Iranian expert Kouhyar Gervand drops technetium-99 into eyes of Zahra Kohanmanesh for her eye scan at the Shariati hospital, in Tehran, in a file photo. Iran has converted a fraction of its stockpile of highly enriched uranium into material that can detect cancers and other diseases. Image Credit: AP

Tehran: Iran has started converting a third of its highly enriched uranium stockpile into material used to produce medical isotopes, potentially reducing tensions amid efforts to revive its landmark nuclear agreement with world powers.

International Atomic Energy Agency (IAEA) monitors verified that Iran began on March 11 irradiating part of its stockpile of uranium enriched to 60% to produce molybdenum targets, according to a two-page restricted document circulated late Wednesday among diplomats in Vienna and seen by Bloomberg. The process renders the material useless for weapons.

“They’ve taken it out of the pipeline,” said Robert Kelley, a US nuclear-weapons engineer who formerly directed inspections for the world’s nuclear watchdog. “It’s no longer suitable for further enrichment or weapons.”

The Islamic Republic’s stockpile of 60% enriched uranium had prompted international concern because the IAEA said it’s technically indistinguishable from the 90% purity typically used in weapons.

Monitors published the report amid a pause in negotiations aimed at salvaging the 2015 accord that reined in Iran’s atomic activities in exchange for sanctions relief. It follows the release of two British-Iranian prisoners on Wednesday and suggests another Iranian step toward addressing some of the most immediate concerns over its nuclear activities.

Historically, medical isotopes have been produced with 90% enriched uranium - a process that persists in some countries - but has been gradually replaced with lower levels in order to reduce proliferation risks.

Though Iran has effectively de-weaponised part of its stockpile, it’s not clear that its engineers will now be able to use the product to efficiently produce medical isotopes, according to Kelley, raising questions over Iran’s original intentions.

Iran maintains that its nuclear program is for civilian uses and has repeatedly denied that it aims to develop a bomb.

“The production of highly enriched uranium up to 60%, have no credible peaceful purpose,” said Louis Bono, the US envoy to the IAEA last week in a statement.

In a statement on Friday, the IAEA said Iran had used 2.1 kilos (4.6 pounds) of its 60% enriched uranium to produce so-called “highly enriched uranium targets” at a facility in Isfahan. Those “targets’’ will be irradiated at the Tehran Research Reactor and later used to produce molybdenum-99, the IAEA said.

3.67% cap on enrichment

Molybdenum-99 decays within days into a form of an isotope called technetium-99m, which is used in scans that can detect cancer and assess blood supply to the heart. In the US, technetium-99m is used in over 40,000 medical procedures a day, according to the Energy Department.

Increasingly, countries around the world use low-enriched uranium to create the needed isotope to avoid the proliferation risks of employing highly enriched uranium.

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Iran’s semiofficial Mehr news agency, quoting unnamed officials it referred to as “informed sources,” acknowledged that some of this material had been reprocessed. The report added that 2 kilos (4.41 pounds) of the material could help 1 million people. The IAEA said that as of February 19, Iran had a stockpile of 33.2 kilos (73.19 pounds) of 60% enriched uranium — material a short, technical step from weapons-grade levels of 90%.

“The materials converted to ‘target,’ was irradiated, and has no danger of spreading, and Western countries cannot criticise Iran over this,’’ the Mehr report said.

Under the 2015 accord, Iran agreed to cap its enrichment as 3.67%, end the use of advanced centrifuges and maintain a stockpile of 300 kilos (661 pounds) under the scrutiny of the IAEA.

As of February 19, Iran had a stockpile of 2,883 kilos (6,355 pounds) with ever-more advanced centrifuges spinning. While Iran long has maintained its program is peaceful, the West and the IAEA say Tehran had an organized military nuclear program that broke up in 2003.

Using the 60% enriched uranium to create isotope material means “for all practical purposes’’ it can’t be reconstituted for the wider stockpile, said Daryl G. Kimball, the executive director of the Washington-based Arms Control Association.

However, he stressed that to bring Iran back to the levels of the 2015 deal, its stockpile would need to be again shipped abroad.

“It may be that at this delicate juncture in the negotiations — the 11th hour — Iran is trying to suggest that it has some better intentions here,’’ Kimball told The Associated Press. “This may be an effort to show that they’re interested in working out a deal.’’

But, he added that “it also may be a justification ex post facto to enrich uranium to 60%. It may be a way to create a cover story for what they’ve already done, which they weren’t supposed to do.’’