When US Chairman of the Joint Chiefs of Staff Admiral Mike Mullen was asked on CNN’s State of the Union recently whether Iran has enough fissile material for a nuclear weapon, his response was dramatic and headline-grabbing. It was also wrong.
“We think they do, quite frankly,” said Admiral Mullen, “and Iran having a nuclear weapon, I’ve believed for a long time, is a very, very bad outcome for the region and for the world.”

Mr. Mullen’s answer was based on a February 19 IAEA report which found that Iran has now stockpiled approximately 1,010 kilograms of low-enriched uranium, an adequate amount (or critical mass) at least theoretically to produce a nuclear weapon, if it were highly-enriched, or bomb grade. And therein lies the rub. The uranium Iran is producing is low-enriched, suitable for use in a nuclear power plant, but in its current form, not for making a bomb.1

[Mr. Mullen’s spokesman later offered a correction to CNN, saying that Mr. Mullen was only referring to the low-enriched uranium identified in the IAEA report.]

“The confusion surrounding the question of what material Iran has and whether or not it has enough for a weapon demonstrates the need to be precise when defining what we know about Iran’s capabilities, especially considering the impact such assessments may have on public perception,” said Peter Crail, a research analyst for the nonpartisan Arms Control Association. Low-enriched uranium is not suitable for making a bomb and the IAEA did not say that Iran had any highly enriched uranium of the sort used in making bombs, Mr. Crail noted.

Mr. Crail added: “With headlines running over the past week stating that Iran had enough material for a bomb, one could easily assume there was not much of a difference [between low-enriched and highly-enriched uranium].” In fact there is quite a difference. The low-enriched uranium (or LEU) used to power the majority of the world’s nuclear power reactors is enriched to about 3.5 percent U-235 and cannot be used as material for a bomb in this state. Weapon-grade uranium, on the other hand, must be highly-enriched to a concentration of over 90 percent U-235 to be suitable for bomb making.

While the differences between low-enriched and highly-enriched, weapon-grade uranium are significant, it should be noted that the same facilities and equipment used to produce LEU fuel for power reactors can produce HEU, if the necessary adjustments are made.2

Right now the IAEA has no evidence that Iran is endeavoring to produce HEU, and Iran faces at least two obstacles to converting its current stockpile of LEU into weapon-grade uranium. First, Iran’s stockpile of LEU is under IAEA safeguards (and all material remains accounted for). To enrich the LEU, Iran would need to remove it from agency containment and surveillance, which, at least under current arrangements, could not be done without the knowledge of the IAEA. Second, to further enrich the LEU, Iran must use a properly equipped enrichment facility. Its declared enrichment facility — at Natanz — is not currently configured to carry out this additional enrichment and doing so would also require actions that would be detected by IAEA inspectors.

Regarding such enrichment, the 2007 US National Intelligence Estimate surmised that Iran would likely use a clandestine facility to escape detection if it decided to produce HEU for weapons purposes. It is not known whether Iran has such a secret facility at this time.

While it is certainly true that the IAEA has no evidence of Iran’s seeking to enrich uranium suitable for a nuclear weapon, that does not mean their most recent report is without alarming news. According to the Arms Control Association’s Peter Crail, “what is far more worrisome than Iran’s stockpile of LEU under IAEA safeguards is the fact that Tehran is not providing the agency with broader access under the agency’s Additional Protocol so that it can better detect any undeclared nuclear activities in the country, including through the monitoring of Iran’s centrifuge manufacturing efforts. The public focus on the known nuclear material seems to gloss over the more critical risk of Iranian efforts that may occur, or may be occurring in secret.”
The IAEA’s report concludes by saying that “unless Iran implements the [requested] transparency measures and the Additional Protocol, as required by the Security Council, the Agency will not be in a position to provide credible assurance about the absence of undeclared nuclear material and activities in Iran.”

When it comes to Iran’s nuclear program, it is then (to borrow a phrase) the unknown unknowns that we should be worried about.

Melissa Gillis

Notes
1.  Read the IAEA’s report at http://iaea.org/Publications/Documents/Board/2009/gov2009-8.pdf.
2. Read more about fissile material production at www.fissilematerials.org.