Nuclear Program of Iran

Iran's nuclear program began in the 1950s with assistance from the United States under the Atoms for Peace initiative. It includes research, uranium conversion and enrichment, power generation and reactor development. Iran says its program is peaceful and that it has a right to nuclear technology under the Nuclear Non-Proliferation Treaty. The United States, Israel and other governments have raised concerns that enrichment and undeclared activities could enable production of nuclear weapons.

The International Atomic Energy Agency (IAEA) monitors Iran's nuclear activities under safeguards agreements. Disputes over declarations, inspections and uranium enrichment led to United Nations sanctions and years of negotiations. The 2015 Joint Comprehensive Plan of Action (JCPOA) restricted Iran's nuclear activities in exchange for sanctions relief. The United States withdrew from the agreement in 2018, and Iran later exceeded several of its limits.

Israeli and U.S. military strikes on Iranian nuclear facilities in June 2025 damaged important sites, but the extent of the program's setback remained uncertain. Iran restricted cooperation with the IAEA, complicating verification of nuclear material and facilities. The program remains a central issue in international security and Iran's relations with Israel, the United States and European states.

History

Early program and revolution

Iran's nuclear program began under Mohammad Reza Shah Pahlavi, who sought nuclear power as part of a modernization effort. In 1957, Iran and the United States signed a civil nuclear cooperation agreement. The Tehran Research Reactor began operating in 1967 with U.S. assistance. Iran signed the Nuclear Non-Proliferation Treaty in 1968 and ratified it in 1970, agreeing to safeguards intended to prevent diversion of nuclear material to weapons.

The Shah planned a large nuclear power program and signed contracts with Western companies. Construction of the Bushehr plant began with German assistance in the 1970s. The 1979 revolution disrupted projects and led many foreign contractors to leave. The new government initially questioned the value of nuclear power, but later revived elements of the program during and after the Iran–Iraq War.

Iran sought technical assistance and equipment from foreign suppliers, including Russia, China and European companies. The program expanded with facilities for uranium conversion, enrichment and heavy-water production. Some efforts were concealed from the IAEA or not declared when required, leading to international scrutiny and claims that Iran had failed to meet its safeguards obligations.

Discovery and negotiations

In 2002, an Iranian opposition group publicly disclosed the existence of undeclared nuclear facilities at Natanz and Arak. The revelations prompted IAEA inspections and negotiations with Britain, France and Germany. Iran agreed temporarily to suspend enrichment activities and signed an additional protocol allowing expanded inspections, though its parliament did not ratify the protocol.

In 2005, Mahmoud Ahmadinejad became president and Iran resumed some nuclear activities. The IAEA reported unresolved questions about past experiments and the completeness of Iran's declarations. The United Nations Security Council adopted resolutions requiring Iran to suspend enrichment and later imposed sanctions. Iran argued that its activities were lawful under the treaty and rejected the demand to stop enrichment.

Talks between Iran and the P5+1 group—the United States, Britain, France, Russia, China and Germany—continued intermittently. Sanctions targeted banking, energy exports and individuals involved in the program. Iran expanded enrichment capacity and accumulated uranium stockpiles, while negotiations repeatedly stalled over verification and the scope of sanctions relief.

JCPOA and U.S. withdrawal

In July 2015, Iran and the P5+1 reached the JCPOA. The agreement placed limits on enrichment levels, centrifuge numbers and uranium stockpiles, and required redesign of the Arak reactor. It provided the IAEA with enhanced monitoring in exchange for the lifting of nuclear-related sanctions. The agency verified Iran's initial implementation.

In May 2018, U.S. president Donald Trump withdrew the United States from the JCPOA and reimposed sanctions. Iran remained in the agreement for a year, then began reducing compliance in stages. It increased enrichment levels and stockpiles and installed advanced centrifuges. European parties sought to preserve the agreement, but efforts to restore it failed.

Iran's expansion reduced the time it might need to produce enough highly enriched uranium for a weapon, though producing a weapon would also require additional steps and decisions. The IAEA reported that monitoring was impaired after Iran removed surveillance equipment and restricted inspections. Governments disagreed over the meaning of Iran's technical capabilities and intentions.

Attacks and escalation

Iran's nuclear facilities and personnel faced sabotage and attacks. Israeli officials did not consistently acknowledge responsibility for covert operations, but reporting attributed explosions and cyberattacks to Israel. Iranian scientists were assassinated, including Mohsen Fakhrizadeh in 2020. Iran blamed Israel and vowed retaliation. The covert campaign increased distrust and hardened positions on both sides.

In June 2025, Israel launched strikes against nuclear and military targets in Iran, including Natanz, Isfahan and Fordow. Senior military commanders and scientists were killed. The United States later struck facilities at Fordow, Natanz and Isfahan using aircraft and missiles. Iran retaliated against Israel and a U.S. base in Qatar. A ceasefire ended the twelve-day war, but the long-term damage to nuclear infrastructure was not independently established.

After the strikes, Iran suspended some cooperation with the IAEA and debated whether to withdraw from the Nuclear Non-Proliferation Treaty. Inspectors faced difficulty verifying the status of enriched uranium and the condition of facilities. The absence of reliable monitoring increased uncertainty and complicated diplomatic efforts.

