The IAEA appears to have found out about Turquzabad in 2018 , when it began investigating the site after information was raised publicly and through intelligence sources. Its later reporting confirmed uranium particles there, and by November 7, 2019, the agency had formally reported those findings to its Board of Governors.

What happened

  • In September 2018, Israel publicly said it had information about nuclear-related material at the site later identified as Turquzabad.
  • The IAEA then requested access and sampled the site in early 2019.
  • On November 7, 2019, the IAEA reported the discovery of natural uranium particles of anthropogenic origin at the location.

Cleanest date

If you mean when the agency first became aware , the best-supported answer is 2018.
If you mean when it officially confirmed the finding , that was November 7, 2019.

TL;DR

The IAEA likely learned about Turquzabad in 2018 , and it publicly confirmed findings from the site in November 2019.