Nuclear experts undercut White House claims about Iran reactor at heart of case for war

The Trump administration has cited Iran’s Tehran Research Reactor as a central justification for its military strikes, but has provided no evidence that the facility — built by the United States and used for civilian research for nearly six decades — was being used to develop nuclear weapons. Multiple nuclear scientists and nonproliferation experts told MS NOW that the reactor does not have the  capacity to serve as an easy conduit to a bomb as asserted by the administration.

The gap between the administration’s numerous claims about Iran and the available evidence has become a focal point of criticism as questions mount over the decision to launch strikes rather than continue negotiations. 

Just 36 hours before the United States opened its military assault, Iran’s nuclear negotiators, along with Oman’s foreign minister as mediator, presented the U.S. with a seven-page proposal for a potential nuclear deal, according to U.S. negotiator Steve Witkoff. But the American negotiators, Witkoff and Jared Kushner — who, according to a senior Middle East diplomat with knowledge of the talks, chose not to include nuclear technical experts in the negotiations — balked at Iran’s request to continue using 20%-enriched uranium at the reactor, a facility for civilian nuclear development that the U.S. first built and provided to Iran in 1967.

“The claim that they were using a research reactor to do good for the Iranian people was a complete and false pretense to hide the fact that they were stockpiling there,” a senior Trump administration official told reporters during a briefing on Tuesday, three days after the attacks began. 

But the Trump administration has yet to provide evidence or intelligence — to the public or to Congress — demonstrating that Iran intended to use the uranium at the Tehran Research Reactor for weapon development or that the facility was being covertly used for stockpiling purposes. In two classified briefings provided to lawmakers since the attacks, administration officials made no assertion that the reactor was being used for stockpiling purposes for a potential weapon, according to two people familiar with their comments.

“The [International Atomic Energy Agency] had evidence that they were stockpiling there and they had enough fuel to run TRR for the next seven or eight years without any additional fuel being delivered,” Witkoff said on “The Mark Levin Show.” “They were stockpiling again at the 20% level.” 

Witkoff alleged that the International Atomic Energy Agency director general, Rafael Grossi, who was a part of the final round of talks just before the military incursion, told Iran that it had stopped “burning anything” at the reactor and, instead, claimed that “all of the fuel is stockpiled.” Witkoff said it was their “‘Perry Mason’ moment.”

The IAEA and Grossi did not respond to MS NOW’s requests for corroboration of Witkoff’s statement over the last four days. 

“As the IAEA has publicly affirmed, Iran was stockpiling near-weapons grade enriched uranium while refusing to participate in serious negotiations with the United States,” White House spokesperson Anna Kelly said in a statement to MS NOW. “Thankfully, President Trump will never stand back and allow a country that chants ‘Death to America’ to ever obtain a nuclear weapon, and Operation Epic Fury is effectively taking out their capabilities of doing so.”

In the week since the start of the U.S.-Israeli attacks, the IAEA and the White House have issued conflicting statements as to how close Iran was believed to be toward the production of a nuclear weapon.

“This is spin, it just isn’t true, and the conversation that did take place with Director General Grossi present has been taken completely out of context by Mr. Witkoff,” a Persian Gulf diplomat who spoke on the condition of anonymity to discuss sensitive deliberations said in response to the claim. 

‘Confusing and misleading’ 

Several nuclear experts who spoke to MS NOW questioned the extent to which Witkoff and Kushner — who led the nuclear negotiations and described the Iranian position to Trump — understood the technical details of the enrichment programs at the heart of the deliberations.

Elena Sokova, the executive director of the Vienna Center for Disarmament and Non-Proliferation, called the administration’s assessments of the Tehran Research Reactor “confusing and misleading” and riddled with “technical errors.” 

“It mixes up different elements of the nuclear program and their potential proliferation capabilities,” Sokova said. “Research reactors are not capable of doing enrichment of uranium, whether for civil or military purposes.”

