A team of American experts says it has uncovered a previously unknown Islamic Republic nuclear weapons development site in Iran.

The Institute for Science and International Security (ISIS) called on Tehran on April 8 to acknowledge the previously undisclosed site to international inspectors.

Founded in 1993, the Institute for Science and International Security is led by former United Nations IAEA nuclear inspector David Albright.

ISIS says that it has evidence the Islamic Republic operated the nuclear weapons development facility in northern Iran until at least 2011 when it was likely destroyed as Western nations began to investigate the country's weapons program.

"Based on documents in the Iran Nuclear Archive, seized by Israel in early 2018, Iran’s Amad Plan created the Shahid Mahallati Uranium Metals Workshop near Tehran to research and develop uranium metallurgy related to building nuclear weapons", ISIS says.

Amad Plan refers to Iran’s alleged roadmap to developing a nuclear weapon.

"The facility was intended as a pilot plant, aimed at developing and making uranium components for nuclear weapons, in particular components from weapon-grade uranium, the key nuclear explosive material in Iranian nuclear weapon cores," the institute disclosed.

The site was meant to be temporary until the production-scale Shahid Boroujerdi facility at Parchin was completed.

Parchin is a village in Hesar-e Amir area in the Central District of Pakdasht County, Tehran Province, 20 kilometers (12.4 miles) southeast of downtown Tehran. In November 2011, the U.N.'s nuclear watchdog, the International Atomic Energy Agency (IAEA) reported that it had "credible" information Parchin was used for implosion testing. The IAEA sought additional access to Parchin, which Tehran rejected.

However, ISIS believes that the key building of the Shahid Mahallati uranium metals workshop, was apparently gutted and abandoned between late 2010 and early 2011, after another Iranian nuclear facility at Fordow was uncovered near the neighboring city, Qom.

"Iran should declare this site to the International Atomic Energy Agency and allow its inspection since the facility was designed and built to handle nuclear material subject to safeguards under Iran's comprehensive safeguards agreement," Albright insisted in the ISIS report, adding, "The IAEA, more generally, should verify sites, locations, facilities, documentation, equipment, and materials involved in the Amad Plan activities, and urge Iran to cooperate fully in these investigations, despite their age, as part of ensuring that Iran has not continued nuclear weapons work up to today."

Meanwhile, Albright told the Washington Free Beacon the site has not been publicly revealed earlier and it is likely Western nations had no knowledge of it prior to Israel's seizure of the nuclear documents.

"This site may have been close to being able to make weapon-grade uranium cores for nuclear weapons, albeit no evidence Iran had any weapon-grade uranium yet," Albright said. "But the site highlights concretely that Iran was putting in place a nuclear weapons production industry, not just a development program, and there is no evidence of its destruction."

The Free Beacon cited a non-proliferation expert and research fellow at the Foundation for Defense of Democracies, Andrea Stricker, as saying, the discovery of this new site "shows the extent to which Tehran lied to international inspectors about its past and possibly ongoing nuclear weapons program.”

"Today, Tehran is closer to a nuclear weapon than previously thought," Stricker said, asserting, "The IAEA needs to undertake a full investigation in Iran to ensure that its nuclear program is strictly peaceful."

Referring to a plethora of complications in building a production-scale uranium metallurgy plant, ISIS report says, "Overcoming these difficulties would typically call for a pilot plant, designed to develop and test critical procedures being planned for Shahid Boroujerdi, the pilot plant starting with surrogate materials, then introducing natural uranium, and later processing weapons-grade uranium, as a template for Shahid Boroujerdi."

Most importantly, ISIS has argued, the weapon-grade uranium would be expected to be in short supply, its preciousness demanding well-tested and practiced metallurgical manufacturing procedures, the goal is to avoid mistakes and blunders potentially resulting in significant losses of expensive weapon-grade uranium.

Read the full report here