Iran nuclear enrichment program stalls

VIENNA -- Iran's output of enriched uranium is stagnating even as its production capacity increases, a sign that Tehran may be running out of the ore needed to make nuclear fuel, diplomats said Tuesday.

If so, it could mean that international sanctions to slow if not stop Iran's nuclear program are taking hold.

The diplomats, who requested anonymity because their information was confidential, said the possibility Iran was running short of uranium oxide was only one of several possible explanations for why it had not increased its production of enriched uranium since May.

But they said it seemed unlikely the Islamic Republic had deliberately decided to curb production. They said that over the past three months the country has expanded its processing capabilities by installing and running hundreds more of the centrifuges used to enrich uranium.

The U.N. Security Council has imposed sanctions against Iran three times since 2006 for its refusal to freeze uranium enrichment. The sanctions grew from fears that Iran is using the pretext of building a peaceful nuclear energy program as a guise to produce weapons-grade enriched uranium.

The country has also been placed on an international watch list to help limit the importation of nuclear materials, which could make it difficult to procure enough uranium oxide to feed its enrichment program.

The International Atomic Energy Agency and independent experts think Iran's rapidly expanding uranium enrichment program has been built on 600 tons of so-called yellowcake, or uranium oxide imported from South Africa during the 1970s. The material was procured as part of plans by the former regime of Shah Mohammad Reza Pahlavi to build a network of nuclear reactors to generate power.

Iran denied it was running out of yellowcake.

"It is not true," said Ali Asghar Soltanieh, Tehran's chief delegate to the IAEA. He said he could not make a substantial comment before the agency publishes its next report on Iran's nuclear program sometime this week.

"This is a technical project with its ups and downs," he said when asked whether output was stagnating. "But everything is going according to plan."

At the State Department, spokesman Ian C. Kelly declined to comment, except to say the U.S. remains intent on stopping Iran from getting a nuclear weapon.

"We are very concerned about the refusal of Iran to adhere to its international obligations," Kelly said.

The spokesman said the Obama administration will comment once the formal IAEA report is available.

In the enrichment process, uranium oxide is processed into uranium hexafluoride which then is spun and re-spun to varying degrees of enrichment, with low enriched uranium used for nuclear fuel and upper-end high enriched uranium for nuclear weapons.

While Iran has built a large stockpile of uranium hexafluoride, it would not be able to replenish its supply if it is running out of ore. That could account for any decision to stop expanding output at Natanz, its cavernous underground enriching facility, in an effort to use up the supply of uranium gas more slowly.

The existence of a secret Iranian enrichment program built on black market technology was revealed seven years ago. Since then the country has continued to expand the program with only a few interruptions as it works toward its aspirations of a 50,000-centrifuge enrichment facility at Natanz.

In its last report on Iran in June, the International Atomic Energy Agency said that nearly 5,000 centrifuges were operating at Natanz by May. Diplomats said Tuesday that had expanded to about 6,000 of the machines by last month.

The Washington-based Institute for Science and International Security has estimated that even using the 5,000-centrifuge figure as a basis, Iran could accumulate enough material to produce weapons-grade uranium for two warheads by February 2010.

While Iran continues to enrich uranium despite the U.N sanctions, it is believed to depend on rapidly diminishing outside sources of uranium oxide, with domestic mining yielding only relatively small quantities of inferior ore.

Working from statistics contained in the IAEA's November report on Iran, ISIS -- the Washington-based think tank -- said it appeared that at that point Iran had used up just under three-quarters of its original South African supply.

"The next six months stand to be revealing," said the ISIS study, noting that Iran is likely to reserve perhaps as much as 100 tons of its South African uranium stock to fuel its soon to be completed Arak heavy water nuclear reactor.

The U.N. sanctions ban exports to the Islamic Republic of all items, materials, equipment, goods and technology that could contribute its enrichment activities, including uranium ore.

In addition, transfers of uranium ore in quantities greater than 500 kilograms -- 1,100 pounds -- annually are subject to close scrutiny of the Nuclear Supplies Group of countries exporting atomic technology.

"These restrictions effectively close the door on legal imports by Iran of significant quantities of uranium ore," said ISIS.

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