Iran’s Khondab Reactor Goes Dark—But 440 kg of Enriched Uranium Remains Unaccounted For
IAEA confirms plutonium production pathway offline after Israeli strikes, yet nuclear weapons timeline hinges on 60%-enriched uranium stockpile now scattered across damaged, unmonitored sites.
The IAEA confirmed on March 30 that Iran’s Khondab heavy water production plant is no longer operational following Israeli strikes on March 27, severing a plutonium production pathway capable of yielding 8-10 kg of weapons-grade material annually—enough for one to two nuclear devices.
The facility shutdown marks the second major bombing campaign against Iran’s nuclear infrastructure in under a year, yet the military strategy confronts a critical limitation: Iran’s stockpile of 440 kg of 60%-enriched uranium, verified by the IAEA last May, remains unaccounted for across partially damaged sites at Natanz, Isfahan, and Fordow. That quantity is sufficient for nine to ten nuclear weapons if further enriched to 90%, according to a CNN analysis citing CIA assessments from February 27.
The Israeli military described Khondab as a “key plutonium production site for nuclear weapons” when announcing the March 27 strike, per Times of Israel reporting. Heavy water reactors use natural uranium and produce plutonium-239 as a byproduct—a parallel enrichment pathway distinct from Iran’s centrifuge operations. The reactor core was previously rendered inoperative under the 2015 JCPOA by removing the calandria and filling it with concrete, but the heavy water production plant itself remained functional until last week.
Maximum Pressure Meets Maximum Deadlock
The strike sequence unfolded amid the Trump Administration’s delivery of a 15-point proposal demanding Iran permanently halt uranium enrichment, dismantle facilities at Natanz, Isfahan, and Fordow, and transfer all enriched material to IAEA custody. Iran rejected the terms within 24 hours on March 25, calling them “extremely maximalist and unreasonable,” according to NPR.
Iran’s counter-proposal included five conditions: reparations for infrastructure damage, sovereignty over the Strait of Hormuz, cessation of all US-Israeli military operations, protection of regional proxy forces, and sanctions relief without preconditions. Iranian military spokesperson Ebrahim Zolfaqari dismissed negotiations outright: “People like us can never get along with people like you. Not now. Not ever.”
Trump subsequently claimed Iran was “begging” for a deal, announcing a pause on energy infrastructure strikes until April 6. White House Press Secretary Karoline Leavitt warned Tehran not to “miscalculate again,” stating the president “is prepared to unleash hell,” according to NPR.
The Limits of Kinetic Degradation
The Khondab shutdown demonstrates a paradox: military strikes can sever production pathways but cannot locate dispersed stockpiles. A confidential February 27 IAEA report obtained by War on the Rocks noted that Iran’s 440 kg of 60%-enriched uranium is now spread across damaged facilities with diminished monitoring—leaving its precise location and condition unknown.
This marks the second nuclear bombing campaign in ten months. June 2025’s Operation Rising Lion killed at least 14 Iranian nuclear scientists and struck centrifuge halls at Natanz and Fordow. The latest operation, launched February 28 as Operation Epic Fury, executed over 900 strikes in the opening 12 hours and killed Supreme Leader Khamenei. Yet uranium enrichment infrastructure damage has proven easier to repair than intelligence agencies anticipated—Iran restored partial centrifuge operations at Natanz within 90 days of the June campaign.
“The nuclear fatwa is dead. Elite opinion as well as public opinion has shifted dramatically on this, which shouldn’t be surprising since Iran has been bombed twice in the midst of negotiations by two nuclear-equipped states.”
— Trita Parsi, Quincy Institute for Responsible Statecraft
The March 27 strikes also targeted a uranium extraction facility in Yazd with an annual yellowcake production capacity of approximately 50 tons, according to Israel Hayom. The facility processes raw uranium ore into uranium hexafluoride feedstock for centrifuge cascades—disrupting the supply chain for future enrichment but leaving existing stockpiles intact.
Hardline Pressure to Weaponise
Iran’s new Supreme Leader Mojtaba Khamenei faces mounting pressure from Islamic Revolutionary Guard Corps commanders to reverse his father’s decades-old fatwa prohibiting nuclear weapons. IRGC officer Ahmad Haqtalab warned in 2024 of “a shift away from previous considerations,” signaling doctrinal flexibility, according to CNN.
Iranian Foreign Minister Abbas Araghchi expressed uncertainty in March about whether Mojtaba would maintain the anti-nuclear stance. Sina Azodi, author of “Iran and the Bomb,” noted that the rationale for forbearance has eroded: “One of the reasons they exercised nuclear forbearance was the fear of attacks by Israel and the US. But at this point where they attacked anyways, all bets are off for them.”
The JCPOA, implemented in January 2016, required Iran to remove the IR-40 reactor core and fill the calandria with concrete to prevent plutonium production. Tehran maintained the heavy water plant itself, using it for isotope production and research applications. The plant’s destruction now closes the plutonium pathway—but Iran’s mastery of centrifuge technology means uranium enrichment remains the faster route to a weapon. Enriching 440 kg of 60%-enriched material to 90% requires weeks, not years.
Parliamentary hardliners introduced legislation on March 28 demanding withdrawal from the Nuclear Non-Proliferation Treaty and immediate resumption of pre-JCPOA enrichment levels, reported Al Jazeera. The bill explicitly frames nuclear weapons development as a defensive necessity against “repeated existential aggression.”
What to Watch
Trump’s April 6 deadline for resuming energy strikes creates a narrow diplomatic window, but Iran’s flat rejection of the 15-point proposal leaves no visible negotiation framework. The key variable is not facility status—Khondab’s reactor core was already inoperative—but whether Tehran decides to weaponise its existing stockpile before further strikes occur.
IAEA monitoring capabilities remain degraded following the February-March campaign. If Iran moves material to hardened mountain facilities or covert sites, detection becomes exponentially harder. Intelligence agencies admit in the February 27 report that command structure decentralisation and scientist dispersal have created blind spots—meaning the next inflection point may only become visible after weaponisation is complete.
The negotiation calculus has inverted from 2015: then, Iran sought sanctions relief in exchange for transparency. Now, after two bombing campaigns and 900+ strikes, hardliners argue that only a nuclear deterrent can guarantee survival. The question is no longer whether Iran will weaponise, but whether military pressure accelerates or delays that decision—and whether 440 kg of unmonitored uranium provides enough of a head start to render the answer moot.