one that touches on your concern over 'secret' facilities...
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"By reimplementation day, Iran would have to fulfill its commitments to the IAEA regarding its ongoing investigation into enriched uranium found at undeclared nuclear sites in Iran. That means Iran would give the IAEA a credible response as to the source of that uranium, and the IAEA would, in turn, close the probes."
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Israel and others in the ME will continue to carry out their own intelligence and 'interdiction' programs, but we'll be able to verify that Iran has scaled back it's nuclear enrichment efforts...that's a very good thing. Unfortunately, the saga is not over and more effort will be required...such is life in the real world.
Link: https://www.jpost.com/middle-east/iran-news/article-715772