In this task you will be given a text passage from a trivia quiz. You should choose the category this question belongs to from these categories: History, Science, Social Science, Fine Arts, Literature. You can only choose one category, so if in doubt, please choose the closest match.

The extraction process for this element requires grinding it up and leeching with sulfuric acid, converting its dioxide into a trioxide. Afterwards, it is enriched by adding elemental fluorine to form its hexafluoride, which is then converted back into the dioxide for conversion into the pellets for its best known use. Available from the pitchblende, this element converts into thorium and potassium in the Earth's core and contains the radioactive 238 isotope. For 10 points, identify this actinide used in nuclear power plants, symbolized U.
Science