Thorium

Uses

Thorium’s most historically visible use was in gas lantern mantles, where thorium dioxide’s ability to glow brilliantly white when heated made it the standard choice for camping and household gas lighting for much of the 20th century; that use has largely disappeared as thorium-free mantles became standard, partly over radiation concerns. Thorium compounds were also once used in high-quality camera and telescope lenses because they bend light in useful optical ways, another application that has mostly been replaced by non-radioactive glass formulations.

The area generating the most current interest is nuclear energy: thorium can be converted inside a reactor into a fissile form of uranium, offering a potential alternative nuclear fuel cycle that some researchers believe could be safer and less wasteful than conventional uranium fuel, and that could make use of more abundant thorium reserves in countries like India. Thorium-based reactors remain largely in the research and development stage rather than widespread commercial use.

History

Thorium was discovered in 1828 by Swedish chemist Jöns Jacob Berzelius, who identified it in a mineral sample sent to him from Norway. He named the new element thorium after Thor, the Norse god of thunder, continuing a pattern of mythological naming common in that era of chemistry. Its radioactivity wasn’t recognized until decades later, once the broader phenomenon of radioactivity was discovered in the late 19th century, after which thorium became an important subject of study in the emerging field of nuclear science.