Even though users can purchase xU3O8 (uranium) with USDC, which is the stablecoin version of the USD dollar, users also need to pay what is known as a "gas fee". This is the fee required by any blockchain to process a transaction, and is paid in the native currency of that chain.
Uranium.io operates on the Etherlink network, where XTZ serves as the native currency. To buy or sell xU3O8, you will need a small amount of XTZ, typically less than 0.05 XTZ per transaction. You can learn how to get XTZ here."