LITTLE ROCK — U.N. nuclear inspectors in Iran have found uranium enriched beyond the highest previously reported levels of 20 percent in samplings taken from its new underground fuel-enrichment plant, according to a quarterly report on Iran’s nuclear program.
The report, delivered Friday to the board of the International Atomic Energy Agency, based in Vienna, said the samplings, taken Feb. 15 from the Fordo enrichment facility built inside a mountain near Iran’s holy city of Qom, “showed the presence of particles with enrichment levels of up to 27 percent.”
Iran also almost doubled its stockpile of 20 percent medium-enriched uranium, to 320 pounds from about 162 pounds in February, the nuclear agency said in the 11-page report. Iran had tripled its production of the material in the three months ending Feb. 24.
The finding of 27 percent enrichment shows that Iran is closer to bomb-grade material even as a group of six world powers is negotiating with Tehran to shift its nuclear program in the opposite direction.
Whether the 27 percent figure represented a trace amount was not made clear in the report.
It said inspectors had requested an explanation from Iran on May 4 and the Iranians had responded May 9 that the production of such particles “may happen for technical reasons beyond the operator’s control.” The report said inspectors were evaluating Iran’s response, had requested more detail and had taken further samples from the same location May 5. “These samples are currently being analyzed,” the report said.
The report is the first since nuclear agency Director General Yukiya Amano returned from Iran on Monday with a commitment from the Islamic Republic’s government to improve cooperation with inspectors. While the Persian Gulf nation insists that its atomic work is peaceful, it has been under agency scrutiny since 2003 over evidence that it has sought nuclear-weapon capabilities.
The report was disclosed less than a day after Iran and the group of six world powers ended a round of difficult negotiations held in Baghdad on Iran’s disputed nuclear program. No substantive progress was made during the talks, but both sides agreed to meet again in Moscow next month. A diplomat in Vienna, speaking on the condition of anonymity because of the issue’s sensitivity, cautioned that the spike in enriched-uranium purity found by inspectors could turn out to be accidental.
Until now, the highest reported level of uranium enrichment for the Iranian program was 20 percent. The Nuclear Nonproliferation Treaty makes no restrictions on how pure a nation can make its enriched uranium, only that it cannot mix the civilian work with military applications.
In Iran’s case, the International Atomic Energy Agency and Western powers have amassed evidence suggesting that Iran has investigated the making of nuclear arms.
Most uranium fuel for reactors is enriched to about 4 percent purity. More than two years ago Iran began producing fuel enriched to 20 percent, saying it was for a research reactor in Tehran.
Bomb-grade fuel requires purity of 90 percent, which, in terms of production efforts, is a comparatively short leap from 20 percent enrichment.
David Albright, president of the Institute for Science and International Security, a Washington research group that tracks the Iranian nuclear program, said he believed that the high enrichment reading had a benign explanation in Iran’s continuing rearrangement of its centrifuges — tall machines that spin fast to purify uranium.
“It’s definitely embarrassing but not nefarious,” Albright said in an interview.
Iran’s rearrangements of its centrifuges, he added, are intended to increase the efficiency of its enrichment. The process involves thousands of centrifuges, interconnected by pipes, that work in stages to heighten the uranium’s purity one step at a time.
The new configuration tends to “overshoot 20 percent” at the start, he said.
“There’s a lot of art to this,” he said of enriching uranium on an industrial scale, “and a lot of learning.”
The U.N. nuclear agency has previously found uranium particles enriched to even higher levels at Iran’s Natanz facility. Those samples were the result of outside contamination, according to the agency.
In Washington, State Department spokesman Victoria Nuland said “there are a number of possible explanations for this, including the one that the Iranians have provided. But we are going to depend on the IAEA to get to the bottom of it.”
In its report, the International Atomic Energy Agency said that while the agency continued to verify over the past three months that Iran hadn’t diverted its declared nuclear material for use in weapons, it was “unable to provide credible assurance about the absence of undeclared nuclear material and activities in Iran.”
The agency said it couldn’t therefore definitively “conclude that all nuclear material in Iran is in peaceful activities.”
The agency found Iran’s stockpile of uranium enriched to less than 5 percent grew to 13,739 pounds from 12,017 pounds reported in February.
And the number of centrifuges, fast-spinning machines that purify the heavy metal, installed at Iran’s fuel-fabrication plant in Natanz, about 186 miles south of Tehran, rose to 9,330 compared with 9,156 in February.
Machines at the Fordo facility, which was built into the side of a mountain, rose to more than 500 from 300 in the previous report. That enrichment facility has drawn particular attention from Israel because it would be difficult to destroy with an airstrike.
Iran has already used onethird of its 20 percent stockpile to make fuel plates for its Tehran research reactor, which is used to produce medical isotopes for cancer treatment. Turning the uranium into metal renders it more difficult to enrich it into weapons material, according to the officials.
About 1,390 pounds of low-enriched uranium, if further purified, could yield the 30 to 50 pounds of weapons-grade uranium an expert needs to produce a bomb, according to the London-based Verification Research, Training and Information Center, a nongovernmental observer to the U.N. nuclear agency that’s funded by European governments.
The agency’s report will be released formally June 4 when the agency’s 35-member board of governors convenes in Vienna.
Information for this article was contributed by William J. Broad of The New York Times; by Jonathan Tirone and Indira A.R. Lakshmanan of Bloomberg News; and by George Jahn and Ian Deitch of The Associated Press.
Front Section, Pages 1 on 05/26/2012