Special Prosecutor Robert Mueller flew to Moscow and gave the FSB 10 grams of Highly Enriched Uranium (HEU) in 2009 https://wikileaks.org/plusd/cables/09STATE85588_a.html…
6. (S/Rel Russia) Action request: Embassy Moscow is
requested to alert at the highest appropriate level the
Russian Federation that FBI Director Mueller plans to deliver
the HEU sample once he arrives to Moscow on September 21.
Post is requested to convey information in paragraph 5 with
regard to chain of custody, and to request details on Russian
Federation's plan for picking up the material. Embassy is
also requested to reconfirm the April 16 understanding from
the FSB verbally that we will have no problem with the
Russian Ministry of Aviation concerning Mueller's September
21 flight clearance.
