Iran has begun using its advanced centrifuge, IR-6s, to enrich uranium at an underground Natanz facility, says an International Atomic Energy Agency report.

The confidential document, circulated to member states and leaked to Reuters news agency Monday, said Iran was using a cascade with up to 174 machines to enrich to 5 percent purity with two other cascades in differing stages of preparation.

It has been known for months that Iran was preparing three cascades of IR-6s at Natanz, but the latest news comes as Tehran reviews a United States response in talks aimed at reviving the 2015 nuclear agreement, the JCPOA (Joint Comprehensive Plan of Action).

Iran has been gradually exceeding limits set by the JCPOA since 2019, the year after the US left the agreement and imposed ‘maximum pressure’ sanctions. The use of IR-6 centrifuges was barred by the JCPOA, which restricted Iran to 6,000 ‘first generation’ machines.

Using the IR-6s at Natanz to enrich to 5 percent exceeds slightly the JCPOA cap of 3.67 percent, but is well below the 20 percent limit Iran has reached in volume with IR-6s at the Ferdow site. The IAEA also reported in June that Iran had 43kg of uranium enriched to 60 percent, little short of the 90 percent considered ‘weapons grade.’

While IR-6 centrifuges have been used at Ferdow and at Natanz above ground to enrich to 60 percent, some specialists have suggested Iran faces technical difficulties with the more advanced machines with progress also hampered by the June 2021 attack on the manufacturing plant at Karaj.

One challenge in the nuclear talks – aside from agreeing which US sanctions violate the JCPOA – has been deciding how Iran’s nuclear program should be brought back in line with the agreement, and particularly whether Tehran should lose or store more advanced centrifuges. With gaps US-Iran gaps remaining after a European Union text was circulated August 8, various compromises have reportedly been mooted.

1,000 IR-6 target in sight

The use of IR-6 centrifuges was mandated by the Iranian parliament as tensions increased following the November 2020 killing of scientist Mohsen Fakhrizadeh, widely attributed to Israel. Legislation passed December 2020 against the wishes of then-president Hassan Rouhani instructed the government to expand the nuclear program and restrict IAEA access. Among other clauses, the law required the installation of 1,000 IR-6 centrifuges by the end of 2021, a target the Atomic Energy Organization of Iran (AEOI) failed to meet.

By May, there were 538 IR-6 centrifuges in two cascades at Fordow and one cascade at the above-ground Natanz pilot plant. The AEOI announced plans in June to install two more IR-6 cascades underground at Natanz, in addition to one already planned there, which would apparently bring the AEOI in line with the 2020 law.

Report: Iran-US overcome another hurdle

Reuters reported Monday, citing “three sources familiar with the matter,” that Washington and Tehran had found a way to overcome an apparent sticking point in the nuclear talks. While President Ebrahim Raisi reiterated Monday that Iran expects the IAEA to drop enquiries into Tehran’s pre-2003 nuclear work as part of JCPOA restoration, the US has insisted the agency’s probe relates to Iran’s ‘safeguards’ commitments under the Nuclear Non-Proliferation treaty and is distinct from the JCPOA.

According to the Reuters report, a form of words has been developed allowing the matter to be postponed, although the agency gave no details.

All sides, including the IAEA, are aware the JCPOA gave the agency greater powers of inspection. IAEA director-general Rafael Mariano Grossi in an interview August 23 suggested questions over the pre-2003 work, which center on unexplained uranium traces, might be better tackled with the JCPOA back in place.