Uranium starts as a rock in the ground, but through a series of chemical processes and high-speed centrifuges, it can become either a city’s power source or a weapon of mass destruction.
Al Jazeera’s Basel Ghazoghli (@baselgazi) breaks down how uranium is processed, enriched, and what it takes to turn it into a nuclear weapon.
Published On 28 Apr 202628 Apr 2026
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United States President Donald Trump has claimed that a new nuclear deal being negotiated with Iran will be “far better” than the 2015 Joint Comprehensive Plan of Action (JCPOA), which the US withdrew from in 2018 during his first term.
On Tuesday, Trump extended the two-week ceasefire with Iran a day before it was set to expire, with hopes for a second round of talks in Islamabad, Pakistan.
Key among the US demands is that Iran stop all enrichment of uranium.
Iran has always insisted its nuclear programme is for civilian use only, such as for power generation, which requires uranium enrichment of between 3 percent and 5 percent. To build nuclear weapons, uranium needs to be enriched to 90 percent.
In this explainer, we visualise what uranium is, how it is enriched and how long it could take Iran to make a nuclear weapon.
Uranium is a dense metal used as a fuel in nuclear reactors and weapons. It is naturally radioactive and usually found in low concentrations in rocks, soil and even seawater. About 90 percent of the world’s uranium is produced in just five countries: Kazakhstan, Canada, Namibia, Australia and Uzbekistan. Reserves of uranium have also been found in other countries.
Uranium is extracted either by digging it out of the ground or, more commonly, through a chemical process that dissolves uranium from within the rock.
Before it can be used as nuclear fuel, uranium is processed through several different forms, including:
Natural uranium exists in three forms, called isotopes. They are the same element, with the same number of protons but different numbers of neutrons.
Most naturally occurring uranium (99.3 percent) is U-238 – the heaviest and least radioactive – while about 0.7 percent is U-235 and trace amounts (0.005 percent) are U-234.
To generate energy, scientists separate the lighter, more radioactive U-235 from the slightly heavier U-238 in a process called uranium enrichment. U-235 can sustain a nuclear chain reaction while U-238 cannot.
To enrich uranium, it must first be converted into a gas, known as uranium hexafluoride (UF₆). This gas is fed into a series of fast-spinning cylinders called centrifuges. These cylinders spin at extremely high speeds (often more than 1,000 revolutions per second). The spinning force pushes the heavier U-238 to the outer walls, while the lighter U-235 stays in the centre and is collected.
A single centrifuge provides only a tiny amount of separation. To reach higher concentrations – or “enrichment” – the process is repeated through a series of centrifuges, called a cascade, until the desired concentration of U-235 is achieved.
The higher the U‑235 percentage, the more highly enriched the uranium is.
Small amounts (3-5 percent) are enough to fuel nuclear power reactors, while weapons require much higher enrichment levels (about 90 percent).
The International Atomic Energy Agency (IAEA) considers anything below 20 percent to be low-enriched uranium (LEU), while anything above 20 percent is considered highly-enriched uranium (HEU).
Low enriched – less than 20 percent
Highly enriched – More than 20 percent
Depleted uranium, which contains less than 0.3 percent U‑235, is the leftover product after enrichment. It can be used for radiation shielding or as projectiles in armour‑piercing weapons.
The effort it takes to enrich uranium is not linear, meaning it is much more difficult to go from 0.7 percent natural uranium to 20 percent LEU than it is to go from 20 percent to 90 percent HEU. Once uranium reaches 60 percent enrichment, it becomes much quicker to reach 90 percent weapons grade.
The effort it takes to enrich uranium is measured in separative work units (SWU).
According to the IAEA, Iran is believed to have about 440kg (970lbs) of uranium enriched to 60 percent – enough to theoretically build 10 or 11 low-technology atomic bombs if refined to 90 percent.
Ted Postol, professor emeritus of science, technology and international security at the Massachusetts Institute of Technology (MIT), told Al Jazeera that before the US attack on Iran’s nuclear facility at Fordow, the country had at least 10 cascades of 174 IR-6 centrifuges in operation – meaning 1,740 IR-6 centrifuges.
