Iran announced Monday that it has surpassed the uranium enrichment limit set by the 2015 Nuclear Deal. The limit was set to prevent Iran from developing nuclear weapons, but Iran said the increased enrichment is solely for use in nuclear power plants.
What Is Uranium Enrichment?
Uranium is naturally composed of two isotopes, U-235 and U-238. (If you recall high school chemistry lessons, an isotope is a variation of an element with a differing atomic mass due to the number of neutrons in its nucleus). Nuclear energy is produced from the fission, or splitting, of U-235 atoms. Natural uranium, however, is made up of less than one percent of U-235, so the ore needs to be enriched in order to be used as fuel.
This is done by converting the uranium into a gas and putting it through a centrifuge. Being different weights, the isotopes move differently in the gas centrifuge’s spinning cylinders. This allows the lighter U-235 to be isolated and collected in a higher concentration than naturally possible, resulting in enriched uranium.
What Has Changed?
The nuclear deal limited Iran’s enrichment to 3.67%, but on Monday the country’s levels reached nearly 4.5%, Behrouz Kamalvandi, a spokesman for the Atomic Energy Organization of Iran, told Iranian news agency Fars News.
These levels are to accommodate Iran’s nuclear energy needs, said Kamalvandi, but higher levels of enrichment are on the table. Uranium enrichment up to 20% is used in research, while 90% and over is considered weapons-grade.
“Twenty percent is not needed now, but if we want we will produce it. Now that we have gone past the 3.67% enrichment, there won’t be any problem with this action,” Kamalvandi told Fars News. “Today if our country’s needs are one thing, we won’t pursue something else just to scare the other side a little more. But they know it’s an upward trend.”
Although the U.S. pulled out of the nuclear deal last year and reinstated sanctions against Iran, European powers remain signed on. Iran has argued that these remaining countries must offset the economic impact of the U.S. sanctions, or else it will not comply with the 2015 deal.
While some progress has been made with the implementation of a new trade deal in June, Iranian Deputy Foreign Minister Seyed Abbas Araqchi said this is “still not enough.”
Monday’s enrichment increase—as well as last week’s overshot uranium stockpile—indicate Iran means to hold the European signers to the deal’s economic guarantees. Kamalvandi said Iran will consider restarting some gas centrifuges shut down by the nuclear deal as well. Any threat of the country developing a nuclear weapon, however, is months away.
More must-read stories from Fortune:
—Why Hong Kong is protesting —and may do so again
—Black women voters will be central to the 2020 election, experts predict
—Trump reportedly wants tanks on the National Mall on July 4
—Supreme Court redistricting decision could reshape politics
—This 31-year-old just torpedoed Italy’s relationship with EU partners
Get up to speed on your morning commute with Fortune’s CEO Daily newsletter.