Western powers and the UN’s International Atomic Energy Agency have long suspected that the Parchin military base might have some connection to Iran’s disputed nuclear program, but the regime of the Islamic Republic has consistently denies inspectors access to the base, citing national security. Suspicion has continued to run high amidst IAEA inspections and international negotiations over the nuclear program, not only because of this Iranian stonewalling but also because satellite imagery has revealed questionable activities at the site, including apparent sanitization of what might have been incriminating evidence.

The latest NCRI report now gives some indication of what that incriminating evidence might have pointed to. Drawing on information collected between early 2012 and just last month, the report indicates that Parchin was the site of one of two explosion chambers constructed by an affiliate company of the Iranian Revolutionary Guard Corps.

“The chambers were to be used for special tests, particularly for high explosive impact as part of the nuclear weapons program of Iran,” the report explained.

Lending further credence to this interpretation of the tests, the NCRI report highlights the secretive nature of the projects, which were overseen by a division of the Organization of Defensive Innovation and Research, or SPND, which the NCRI previously identified as the government agency in charge of Iran’s nuclear weapons program.

The new report also details the involvement of individual Iranian scientists and IRGC officers at the head of the project, front companies, and the Iranian Presidential Center for Innovation and Technology Cooperation (CITC), the task of which the NCRI says is “to circumvent international sanctions and to obtain illicit information on weapons of mass destruction, including nuclear weapons.”

The NCRI also finds that the CITC has been responsible for recruiting foreign scientists as advisers to the nuclear program, including Vycheslav V. Danilenko of the Ukraine, who is named in the latest report as a contributor to the explosion chamber project who also provided Iranian heads of that project with “expertise and experiences… in the areas of nanodiamonds, explosive impact and other aspects of a nuclear warhead.”

Emphasizing that no one but Danilenko, his overseers, and other direct participants in the explosion chamber installation were granted access to Parchin while that project was going on, the NCRI report paints a picture of an elaborate conspiracy by regime officials and the IRGC to pursue nuclear weapons research and development while maintaining the highest levels of secrecy for those activities.

Barring another extension of talks, negotiations between Iran and six world powers over Iran’s nuclear program are entering their final two weeks. Meanwhile, the IAEA has continued Iran to show greater transparency as the agency works to complete a probe of the possible military dimensions of Iran’s nuclear research. The NCRI report may provide a degree of that transparency, albeit against the regime’s will.