Iran is taking back another batch of the 20% enriched uranium stockpiles that were sent to Russia as part of the 2015 nuclear deal. 11 tons of low enriched uranium was originally sent from Iran to Russia. Iran has already gotten some of that material back from Russia and Iran is asking for more back.
Iran would sell its enriched uranium material and buy natural uranium or yellowcake in return. Russia had sent back 149 tons of raw yellowcake uranium.