The journalists, invited to accompany President Mohammad Khatami on an inspection of the 450-hectare (1,110-acre) site, were taken deep inside a building where, two levels below ground, they were shown a vast empty hall designed to house 50,000 enrichment centrifuges. Centrifuges purify uranium fluoride gas into reactor or bomb fuel by spinning at high speeds. Low-grade enriched uranium is used in atomic power plants but highly enriched uranium can be used in the core of a bomb.
Iranian officials said the enrichment facility had been built more than 18 meters (54 feet) below ground due to "security problems." Defense experts say this is a precaution against possible aerial attack by the United States or Israel, which have vowed to stop Iran acquiring nuclear arms. Approaching the complex, ringed by arid mountains, journalists counted at least 10 anti-aircraft batteries. At the heavily guarded main gate there were no signs to indicate the nature of the sprawling site whose existence was first revealed by an Iranian exile group in late 2002, prompting international concern about Iran's atomic ambitions.
International Atomic Energy Agency (IAEA) inspectors first visited Natanz in early 2003. In October, 2003 the U.N. watchdog sealed Natanz's pilot enrichment facility, containing dozens of centrifuges, as part of an agreement between Iran and the EU. The EU wants Iran to permanently scrap Natanz and other nuclear fuel work in return for assistance with developing nuclear energy and other economic and security cooperation.
Iran says the suspension of nuclear fuel work is merely a temporary confidence-building measure. "IAEA inspectors visit this facility at least once a month and also use a monitoring system to check the suspension," Mohammad Saeedi, deputy head of Iran's Atomic Energy Organization, told reporters. "We can start test enrichment at any time," said Ehsan Monajemi, construction project manager at Natanz. "The sealing of the facilities has affected the morale of our people. It would be sad if it continued."
Sensitive fuel work has also been frozen at the Uranium Conversion Facility in Isfahan, which the journalists visited and which is designed to prepare the uranium gas for Natanz. European diplomats say Iran has offered to limit Natanz to a small pilot facility of around 500 centrifuges. While the pilot facility would be too small to produce usable quantities of weapons-grade material, it would allow Iran to master the technical know-how to do so in future and is therefore unlikely to be acceptable to Washington, which wants Iran's case sent to the U.N. Security Council.
But a senior Iranian official denied any such proposal was on the table. "Iran has not offered any limitations on its enrichment facilities and will not accept this in the future," Ali Aghamohammadi, head of the Propaganda Office at the Supreme National Security Council, told Reuters.