, it freezes the assets of certain listed entities identified as being involved in Iran’s development of nuclear weapons or their delivery systems, or as being affiliated with the Islamic Revolutionary Guards Corps (IRGC).

Second, EU export controls contained in Regulation 267/2012 go beyond the limitations set out by the NSG by imposing further restrictions on the transfer of dual-use items to Iran by entities under the jurisdiction of EU member states. There are exceptions for nuclear transfers specified in the JCPOA, for example transfers related to light water reactors.

United States

The United States maintains comprehensive sanctions that directly target Iran’s nuclear program as well as the economic sectors that provide revenue for it, including Iran’s banking, energy, and shipping industries. These sanctions are based on a number of laws and executive orders crafted by Congress and successive presidential administrations since the early 1980s.

U.S. sanctions targeting entities contributing to Iran’s nuclear program are usually imposed pursuant to Executive Order (E.O.) 13382, a 2005 order that targets proliferators of weapons of mass destruction (WMD) and their delivery systems. E.O. 13382 freezes the assets of entities that contribute to WMD proliferation. The Iran, North Korea, and Syria Nonproliferation Act (INKSNA), first passed in 2000, is also used to impose sanctions on foreign entities that knowingly traffic goods, services, or technology that contribute to Iran’s development of nuclear weapons or missiles. INKSNA sanctions last for periods of two years and include bans on U.S. government assistance, U.S. arms sales, and U.S. government procurement, as well as the denial of U.S. exports that require a license. The U.S. Department of Commerce also places entities connected to Iran’s WMD programs on its Entity List, which imposes a licensing requirement for companies and individuals to export U.S.-origin goods to them. U.S. policy for considering exports to listed Iran-related entities generally presumes that a license will be denied.

Most U.S. sanctions on Iran include secondary sanctions that may be enforced against companies or individuals outside of the United States that do business with sanctioned sectors of Iran’s economy or with designated entities. Parties that are sanctioned in this way can have their assets frozen and be blocked from the U.S. financial system, including being barred from using the U.S. dollar, which underpins much of the global financial infrastructure. U.S. sanctions, and their enforcement through U.S. courts and diplomacy, thus have an impact beyond the borders of the United States.

The Role of Export Control

Export controls alone cannot bring a determined nuclear program to a full stop. As the Atomic Archive demonstrates, Iran clandestinely received equipment, weapon designs, and expertise from abroad. Moreover, as various court cases and export enforcement actions have shown, Iran has managed to procure dual-use equipment from countries in Europe and North America that have strong export control systems. Iran has also improved its self-sufficiency in the production of key nuclear-related equipment and consequently relies less on foreign suppliers.

Still, export controls can perform three functions related to nuclear proliferation: slow proliferation-related procurement and raise its costs; provide information about the acquisition methods and procurement interests of nuclear weapon aspirants; and force proliferators to undertake activities that constitute both warning and evidence of illicit nuclear activities. All of these effects have influenced the course of Iran’s multi-decade nuclear program.

If well-enforced, export controls will continue to hinder the next steps of Iran’s nuclear development. For example, some experts have argued that Iran has struggled to manufacture carbon fiber bellows for its IR-6 centrifuge, resulting in that centrifuge model operating less efficiently than it was expected to. Similarly, Iran’s most advanced centrifuge designs – the IR-8 and IR-9, presumably both constructed from carbon fiber – have languished in single-machine testing for years rather than enter mass production. This production difficulty may be linked to Iran’s apparent inability to domestically produce polyacrylonitrile (PAN), a key ingredient for making high-quality carbon fiber.

Limiting the efficiency of Iran’s centrifuges has counterproliferation value: it would limit Iran’s ability to hide sites used for the clandestine production of weapons-grade uranium. More powerful centrifuges would enable Iran to use smaller sites to enrich weapon quantities of uranium. The smaller the site, the more difficult it would be to detect. Intelligence agencies have long predicted that if Iran makes nuclear weapons, it would do so at secret sites. Should Iran become an onward proliferator of nuclear technology to other states or non-state groups, moreover, as it has with regard to missiles and drones, it makes a meaningful difference for such transferred technology to not be state-of-the-art.

