Nuclear program of Iran

thumb|Map of reported nuclear-related sites in Iran

The nuclear program of Iran consists of an extensive infrastructure of research sites, uranium mines, research reactors, uranium processing facilities, enrichment sites, the Bushehr Nuclear Power Plant—the country’s sole operational power reactor, currently expanding with two additional units—and the developing Darkhovin Nuclear Power Plant in Khuzestan. The program’s research capabilities are anchored by several facilities, most notably the Tehran Research Reactor and the heavy water reactor at Khondab. Its uranium processing infrastructure is centered in Isfahan, which serves as a hub for conversion and fuel fabrication, while primary enrichment activities are conducted at Natanz, Fordow, and within the Isfahan complex. Iran’s stated objective is a self-sufficient nuclear energy cycle to diversify its power grid and produce medical radioisotopes, citing a legal right to peaceful technology under the Non-Proliferation Treaty (NPT). While viewed as a cornerstone of Iranian technological nationalism, the program has been the subject of a decades-long diplomatic and military standoff, particularly with the United States and Israel, culminating in large-scale conflicts in 2025 and 2026.

The program began in 1957 as part of the US-led Atoms for Peace initiative and expanded significantly during the 1970s under the Pahlavi era, which saw the start of the Bushehr project with Western assistance. Following the 1979 Iranian Revolution, the program was initially deprioritized but was revived in the late 1980s. During the 1990s and early 2000s, Iran developed several undeclared sites, which were identified by international observers in 2002 and 2009. Following the collapse of negotiations with the EU-3 in 2005, the International Atomic Energy Agency (IAEA) Board of Governors found Iran in non-compliance with its NPT safeguards agreement, leading the United Nations Security Council (UNSC) to pass a series of resolutions between 2006 and 2010 demanding a suspension of Iran's enrichment-related activities and targeting Iran’s banking, trade, and energy sectors. While Western intelligence agencies assessed that a dedicated weaponization project, the AMAD Project, was discontinued in 2003, Iran's ongoing enrichment activities led to a decades-long cycle of international sanctions and a sustained campaign of covert sabotage, including the 2009 Stuxnet cyberattack, multiple assassinations of Iranian nuclear scientists, and strikes on facilities in 2020 and 2021, which Iran characterized as "nuclear terrorism."

In 2015, the Joint Comprehensive Plan of Action (JCPOA) was signed by Iran, China, France, Russia, the United Kingdom, the US, and Germany, under which Iran agreed to strict enrichment limits and extensive international monitoring at its nuclear facilities in exchange for sanctions relief. Although the JCPOA briefly stabilized the situation, this period of oversight ended in 2018 following the unilateral withdrawal of the United States and the subsequent "Maximum Pressure" campaign. In response to the US withdrawal, and citing ongoing acts of US and Israeli sabotage, Iran incrementally reduced its compliance and raised enrichment levels to 60%, a move the Iranian government characterized as diplomatic leverage to secure the removal of reinstated sanctions. In August 2025, France, Germany, and the UK triggered the snapback mechanism, reinstating UN sanctions, and, that October, Iran, Russia, and China declared they viewed JCPOA terminated and the UN sanctions legally void.

The standoff escalated into direct military conflict with the Twelve-Day War in June 2025 and a larger joint U.S.-Israeli campaign in February 2026 targeting nuclear and ballistic missile infrastructure. These strikes, which included the assassination of high-ranking Iranian officials, were justified by the U.S. and Israel as preemptive measures to prevent a nuclear breakout. Following a Pakistan-mediated ceasefire in April 2026, the parties entered high-level negotiations in Islamabad. However, a lasting settlement remains elusive; while the U.S. has demanded a permanent end to all uranium enrichment, Iran maintains its legal right to a civilian program. Analysts remain divided on the long-term impact of the conflict, debating whether the physical damage has permanently delayed the program or instead incentivized a transition from nuclear latency to the pursuit of a completed deterrent.

History

Origins under the Shah (1950s–1970s)

thumb|An Iranian newspaper clip from 1968 reads: "A quarter of Iran's nuclear energy scientists are women." The photograph shows some female Iranian PhDs posing in front of [[Tehran's research reactor.]]

