President Ahmadinejad announced that Tehran is expanding its nuclear enrichment program at the Natanz nuclear plant by installing 6,000 new uranium enrichment centrifuges there. The Iranian president said the new phase began on Tuesday. Last year, Iran announced that it had successfully installed, and was operating, 3,000 centrifuges at Natanz. Uranium gas is enriched in cascades of centrifuges linked together. The result can be low-grade fuel used for generating electricity, or higher-grade fuel appropriate for nuclear weapons. Speaking to a crowd near the nuclear power station in the city of Bushehr, Mahmoud Jafarai, a plant official, confirmed that Iran is moving ahead with nuclear enrichment.