Not neutralized: Iran’s uranium only 'temporarily' converted, experts say

Iran has pledged to chemically convert its cache of enriched uranium into a less dangerous substance as part of a deal struck on Sunday, but that conversion can be undone through a well-known process, experts tell FoxNews.com.

The weekend deal reached by the U.S. and five other world leaders to curb Iran’s nuclear program in exchange for lifting some sanctions requires Iran to take uranium that had been enriched to 20 percent -- most of the way to weapons-grade -- and convert it into uranium dioxide (UO2). But that process is readily undone, explained Charles D. Ferguson, president of the Federation of American Scientists.

“This is a meaningful barrier right now, but it’s not a permanent barrier,” Ferguson told FoxNews.com. “They might have the ability to make a facility to reconvert it … close to a dozen countries have that process.”

'There are several chemical steps, but Iran knows how to do them.'

— David Albright, founder of the Institute for Science and International Security

Ferguson, who has consulted with the National Nuclear Security Administration and served in the Office of the Senior Coordinator for Nuclear Safety at the U.S. Department of State, said the chemistry process is well understood. But the weekend agreement does buy some time for diplomacy.

“I don’t think this deal is perfect but each side has a compromise -- and at least this buys some time for about six months,” he said.

Iran has already converted some of its 440 pounds of 20-percent uranium into uranium dioxide at facilities within the country, but those plants can’t convert the oxide back into nuclear fuel, explained David Albright, a physicist and founder of the non-profit Institute for Science and International Security (ISIS) in Washington, D.C.

It’s reversible, but not that quickly,” Albright told FoxNews.com. “There are several chemical steps, but Iran knows how to do them.”

To get weapons-grade fuel, uranium hexafluoride (UF6) gas is pumped through a centrifuge to remove fluorine atoms -- essentially a giant salad spinner that concentrates the fissile isotope U235 in the gas. After multiple passes through the spinning centrifuge, the concentration of that isotope increases, Ferguson explained.

Centrifuges can refine UF6 to three different stages: At 3.5 percent, the output is good enough for reactor fuel. Enriched to 20 percent, it can be used in scientific and medical research. But it's also just a step away from the 90-percent level, where it can be used as weaponized uranium.

“It may seem at first that 20 to 90 is a big gap. But b enriching up to that 20-percent level, you’re actually doing the work you need to get up to weapons-grade levels ... it’s relatively quick to [convert it] to 90 percent,” Ferguson told FoxNews.com.

Converting 20-percent uranium into oxide would take it a step away from weapons-caliber. For Iran to then reconvert it, the country would need to construct a sizable building for the multi-stage process.

“They would have to create a facility where the chemical forms can be changed,” Albright explained.

There are several intermediate steps behind between uranium oxide and UF6. Oxygen must be stripped out and fluorine added back in, a substance that is extremely toxic and corrosive and therefore requires special facilities.

“Iran can do it, but it’s not something they can set up in a day,” he told FoxNews.com.