The IR-6 is one of Iran’s most advanced centrifuge models. The country also has tens of thousands of older centrifuges.
Little is known about the conditions of these centrifuges or the stocks of uranium hexafluoride, which are still believed to be buried underground.
Postol has calculated that Iran’s cascade of centrifuges could produce 900 to 1,000 SWUs annually.
“Getting from natural uranium to 60 percent enrichment, which Iran has already achieved, takes roughly five years, and about 5,000 SWUs using Iran’s cascades.”
“If I want to go from 60 to 90 percent, I only need 500 SWUs. So, instead of five years, [by] starting with the 60 percent here, this might take me four or five weeks. Because I am already very enriched,” Postol said.
Using an analogy of a clock, Postol explained: “Let’s say it takes seven minutes to get 33 percent enrichment, and then eight minutes to get to 50 percent enrichment. It only takes me one minute to get to total [90 percent] enrichment.”
Postol said Iran’s stockpile is held underground, meaning a military strike would not necessarily eliminate the nuclear threat.
A single centrifuge cascade capable of enriching weapons-grade uranium could take up “no more floor space than a studio apartment, making it easily hidden in a small laboratory”, he said, estimating the area at 60sq metres (600sq feet).
“A single Prius Compact Hybrid car can produce enough electric power to run four or more of these cascades at a time,” Postol added, meaning “Iran can covertly convert its 60 percent uranium into weapons-grade uranium metal”.
“What they have done is put themselves in a position where anybody who thinks about attacking them with nuclear weapons has to know that they could be sitting in those tunnels after such an attack, refining [and] enriching the final step they need to build atomic weapons and converting it to metal, and building a nuclear weapon, and that they have the means to deliver it,” Postol said.
“They would have all of the technical equipment they need to build the atomic weapons. And they have the missiles, which are also in the tunnels and can be manufactured in addition to what they already have. And the atomic weapon would not need to be tested, because uranium weapons do not need to be tested before they’re used.”
The Treaty on the Non-Proliferation of Nuclear Weapons (NPT), established in 1968, is a landmark international agreement aimed at preventing the spread of nuclear weapons and promoting peaceful uses of nuclear energy. Iran is a signatory to this pact.
The treaty supports the right of all signatories to access nuclear technology and enrich uranium for peaceful purposes, including energy, medical or industrial purposes, with precise safeguards to ensure it is not diverted to make weapons.
Under the NPT, nuclear-weapon states agree not to transfer nuclear weapons or assist non-nuclear-weapon states in developing them. Non-nuclear-weapon states also agree not to seek or acquire nuclear weapons.
Despite this, most nuclear powers are currently modernising their arsenals rather than dismantling them.
Most of the countries are signatories, except five: India, Pakistan, Israel, South Sudan and North Korea.
In 2015, under the Obama administration, Iran struck a deal with six world powers — China, France, Germany, Russia, the United Kingdom and the US — plus the European Union, known as the JCPOA.
Under the pact, Tehran agreed to scale down its nuclear programme, capping enrichment to 3.67 percent, in exchange for relief from sanctions.
“The Iranians agreed to it, and they were following the treaty. There was no problem with the treaty at all, absolutely no problem,” Postol said.
“They were allowed to have 6,000 centrifuges, which, if they had natural uranium, they could probably build a bomb within a year if they were secretly using these centrifuges, but that was all under inspection. They were just simply going to enrich to 3.67 percent, which is for a power reactor. They’re allowed to do that by the Non-Proliferation Treaty.”
But in 2018, Trump pulled out of the deal, calling it “one-sided” and reimposing sanctions on Iran. Iran responded by eventually resuming enrichment at Fordow.
After the US killed Iran’s General Qassem Soleimani in January 2020, Tehran stated it would no longer follow the set uranium enrichment limits.
Former President Joe Biden made attempts to revive the deal, but it never came to fruition due to disagreements over whether sanctions should be lifted first or Iran should rejoin the JCPOA first.
Trump has repeatedly said Iran should not have the ability to produce nuclear weapons. It has been one of Washington’s red lines during talks with Iranian officials over the past year, and was also the central justification that Washington used when it bombed Iranian nuclear facilities during the 12-day US-Israel war on Iran last year.
