Sergei Kiriyenko, head of Russia's state nuclear agency Rosatom, visited the plant today, along with his Iranian counterpart, Gholam Reza Aghazadeh.
Building on the 1000-megawatt power plant started in 1974 by a German company but was not completed because of the Islamic revolution in 1979.
A Russian Company named "Atomstroyexport" signed a contract to complete the project in 1995, which it did last year for at a cost of about US$ 1 billion
Kiriyenko said the construction of the plant was now complete and that it was in its pre-commissioning stage.
Iranian media said Wednesday's event would include testing of all of Bushehr's activities with special computer software.
Shirazi said that if the tests were successful fuel rods with enriched uranium would be used instead of lead.
The United States and other Western countries accuse Iran of building nuclear weapons and have called for new sanctions because of Iran’s refusal to allow inspections by the International Atomic Energy Agency (IAEA).
Iran, which is the world’s fourth largest oil producer, has insisted all along that its nuclear programme is designed to generate electrical power.
Russia has resisted attempts by the West to impose sanctions on Iran, but has also repeatedly urged Tehran to co-operate with the IAEA.
Iran’s nuclear programme still seems central to its relations with Russia after US President Barack Obama said the United States was prepared to talk to Tehran.