The Wisconsin Project on Nuclear Arms Control, American's scientific watchdog on world nuclear weapons production, estimates that by Dec. 2008, Iran had accumulated enough U-235 to fuel one nuclear bomb; by 2009, enough for a second, by August 2010 material for a third bomb and by April 2011, enough enriched uranium for a fourth bomb.

These estimates presuppose an Iranian decision to further process low-enriched material to weapons grade - a process taking no more than a couple of months.
Iran, says the Wisconsin Project, is consolidating its status as a "virtual" nuclear weapon state – meaning it can set about building a bomb whenever its rulers so decide.
In its twice-annual report published Thursday, June 2, Wisconsin revealed three further developments in Iran's nuclear drive:
1. Since November 2010, when Iran stopped enriching uranium in all cascades at the Natanz plant for about a week (the report does not give the reason for the stoppage – possibly a Stuxnet virus invasion of its computer control system), the enrichment rate has increased. The 5,000 centrifuges spinning in February 2011 increased to nearly 6,000 in May 2011.
debkafile's Iranian sources add: Prof. Ferei-doon Abbasi Davani has taken over as director of the enrichment complex at Natanz. He was formerly in charge of combating the Stuxflex worm.  Last November, Prof. Abbasi Dayani escaped with light injuries from an attack by a pair of motorcyclists who attached a sticky bomb to his car. It occurred near the Imam Hossein University in Tehran where most of Iran's secret nuclear labs are located.
2.  Wisconsin quotes the International Atomic Energy Agency's May 2011 report that one of its seals was broken in the "feed and withdrawal area" of the Natanz enrichment plant.
This means that Iran took action to conceal the real amount of is enriched uranium stockpile from the nuclear watchdog and the fact, as Wisconsin reports, that it has accumulated enough material for building four nuclear bombs. Its steady progress will go undetected until the next IAEA inventory in October or November.
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