Iran's Nuclear Complex: A Post-12-Day War Refresher
The June 13-24, 2025, “12-Day War” was a direct escalation of long-standing tensions.
Israel launched Operation Rising Lion with massive airstrikes on Iranian nuclear and military targets, later joined by U.S. strikes on June 22 targeting key enrichment and conversion sites.
The campaign aimed to degrade Iran’s nuclear program, which the IAEA had declared non-compliant days earlier. While physical damage was extensive, Iran retained its scientific expertise, much of its enriched uranium stockpile (~400 kg of 60% Highly enriched uranium, HEU) and is now fortifying deeper underground facilities.
With U.S.-Iran talks ongoing and satellite imagery showing repair and hardening efforts, here is a site-by-site status update on the major facilities.
Tehran Nuclear Research Center (TNRC) and Research Reactor
The TNRC houses Iran’s primary research reactor: the Tehran Research Reactor (TRR), a 5 MW light-water unit supplied decades ago by the U.S. and used for medical isotope production and research. It operates on high assay low-enriched uranium (HALEU) and remains under IAEA safeguards. During the war, one building linked to centrifuge or fuel activities sustained damage, but the TRR avoided any issues. No major radiological issues were reported.
Natanz Uranium Enrichment Complex
Iran’s flagship enrichment site in central Iran features the underground Fuel Enrichment Plant (FEP) and above-ground Pilot Fuel Enrichment Plant (PFEP). Israeli strikes destroyed most of the above-ground infrastructure, while subsequent U.S. bunker-busters further damaged underground halls. Centrifuge cascades were severely affected, rendering large-scale enrichment inoperable. As of early 2026, satellite imagery shows limited cleanup, roof repairs over damaged structures, and fortification of utilities. The site remains a shadow of its former capacity.
Fordow Uranium Enrichment Complex
Buried deep in a mountain, this hardened site was Iran’s key location for higher-level enrichment (up to 60%).
Israeli strikes caused initial damage, but U.S. B-2 bombers delivered 12-14 GBU-57 MOPs on June 22, penetrating and destroying ventilation shafts, tunnel portals, and “almost all sensitive equipment,” per IAEA Director General Rafael Grossi.
The facility is effectively inoperable for enrichment. Minimal post-war activity has been observed. Entrances remain damaged or reinforced.
Esfahan Nuclear Complex
This site south of Tehran serves as the hub for uranium conversion (yellowcake to UF6 gas), fuel fabrication (for the TRR), chemical labs, and a nuclear technology/research center. It includes small research reactors, such as a Chinese-supplied miniature neutron source reactor (MNSR ~30 kW) and subcritical assemblies for training and experiments. Israeli strikes damaged multiple buildings including the central lab, uranium conversion sections, TRR fuel manufacturing plant, and a uranium metal processing facility under construction. U.S. Tomahawk strikes targeted tunnel entrances possibly used for HEU storage. Post-war: roofs have been added over some damaged buildings for protection. Tunnel entrances have been sealed with earth and fortified. The small research reactors’ exact operational status is unclear amid restricted access.
Pickaxe Mountain (Kuh-e Kolang Gaz La) Underground Complex
Approximately 2 km south of Natanz, this buried site was notably not targeted during the 12-Day War. Construction began years earlier and accelerated afterward.
Satellite imagery from late 2025 into February 2026 shows ongoing fortification – strengthened tunnel entrances with concrete, soil/rock cover, security perimeters, and additional barriers. Iran has declared it for advanced centrifuge assembly, but analysts assess it could host covert enrichment, HEU storage, or a hardened fallback plant.
It remains uninspected by the IAEA and represents Iran’s clearest effort to reconstitute capabilities in a strike-resistant location.
Activity here stands out amid stagnation at traditional sites.
Arak (Khondab) Heavy Water Reactor and Related Facilities
The IR-40 heavy water reactor near Arak was intended for plutonium production but never fueled or operational under JCPOA redesign commitments. It was struck by Israel on June 19. The containment dome was breached, the core destroyed, and adjacent heavy water production infrastructure damaged. With no nuclear material inside, there was no radiological release. The reactor is now permanently crippled and will not be completed in its prior form, effectively closing Iran’s plutonium route for the foreseeable future.
Key Changes Since the 12-Day War
The strikes destroyed or degraded above-ground and semi-buried infrastructure at Natanz, Isfahan, and Fordow, killed several nuclear scientists, and forced Iran to suspend IAEA cooperation. The enriched uranium stockpile largely survived but its precise location is unverified. The most common assumption is that it is being stored in the Pickaxe/Esfahan tunnels. Repair efforts include roofs over damaged Natanz/Isfahan buildings and Pickaxe fortification. The program is delayed but not eliminated.
Bushehr’s operating 1,000 MW VVER power reactor was untouched to avoid a Chenobyl-like catastrophe.
Ongoing U.S.-Iran talks focus on enrichment limits, stockpile disposal, and sanctions relief, but gaps remain wide. There have been some indications recently that Iran is willing to limit its enrichment pursuit.
