Iran has had a civilian nuclear program since before the 1979 revolution. However, since the revolution, as Iran's regime and overal policies have drastically changed, there have been some worries concerns that it could use this program to develop nuclear weapons. These worries have been raised by the revelation, in August 2002, by Alireza Jafarzadeh, a prominent associate of MKO, of the existence of two secret nuclear sites: a uranium enrichment facility in Natanz (part of which is underground), and a heavy water facility in Arak. There is however no proof at this stage that this program is not purely civilian.