Iran uranium raises weapons questions

VIENNA – United Nations experts are investigating why tiny particles of uranium found in an underground Iranian nuclear facility had been enriched beyond levels previously acknowledged, a discovery that raised questions about whether Iran is getting closer to creating weapons-grade material for a nuclear bomb.

Inspectors from the International Atomic Energy Agency found traces of uranium enriched up to 27 percent – more than the 20 percent maximum level Iran has claimed – when they visited the Fordow enrichment facility in February. About 90 percent enrichment is needed for a nuclear bomb, though the path from 20 percent to weapons-grade is technically short.

The Obama administration and diplomats cautioned that the trace particles don’t necessarily mean Iran is secretly seeking higher enrichment levels. They said Iran’s technicians may have initially miscalibrated highly sensitive cascades of centrifuges, which spin at intense speeds to enrich uranium before adjusting them down to the 20 percent level.

But the revelation, made public in a United Nations report released Friday, may complicate diplomacy aimed at curbing Iran’s nuclear program by providing ammunition to those who contend that the government intends to develop a nuclear weapons capability.

The disclosure came after two days of inconclusive talks in Baghdad between Iranian officials and negotiators from the five permanent members of the U.N. Security Council plus Germany.

The chief U.S. negotiator, Undersecretary of State Wendy Sherman, flew Friday to Israel, where Prime Minister Benjamin Netanyahu and other officials have warned that Iran is trying to use the talks as a delaying tactic to move closer to a nuclear weapons capability. Israel has threatened to use military action if necessary to stop Iran’s nuclear progress.

In Washington, Obama administration officials said they believed the higher-enriched particles probably were produced during the centrifuge cascade startup, not by secret enrichment activity.

“There are a number of possible explanations for this, including the one that the Iranians have provided,” Victoria Nuland, the State Department spokeswoman, said at a news briefing. “We are going to depend on the IAEA to get to the bottom of it.”

The IAEA, the U.N.’s nuclear monitoring agency, asked Iran for an explanation this month, and the government responded May 5. The “production of such particles ‘above the target value’ may happen for technical reasons beyond the operator’s control,” they wrote.

A diplomat in Vienna said the explanation was plausible and that inspectors previously had found particles enriched above expected levels at Natanz, Iran’s other main enrichment facility.