Sarah Baxter, Washington
The Arak plant in central Iran can now make eight tons of heavy water a year, with output expected to rise tenfold.
Heavy water aids nuclear fission and the plutonium by- product could be used to make warheads. But the reactor to produce plutonium is still under construction.
The Iranian president insisted the plant was for peaceful purposes. We are not a threat to anybody, he said at the opening. There is no talk of nuclear weapons.
Araks construction was kept secret until the opposition National Council of Resistance of Iran revealed its existence along with the Natanz uranium enrichment facility in 2002.
An Iranian nuclear official claimed there was no need for the International Atomic Energy Agency to supervise Arak as it did not have a military purpose. But experts warned plutonium production could pose a greater threat than uranium enrichment.
With uranium its much easier to put in safeguards to monitor the atmosphere and instruments, said Paul Ingram, a nuclear analyst with the British American Security Information Council. Arak could produce enough plutonium for one or two nuclear weapons a year.
Ephraim Sneh, a senior Israeli MP, said Arak marked another leap in Irans advance towards a nuclear bomb.
The Iranian media reported last week that an announcement concerning the nuclear birth of the nation would be made within days. Ahmadinejads inauguration of Arak could be it, but there is speculation that the regime plans more surprises before a UN deadline for suspension of its uranium enrichment programme expires on Thursday.