Witkoff and Kushner did not bring technical experts from the U.S. to sit in on their talks in Geneva, according to a senior Middle East diplomat with knowledge of the talks, and the White House opted to forgo scheduled technical talks set for this past Monday in Vienna, where more detailed nuclear details were expected to be addressed.

“When it comes to nuclear nonproliferation discussions, the details matter,” said Daryl Kimball, executive director of the Arms Control Association. “And working out the details requires time and technical expertise, and the administration was not patient enough to apply either to this effort.”

Witkoff defended his credentials last week to lead the nuclear talks.

“I wouldn’t tell you I’m an expert in nuclear, but I’ve learned quite a bit, and I’ve studied it and have read quite a bit about it, and I’m competent to sit at the table and discuss it, and Jared [Kushner] is as well,” Witkoff said on “The Mark Levin Show.”

A 60-year-old facility

The U.S. first built and provided the Tehran Research Reactor to Iran in 1967 as part of the “Atoms for Peace” program that began under President Dwight Eisenhower. The initiative aimed to expand civilian nuclear capabilities for electricity, medicine and other domestic purposes. 

The reactor requires 20%-enriched fuel and a relatively minimally enriched amount compared with the material required for the production of a nuclear weapon. Under the 2015 Iran nuclear agreement, known as the JCPOA, the reactor would have access to no more than 5 kilograms of 20%-enriched uranium at a time, supplied from outside the country and monitored by inspectors.

The reactor has not come under IAEA scrutiny for suspected nuclear development in more than 25 years, according to Katariina Simonen, a board member of Pugwash Conferences of Science and World Affairs and an adjunct professor at the Finnish National Defence University.

“TRR is not ideal for any other activity than what it is designed for — i.e., civilian use (isotopes, research, training),” Simonen told MS NOW. “It is a small, light-water reactor supplied by the U.S. under the Atoms for Peace program.”

The dispute over 20% enrichment

At the heart of the Trump administration’s case is the 20%-enriched uranium that Iran uses at the Tehran Research Reactor. In the seven-page proposal presented at negotiations in Geneva last week, the Iranians sought to maintain a certain level of enrichment at 20% for the purposes of producing radioisotopes and medicine — standard civilian applications — at the facility.

Witkoff argued that the 20% enrichment level gave Iran “five times the level that the JCPOA would have allowed,” referring to the Obama-era agreement’s cap of 3.67% for Iran’s broader enrichment activities. But the JCPOA separately provided for 20%-enriched fuel to be supplied from outside Iran specifically to meet the reactor’s needs, capped at 5 kg at any given time and subject to international monitoring by inspectors.

“The TRR reactor requires 20% fuel — that’s how the reactor is designed,” said Kimball of the Arms Control Association. “Is [the TRR] all a cover for nuclear weapons? One can make that claim. But at the same time, Iran was in the talks describing what they think their future nuclear energy needs might be and why, at some point in the future, they want to have the option to enrich uranium.”

Administration officials argued this week that the Iranians had effectively sought to convert the reactor from a civilian nuclear facility into a cover for stockpiling industrial-grade material that could eventually be further enriched to weapons grade. Uranium enriched to 20% is roughly 90% of the way to weapons-grade material, and Trump administration officials explicitly contend that Iran would be “three or four weeks away” from achieving that threshold.

But the administration has not provided evidence of its assertion that Iran intended to use the 20% fuel for weapon production, nor that Iran had amassed enough material that could potentially be further enriched to power a single small weapon. For Iran to make a bomb, the uranium would need to be enriched to a higher level. Last year’s strikes destroyed nearly all of Iran’s centrifuges, and there’s no evidence that enrichment has resumed.

“An [active] operating reactor cannot be used as storage,” said Claus Montonen, a retired nuclear physicist and an adjunct professor at the University of Helsinki and board member of the International Network of Engineers and Scientists for Global Responsibility. “I am not aware of this ever having happened.”