It also remains the case that export controls on technology that Iran has mastered or items that it can produce domestically may nonetheless increase the cost and time required for Iran to manufacture items for its nuclear program, relative to what Iran would be able to accomplish with unimpeded access to foreign markets. Export controls thus have a continuous utility with regard to Iran’s nuclear development. Nonetheless, they must be coupled with diplomacy, monitoring, sanctions, interdictions, and other measures to prevent Iran from crossing the nuclear weapon threshold.

Key Sources

International Atomic Energy Agency reports on Iran dating back to 2003, which can be found at https://www.iaea.org/newscenter/focus/iran/iaea-and-iran-iaea-board-reports. In particular:

"Implementation of the NPT Safeguards Agreement in the Islamic Republic of Iran,” International Atomic Energy Agency, GOV/2003/75, November 10, 2003, available at https://www.iaea.org/sites/default/files/gov2003-75.pdf

"Implementation of the NPT Safeguards Agreement in the Islamic Republic of Iran,” International Atomic Energy Agency, GOV/2005/87, November 18, 2005, available at https://www.iaea.org/sites/default/files/gov2005-87.pdf

“Implementation of the NPT Safeguards Agreement and relevant provisions of Security Council resolutions in the Islamic Republic of Iran,” International Atomic Energy Agency, GOV/2011/65, November 8, 2011, https://www.iaea.org/sites/default/files/gov2011-65.pdf

“Final Assessment on Past and Present Outstanding Issues regarding Iran’s Nuclear Programme,” International Atomic Energy Agency, GOV/2015/68, December 2, 2015, available at https://www.iaea.org/sites/default/files/gov-2015-68.pdf

“NPT Safeguards Agreement with the Islamic Republic of Iran,” International Atomic Energy Agency, GOV/2021/15, February 23, 2021, available at https://www.iaea.org/sites/default/files/21/03/gov2021-15.pdf

David Albright, Sarah Burkhard, Olli Heinonen, and Frank Pabian, “New Information about the Parchin Site: What the Atomic Archive Reveals About Iran’s Past Nuclear Weapons Related High Explosive Work at the Parchin High Explosive Test Site,” Institute for Science and International Security, October 23, 2018, available at https://isis-online.org/isis-reports/mobile/new-information-about-the-parchin-site

David Albright, Olli Heinonen, Frank Pabian, and Andrea Stricker, “A Key Missing Piece of the Amad Puzzle: The Shahid Boroujerdi Project for Production of Uranium Metal & Nuclear Weapons Components,” Institute for Science and International Security, January 11, 2019, available at https://isis-online.org/isis-reports/detail/a-key-missing-piece-of-the-a...

Aaron Arnold, Matthew Bunn, Caitlin Chase, Steven E. Miller, Rolf Mowatt-Larssen, and William H. Tobey, “The Iran Nuclear Archive: Impressions and Implications,” Harvard Kennedy School, Belfer Center for Science and International Affairs, April 2019, available at https://www.belfercenter.org/sites/default/files/files/publication/The%20Iran%20Nuclear%20Archive_0.pdf

Akbar Etemad, "Iran,” in A European Non-Proliferation Policy, ed. Harald Muller. Oxford: Clarendon Press, 1987. p. 207.

“Iran’s Nuclear Program: Status,” Congressional Research Service, December 20, 2019, available at https://crsreports.congress.gov/product/pdf/RL/RL34544

Iran Nuclear Milestones: 1967-2023,” Iran Watch, last updated April 25, 2023, available at https://www.iranwatch.org/our-publications/weapon-program-background-report/iran-nuclear-milestones-1967-2023.

Joint Comprehensive Plan of Action, July 14, 2015, available at https://www.iranwatch.org/sites/default/files/iran_joint_comprehensive_p....

“A.Q. Khan and Onward Proliferation from Pakistan,” in Nuclear Black Markets: Pakistan, A.Q. Khan and The Rise of Proliferation Networks, ed. Mark Fitzpatrick, London: International Institute for Strategic Studies, 2007, pp. 65-91.

U.N. Security Council Resolution 2231, July 20, 2015, available at https://www.iranwatch.org/sites/default/files/res2231e.pdf.