REPORT: Natanz, Fordow, Isfahan — What IAEA Inspectors Will Find, Hope For, and Dread

REPORT: Natanz, Fordow, Isfahan — What IAEA Inspectors Will Find, Hope For, and Dread

Introduction: A Door Opening One Year After the Strikes

June 26, 2026 — Rafael Grossi Announces Imminent Access

On June 26, 2026, the Director General of the International Atomic Energy Agency, Rafael Grossi, publicly declared that inspections of Iranian enrichment sites will happen. "They will occur," he said — a formulation deliberately free of a precise date, but firm in its direction. The declaration came the day after the signing of a preliminary agreement between the United States and Iran providing for a cessation of hostilities, an easing of sanctions, and — the central point — IAEA access to nuclear sites, including those that were struck.

For the international arms control community, this is a moment long awaited since the American-Israeli strikes on Natanz and Fordow took place in the spring of 2025. Since then, Iran has kept these sites in complete opacity — refusing inspector access, invoking national security imperatives, contesting the legitimacy of inspections in the context of a military attack. The question everyone has been asking for a year: what actually remains of the Iranian nuclear program?

A Preliminary Agreement, a 14-Point Text, and Many Uncertainties

According to information available on June 26, 2026, the agreement between Washington and Tehran is presented as a 14-point memorandum of understanding — a framework document establishing principles without being a formal treaty. It provides notably for partial lifting of sanctions against Iran, the opening of the Strait of Hormuz to international navigation (which had been temporarily closed during hostilities), and IAEA access to nuclear sites. In exchange, Iran commits to not resuming enrichment at high levels and to cooperating with inspectors.

But the details remain vague. The word "cooperate" conceals a considerable technical negotiation: exactly which sites will the IAEA have access to? With what equipment? Under what protocols? On what timelines? Tehran has historically used every ambiguity in agreement texts to limit inspections, delay access, or contest inspectors' conclusions. And this time, there is a new variable: the physical damage caused by the strikes complicates the assessment, since some equipment may have been destroyed, moved, or buried more deeply before inspections begin.

Natanz — The Heart of Iran's Enrichment Program

What the Strikes Targeted and What They May Have Destroyed

The Natanz complex is the most important site in Iran's uranium enrichment program. Located in Isfahan province, approximately 250 kilometers south of Tehran, it includes two large underground facilities — the Fuel Enrichment Plant and the Pilot Fuel Enrichment Plant — along with several surface structures. Before the 2025 strikes, Natanz housed several thousand advanced centrifuges of types IR-1, IR-2m, IR-4, and IR-6, with uranium enrichment capacity ranging from 5% to 60% — and potentially more according to IAEA reports from 2024.

The 2025 strikes targeted the underground structures using high-powered penetrating munitions. Post-strike assessments based on public satellite imagery suggest significant damage to surface buildings and possibly to the upper levels of the underground facilities. But the depth of the most protected installations — several dozen meters of concrete and rock — leaves open the question of the actual extent of damage to operational centrifuges and stocks of uranium hexafluoride. Only on-site inspections can answer this question.

What the IAEA Will Be Looking for at Natanz

The IAEA inspectors will arrive at Natanz with several distinct objectives. First, establish an inventory of surviving centrifuges — their number, condition, and residual capacity. Second, locate enriched uranium stockpiles — particularly the stocks at 60% that most concerned the international community before the strikes, and verify whether they were moved, destroyed, or concealed. Third, assess structural damage to understand the site's residual resistance to potential future strikes. Finally, detect any reconstruction activity that may have begun before their arrival.

The Institute for Science and International Security (ISIS), in its June 2026 analysis of IAEA verification and monitoring reports, notes that Iran maintained an unprecedented level of access restrictions since the spring of 2025. IAEA surveillance cameras, which were in place before the strikes, were disconnected or their data withheld. Inspection teams were denied access to the sites for more than a year. This prolonged opacity means inspectors will arrive with a considerable information gap — and corresponding uncertainty about what they will find.

