Nuclear Expansion: Iran Approves $25 Billion Russian-Built Reactors

International oversight of Iran’s nuclear program has weakened as Tehran and Moscow accelerate their construction of new power infrastructure. The International Atomic Energy Agency reported in June that it could not inspect four uranium enrichment facilities during its latest reporting period. This gap in monitoring coincides with the signing of a multibillion-dollar agreement for a new Russian-built nuclear plant in southern Iran.

In September 2025, the two nations signed a deal worth $25 billion to construct the Sirik nuclear power plant in Hormozgan Province. The site is located near the Strait of Hormuz. Iranian state news agency IRNA reported that the completed facility would generate approximately 5 gigawatts of electricity. For comparison, the finished Bushehr complex on Iran’s southern coast will have a capacity of under 3 gigawatts.

Rosatom, Russia’s state nuclear corporation, is building the new facility. The corporation has also continued operations at the existing Bushehr plant despite regional conflicts. Following the start of the US-Iran war in February, Rosatom evacuated most of its staff. By October 11, the agency reported that 135 engineering and technical specialists had returned to the site. Construction on a second Bushehr reactor unit is more than 60 percent complete, with operations targeted for 2029. Work on a third unit is also underway.

The legal framework for this cooperation is the Comprehensive Strategic Partnership Treaty, which entered into force in October 2025. The practical details are outlined in the intergovernmental Cooperation Plan for 2024 to 2026, approved in September 2024. This partnership provides Russia with commercial opportunities and a foothold in the Middle East. For Iran, the arrangement offers access to nuclear technology, expertise, and fuel supplies.

Analysts suggest the relationship favors Moscow. Nikita Smagin, a researcher at the Carnegie Endowment for International Peace, wrote in November 2025 that the balance in the relationship is shifting in Russia’s favor. He noted that Iran is in dire need of investment and that Russia remains one of the few available sources. Dmitry Kovchegin and Arkady Mil-Man of Israel’s Institute for National Security Studies described Moscow’s policy as a calculated balancing strategy. They argued that Russia provides limited assistance to avoid affecting the balance of power while seeking to improve relations with the United States.

The expansion of nuclear projects has raised concerns among nonproliferation specialists. The IAEA stated in its June 4 report that it could not verify the status of nuclear material at unvisited sites. The agency also could not confirm whether Iran had suspended uranium enrichment, reprocessing of spent reactor fuel, and heavy-water-related activities. These processes can support the production of nuclear weapons.

Some experts point to Iran’s accumulation of uranium enriched to 60 percent. This level is not weapons-grade but can be further enriched to around 90 percent, the level generally associated with nuclear weapons. The US-based Arms Control Association stated in a June 2025 analysis that enrichment to 60 percent has no civil justification. The group said this level puts Iran in a better position to quickly produce enough weapons-grade material for a bomb.

Western sanctions continue to pressure both economies. Russia faces extensive sanctions imposed after its full-scale invasion of Ukraine in February 2022. These measures target key sectors including energy, finance, trade, and defense. Iran has faced decades of US and international sanctions over its nuclear program and support for armed groups in the Middle East. Recent restrictions also target Iran’s ballistic missile program and military cooperation with Russia, including Tehran’s supply of drones used in the war against Ukraine.