Uranium concentrate. Worker placing a lid on a barrel full of yellowcake, a uranium oxide mixture obtained from uranium ores, and containing high concentrations of uranium. After being mined from the ground, the uranium ore is crushed and dissolved in strong acid or alkaline solutions and precipitated to produce yellowcake concentrates. These contain up to 60 percent uranium. The uranium is then enriched to increase the concentration of the radioactive isotope U-235. It is this isotope that is used in nuclear power stations to create a controlled nuclear fission reaction. This is the Comurhex factory in Malvesi, France. Photographed in 2004.