Fordow — The Most Secret, Deepest, Most Resistant Site

A Facility Dug Into a Mountain — Built to Survive Strikes

Fordow is different from Natanz. Located 27 kilometers north of Qom, it is buried approximately 80 to 90 meters underground, inside a mountain — a depth that exceeds the penetration capability of most conventional munitions. Initially built in secret and revealed to the international community in 2009 through American, French, and British intelligence, Fordow was presented by Iran as a research facility, then as a production site. In 2023–2024, it was operating with advanced centrifuges enriching uranium to 60% — a level very close to weapons-grade (90%).

The 2025 strikes on Fordow are those whose effectiveness is least known. Satellite imagery shows damage to the tunnel entrance and surface structures, but the deep underground facilities would potentially be intact according to several non-proliferation analysts. If so, Fordow could represent a significant residual enrichment capacity — perhaps the most significant of the struck sites, precisely because it was designed to survive this type of attack.

Iran's Contradictory Position on Fordow

Iran has adopted since the strikes a publicly contradictory position on Fordow. On one hand, officials claimed the strikes caused "significant" damage to the facilities — which serves both to protest the military aggression and to seek compensation in the negotiation framework. On the other, sources close to the Islamic Revolutionary Guard Corps hinted in semi-official media that essential capabilities remained intact.

This ambiguity is deliberate. Tehran has an interest in maintaining maximum uncertainty about the actual state of its nuclear program — it strengthens its negotiating leverage and maintains a form of deterrence even if real capabilities have been reduced. The IAEA inspections will reduce this ambiguity — but not necessarily eliminate it, if Iran manages to limit access to certain areas.

Isfahan — The Uranium Conversion Facilities

The Chain Link That Transforms Ore Into Hexafluoride

Isfahan houses the uranium conversion complex — the facility that transforms uranium concentrate (yellowcake) into uranium hexafluoride (UF6), the gaseous form needed for enrichment in centrifuges. Without this conversion, enrichment is impossible. It is therefore a cornerstone of the Iranian nuclear chain — and a priority target for anyone seeking to interrupt the complete cycle.

The 2025 strikes also targeted Isfahan, with documented damage to conversion facilities. But as with Natanz and Fordow, precise assessment of this damage and residual production capacity is only possible with direct inspector access. The IAEA will want to know: how much UF6 stockpile was present before the strikes? What volume was destroyed, moved, or preserved? Has Iran begun remediation operations? Can traces of new UF6 stock manufacturing be detected?

The Stakes of Uranium Stockpiles Enriched to 60%

Before the strikes, Iran possessed, according to IAEA reports from 2024, stockpiles of uranium enriched to 60% of sufficient scale to, after further enrichment to 90%, potentially produce several nuclear bombs. These stockpiles represent the central node of international community concerns. Were they destroyed by the strikes? Dispersed to undisclosed secondary sites? Buried more deeply? Or preserved in protected areas of Fordow?

The answer to this question is probably the IAEA inspectors' number one priority. If these stockpiles are found intact and inventoried, they can be subjected to reinforced verification measures — potentially up to their dilution or neutralization under a final agreement. If a portion is untraceable, this represents a major potential proliferation problem: uranium at 60% whose location is unknown and which could be quickly moved toward weapons-grade.

The U.S.–Iran Preliminary Agreement: What It Says and What It Doesn't

A 14-Point MOU — General Framework Without Binding Details

The agreement signed between Washington and Tehran on June 25, 2026, as described in available sources, is a memorandum of understanding — not a treaty, not a legally binding agreement under international law. It establishes principles: cessation of hostilities, lifting of certain sanctions, opening of the Strait of Hormuz, IAEA access. But the precise conditions of each provision remain to be negotiated in a subsequent phase.

This architecture — principles first, details later — is familiar in Iranian nuclear diplomacy. It is essentially the same model as the Lausanne framework agreement of 2015 that preceded the JCPOA. This model has the advantage of allowing a rapid political announcement. It has the disadvantage of leaving the hardest questions — on which sites exactly, with what equipment, on what timelines — to technical negotiations that can drag on for months or years.

Grossi and the IAEA — Between Impatience and Caution

Grossi said the inspections will happen. But he also acknowledged, according to available sources, that Iran had expressed reservations about access to certain parts of sites — citing security concerns related to post-strike structural damage. This formulation is potentially problematic: "structural damage" can be used as a pretext to limit access to the most sensitive areas, precisely those inspectors are seeking to examine.