Iran's nuclear program began under the rule of Shah Mohammad Reza Pahlavi, with support from the United States and Western Europe. In 1957, Iran and the US signed a civil nuclear cooperation agreement as part of President Dwight Eisenhower's Atoms for Peace program, leading to the construction of Iran's first nuclear research facility Tehran. In November 1967, the Tehran Research Reactor (TRR)—a 5 megawatt thermal light-water reactor—went critical, initially fueled with 93% highly enriched uranium (HEU) provided by the US. Iran became one of the original signatories of the NPT when it entered into force in March 1970, committing as a non-nuclear-weapon state not to pursue nuclear arms.

By the mid-1970s, the Shah expanded the program, citing the need for "alternative sources of fuel for the day when the oil reserves would be depleted." In 1974 he established the Atomic Energy Organization of Iran (AEOI) and announced plans to produce 23,000 megawatts of electricity from a network of nuclear power plants over 20 years. Contracts were signed with Western firms: Iran paid over $1 billion for a 10% stake in the French Eurodif consortium's uranium enrichment plant, and West Germany's Kraftwerk Union agreed to build two 1,200 MWe pressurized water reactors at Bushehr. Construction of the Bushehr Nuclear Power Plant began in 1975, and Iran also negotiated with France's Framatome to supply additional reactors. Plans were made for a full domestic nuclear fuel cycle, including uranium mining and fuel fabrication, with a new Nuclear Technology Center established at Isfahan. Further resolutions (1747 in 2007, 1803 in 2008, and 1929 in June 2010) broadened the sanctions to include arms embargoes, asset freezes on key individuals and entities, and restrictions on financial dealings. The final agreement is based upon "the rules-based nonproliferation regime created by the Nuclear Non-Proliferation Treaty (NPT) and including especially the IAEA safeguards system".

Enrichment was capped at 3.67% for 15 years, and the enriched uranium stockpile limited to 300 kg. Only 5,060 first-generation IR-1 centrifuges could operate at Natanz, and Fordow was repurposed for non-enrichment research. The Arak IR-40 reactor was to be redesigned and rebuilt, with its original core removed and filled with concrete to eliminate plutonium production capability. Iran agreed to provisionally implement the IAEA Additional Protocol, and accepted enhanced verification, including continuous surveillance of enrichment and conversion facilities, monitoring of uranium mines and mills, and oversight of centrifuge manufacturing. Iran's excess enriched uranium, including the bulk of its 20% material, was to be shipped abroad or down-blended. Over 13,000 centrifuges were dismantled. Limited R&D on advanced centrifuges was allowed under controlled conditions without accumulating enriched uranium.

In exchange, the UN, US, and EU committed to stepwise sanctions relief: UN Security Council Resolution 2231 endorsed the JCPOA. It retained a conventional arms embargo for five years and ballistic missile restrictions for eight, and introduced a "snapback" mechanism allowing reimposition of sanctions in case of noncompliance. US and EU sanctions targeting Iran's energy, finance, shipping, and trade sectors were suspended. On "Implementation Day" (January 16, 2016), the IAEA verified Iranian compliance, leading to the unfreezing of billions in Iranian assets and restoration of access to international banking (e.g., SWIFT). Some US sanctions tied to terrorism and human rights remained in force.

United States withdrawal and Iranian violations (2018–2025)

In 2018, the Mossad reportedly stole nuclear secrets (a cache of documents from Iran's weaponization program) from a secure warehouse in the Turquzabad district of Tehran. According to reports, the agents came in a truck semitrailer at midnight, cut into dozens of safes with "high intensity torches", and carted out "50,000 pages and 163 compact discs of memos, videos and plans" before leaving in time to make their escape when the guards came for the morning shift at 7 am. According to a US intelligence official, an "enormous" Iranian "dragnet operation" was unsuccessful in recovering the documents, which escaped through Azerbaijan. demonstrated that the AMAD Project aimed to develop nuclear weapons, that Iran had a nuclear program when it claimed to have "largely suspended it", and that there were two nuclear sites in Iran that had been hidden from inspectors.

In 2018, the United States withdrew from JCPOA, with President Donald Trump stating that "the heart of the Iran deal was a giant fiction: that a murderous regime desired only a peaceful nuclear energy program". The US also contended that the agreement was inadequate because it did not impose limitations on Iran's ballistic missile program, and failed to curb its backing of proxy groups.

