https://wikileaks.org/plusd/cables/09STATE85588_a.html#efmBbpBlP
Non-story, that was a very small sample of uranium seized by the US during a uranium smuggling sting in Georgia (the country, not the state). Russia requested the sample to compare to their own uranium stores to see if it was stolen from them.
Not saying Mueller isn’t a crooked POS... just saying this particular incident was not nefarious at all.