The IAEA has the technical capability to assess nuclear damage — it is part of its mandate in post-conflict situations. But it does not have the capability to force access. If Iran blocks entry to a specific room citing radiological or structural risks, inspectors can note the refusal, but cannot force their way in. The credibility of the agreement therefore depends entirely on Tehran's political will to honor its commitments — a variable no contractual clause can guarantee.

The Geopolitical Dimension — Between Facade Agreement and Real Disarmament

What Washington Really Wants to Achieve

The American-Iranian agreement of June 25, 2026 fits into a very particular geopolitical context. The 2025 strikes were declared to have the objective of destroying Iranian nuclear capacity or at least significantly delaying it. If IAEA inspections reveal that damage was substantial — centrifuges destroyed, uranium stockpiles reduced or destroyed — Washington will be able to present the agreement as a double victory: military and diplomatic.

If, conversely, inspections reveal that essential capabilities survived — notably at Fordow — Washington will face a dilemma: acknowledge the limits of the military operation and negotiate from a weaker position, or claim a partial victory that doesn't convince the international community. Inspection transparency is therefore simultaneously a verification requirement and a major political challenge for the American administration.

Israel — The Actor Absent From the Agreement

Israel participated in the 2025 strikes but is not a party to the American-Iranian agreement. Its government has expressed concerns that a preliminary agreement allowing an easing of sanctions before complete verification of the nuclear program would be premature. Tel Aviv demands that any sanctions relief be conditional on complete and independent verification — not only of known sites, but also of the absence of undisclosed sites.

This Israeli position is not merely strategic — it reflects an intelligence assessment on whether the strikes actually achieved their objectives. If Israel maintains its reservations, it may be because its own assessments suggest that residual Iranian capabilities remain significant. This divergence between Washington and Tel Aviv on the pace and conditions of concessions to Iran is a potential source of tension in an alliance already complicated by the events of 2025.

What the Inspectors Will Concretely Do

Post-Conflict Inspection Protocol — New Ground for the IAEA

The IAEA has extensive experience of inspections in politically difficult contexts — Iraq after 1991, Libya after 2003, North Korea before its withdrawal from the NPT. But inspecting nuclear sites after direct military strikes represents a different challenge. Facilities may be structurally unstable, radiologically contaminated, or partially collapsed. Equipment may have been displaced in rubble in ways that complicate inventory. And Iran has a strong incentive to present the damage in the manner most favorable to its negotiating position.

The inspection team will have access to portable gamma spectrometry to detect the presence of nuclear materials, environmental sampling to measure uranium traces and isotopes associated with different enrichment levels, and industrial inspection cameras to assess physical damage. It will work with facility plans that Iran is supposed to provide and with historical surveillance data the IAEA holds up to the moment the surveillance cameras were disconnected.

The Optimistic Scenario and the Realistic Scenario

The optimistic scenario: inspections proceed quickly, Iran cooperates fully, damage to the main facilities is documented as substantial, enriched uranium stockpiles are found intact and inventoried, and the verification process can be completed within a few months. This would open the path to a final agreement durably reducing Iran's nuclear ambitions in exchange for complete sanctions relief.

The realistic scenario, based on the history of Iranian nuclear negotiations: inspections start with delays, access to certain areas is contested, IAEA conclusions are partial, negotiations for a final agreement drag on for years, and Iran maintains residual enrichment capabilities that are permanently debated among Western capitals. This is not a cynical projection — it is simply what happened at each previous stage of Iranian nuclear diplomacy since 2003.

Post-Conflict Verification as a New International Standard

What the IAEA Can Do — and What It Cannot Do Alone

The upcoming inspections in Iran represent a test for the IAEA as an institution. Rafael Grossi has built his personal credibility on his organization's ability to maintain dialogue with Tehran even during maximum crisis. If inspections reveal substantial damage and Iran cooperates fully, the IAEA emerges from this crisis with reinforced authority. If, conversely, access is limited, conclusions are partial, and verification is compromised, the international inspection model will be weakened precisely when the world needs it most.

