Inside Iran’s Nuclear Program: Major Sites Explained

Prior to the Israeli airstrikes on Friday, Washington and Tehran had engaged in multiple discussions regarding Iran’s nuclear program as worries escalated about its swift growth.

In recent years, Iran has considerably intensified its nuclear endeavors after a significant agreement with global powers to limit its nuclear activities in exchange for sanctions relief began to fall apart in 2018, when the United States withdrew unilaterally.

As of mid-May, Iran’s total stockpile of enriched uranium was reported to be around 9,247.6 kilograms—more than 45 times the cap established in the 2015 deal—according to the latest report by the International Atomic Energy Agency (IAEA).

Within this stockpile, an estimated 408.6 kilograms of uranium is enriched to 60%, a mere step away from the 90% required for a nuclear weapon.

Theoretically, Iran has enough material of near-weapons grade to produce roughly 10 nuclear bombs, as defined by the Vienna-based IAEA.

However, Iran has continually denied any intention of pursuing nuclear weapons.

Below is a list of Iran’s significant nuclear facilities, which are subject to regular inspections by the UN nuclear watchdog:

Uranium Enrichment Facilities

Natanz

Located about 250 kilometers (150 miles) south of Tehran, Natanz is Iran’s primary uranium enrichment site, heavily fortified and revealed to the public in 2002.

This facility operates nearly 70 cascades of centrifuges across its two enrichment plants, one of which is underground. A cascade refers to a series of centrifuges—the machinery used for enriching uranium.

The site suffered damage in April 2021, which Iran attributed to sabotage by Israel.

On Friday, Israeli operations targeted Natanz, described by Israeli Prime Minister Benjamin Netanyahu as an assault on the “core of Iran’s nuclear enrichment program,” focusing on the facility and its nuclear scientists.

IAEA Director Rafael Grossi confirmed that Natanz was indeed “among the targets.”

Fordo

This secret facility, built in defiance of UN resolutions beneath a mountain near the sacred city of Qom, was first publicly disclosed in 2009.

Initially labeled as an “emergency” site designed to withstand potential airstrikes, Fordo is now acknowledged to be an enrichment facility capable of accommodating around 3,000 centrifuges.

In 2023, uranium particles enriched up to 83.7% were found at Fordo, which Iran attributed to “unintended fluctuations” during the enrichment process.

Uranium Conversion and Research Reactors

Isfahan

At Isfahan’s uranium conversion facility in central Iran, mined uranium is processed into uranium tetrafluoride (UF4) and subsequently into uranium hexafluoride (UF6), which serves as feed gas for centrifuges.

The facility underwent industrial testing in 2004 upon completion and also houses a nuclear fuel fabrication center, launched in 2009, producing low-enriched fuel for electricity generation.

In July 2022, Iran declared intentions to build a new research reactor at this facility.

Arak

Construction on the heavy-water research reactor in Arak, located near the village of Khondab, commenced in the 2000s but was suspended under the stipulations of the 2015 agreement.

Iran has since informed the IAEA of its plans to operationalize the reactor by 2026.

This research facility is officially designated to produce plutonium for medical research and includes a heavy-water production plant.

Tehran

The Tehran Nuclear Research Center contains a reactor provided by the United States in 1967 for generating medical radioisotopes.

Nuclear Power Plant

Bushehr

Iran’s sole nuclear power plant, located in the southern city of Bushehr, was constructed by Russia and began operating at reduced capacity in 2011 before integrating into the national power grid in 2012.

Russia continues to supply nuclear fuel to the plant, which operates under IAEA oversight.

Originally, a German company initiated the plant’s construction, designed for a nominal capacity of 1,000 megawatts, although the project was halted following the 1979 Islamic revolution. Moscow later saw it to completion.

Darkhovin and Sirik

Iran kicked off construction on a 300-megawatt power plant in Darkhovin in late 2022. In early 2024, work began on a new complex of four plants in Sirik, situated in the Strait of Hormuz, boasting a total capacity of 5,000 megawatts.