What Is Enriched Uranium and Why Does Iran Want More of It?

Iran's nuclear energy body has warned that within just 10 days—on June 27—the country's stockpile of enriched uranium will surpass the limits set by the Joint Comprehensive Plan of Action (JCPOA)—also known as the Iran nuclear deal.

"The countdown has begun," Behrouz Kamalvandi—a spokesperson for the agency—told assembled media at Iran's Arak heavy water facility on Monday, the Associated Press reported.

Iran's apparent intention to break the 2015 nuclear deal could spell the end for the multinational agreement, which imposed restrictions on Iran's nuclear capability in exchange for the lifting of international sanctions.

President Donald Trump's withdrawal form the deal in May 2018 severely undermined it, though the other cosignatories—the U.K., Germany, France, Russia, China and the European Union—have been working to keep it alive and protect business with Iran. But under the pressure of new American sanctions, their efforts are faltering.

Uranium is required to produce nuclear power and create nuclear weapons. However, the naturally-occurring form of the element does not have the right amount of the fissile isotope—known as U-235—to set off a nuclear reaction. To make it suitable for nuclear use, the amount of U-235 in uranium must be increased through a process of enrichment.

Uranium enriched to between 3 and 4 percent can be used for nuclear power plant fuel, but it must be enriched to around 90 percent for use in weapons. The JCPOA set a limit of 3.67 percent enrichment and a stockpile limit of around 660 pounds for 15 years. This represented a 98 percent reduction in Iran's existing enriched uranium stockpile.

The most common modern method of enrichment is known as centrifugation. Before the JCPOA was signed, Iran operated 20,000 centrifuges at two separate facilities. The agreement dictated that only 5,060 of the oldest and least efficient centrifuges could be used at one site.

Kamalvandi told reporters that the country would increase uranium enrichment "based on the country's needs," and that European nations should "make efforts" if "keeping the nuclear deal is important to them."

Surpassing the 3.67 percent limit would allow Iran to provide fuel for its power plant in Bushehr that needs 5 percent enriched uranium, and also for a research reactor in Tehran that needs 20 percent enrichment, the AP explained.

Mined uranium has around 140 atoms of unwanted U-238 isotopes for every atom of U-235, the AP reported. To get the fuel up to 3.67 percent purity requires the removal of 114 atoms of U-238 for each U-235 atom.

To then reach 20 percent, 22 more unwanted isotopes must be removed per atom of U-235. To get to 90 percent—i.e. suitable for use in nuclear weapons—requires the removal of just four more U-238 isotopes per U-235 isotope. This means reaching the threshold of weapons-grade material is a relatively quick process, making it of great concern to those seeking to keep Iran from achieving a nuclear arsenal.

But for now, the risk of an Iranian nuclear arsenal is still some way off. Kelsey Davenport, the director of nonproliferation policy at the Arms Control Association, told Newsweek that while any threat to violate the nuclear deal is concerning, "exceeding the limit on enriched uranium will not pose a near-term proliferation risk.

"Iran currently possesses less than 300 kilograms [660 pounds] of low-enriched uranium," she explained. "Iran needs to produce about four times that amount, and then enrich it to weapons grade, to produce enough nuclear material for a bomb."

"More concerning are the steps that Iran may take down the road that pose more of a proliferation risk if the Europeans, Russians, and Chinese do not deliver sanctions relief," Davenport added.

"Iran's frustration with the Trump administration's attempts to deny Tehran any benefits from complying with the nuclear deal is understandable, but starting down the slippery slope of violating the deal in retaliation risks igniting a new nuclear crisis."

Nuclear weapon production also requires plutonium. This is produced using heavy-water nuclear facilities, such as the one in Arak where Kamalvandi spoke on Monday. Under the guidance of the JCPOA, the reactor there was redesigned so it could not produce weapons-grade plutonium. The deal also said no new heavy-water reactors could be built for 15 years and that only around 143 tons of heavy water could be stockpiled.

Iran has said that if the JCPOA fails it will halt its redesign of the reactor at Arak, the BBC noted. Spent fuel from the reactor would contain plutonium suitable to build nuclear weapons.

European powers have warned Iran they are ready to reimpose sanctions if Tehran violates the deal. This, Davenport said, would be a lose-lose situation.

"Nobody wins if the deal dies," she explained. "Despite Iran's legitimate frustration with U.S. attempts to deny sanctions benefits under the deal, it remains in Iran's interests to continue meeting its obligations under the deal and working with the Europeans, Russians, and Chinese on options to facilitate legitimate trade and economic opportunities."

This article has been updated to include comments from Kelsey Davenport.

Iran, nuclear weapons, enriched uranium, Arak
This file photo shows a general view of a heavy water plant in Arak, Iran, on 26 August 2006. On Monday, an Iranian nuclear agency spokesperson told reporters at the plant that the country's enriched uranium stockpile would soon surpass the limit allowed under the beleaguered Iran nuclear deal. Getty/ATTA KENARE/AFP