The IAEA cannot force access. It negotiates, documents, reports. If Tehran blocks, the organization can escalate the matter to the UN Security Council — but this mechanism is also subject to the veto rights of Russia and China, which have economic and strategic interests in not seeing Iran completely isolated. International nuclear verification is fundamentally dependent on the voluntary cooperation of states — a structural limitation the Iranian crisis exposes with stark clarity.

Lessons for Future Non-Proliferation Crises

What the international community is learning through the Iran-2025 crisis will have implications for future nuclear crises. North Korea is watching. Pakistan is watching. Other states with nuclear ambitions operate in gray zones watched carefully by their leaders. If the American-Israeli strikes of 2025 are perceived as effective and followed by a credible diplomatic agreement, they send a deterrence message. If they are perceived as ineffective — if Fordow is intact and Iran emerges diplomatically stronger — they send the opposite message: nuclear proliferation is a life insurance policy against military intervention.

The post-conflict verification the IAEA is about to conduct is therefore one of the most consequential episodes in the decade's non-proliferation history. Not just for Iran, but for the global nuclear security architecture. If inspectors discover an uncomfortable truth — residual capabilities, missing stockpiles, partially intact infrastructure — the international community's response to that truth will define the rules of the game for the next nuclear crisis. The stakes extend far beyond Iranian borders.

Conclusion: The Truth Hides Under 80 Meters of Concrete

What the Coming Weeks Will Reveal — and What They Won't

The IAEA inspections at Natanz, Fordow, and Isfahan will produce data. Data on damage, on residual capabilities, on uranium stockpiles. This data will be important — it will allow the international community to calibrate its diplomatic response and define the terms of a possible final agreement. But it will not be able to answer certain fundamental questions: does Iran have undisclosed sites? Were stockpiles moved before access was granted? Is the political will in Tehran to abandon nuclear ambitions real or tactical?

These questions — the most important ones — are not resolved by inspections. They are resolved over time, through continuous surveillance, through consistency between declarations and behavior, through the maintenance of sustained diplomatic and economic pressure. The agreement of June 25, 2026 is perhaps a starting point. It is far from a conclusion.

The Regional Balance After the Strikes

Regardless of what the inspections reveal, the 2025 strikes have already permanently altered the regional balance. They demonstrated that the West and Israel were willing to use force to prevent Iran from accessing the bomb. They — potentially, pending the upcoming inspections — reduced Iranian nuclear capabilities. But they also hardened Tehran's position, consolidated the most anti-Western factions within the Iranian political system, and fueled internal debates about the need to accelerate deterrence rather than negotiate. The real result of the 2025 strikes — stabilization or long-term acceleration of Iranian nuclear ambitions — will only be known in the years ahead. The IAEA inspections are the first brick in that edifice of knowledge.

By Maxime Marquette, columnist

Columnist's transparency note

My Limits on This Subject

I am not a nuclear non-proliferation expert. This report rests on public sources — Grossi's statements, analyses from ISIS (Institute for Science and International Security), information from CNBC and Euronews on the American-Iranian agreement. I have no access to classified intelligence assessments or IAEA internal technical reports. The technical specifications of Iranian nuclear sites I cited are based on public IAEA reports dating from before the strikes — their current state is precisely what the inspections will determine.

What I Don't Know

I don't know what the inspectors will actually find. I don't know whether Iran has active undisclosed facilities. I don't know whether the strikes genuinely destroyed the main enrichment capabilities or primarily damaged surface structures. All my projections in this article are scenarios based on logic and history, not exclusive information.

Sources

Primary sources

CNBC — Preliminary U.S.-Iran agreement, nuclear access, 14-point accord — June 26, 2026

Euronews — Grossi: IAEA nuclear inspections at Iranian enrichment sites "going to happen" — June 24, 2026

WTOP/AP — U.S. and Iran sign initial deal, end of war, sanctions relief, strait — June 25, 2026

Secondary sources

ISIS — Analysis of IAEA reports on Iran verification, June 2026, access denied since 2025

Euronews — Context: Strait of Hormuz closure, maritime disruptions, EU sanctions — June 9, 2026

Xinhua — Context: EU Russia sanctions, Strait of Hormuz, oil market stabilization — June 20, 2026