WASHINGTON — Iran is expanding the capacity of its underground nuclear facility, a U.N. report said Friday, as its leaders move to increase production of a more purified form of enriched uranium in defiance of Western demands for a freeze.
U.N. inspectors who visited the plant near the city of Qom this month saw hundreds of newly installed centrifuges amid steady progress in boosting the capability of the facility, which has come to symbolize international concerns about Iran's possible pursuit of nuclear weapons.
The inspectors also discovered traces of a form of uranium that is closer to the kind needed to make weapons-grade fuel than the Iranians have previously acknowledged making. The particles were believed to have resulted from a technical glitch, but officials from the International Atomic Energy Agency were still investigating.
Evidence of the plant's expansion is likely to add to worries about Iran's nuclear ambitions, while enhancing the country's bargaining position going into a new round of nuclear talks set for June, weapons experts said.
"Iran is dealing itself more cards for the negotiations," said Joshua Pollack, a government consultant on nuclear issues and a contributor to ArmsControlWonk.com. "The West is piling on sanctions while they're adding more (centrifuges) underground. We'll see who blinks first."
The agency's report, a summary of findings from its inspections inside Iran, documented a jump in the country's overall production of enriched uranium, suggesting Iran is continuing to recover from a disastrous computer virus two years ago and other technical setbacks.
"The machines seem to be operating better, and overall, they're enriching more efficiently," said David Albright, a former agency inspector.
The trace particles of a form of more highly enriched uranium were discovered during the agency's tests in a previous inspection at Qom in February. The particles were found to have been enriched to 27 percent purity. Although that is a level higher than Iran has previously acknowledged making, it is still well below the 90 percent level needed for nuclear weapons.
When pressed about the anomaly, Iran said a spike in enrichment levels could happen "for technical reasons outside the operator's control," the report said. Agency officials have taken more samples as an inquiry continues. Some nuclear experts said the unusual particles could have resulted from ordinary fluctuations in the enrichment process.
Iran says it needs the enriched uranium to fuel nuclear power plants. Western governments suspect Iran's activities are a cover for a secret weapons program.