Iran has removed the core of its Arak heavy water reactor and filled part of it with cement, a crucial step under a soon to be implemented nuclear agreement with world powers.
A spokesman for Iran's Atomic Energy Organization told state television the work was done on Wednesday, paving the way for UN nuclear inspectors to announce Iran has met its commitments.
Asked on Thursday if the core had been removed from the reactor, spokesman Behrouz Kamalvandi replied: "Yesterday we finished the central part and the openings have been filled with cement."
Such measures mean the reactor will not be able to produce any weapons-grade plutonium from spent nuclear fuel, cutting off a potential pathway to an atomic bomb – an aim Iran has always denied pursuing.