The safeguards dispute concerns both undeclared materials and the completeness of Iran's declarations. The IAEA reported that it had questions about uranium particles found at sites Iran had not declared and sought explanations about past activities. Iran disputed some findings and said the agency's questions were politically motivated. The agency's technical assessments distinguished verified material from unresolved issues.

Iran's enrichment program depended on centrifuges that separate uranium isotopes. Older IR-1 machines were replaced in part by more advanced models, which can enrich uranium faster. The number and type of centrifuges, the level of enrichment and the amount of stored material are key measures used by inspectors and governments to estimate proliferation risk.

Main facilities

Natanz

Natanz is Iran's main uranium enrichment complex, located in central Iran. It includes underground halls designed to protect centrifuges and above-ground buildings. The site has hosted enrichment using older and advanced centrifuge models. Natanz was damaged in explosions and military strikes, and Iran subsequently reported repairs and construction of additional underground facilities.

The IAEA monitors declared parts of the site through cameras, seals and inspections when access is permitted. Disruptions to monitoring have made it harder to verify the size and location of Iran's stockpile. Natanz remains central to the technical and diplomatic dispute because of its scale and enrichment capacity.

Fordow

Fordow is an enrichment facility built within a mountain near Qom. Its location offers protection against air strikes. Iran disclosed the facility to the IAEA in 2009 after Western intelligence agencies learned of its existence. Under the JCPOA, enrichment at Fordow was restricted and the site was to be converted for research. Iran later resumed enrichment there beyond the agreement's limits.

During the June 2025 war, U.S. forces struck Fordow with specialized munitions. The extent of damage to underground areas remained uncertain. Satellite imagery and official statements provided partial information, but access for independent verification was limited.

Isfahan, Arak and Bushehr

The Isfahan Nuclear Technology Center converts uranium into forms used in enrichment and fuel production. It has facilities for conversion, fabrication and research. The Arak heavy-water reactor was redesigned under the JCPOA to reduce its potential production of plutonium. Iran later continued development at the site, while international negotiations addressed the reactor's configuration and spent fuel.

Bushehr is Iran's operating nuclear power plant on the Persian Gulf coast. Russia helped complete the first reactor, which began generating electricity in 2011, and supplied fuel under an agreement. Bushehr is subject to IAEA safeguards and is distinct from the enrichment facilities at Natanz and Fordow.

Iran has also built research centers, uranium mines and fuel-cycle facilities. The program relies on a network of technical institutions, universities and state organizations. Sanctions and export controls shaped procurement and encouraged domestic production, though Iran continued seeking foreign expertise and equipment.

The IAEA's access evolved over time. Iran implemented the Additional Protocol for a period but later stopped applying it after the United States withdrew from the JCPOA. Inspectors lost access to some cameras and monitoring data, and the agency's ability to reconstruct continuity of knowledge weakened. These gaps increased uncertainty even when inspectors could visit declared facilities.

The Nuclear Non-Proliferation Treaty allows member states to develop nuclear energy for peaceful purposes under safeguards. Iran argued that it had not violated the treaty by enriching uranium, while other governments emphasized its safeguards violations and past concealment. The legal debate focused on treaty obligations, transparency and whether Iran's activities were consistent with its stated civilian aims.

International sanctions were imposed through United Nations resolutions and national measures. Restrictions on banking, oil sales, shipping and technology procurement were intended to pressure Iran to suspend enrichment and cooperate with inspectors. The sanctions also affected civilian trade and economic conditions, producing debate over whether economic pressure achieved its security objectives.

Costs

The program required major public investment in facilities, personnel and security. International sanctions reduced oil exports, restricted access to financial markets and raised the costs of acquiring equipment. The economic burden was borne by the Iranian state and population, while the government argued that nuclear technology would provide energy and scientific development.

The economic costs of sanctions were difficult to separate from other factors, including oil prices, domestic policy and corruption. Restrictions affected trade and investment and contributed to inflation and currency pressure. The value of the nuclear program was debated inside Iran, where supporters emphasized sovereignty and technological independence while critics questioned whether it justified the economic impact.

Military strikes added direct damage to facilities and threatened future energy and research infrastructure. The costs included repair, replacement and the loss of specialized scientists and technicians. Uncertainty about facility damage and nuclear material increased the economic and security consequences of the conflict.

Analysis

Iran's nuclear program presents a distinction between technical capability and a political decision to build a weapon. Enrichment can produce low-enriched fuel for power reactors or, at higher levels, material suitable for a weapon. Monitoring, stockpile declarations and access to facilities are essential to assess the program's direction. Governments disagree about how much time remains before Iran could produce a weapon and whether it has made a decision to do so.

Supporters of the JCPOA argued that inspections and limits reduced risk and provided visibility. Critics said the agreement's duration and scope did not address missiles or Iran's regional activities. After the U.S. withdrawal, Iran's enrichment expanded and inspectors lost access. Military attacks damaged infrastructure but could not eliminate scientific knowledge or guarantee that nuclear work would stop.

Analysts warned that strikes could delay the program while increasing Iran's motivation to seek a weapon or withdraw from international commitments. Others argued that failing to act could allow Iran to cross a threshold that would be difficult to reverse. The policy challenge is to combine verification, diplomacy and deterrence without triggering a wider war.