“Discussions are still ongoing” to determine the origin of these particles, the International Atomic Energy Agency (IAEA) said in a report.
The report added that during an inspection “on 22 January 2023, the agency took environmental samples… at Fordow (sic) Fuel Enrichment Plant (FFEP), the analytical results of which showed the presence of high enriched uranium particles containing up to 83.7 percent U-235”.
“These events clearly indicate the capability of the agency to detect and report in a timely manner changes in the operation of nuclear facilities in Iran,” it continued.
Iran denies seeking nuclear weapons, stressing its nuclear technology is solely for civil purposes.
Asked about the presence of the particles, Iran stressed that “unintended fluctuations” during the enrichment process “may have occurred”.
Last week, Tehran announced it had not made any attempt to enrich uranium beyond 60 percent.
“The presence of a particle or particles of uranium above 60 percent in the enrichment process does not mean enrichment above 60 percent,” stated the spokesperson for the Atomic Energy Organisation of Iran, Behruz Kamalvandi.
The IAEA report comes as the head of the UN’s nuclear watchdog, Rafael Grossi, is expected to visit Tehran “in the coming days”, following an official invitation by the AEOI.
In the report, the IAEA said that Iran’s estimated stockpile of enriched uranium had reached more than 18 times the limit set out in the 2015 accord between Tehran and world powers.
It estimated Iran’s total enriched uranium stockpile was 3,760.8 kilogrammes (8,291 pounds) as of February 12, an increase of 87.1 kilogrammes compared to the last report in November.