Tehran’s Uranium Enrichment Operations: Strategic Importance of Its Underground Facilities

Iran’s nuclear program and its history date back to its pre-revolutionary past. In the current period, the importance of Tehran's uranium enrichment operations has extended owing to its importance in the geopolitical developments in West Asia. Over the years, Tehran has accelerated its uranium enrichment program, which has raised a series of international alarms.

Illustration by The Geostrata

Since Iran's partial withdrawal from the Joint Comprehensive Plan of Action (JCPOA), it has gradually escalated its enrichment levels, reaching 60% uranium-235 isotope. Such facilities have attracted aerial attacks and sabotage activities. Since the early 2000s, Iran has deliberately invested in deep-underground uranium enrichment facilities including Natanz and Fordow. For Instance, June 2025 witnessed the U.S. and Israeli forces deploying bunker-buster munitions in Operation Midnight Hammer. 

This underground design remains Iran’s bulwark, preserving centrifuges and infrastructure, shielding uranium reserves and deterring ,international intervention. Therefore, the strategic value of these underground havens defines the evolving balance between the non-proliferation enforcement and Iran’s nuclear sovereignty. This article has attempted to explore how the underground nuclear facilities are important for Iran’s uranium enrichment activities.

REDUCTION OF CHANCES OF AERIAL AND SABOTAGE ACTIVITIES 

The deeply buried facilities provide Iran with the capability to prevent its adversaries from sabotaging its nuclear ambitions. In such cases, the construction attempts to replace its operational systems above the ground, often considered one of the prime targets of its adversaries. The attack on its underground nuclear facility, Natanz, is a case in point.

The attack resulted in an explosion and fire. While the above-ground electrical systems were destroyed, the underground centrifuge halls remained largely intact. This is an exemplary instance of the resilience of the fortified infrastructure.

In the majority of cases, the construction of underground facilities by Iran is to prevent its adversaries from positioning its facilities beyond the range of weapons of any resident Western powers in the region.  It also enables Iran to prevent any potential military hostilities and actions.

Therefore, it reduces the chances of operations by conventional forces ineffective. Iran’s strategic ambition is the imposition of high operational and financial costs on any military intervention which deters adversaries due to the sheer difficulty of destroying these facilities. Iran will attempt to shield its activities from attacks and transfer valuable logistics to safer areas in the current period.

Such a case can be observed in the case of relocating the activities of the Iran Centrifuge Technology Company (TESA) located in Karaj to Natanz. Therefore, the attempts by Iran to transfer and guard its assets and centrifuge parts are evident in its latest actions. This move followed the 2021 sabotage of the Karaj site, widely attributed to Israel, which resulted in the damage of precision machinery used in centrifuge production.

Such cases are evident by its adversaries who attempt to disrupt its capabilities concerning uranium enrichment and weapon capabilities. Recently, several centrifuge facilities have been the object of explosions and power outages damaging thousands of centrifuge facilities.

According to IAEA reports, these attacks have failed to halt Iran’s progress. Its enriched uranium stockpiles continued to grow. Such cases attempt to protect their facilities from precision-guided weapons and bombs with capabilities to burst bunker facilities. The facilities are usually located 80 to 100 metres deep.

This depth is protected by mountainous terrain, making it beyond the penetration range of most known conventional military weapons. Such facilities make it difficult to destroy even with the use of sophisticated weapons systems like the GBU-57 that can destroy an underground facility 60 metres deep before detonating.

In the current scenario, the existing weapons systems cannot destroy underground facilities utilised for uranium enrichment purposes. Therefore, Iran’s facilities in the present era not only prevent aerial bombardments but also sabotage attempts. 

UNDERGROUND FACILITIES IN RESPONSE TO IMMEDIATE TENSIONS

The trends of Iran’s expansion and construction of new facilities have been triggered by immediate tensions surrounding attacks by its adversaries. The construction operations in Fordo, following the killing of an Iranian scientist in Tehran is a case in September 2021, is a case in point.

