Group 3 element it from pitchblende residues left by Marie and Pierre Curie after they had extracted radium. In 1899, Debierne described the substance as similar to titanium and (in 1900) as similar to thorium. Friedrich Oskar Giesel independently discovered actinium in 1902 as a substance being similar to lanthanum and called it "emanium" in 1904. After a comparison of the substances half-lives determined by Debierne, Hariett Brooks in 1904, and Otto Hahn and Otto Sackur in 1905, Debierne's chosen name for the new element was retained because it had seniority, despite the contradicting chemical properties he claimed for the element at different
Peak uranium amount of energy to be produced per mass unit of uranium, because U-238, which constitute 99.3% of natural uranium, is not used in conventional reactors which instead use U-235 which only represent 0.7% of natural uranium. In 1983, physicist Bernard Cohen proposed that the world supply of uranium is effectively inexhaustible, and could therefore be considered a form of renewable energy. He claims that fast breeder reactors, fueled by naturally-replenished uranium-238 extracted from seawater, could supply energy at least as long as the sun's expected remaining lifespan of five billion years., making them as sustainable in fuel availability terms as