"The reactor cap was successfully installed," Atomic Energy Organization of Iran (AEOI) Chief Ali Akbar Salehi said.

Once the reactor cap is in place, the process of injecting nuclear fuel into the core, which began on October 26, is considered complete.

Salehi said in late October that the plant would be connected to the national grid and begin to produce electrical energy in mid-February 2011.

The Bushehr plant in southern Iran was launched on August 21 with Russian assistance after decades of construction delays.

Under a bilateral agreement, which has received approval from the International Atomic Energy Agency, Russia will initially operate the plant, supplying its fuel and taking away all the spent fuel for the next two or three years, but will eventually hand over full control to Iran.