Iran's Nuclear Program After the 2025 U.S.-Israeli Strikes: What Survived, What's Missing, and How Fast Could Iran Rebuild?

The Campaign: Two Rounds of Strikes

Israel launched a 12-day campaign in June 2025 targeting the Natanz, Fordow, and Isfahan (Esfahan) enrichment plants . The United States followed with Operation Midnight Hammer, striking the same three facilities in a campaign Vice President J.D. Vance described as "very narrowly tailored" to destroying Iran's nuclear weapons program . The attacks caused substantial damage to uranium conversion and enrichment facilities, briefly restricting the production of highly enriched material .

Iran's centrifuge capacity was initially cut significantly, but by February 2026 it had restored approximately 40% of its pre-strike capacity, according to intelligence assessments . The majority of operational cascades are located at Fordow and at least one previously undisclosed facility identified in satellite imagery .

What Iran Had Before the Strikes

As of June 13, 2025 — the day before the first Israeli attacks — the IAEA estimated Iran's total enriched uranium stockpile in uranium hexafluoride (UF6) form at 9,040.5 kg . This included:

• 2,391.1 kg enriched up to 2% U-235
• 6,024.4 kg enriched up to 5% U-235
• 184.1 kg enriched up to 20% U-235
• 440.9 kg enriched up to 60% U-235 (near weapons-grade)

That 440.9 kg of 60% material was enough, if further enriched to weapons-grade 90%, to produce roughly 10 nuclear weapons . Nearly all of this highly enriched material was in gas form (UF6) stored in small canisters .

The Big Unknown: What Survived?

After the strikes, the IAEA has been unable to determine the current volume, location, or composition of Iran's enriched uranium stockpile . Iran has not reported how much material survived the bombings or where it is stored . The agency simply states it "cannot provide any information" on the status of the stockpile .

IAEA Director General Rafael Grossi has assessed that the bulk of the 60% enriched uranium is likely still at the Isfahan tunnel complex, with no evidence it was relocated . The tunnel complex appears to be the only target that was not badly damaged in the June 2025 attacks . Grossi said in March 2026 that "what we believe is that Isfahan had until our last inspection a bit more than 200 kilograms" of the 60% material, implying roughly half of the pre-strike stockpile is still there . However, the exact amount and condition of that material remains unverifiable .

A "significant quantity" of near-weapons-grade uranium — including material stored underground at Isfahan — remains unaccounted for, according to a February 2026 IAEA report . The Institute for Science and International Security (ISIS) reports that more than two-thirds of Iran's 440 kg of 60% enriched uranium was likely stored at Isfahan .

IAEA Access: Near-Total Loss of Monitoring

The IAEA has not been granted access to any of the bombed nuclear facilities — Natanz, Fordow, or Isfahan — since the June 2025 strikes . It has only been able to monitor sites that were not targeted . Since February 2026, after the full-scale war escalated, the IAEA has lost even that limited physical presence . The result, as described by the Institute for Science and International Security, is a "near-total, ongoing loss of monitoring" of Iranian nuclear sites .

In June 2026, the IAEA Board of Governors passed a U.S.-backed resolution demanding Iran disclose its remaining stockpiles and allow inspections . Iran resisted, insisting access would only come after a final nuclear deal . An interim U.S.-Iran peace accord signed in June 2026 opened the door for inspections, but Tehran later indicated that key-site access remained contingent on a final agreement and sanctions relief .

Iran's Potential to Rebuild Weapons-Grade Production

Pre-strike breakout timeline

Before the strikes, Iran could produce enough weapons-grade uranium (90% U-235) for one bomb in as little as one week from its 60% stockpile .

Post-strike delay

After the June 2025 attacks, U.S. intelligence assessed that Iran's timeline to produce a nuclear weapon had been pushed back to up to a year .

No further delay by May 2026

By May 2026, however, U.S. intelligence assessments showed that the breakout timeline had not changed since the previous summer — meaning the additional months of conflict had not further degraded Iran's capacity .

Current capacity estimates

With roughly 200 kg of 60% enriched uranium believed still intact, and Iran having rebuilt approximately 40% of its centrifuge capacity, experts assess that Iran could enrich to weapons-grade 90% within weeks or even days if it chose to . One comprehensive analysis estimates 2–4 weeks to produce weapons-grade material from surviving stockpiles, with 6–18 months needed to weaponize it into a deliverable warhead .

For context, moving from 60% to 90% enrichment requires approximately 500 SWU (separative work units) per weapon, compared to roughly 5,000 SWU to go from natural uranium to 60% . This means the shortest path to a bomb would use the existing 60% stockpile rather than starting from scratch.

The key unknown

Because the IAEA cannot verify the current stockpile size, centrifuge status, or whether any undeclared facilities exist, all breakout estimates carry wide uncertainty . The agency has warned that it is "unable to discharge its safeguards responsibilities" under the Nuclear Nonproliferation Treaty .

Summary of Expert Findings

• Damage to facilities: Substantial, but Natanz and Fordow are assessed as at least badly damaged, not destroyed . The above-ground Pilot Fuel Enrichment Plant at Natanz was destroyed . Iran has recovered ~40% of centrifuge capacity .
• Surviving enriched uranium: Likely over 200 kg of 60% enriched uranium at Isfahan, of unknown condition . A significant quantity of the remaining ~200 kg is unaccounted for .
• IAEA monitoring: Near-total loss since February 2026 .
• Breakout timeline: Pre-strike: 1 week . Post-strike (June 2025): ~1 year . By May 2026: no change from June 2025 . Current estimate: weeks to months from surviving stocks .
• Weaponization: 6–18 months after fissile material production to produce a deliverable warhead .