Are you an EPFL student looking for a semester project?
Work with us on data science and visualisation projects, and deploy your project as an app on top of Graph Search.
Concept
Uranium dioxide
Summary
Uranium dioxide or uranium(IV) oxide (), also known as urania or uranous oxide, is an oxide of uranium, and is a black, radioactive, crystalline powder that naturally occurs in the mineral uraninite. It is used in nuclear fuel rods in nuclear reactors. A mixture of uranium and plutonium dioxides is used as MOX fuel. Prior to 1960, it was used as yellow and black color in ceramic glazes and glass.
Uranium dioxide is produced by reducing uranium trioxide with hydrogen.
UO3 + H2 → UO2 + H2O at 700 °C (973 K)
This reaction plays an important part in the creation of nuclear fuel through nuclear reprocessing and uranium enrichment.
The solid is isostructural with (has the same structure as) fluorite (calcium fluoride), where each U is surrounded by eight O nearest neighbors in a cubic arrangement. In addition, the dioxides of cerium, thorium, and the transuranic elements from neptunium through californium have the same structures. No other elemental dioxides have the fluorite structure. Upon melting, the measured average U-O coordination reduces from 8 in the crystalline solid (UO8 cubes), down to 6.7±0.5 (at 3270 K) in the melt. Models consistent with these measurements show the melt to consist mainly of UO6 and UO7 polyhedral units, where roughly of the connections between polyhedra are corner sharing and are edge sharing.
UO2 Powder.jpg|Uranium dioxide
UO2 Pellet.jpg|Sintered uranium dioxide pellet
Uranium dioxide is oxidized in contact with oxygen to the triuranium octaoxide.
3 UO2 + O2 → U3O8 at 700 °C (970 K)
The electrochemistry of uranium dioxide has been investigated in detail as the galvanic corrosion of uranium dioxide controls the rate at which used nuclear fuel dissolves. See spent nuclear fuel for further details. Water increases the oxidation rate of plutonium and uranium metals.
Uranium dioxide is carbonized in contact with carbon, forming uranium carbide and carbon monoxide.
UO2 \ + \ 4C -> UC2 \ + \ 2CO.
This process must be done under an inert gas as uranium carbide is easily oxidized back into uranium oxide.
Official source
About this result
This page is automatically generated and may contain information that is not correct, complete, up-to-date, or relevant to your search query. The same applies to every other page on this website. Please make sure to verify the information with EPFL's official sources.