In February 2019, the IAEA certified that Iran was still abiding by the international Joint Comprehensive Plan of Action (JCPOA) of 2015. However, on 8 May 2019, Iran announced it would suspend implementation of some parts of the JCPOA, threatening further action in 60 days unless it received protection from US sanctions. In July 2019, the IAEA confirmed that Iran has breached both the 300 kg enriched uranium stockpile limit and the 3.67% refinement limit. On 5 November 2019, Iranian nuclear chief Ali Akbar Salehi announced that Iran will enrich uranium to 5% at the Fordow Fuel Enrichment Plant, adding the country had the capability to enrich uranium to 20% if needed. Also in November, Behrouz Kamalvandi, spokesman for the Atomic Energy Organization of Iran, stated that Iran can enrich up to 60% if needed. President Hassan Rouhani declared that Iran's nuclear program would be "limitless" while the country launches the third phase of quitting from the 2015 nuclear deal.

On January 3, 2020, the US assassinated Iranian Quds Force commander Qasem Soleimani, and Iran responded with missile strikes on US. bases. Two days later, Iran's government declared it would no longer observe any JCPOA limits on uranium enrichment capacity, levels, or stockpile size. In March 2020, the IAEA said that Iran had nearly tripled its stockpile of enriched uranium since early November 2019. In late June and early July 2020, there were several explosions in Iran, including one that damaged the Natanz enrichment plant (see 2020 Iran explosions). In September 2020, the IAEA reported that Iran had accumulated ten times as much enriched uranium as permitted by the JCPOA. On 27 November 2020, Iran's top nuclear scientist, Mohsen Fakhrizadeh, was assassinated in Tehran. Fakhrizadeh was believed to be the primary force behind Iran's covert nuclear program for many decades. The New York Times reported that Israel's Mossad was behind the attack and that Mick Mulroy, the former Deputy Defense Secretary for the Middle East said the death of Fakhirizadeh was "a setback to Iran's nuclear program and he was also a senior officer in the Islamic Revolutionary Guard Corps, and that "will magnify Iran's desire to respond by force."

Throughout 2021 and 2022, Iran installed cascades of advanced centrifuges (IR-2m, IR-4, IR-6) at Natanz and Fordow, significantly increasing its enrichment output. In April 2021, a sabotage attack struck the Natanz enrichment plant, causing an electrical blackout and damaging centrifuges. Iran responded by further upping enrichment: days later, it began producing 60% enriched uranium, an unprecedented level for Iran, just short of weapons-grade (90% and above). This 60% enrichment took place at Natanz, and later at Fordow as well, yielding a stockpile that as of early 2023 exceeded ~70 kg of 60% uranium. On 25 June 2022, in a meeting with the senior diplomat of the EU, Ali Shamkhani, Iran's top security officer, declared that Iran would continue to advance its nuclear program until the West modifies its "illegal behavior".

In July 2022, according to an IAEA report seen by Reuters, Iran had increased its uranium enrichment through the use of sophisticated equipment at its underground Fordow plant in a configuration that can more quickly vary between enrichment levels. In September 2022, Germany, United Kingdom and France expressed doubts over Iran's sincerity in returning to the JCPOA after Tehran insisted that the IAEA close its probes into uranium traces at three undeclared Iranian sites. The IAEA said it could not guarantee the peaceful nature of Iran's nuclear program, stating there had been "no progress in resolving questions about the past presence of nuclear material at undeclared sites". United Nations Secretary-General António Guterres urged Iran to hold "serious dialogue" about nuclear inspections and said IAEA's independence is "essential" in response to Iranian demands to end probes. In February 2023, the IAEA reported having found uranium in Iran enriched to 84%. The Iranian government has claimed that this is an "unintended fluctuation" in the enrichment levels, though the Iranians have been openly enriching uranium to 60% purity, a breach of the 2015 nuclear deal. In 2024, Iranian President Masoud Pezeshkian expressed interest in reopening discussions with the United States on the nuclear deal.

In late October 2024, during a series of Israeli airstrikes in Iran carried out in response to a ballistic missile attack earlier that month, Israel reportedly destroyed a top-secret nuclear weapons research facility known as the Taleghan 2 building, located within the Parchin military complex. In November 2024, Iran announced that it would make new advanced centrifuges after IAEA condemned Iran's non-compliance and secrecy.

