BRUSSELS — United Nations inspectors have found new evidence of undeclared nuclear activities in Iran, according to three diplomats briefed on the discovery, raising new questions about the scope of the country’s atomic ambitions.
Samples taken from two sites during inspections in the fall by the U.N.’s International Atomic Energy Agency contained traces of radioactive material, the diplomats said, that could indicate Iran has undertaken work on nuclear weapons, based on where it was found. The diplomats said they didn’t know the exact nature of what was found.
Last year, Iran blocked IAEA inspectors from checking the sites involved for seven months, leading to a standoff. Tehran has long denied that it has sought to make an atomic bomb and said all of its nuclear work is for peaceful purposes such as power generation and health care. There was no immediate comment from Iran on the findings.
In recent months, Iran has scaled up its nuclear activities, breaching many of the limits in the 2015 nuclear agreement it sealed with the U.S., European powers, Russia and China. These moves started over a year after the Trump administration exited the deal in May 2018 and then imposed broad sanctions on Iran, which had been lifted under the agreement.
It has also threatened to restrict IAEA inspectors’ access to sites later this month. These steps have caused growing concern in Washington about Iran’s nuclear intentions.
U.S. and Israeli officials have said Iran’s retention of nuclear material, equipment and information, contained in a nuclear archive raided by Israel in 2018, show the country plans to rev up its nuclear weapons work again.
The IAEA listed in a report in June questions it was asking Iran to clarify on a range of work that could be used for nuclear weapons. One suspicion was Iranian drilling of a uranium metal disc that could be used to create material for a neutron initiator, experts say, a key component of a nuclear weapon. A second suspicion was that nuclear material had been introduced at a site where Iran may have tested high explosives that can be used to detonate a nuclear weapon.
The agency is also asking Iran about another undeclared site where illicit uranium conversion and processing may have taken place, it said.
All the suspected activities took place in the early 2000s or earlier, according to the agency. Two of the sites were razed years ago. Another site was sanitized by Iran in 2019, the IAEA reported. The IAEA said it has not ruled out that materials from this nuclear work have been used more recently.
“The discovery of radioactive material at these sites would indicate that Iran does indeed have undeclared nuclear material, despite its denials,” said David Albright, a former weapons inspector and president of the Institute for Science and International Security in Washington. “It would indicate that Iran did have a nuclear weapons program in the past, likely leading the IAEA to call for access to more sites and more explanations from Iran.”
The IAEA said in 2015 it thought Iran had a structured nuclear weapons program until 2003 and continued some activities after that. Washington and European powers have come to similar conclusions.
The IAEA hasn’t yet reported the latest findings to member states, the diplomats said. It is currently asking Iran to provide an explanation for the material, one of them said, a standard practice. The agency declined to comment on the new findings.
The IAEA has previously said it found multiple undeclared uranium particles, including enriched uranium, at a separate secret site in Tehran in 2019, believed to be a warehouse for nuclear equipment. It was that finding that led the agency to seek access to other sites in Iran.
The U.S., European powers and others have urged Iran to cooperate fully with the agency’s widening probe into Iran’s past nuclear activities.
Tensions have been growing for the past 18 months over the IAEA’s probe into the undeclared material. The IAEA’s core function is to safeguard nuclear material used for civilian purposes and ensure it is not diverted for nuclear weapons. Iran is supposed to declare all nuclear material in the country under its international obligations.
Last year, member states on the IAEA board voted to censure Iran for failing to cooperate. Iran rejected the move as unfair pressure and was backed by Russia and China.
Iran says the IAEA probe is based on fabricated Israeli information and has pushed for the agency to complete its work quickly. Iran’s threat to restrict IAEA inspectors’ access to sites later this month if the U.S. doesn’t lift sanctions on Tehran could limit the agency’s ability to deepen the probe.
After the IAEA requested access to the two sites in January 2020, Iran repeatedly refused until IAEA Director General Rafael Grossi traveled to Tehran in August and struck a deal . Inspectors took samples at the two sites and carried out an additional inspection at another location soon after.
While the samples were being tested in labs, Mr. Grossi stepped up pressure on Iran to properly explain the presence of the uranium particles found at the Tehran site in 2019.
Mr. Grossi has vowed to continue the IAEA investigation until Iran accounts for all the undeclared material. In November he described Iran’s explanations for the uranium particles found at a site in Tehran as “not technically credible” and said Iran needs to account for the material “fully and promptly.” Iran has said it is cooperating with the agency.