In the current negotiations, Iran has said it is willing to “downblend” its 60 percent enriched uranium to about 20 percent – the threshold for low-enriched uranium. The process of downblending involves mixing stocks with depleted uranium to achieve a lower percentage of enriched U-235 overall.
“From the point of view of showing goodwill, I think it’s good, it shows that the Iranians are thinking of ways to address what the Americans claim are their concerns,” Postol said.
Nine countries possessed roughly 12,187 nuclear warheads as of early 2026, according to the Federation of American Scientists. Approximately two-thirds are owned by two nations – Russia (4,400) and the US (3,700), excluding their retired nuclear arsenals.
Some 9,745 of the total existing nuclear weapons are military stockpiles for missiles, submarines and aircraft. The rest have been retired. Of the military stockpile, 3,912 are currently deployed on missiles or at bomber bases, according to the Federation of American Scientists. Of these, some 2,100 are on US, Russian, British and French warheads, ready for use at short notice.
While Russia and the US have dismantled thousands of warheads, several countries are thought to be increasing their stockpiles, notably China.
The only country to have voluntarily relinquished nuclear weapons is South Africa. In 1989, the government halted its nuclear weapons programme and began dismantling its six nuclear weapons the following year.
Israel is believed to possess nuclear weapons, with a stockpile of at least 90. It has consistently neither confirmed nor denied this, and despite numerous treaties, it faces little international pressure for transparency.
Rafael Grossi, director general of the International Atomic Energy Agency, speaks at a press briefing at the Four Seasons Hotel in Seoul on April 15. Photo by Asia Today
April 15 (Asia Today) — Rafael Grossi said Tuesday that North Korea has built a new uranium enrichment facility in the Yongbyon area, signaling a significant expansion of its nuclear capabilities.
Speaking at a press briefing in Seoul, Grossi said assessments by the International Atomic Energy Agency show North Korea’s nuclear activities have expanded across multiple facilities, including a 5-megawatt reactor, reprocessing plants and a light-water reactor.
He said the newly identified building appears similar in scale and infrastructure to the Kangson enrichment facility, indicating a substantial increase in uranium enrichment capacity.
“While it is difficult to calculate exact production levels without on-site access, the external features suggest a significant expansion,” Grossi said. “This points to a serious increase in the ability to produce dozens of nuclear warheads.”
The agency had previously monitored the construction of the facility, noting similarities in cooling and supply systems to existing enrichment sites.
Grossi also warned that nuclear weapons development fuels proliferation and accelerates arms competition, adding that such capabilities do not necessarily improve national security.
On South Korea’s potential pursuit of nuclear-powered submarines, Grossi stressed the need for strict safeguards under the Nuclear Non-Proliferation Treaty.
He raised concerns that nuclear material used in submarines could fall outside routine inspection regimes due to extended underwater operations, particularly if highly enriched uranium is used.
Grossi said South Korea would need to establish special procedures and coordination mechanisms with the agency to ensure transparency and prevent diversion of nuclear material.
He added that discussions with the government, navy and industry would follow if the project proceeds, noting that the development process would take years and involve multiple stages.
— Reported by Asia Today; translated by UPI
© Asia Today. Unauthorized reproduction or redistribution prohibited.
Original Korean report: https://www.asiatoday.co.kr/kn/view.php?key=20260416010004885
Washington, DC – Tulsi Gabbard, the director of US National Intelligence, said that the United States intelligence community had assessed that Iran was not rebuilding its nuclear enrichment capabilities following US and Israeli attacks last year.
The revelation on Wednesday appeared to undercut one of President Donald Trump’s key justifications for joining Israel in launching the latest war against Iran.
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Trump and his top officials have repeatedly cited Iran’s nuclear ambitions as one of the main reasons for abandoning ongoing diplomatic talks in favour of military action.
“As a result of Operation Midnight Hammer,” Gabbard said in written testimony to the Senate intelligence committee, referencing the June 2025 US strikes on Iran’s nuclear facilities, “Iran’s nuclear enrichment program was obliterated”.