Current status and recent escalations (2025–present)

In January 2025, the exiled opposition group NCRI alleged that Iran is developing long-range missile technology under the Islamic Revolutionary Guard Corps (IRGC), with some designs based on North Korean models. The NCRI said that these missiles, such as the Ghaem-100 and Simorgh, could carry nuclear warheads and reach targets as far as away, including parts of Europe. These allegations have not been independently confirmed, but given that several past NCRI claims were later verified by inspectors, they warrant investigation.

In March 2025, US President Donald Trump sent a letter to Ali Khamenei seeking to reopen negotiations. Ayatollah Ali Khamenei later said, "Some bullying governments insist on negotiations not to resolve issues but to impose their own expectations," which was seen as in response to the letter.

In late March 2025, Khamenei's top advisor Ali Larijani said Iran would have no choice but to develop nuclear weapons if attacked by the United States, Israel or its allies.

In April 2025, Trump revealed that Iran had decided to undertake talks with the United States for an agreement over its nuclear program. On 12 April, both countries held their first high-level meeting in Oman, followed by a second meeting on 19 April in Italy. On May 16, Trump sent Iran an offer and said they have to move quickly or else bad things would happen. On May 17, Khamenei condemned Trump, saying that he lied about wanting peace and that he was not worth responding to, calling the US demands "outrageous nonsense". Khamenei also reiterated that Israel is a "cancerous tumour" that must be uprooted.

On May 31, 2025, IAEA reported that Iran had sharply increased its stockpile of uranium enriched to 60% purity, just below weapons-grade, reaching over 408 kilograms, a nearly 50% rise since February. The agency warned that this amount is enough for multiple nuclear weapons if further enriched. It also noted that Iran remains the only non-nuclear-weapon state to produce such material, calling the situation a "serious concern".

On June 10, Trump stated that Iran was becoming "much more aggressive" in the negotiations. On 11 June, the Iranian regime threatened US bases in the Middle East, with Defense Minister Aziz Nasirzadeh stating, "If a conflict is imposed on us... all US bases are within our reach, and we will boldly target them in host countries." The US embassy in Iraq evacuated all personnel. The Iran-backed Yemen-based Houthi movement threatened to attack the United States if a strike on Iran were to occur. CENTCOM presented a wide range of military options for an attack on Iran. UK issued threat advisory for ships on Arabian Gulf. US Secretary of Defense Pete Hegseth told Congress that Iran was attempting a nuclear breakout.

On 12 June 2025, IAEA found Iran non-compliant with its nuclear obligations for the first time in 20 years. Iran retaliated by announcing it would launch a new enrichment site and install advanced centrifuges.

In the early hours of June 13, Israel initiated Operation Rising Lion, a large‑scale aerial assault targeting Iranian nuclear facilities, missile factories, military sites, and commanders across cities including Tehran and Natanz, marking the start of what would come to be known as the Twelve-Day War of 13 to 24 June 2025. Iranian forces said they had shot down an Israeli drone.

On 21 June, the US bombed the Fordow Fuel Enrichment Plant, the Natanz Nuclear Facility, and the Isfahan Nuclear Technology/Research Center in an operation code named Operation Midnight Hammer. In an address from the White House, Trump claimed responsibility for the destruction of the Fordow facility, stating "Iran's key nuclear enrichment facilities have been completely and totally obliterated."

In early July 2025, Iran suspended co-operation with the United Nations' International Atomic Energy Agency (IAEA). and all IAEA inspectors left Iran by July 4.

In August 2025, Iran and European nations reached an agreement to recommence discussions focused on the complete restoration of Tehran's nuclear enrichment operations.

France, Britain, and Germany have indicated that they may reinstate UN sanctions on Iran through a "quick return" mechanism should Tehran fail to engage in negotiations.

