On April 19, 2024, in a dramatic escalation of tensions in the Middle East, Israel carried out targeted airstrikes on an air defense site located in Isfahan, Iran. This significant event has drawn global attention not only due to its immediate military implications but also because Isfahan is home to two of Iran’s major nuclear facilities: the Nuclear Technology Center in Isfahan and the Natanz Enrichment Center. The proximity of the airstrike to these pivotal sites has set the international media abuzz with speculation regarding the status and potential targeting of Iran’s nuclear infrastructure.
Since 2018, Iran has systematically reduced the scope of work for international inspectors, significantly diminishing the availability of public information regarding its nuclear activities. The 2015 Joint Comprehensive Plan of Action (JCPoA)—an accord intended to prevent Iran from rapidly developing nuclear weapons in exchange for the lifting of economic sanctions—sought to limit Iran’s nuclear reserves, ensuring that it would take at least a year to develop a nuclear weapon. The United States had calculated that this 12-month window would provide sufficient time for its intelligence agencies to detect any nuclear weapon development in Iran and facilitate diplomatic intervention. However, the landscape has shifted dramatically since 2021, with Iran enriching uranium to 60% purity and higher, drastically lowering the time needed for a nuclear breakout.
Enriching uranium involves increasing the concentration of uranium-235, the isotope necessary for nuclear reactions. Natural uranium contains approximately 0.7% of uranium-235. To manufacture a nuclear weapon, uranium needs to be enriched to about 90% uranium-235. Achieving 60% enrichment is a significant milestone towards reaching weapons-grade material, which accelerates the timeline required for producing a nuclear weapon.
**Principal Conclusion-1:** If Iran resolves to pursue a nuclear weapon, it is highly probable that it could develop the requisite capabilities in a short period.
On April 23, 2024, an Iranian lawmaker sparked further concerns by announcing that Iran could commence testing nuclear weapons within a week of receiving the order. In March 2023, U.S. estimates suggested that Iran could amass enough high-enriched uranium (HEU) to construct a bomb in just 10-15 days. However, the Royal United Services Institute (RUSI), a British defense and security think tank, highlighted that integrating a nuclear warhead onto a missile would likely take between six months to a year.
In December 2023, Israeli intelligence indicated that Iran had not yet decided to actively pursue the development of a nuclear weapon. Despite this cautionary assessment, the rapid advances in uranium enrichment initiated by Iran in April 2021 significantly reduced the time necessary for any potential breakout. According to the International Atomic Energy Agency (IAEA), Iran now possesses enough enriched material to manufacture at least two nuclear weapons.
**Principal Conclusion-2:** Since 2021, the restricted number of international inspections likely has not deterred Iran from expanding its undisclosed nuclear sites.
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In March 2024, U.S. intelligence posited that if Iran decided to move towards developing a nuclear weapon, it would probably use secret, rather than officially declared, nuclear facilities. Back in 2018, the IAEA had identified four undeclared nuclear sites in Iran, each established before 2003. Since the publication of this report, there has been no discernible indication of new or expanded undeclared sites.
However, the strategic focus of Iran has evolved since 2021. Rather than hiding its nuclear facilities, Iran has concentrated on enhancing their toughness and security. This shift in strategy stems partially from the repercussions of an Israeli attack in July 2020 on the Natanz centrifuge production center, a critical facility for uranium enrichment. This attack prompted Iran to relocate the facility underground to better safeguard its operations.
**Principal Conclusion-3:** It is doubtful that airstrikes could effectively halt Iran’s nuclear weapons development.
The Joint Military Commission for Nuclear Affairs (JMCN)—an organization dedicated to assessing and reporting on the military aspects of nuclear programs and facilities—estimates that the Natanz nuclear facility is situated approximately 80-100 meters underground. In contrast, the most powerful bunker-busting bomb available to Israel and the West, the American-made GBU-57A/B Massive Ordnance Penetrator (MOP), can penetrate only around 60 meters before detonation.
While most of Iran’s nuclear sites are located above ground, the underground Natanz facility remains its principal enrichment location, housing around 50,000 centrifuges essential for the nuclear fuel cycle. Centrifuges function by spinning uranium hexafluoride gas at high velocities to increase the concentration of the uranium-235 isotope. This process effectively separates the lighter uranium-235 from the heavier uranium-238. The level of enrichment varies depending on the intended use, with lower levels required for nuclear power and higher levels necessary for nuclear weapons.
Israel has a history of employing diverse tactics to inhibit Iran’s nuclear ambitions, including clandestine operations and cyber-attacks. In April 2021, U.S. intelligence reported that an Israeli cyber attack on the Natanz facility had delayed Iran’s nuclear progress by approximately nine months.
**Summary of Analysis:**
It is assessed with moderate confidence that Iran could potentially develop nuclear weapons within 12 months, assuming it utilizes its declared nuclear facilities. However, if Iran opts for leveraging hidden facilities for its breakout, it would likely take significantly more than 12 months to develop such capabilities.
