Who was the inventor of nuclear fuel?

Answer 1

I think you could say the inventors were Enrico Fermi and Leo Szilard.

The first fission reaction was the Chicago Pile-1, which was created by Fermi and Szilard. Fermi had previously headed the team that first split the atom, and Szilard had been perhaps the most important of the scientists who realized a chain reaction was possible.

Their fuel was, by current standards, rather crude. And there are lots of fuel types, each with its own inventor. But the fuel by Fermi and Szilard was first.