Following the July explosion at the Natanz nuclear site, Tehran said it would build a new, more secure, structure in the mountains around the area.
Ali Akbar Salehi, the head of Iran's nuclear department, last month told state television the destroyed above-ground facility was being replaced with one “in the heart of the mountains around Natanz.”Natanz hosts the country’s main uranium enrichment facility.
Natanz became a flashpoint for Western fears about Iran’s nuclear program in 2002, when satellite photos showed Iran building an underground facility at the site, some 200 kilometers (125 miles) south of the capital, Tehran.
In 2003, the IAEA visited Natanz, which Iran said would house centrifuges for its nuclear program, buried under some 7.6 meters (25 feet) of concrete.
Still though, Iran has continued to allow IAEA inspectors full access to its nuclear facilities, including Natanz, Grossi said.