History of chemistry element among the fractions that resulted. Working with the mineral pitchblende, the pair discovered a new radioactive element in 1898. They named the element polonium, after Marie's native country of Poland. On December 21, 1898, the Curies detected the presence of another radioactive material in the pitchblende. They presented this finding to the French Academy of Sciences on December 26, proposing that the new element be called radium. The Curies then went to work isolating polonium and radium from naturally occurring compounds to prove that they were new elements. In 1902, the Curies announced that they had produced a decigram
Uranium-238 about five times better as a gamma ray shield than lead, so a shield with the same effectiveness can be packed into a thinner layer. DUCRETE, a concrete made with uranium dioxide aggregate instead of gravel, is being investigated as a material for dry cask storage systems to store radioactive waste. The opposite of enriching is downblending. Surplus highly enriched uranium can be downblended with depleted uranium or natural uranium to turn it into low enriched uranium suitable for use in commercial nuclear fuel. U from depleted uranium and natural uranium is also used with recycled Pu-239 from nuclear weapons