Renewed construction attempts have been observed during a similar period in Fordo. The facility is located northwest of the holy site in the Shiite city of Qom, around 90 kilometres from Tehran. In such cases, major developments with detrimental effects on Iran’s nuclear programs result in attempts to guard its facilities in secure locations.  U.S. officials ' exposure of the facility in Fordo is a case in point.

The investigation attempts resulted in public revelations of the facility’s importance in Iran’s military purposes. 

Therefore, the regime in Tehran attempts to secure its locations by placing them in secure locations guarded by anti-aircraft guns and other fortifications, making it capable of housing at least 3,000 centrifuges in small and undetectable locations. 

IMPROVED CAPABILITY OF ITS UNDERGROUND FACILITIES 

The underground facilities provide Iran with opportunities to conduct uranium replenishment measures beyond the 4.1% threshold. Such a case can be seen in the enrichment facility in Fordo, where Iran has enriched U-235 beyond the threshold. As per the reports by the International Atomic Energy Agency (IAEA), Iran has enriched around 20% of its six centrifuge cascades.

Similar reports by IAEA in November 2022 and April 2021 revealed Iran has enriched uranium up to 60% in both Natanz and Fordo facilities.

The reports by IAEA have confirmed that Iran has attempted to increase its enrichment capacities in these centres by deploying six additional IR-6 cascades in Fordo, making it capable of enriching uranium to 20%.

Therefore, the improved capabilities of Iran to produce more than 4.1% of uranium replenishment demonstrates its improved capability and capacity of its underground centres. The functioning of the nuclear facilities are not the only functioning bodies. In most cases, nuclear reactors are working at extended capacity.

This has resulted in the production of enriched uranium and nuclear weapons. Such capacities not only demonstrate Iran’s expanded capacity but also its gradual transformation to produce uranium-ready atomic weapon systems. 

FAILURE OF JCPOA AND STRATEGIC IMPORTANCE OF UNDERGROUND FACILITIES

Before the existence of the JCPOA in 2015, Iran maintained its capability to increase its uranium enrichment activities from 5% to 20%. Under the JCPOA, Iran agreed to limit uranium enrichment to 3.76%, reduce its low-enriched uranium (LEU) stockpile to 300kg of UF-6, dismantle over 13,000 centrifuges, and deactivate Fordow’s enrichment cascades for 15 years.

However, the fortified underground nuclear sites of Natanz and Fordow critically undermine the objectives of the JCPOA. Additionally, the withdrawal of the U.S. in 2018 made Iran increase its stockpile, with facilities like Fordo and Natanz producing 60% of enriched aluminium with metal.

Therefore, the deal’s failure resulted in increased strategic importance to its underground facilities, enabling them to enrich uranium in an expanded capacity. These sites now play a vital role in safeguarding enrichment capabilities from foreign intervention. As captured in June 2025 satellite imagery, heavy equipment was actively repairing Fordow after U.S. bunker-buster strikes, while IAEA assessments suggest these facilities remain fully repairable within months.

Therefore, JCPOA’s collapse elevated the strategic importance of Iran’s subterranean infrastructure. Their deep placements ensure that even if international powers re-engage diplomatically, Iran retains a protected breakout capability and continues to hold significant leverage in any future negotiations.

In conclusion, Iran’s nuclear program is dependent on underground facilities that have proved key to its uranium enrichment exercises. The instances of the latest attacks on its above-ground facilities and human resources have increased its tendencies to shift its operations below the surface level to fast-track its development of weapons-grade nuclear facilities.

Therefore, what emerges is not merely a tactical response to threats but a strategic, long-term architectural doctrine that increases its leverage. Tehran has attempted to fulfil its objectives of a nation capable not only of acquiring atomic weapons but also of protecting its associated assets using its facilities constructed by taking advantage of its varied geography.

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BY ANIRBAN DUTTA AND SHAINA ARORA

CENTRE FOR DIPLOMACY INNOVATION

TEAM GEOSTRATA

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