On August 28, 2025, E3 members, France, Germany, and the United Kingdom, initiated the process of the snapback mechanism, with the prospect of freezing Iranian overseas assets, blocking arms deals with Iran, imposing penal action against development of Iran's ballistic missile program and further restricting Iran's military and nuclear activities. In a letter addressed to the president of the UN Security Council, the foreign ministers of the E3 stated that since 2019, Iran had "increasingly and deliberately ceased performing its JCPOA commitments", including "the accumulation of a highly enriched uranium stockpile which lacks any credible civilian justification and is unprecedented for a state without a nuclear weapons program". The letter detailed additional Iranian violations of the agreement despite the fact that the E3 "have consistently upheld their agreements under the terms of the JCPOA". The activation opened a 30-day window, intended to reengage Iran, "whose refusal to cooperate with the International Atomic Energy Agency's (IAEA) inspectors started the crisis", in diplomatic negotiations before full restoration of sanctions. According to Euronews, Iran's Foreign Minister Abbas Araghchi declared that it was "unjustified, illegal, and lacking any legal basis" and promised that "The Islamic Republic of Iran will respond appropriately". On 28 September, UN sanctions were officially reimposed on Iran.

In October 2025, former defence minister and current political adviser to the Supreme Leader, Ali Shamkhani, stated "If I returned to the defence portfolio, I would move toward building an atomic bomb", and declared that if he could return to the 1990s, "we would definitely build the atomic bomb".

On 3 March 2026, the International Atomic Energy Agency (IAEA) confirmed that while recent bombings had failed to destroy the Natanz nuclear facility, the significant damage which had been done to its entrance buildings had now made it inaccessible. The report stated that although such warheads would require uranium enriched to 90%, this could be achieved in a matter of weeks if Iran were to process its existing stockpile of 441 kg of 60% uranium with its advanced IR-4 and IR-6 centrifuges; However, according to a US official, the methods Iran had been exploring at the time could produce a nuclear weapon, though not one which could be delivered by a ballistic missile. The facility includes an underground Fuel Enrichment Plant (FEP) housing large cascades of gas centrifuges, as well as a smaller Pilot Fuel Enrichment Plant (PFEP) above the ground. Iran has installed thousands of first-generation IR-1 centrifuges and more advanced models (IR-2m, IR-4, IR-6) here. , Natanz was enriching uranium up to 60% , a level approaching weapons-grade.

In the past, the site saw multiple sabotage attacks, including the US-Israeli Stuxnet cyberattack, and explosions in 2020 and 2021, both attributed to Israel. On 22 June 2025, the facility was bombed by the United States military. On 2 March 2026, the facility was again bombed by the United States, with its entrance buildings suffering significant damage. While the facility, which is based underground, remains intact, the significant damage to the entrance buildings which was sustained in these bombings also made it now no longer able to be accessible.

Kuh-e Kolang Gaz La ("Pickaxe Mountain")

Another site excavated by Iran is described as a future centrifuge assembly facility deep beneath Kūh-e Kolang Gaz Lā ("Pickaxe Mountain"), near the Natanz nuclear complex. The installation, which has been under construction, has been reinforced and gradually expanded since around 2021.

According to an analysis of satellite images by the Washington Post, after the American strikes on June 22, Iran began accelerating construction on the underground site of Kūh-e Kolang Gaz Lā tunneled into the Zagros mountain range approximately one mile (1.5 km) to the south of the Natanz nuclear facility. Although work on the site began in 2020, international inspectors were never given access, Fordow's smaller size and heavy fortification make it a particular proliferation concern. The IAEA still inspects Fordow, but Iran's suspension of the Additional Protocol means inspectors no longer have daily access. In June 2025, Iran revealed plans to install advanced centrifuges at the facility. In September 2025, IAEA head Rafael Grossi confirmed that the Fordow facility had in fact sustained significant damage in the June 2025 U.S. strike, including total destruction of "almost all" of the site's "sensitive equipment."

Bushehr

Bushehr is Iran's only commercial nuclear power station, situated on the Persian Gulf coast in southern Iran. Under the JCPOA, Iran agreed to halt work on Arak and redesign the reactor to a smaller, proliferation-resistant version. In January 2016, Iran removed and filled Arak's original reactor core with concrete, disabling it.

Isfahan Nuclear Technology Center

Isfahan, located ~350 km south of Tehran, is another major hub of Iran's nuclear fuel cycle and research activities. The site hosts the Uranium Conversion Facility (UCF) where yellowcake (uranium ore concentrate) is converted into uranium hexafluoride (UF<sub>6</sub>) gas – the feedstock for enrichment. and then by the United States on 22 June 2025.