As an extension of the administration’s argument for further destroying any would-be Iranian nuclear operations, Witkoff warned in a Fox News interview this week that Iran “controlled 460 kg of 60%” enriched uranium at the facility — a level that would bring Iran roughly one week away from being able to have weapons-grade material.

However, during negotiations, the Iranians told Witkoff and Kushner that they would turn over that uranium as part of a new nuclear agreement with the U.S., according to the Persian Gulf diplomat who spoke with MS NOW. The Iranians also told Witkoff that the country enriched the uranium after President Donald Trump withdrew from the JCPOA brokered by the Obama administration. 

The senior Trump administration official acknowledged on Tuesday that Iran had, in fact, “talked about turning over material to us” as part of the talks, which ended abruptly when the U.S. launched military strikes roughly 36 hours after Witkoff and Kushner left the third round of talks in Geneva. 

On Wednesday, Grossi, the head of the IAEA, reiterated that the organization has “no evidence of Iran building a nuclear bomb.” In a CNN International interview last week, Grossi said that Iran, prior to the airstrikes, was not “days or weeks away from building a bomb.” He said that there was an “unjustified accumulation of almost military-grade material,” but added that the agency “never had information indicating there was a structured, systematic program to build, construct a nuclear weapon.”

On Tuesday, U.S. officials pushed back on that assessment, telling reporters that Grossi “hasn’t been on the premises in Iran since Operation Midnight Hammer.” They asserted that Iran could have “easily had a World War II-type weapon” and that Grossi directly told the Trump administration that the IAEA had intelligence that Iran had recently tested “casements” and “detonators.” 

‘Plenty of time’ for congressional authorization

Rep. Bill Foster, D-Ill., the sole physicist in Congress, has called for answers from the administration about existing Iranian stockpiles and disputed the administration’s argument that potential accumulation of 20%-enriched uranium would require immediate military action.

“If they’re talking about inventories of 20%-enriched uranium, the timeline to convert that into higher enriched uranium and into a metal and then into a weapon gives you plenty of time to go to the United States Congress and say that the nuclear talks have broken down and to request military action — and that was not done,” said Foster.

Witkoff and Kushner have yet to appear in classified briefings with lawmakers, but last week administration officials — Secretaries Marco Rubio and Pete Hegseth, CIA Director John Ratcliffe and chairman of the Joint Chiefs of Staff Dan Caine — did not discuss the Tehran Research Reactor or other civil nuclear facilities and made no assertion that they were being used to stockpile uranium for a potential nuclear weapon, according to two people familiar with the administration officials’ comments in two of the briefings provided to lawmakers since the attack on Iran.

Inspections cut off by prior strikes

Iran cut off the IAEA’s oversight access to the reactor last summer after the U.S. and Israel bombed three of its enrichment facilities — strikes that also took place while Witkoff was actively negotiating with Iran. Iran’s stockpile of 1,000 pounds of enriched uranium is believed to be buried underground in tunnels beneath the three sites targeted in those strikes.

“One of the most effective ways to ensure that Iran, or any other country, does not divert nuclear materials from an energy program towards a weapons program, is through the inspections that the International Atomic Energy Agency carries out in many countries around the world,” said Alicia Sanders-Zakre, head of policy of the International Campaign to Abolish Nuclear Weapons. “Israeli and U.S. military strikes on Iran stopped these international inspections. The only successful nonproliferation path forward lies in negotiations, not military action.”

Iranian Foreign Minister Seyed Abbas Araghchi, who led Iran’s negotiating team, criticized Witkoff and Kushner for leaving the nuclear negotiating table.

“When complex nuclear negotiations are treated like a real estate transaction, and when big lies cloud realities, unrealistic expectations can never be met,” Araghchi wrote last week. “The outcome? Bombing the negotiation table out of spite.”

Laura Barrón-López contributed reporting to this article.

CORRECTION (March 9, 2026, 9:19 a.m. ET): A previous version of this article misspelled the name of the board member of Pugwash Conferences of Science and World Affairs and adjunct professor at the Finnish National Defence University. She is Katariina Simonen, not Simonenan.