The location of Iran’s 440 kilograms of uranium enriched to 60 per cent has become one of the most significant unresolved issues in the ongoing dispute between the United States and Iran, following the suspension of on-site inspections by the International Atomic Energy Agency (IAEA) after the 2025 conflict.
The interruption of physical inspections has left the United Nations nuclear watchdog without direct access to key Iranian nuclear facilities, preventing independent verification of the country’s enriched uranium stockpile. While satellite imagery continues to provide information about activity at nuclear sites, experts say it cannot replace in-person inspections needed to confirm the movement or storage of nuclear material.
Satellite images published in March showed a flatbed truck transporting blue containers under security escort toward the underground tunnel complex at Iran’s nuclear facilities in Isfahan. The images prompted public discussion about whether the containers could have been carrying highly enriched uranium. Olli Heinonen, the former head of safeguards at the IAEA, cautioned against drawing conclusions from the photographs alone, stating that satellite imagery has significant limitations and cannot determine either the origin of vehicles or the contents of containers without additional evidence.
According to Heinonen, much of Iran’s nuclear research and supply chain is spread across multiple locations, including sites that remain unknown. He said satellite monitoring is valuable but cannot substitute for continuous physical verification, particularly when assessing the movement of sensitive nuclear materials.
The issue has gained renewed prominence following the 2025 U.S. and Israeli strikes on Iranian nuclear and military facilities. Although U.S. President Donald Trump declared after the June 2025 attacks that Iran’s nuclear programme had been completely destroyed, the United States later launched Operation Epic Fury in February, stating that Iran would never be allowed to obtain a nuclear weapon. The conflict expanded into a prolonged regional war, resulting in thousands of deaths and injuries in Iran and Lebanon, according to the source text.
IAEA Director General Rafael Grossi warned shortly after the conflict began that although the agency had found no evidence that Iran was building a nuclear weapon, the country’s large stockpile of uranium enriched to near weapons-grade levels, combined with restrictions on inspector access, represented a serious concern. Grossi said the agency could no longer provide assurances that Iran’s nuclear programme was exclusively peaceful under the existing inspection conditions.
Former IAEA chief inspector Robert Kelley distinguished between the agency’s technical ability to verify declared nuclear material and its broader assessments regarding a state’s intentions. Kelley said IAEA inspectors remain the only international experts capable of independently verifying Iran’s declared nuclear material and described their technical work as essential. However, he argued that judgments regarding whether a nuclear programme is peaceful had become increasingly politicised.
Kelley noted that the missing stockpile of 440 kilograms of uranium enriched to 60 per cent would occupy only about 50 containers roughly the size of scuba diving cylinders, underscoring how difficult such material could be to locate without direct inspections. He said Iranian authorities know the exact location of the uranium, while the absence of independent verification allows uncertainty to persist.
Iran’s ambassador to the IAEA, Reza Najafi, has denied that Tehran resumed uranium enrichment following the 2025 attacks on its nuclear facilities.
Kelley proposed a negotiated solution in which Iran would surrender its entire stockpile of uranium enriched to 60 per cent while retaining the ability to enrich uranium up to 20 per cent for civilian purposes under continued IAEA monitoring. He said such an arrangement could preserve Iran’s civilian nuclear industry while removing the material that generates the greatest international concern, drawing comparisons with previous international programmes that converted military nuclear material into civilian fuel.
Following the memorandum of understanding signed by the presidents of Iran and the United States on June 17, Grossi said the agreement explicitly assigns the IAEA responsibility for supervising nuclear activities involving nuclear material. He stated that inspections would resume, although no timetable has yet been announced.
