Iran atom bomb seen attainable despite snags: study

VIENNA (Reuters) - Iran is on course to produce enough highly enriched uranium to make nuclear weapons despite technical problems, a new study says.

But increased mechanical difficulties with centrifuges mean it is unlikely to be able to make enough lower-grade fuel for civilian nuclear power plants for a long time, if ever, the study by a think-tank tracking nuclear proliferation says.

Its report came out as Iran adjusted some centrifuges to enrich uranium to a higher grade than that needed to generate electricity, stoking Western concern over its intentions.

Citing U.N. inspection and intelligence findings, the report said Iran's main Natanz enrichment plant was dogged by centrifuge breakdowns and maintenance outages, with the machines refining uranium at only about half their nominal capacity.

It noted a 20 percent fall in numbers of operating machines in the year to last November, after a headlong expansion pursued for political purposes in a stand-off with world powers trying to curb Iran's programme and throw it open to U.N. scrutiny.

A senior diplomat close to the International Atomic Energy Agency (IAEA) told Reuters on Thursday there had been "no big changes" in active centrifuge capacity since November, suggesting technical woes were still restraining growth.

"Iran's problems in its centrifuge programme are greater than expected a year ago," said the report by David Albright and Christina Walrond of the Institute for Science and International Security (ISIS), based in Washington.

"Iran is unlikely to deploy enough gas centrifuges to make enriched uranium for commercial nuclear power reactors (Iran's stated nuclear goal) for a long time, if ever, particularly if (U.N.) sanctions remain in force," the report said.

"As such, one of the most striking lessons of reviewing Iran's accomplishments at Natanz is just how unachievable a commercial enrichment programme remains, while how little is required to create a nuclear weapons capability.

ATOMIC BOMB CAPACITY IN REACH

"While Iran may take longer than expected to make sufficient weapons-grade uranium, few believe it will fail in that effort."

The U.S. intelligence community has estimated Iran will not be technically capable of weaponizing enrichment before 2013.

Iranian leaders asserted on Thursday, amid celebrations marking the Islamic Revolution anniversary, that Tehran could enrich uranium to over 80 percent and even 100 percent already.

The United States was dismissive. "Iran has made a series of statements that are ... based on politics, not on physics," White House spokesman Robert Gibbs told reporters.

Iran denies having mechanical problems at Natanz. It says it is proceeding with enrichment according to plan and the goal of enriching uranium to 20 percent purity is to replenish the fuel reserve of a Tehran reactor that makes medical isotopes.

But more than half of its roughly 8,500 installed centrifuges were idle as of late last year -- an update will come in a fresh IAEA report due next week -- and ISIS said the plant suffered "a daily attrition of centrifuges from breakage."

Still, ISIS said, Iran had established enough capacity to make fissile material for one atom bomb within six months if it drew from its current stock of low-enriched (3.5 percent) enriched uranium (LEU), estimated to be close to two tonnes.

Iran's LEU stockpile is subject to IAEA surveillance to deter diversions of the material for military purposes.

However, "given Iran's announced plans to build 10 more enrichment plants without notifying the IAEA about their location or status until six months before it introduces nuclear material, Iran's capability to make weapons-grade uranium either in a secret parallel programme or in a 'breakout' is likely to grow with time," the ISIS report said.

For its ostensible civilian energy purpose, Natanz could only be classified as a development facility, not a production plant, since Iran was still struggling to master the operation of many thousands of centrifuges in unison, ISIS said.

It noted that Iran's centrifuges were a 30-year-old vintage, sanctions made it hard for Iran to import top-quality components and domestically-made substitutes were probably inferior.

Another possible explanation for problems, ISIS said, was that Western secret services had apparently slipped defective hardware into the nuclear black market plied by Tehran.

(Additional reporting by Washington bureau; Editing by Charles Dick)