A binary or ternary metallic fuel composition having a metal dopant content of about 1 at. % to 25 at. %. A metal dopant is added to the binary or ternary metallic fuel composition to extend metal fuel burnup. The metal dopant will pin the lanthanides in the fuel phases. For binary U--Zr fuels, the metal dopant is generally palladium or titanium. For ternary U--Pu--Zr fuels, the metal dopant is generally palladium or a mixture of silver and titanium.
 This invention was made with government support under Contract Number DE-AC07-05ID14517 awarded by the United States Department of Energy. The government has certain rights in the invention.