From abstract: "Background material leading to the development of the metal quality of reactor-grade thorium is given. The metal should be sound and of uniform hardness, free of internal cracks and inclusions, and corrosion resistant. It should contain only small amounts of natural uranium, thorium oxide, and elements that act as reactor poisons. Because of their effect upon metal quality, various methods for the production of thorium are discussed. Use of consumable electrode arc melting as the final step has contributed much to the production of thorium of excellent quality for reactor use."