“There have been no efforts since then to try to rebuild their enrichment capability,” Gabbard said in the written testimony.
Notably, Gabbard did not read that portion of her testimony, which was provided to members of the committee, during her publicly televised oral testimony. When pressed on why she omitted the portion, Gabbard said simply that she did not have enough time. She did not deny the assessment.
“You chose to omit the parts that contradict Trump,” Senator Mark Warner, a Democrat, responded.
Trump has repeatedly said the June 2025 attacks, which came at the end of a 12-day war between Israel and Iran, had “obliterated” Iran’s nuclear capacity, even as he warned that Iran’s alleged nuclear ambitions presented an immediate threat to the US.
Tehran has for years denied it is seeking a nuclear weapon. Nuclear and arms monitors have maintained that even if Tehran were seeking a nuclear weapon, it did not represent a short- or medium-term threat.
The foreign minister of Oman, who had mediated the latest round of US-Iran indirect nuclear talks ahead of the war, has refuted Trump officials’ claims that the most recent negotiations were not yielding any progress.
The Guardian newspaper also reported this week that the United Kingdom’s national security adviser, Jonathan Powell, had attended the final session of talks and assessed that the Iranian position did not justify an immediate rush to war, citing sources familiar with the situation.
The administration has not settled on any single justification for launching the war, also pointing to Iran’s ballistic capabilities, its potential threat to Israel and US forces in the Middle East, and the totality of the Iranian government’s actions since the 1979 Islamic Revolution.
The concept of an “imminent threat” is significant in determining the legality of Trump’s decision to strike a sovereign country under international law.
It is also significant for US domestic law, under which presidents can commit the military only in instances of immediate self-defence. Only Congress can officially declare war or authorise extended military campaigns.
The White House said earlier this week that Iran’s ballistic missile capacity was “functionally destroyed”, with the Iranian navy “effectively destroyed” and the US and Israel dominating the country’s airspace.
Experts have assessed that Iran still maintains the military capacity to inflict significant damage in the region, and it has continued to wield its military influence over the Strait of Hormuz.
Gabbard, meanwhile, offered a more sober assessment than the White House, saying that despite the killings of Iranian supreme leader Ayatollah Ali Khamenei, top military officials, and most recently the head of the Supreme National Security Council, Ali Larijani and the intelligence minister, Esmail Khatib, “the regime in Iran appears to be intact but largely degraded by Operation Epic Fury”.
“Even so, Iran and its proxies remain capable of and continue to attack US and allied interests in the Middle East. If a hostile regime survives, it will seek to begin a years-long effort to rebuild its missiles and UAV [drone] forces,” she said.
Gabbard also listed Iran, alongside Russia, China, North Korea and Pakistan, as among the countries “researching and developing an array of novel, advanced, or traditional missile delivery systems, with nuclear and conventional payloads, that put our homeland within range”.
The Washington, DC-based Arms Control Association has said that US intelligence as of 2025 had said it may take Iran until 2035 or longer to develop a missile capable of hitting the US, if it did indeed seek to do so.
Gabbard spoke a day after a top official in her agency, Joe Kent, the director of the US National Counterterrorism Center, resigned in opposition to Trump’s war with Iran.
In his resignation, Kent said that Iran “posed no imminent threat” to the US and that Trump’s decision to enter the war went against his “America First” pledges.
Kent is the first high-profile member of the Trump administration to step down in response to the war.
Gabbard herself had previously been a vocal opponent to indefinite military engagement in the Middle East and war with Iran. A former member of the US House of Representatives from Hawaii, she left the Democratic Party and supported Trump, in part, due to his anti-war vows.
However, in a post on X on Tuesday, Gabbard defended Trump’s decision to go to war.
“As our Commander in Chief, he is responsible for determining what is and is not an imminent threat, and whether or not to take action he deems necessary to protect the safety and security of our troops, the American people and our country,” she said.
She said her agency’s role was to funnel US intelligence to Trump.
“After carefully reviewing all the information before him, President Trump concluded that the terrorist Islamist regime in Iran posed an imminent threat and he took action based on that conclusion,” she said.