Tehran Research Reactor (TRR)

Located in Tehran at the headquarters of the Atomic Energy Organization of Iran, the Tehran Research Reactor is a 5 MW pool-type research reactor. Two other sites, Varamin and Marivan, also yielded undeclared man-made uranium particles when IAEA inspectors were granted access in 2020. China, Russia, Belarus, Venezuela, Cuba, and Nicaragua echoed Iran's perspective of "UNSC Resolution 2231 remain[ing] valid and [it having to] be implemented by all countries" with "[t]he unilateral withdrawal of the United States from the JCPOA [being] the primary cause of the [then] current situation." Concerning the specifics of concerns over the uranium particles detected at three sites, the countries believed in the ability of the organization to "verify the non-diversion of nuclear material" arising from pre-2003 nuclear safeguards issues refuted in an IAEA December 2015 resolution, and discounted the report due to not being mandated by IAEA director Rafael Grossi and instead by a November 2024 "politically-motivated, non-consensus resolution".

On 12 June 2025, a day before the start of the Twelve-Day War, Iran announced the activation of a third main uranium enrichment site with active centrifuges following the IAEA's first formal censure of Iran in two decades. While the location has not been disclosed, Iranian officials described it as "secure and invulnerable". In response to Grossi's 19 June 2025 remark "[w]e did not have any evidence of a systematic effort [by Iran] to move into a nuclear weapon" in regard to concerns raised by the May 2025 report, Iran’s Foreign Ministry spokesman Esmaeil Baghaei decried its timing, linking the "absolutely biased report" with Israel's subsequent attacks against "peaceful nuclear facilities [and] innocent civilians". Iran has vowed to continue enriching uranium following the Twelve-Day War.

Costs

Direct financial expenditures

Estimating the direct costs of Iran's nuclear program is complicated by secrecy, but available assessments suggest significant expenditures.

{| class="wikitable"

!Category

!Estimated cost

|Bushehr nuclear plant

|>$10 billion (vs $2B official)

|Broader nuclear infrastructure

|>$100 billion

|Annual operational costs

|$250–$300 million

|Total spending estimate

|>$30 billion

|Rial devaluation (2014–2025)

|~95%

|Energy renovation cost (alternative)

|~$54 billion

Despite the vast reserves of natural gas and abundant solar and renewable energy potential, Iran continues to invest in extremely high-cost nuclear projects. Former Foreign Minister Zarif admitted that financial expenditures spent on nuclear projects could have upgraded the entire energy sector over 20 times. The program has also been closely tied to Iranian techno-nationalist pride, symbolizing scientific progress and national independence. EU, Russian officials and analysts said Iran was pursuing nuclear latency, developing the technical infrastructure to assemble a weapon on short notice while refraining from actual production. The Bulletin of Atomic Scientists said that Iran was using its enrichment program and uranium stockpiles for leverage in international negotiations, and was willing to dilute or export its higher-level enriched uranium in exchange for sanctions relief and prevention of future attacks. Others in the West have cited US and Israeli aggression toward Iran, especially after the 2025 and 2026 escalations, as a strong incentive to weaponize. Some scholars have argued that Israel's nuclear weapons may have incentivized Iran to pursue its own, risking a regional nuclear arms race.

thumb|The words "[[Death to Israel" in Persian displayed on a parade in Iran. Some analysts view Iran's nuclear program as a threat to Israel's security. heightening fears of nuclear terrorism. Alireza Nader argued that a nuclear-armed Iran could feel emboldened to increase its support for non-state militant groups while deterring retaliation through its newfound nuclear leverage. Some analysts and US officials maintain that a nuclear-capable Iran would likely attempt to destroy Israel or threaten its existence. In the 21st century, many Western and Israeli politicians have stated "Iran can never have a nuclear weapon", a political slogan of Israel's government and its international supporters.

Notes

References

External links

The first-ever English-language website about Iran's nuclear energy program
Iran's Atomic Energy Organization
In Focus: IAEA and Iran, IAEA
Iran's Nuclear Program collected news and commentary at The New York Times
Iran Nuclear Resources, parstimes.com
Annotated bibliography for the Iranian nuclear weapons program from the Alsos Digital Library for Nuclear Issues