On April 19, 2024, Israel carried out a significant military operation, launching airstrikes on an air defense site in Isfahan, Iran. This strategic location is notably near Iran’s major nuclear facilities—the Nuclear Technology Center in Isfahan and the Natanz Enrichment Center. The proximity of this airstrike to critical nuclear sites has prompted global media to speculate about the status of Iran’s nuclear program and whether these facilities were the intended targets.
Since 2018, Iran has restricted access for international inspectors, thereby reducing the transparency around its nuclear program. In 2015, the Joint Comprehensive Plan of Action (JCPoA) was instituted to curtail Iran’s nuclear capabilities and provide assurances that it would take at least one year for Iran to develop a nuclear weapon, in exchange for lifting economic sanctions. The United States hoped that this 12-month window would offer sufficient time for intelligence agencies to detect any advance toward nuclear weapon development and respond diplomatically. However, developments since 2021 have cast shadows over these assurances.
Starting from 2021, Iran began enriching uranium to 60% purity and higher, a substantial step toward achieving weapons-grade material, which requires around 90% uranium-235. Natural uranium contains only about 0.7% of uranium-235, the isotope essential for nuclear reactions. Enriching uranium to 60% significantly reduces the time required to enrich it further to weapons-grade level.
Principal Conclusion-1: If Iran determines to pursue the development of a nuclear weapon, it is highly probable that it could achieve this capability within a very short time frame.
On April 23, 2024, an Iranian lawmaker announced that Iran could start testing nuclear weapons within a week of receiving the order. In March 2023, U.S. intelligence had estimated that Iran could generate enough high-enriched uranium (HEU) to construct a bomb in merely 10-15 days. However, the Royal United Services Institute (RUSI), a British defense and security think tank, noted that it would likely take between six months to a year to fit a nuclear warhead onto a missile.
Further complicating the matter, in December 2023, Israeli intelligence reported that Iran had not committed to developing a nuclear weapon. Despite this, the enrichment activities starting in April 2021 represented a significant stride in reducing the time required for a ‘breakout’ effort. According to the International Atomic Energy Agency (IAEA), Iran currently possesses enough nuclear material to produce two nuclear weapons.
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Principal Conclusion-2: The reduction in international inspections since 2021 has possibly not dissuaded Iran from expanding its undisclosed nuclear sites.
In March 2024, U.S. intelligence suggested that if Iran were to advance its nuclear weapons program, it would likely utilize hidden, rather than its declared, nuclear facilities. In 2018, the IAEA identified four undeclared nuclear sites in Iran, established prior to 2003. Since the release of this report, there has been no indication of new or expanded undeclared sites. Instead, since 2021, Iran’s strategy has shifted towards fortifying and securing its nuclear facilities rather than concealing them. This change was motivated by an Israeli attack in July 2020 on the Natanz centrifuge production center, prompting Iran to relocate this facility underground.
Principal Conclusion-3: Airstrikes are unlikely to effectively halt Iran’s nuclear weapons development.
The Joint Military Commission for Nuclear Affairs (JMCN) estimates that the Natanz nuclear facility is located 80-100 meters underground. In contrast, the most powerful bunker-busting bomb available to Israel and Western allies, the American-made GBU-57A/B Massive Ordnance Penetrator (MOP), can penetrate only up to 60 meters before exploding.
While most of Iran’s nuclear infrastructure is above ground, the Natanz underground facility is the primary enrichment site, housing 50,000 centrifuges essential for the nuclear fuel cycle. These centrifuges operate by spinning uranium hexafluoride gas at high speeds to increase the concentration of uranium-235. The level of enrichment is dictated by the intended application, with lower levels for nuclear power and higher levels for nuclear weapons.
Previously, Israeli efforts to disrupt Iran’s nuclear ambitions included clandestine operations and cyber attacks. For instance, in April 2021, U.S. intelligence reported that an Israeli cyber attack on the Natanz facility delayed Iran’s progress by approximately nine months.
Summary of Analysis:
It is assessed with moderate confidence that Iran could potentially develop nuclear weapons within 12 months if it uses its declared nuclear facilities. However, should Iran choose to utilize hidden facilities for a breakout, it would likely require significantly more than 12 months to achieve such a capability.
