Element 90 in our International Year of the Periodic Table series is thorium. Thorium was used in streetlights before the advent of electricity and might be used in a number of countries to generate it in the future in nuclear reactors.

Current nuclear reactors use uranium as a fuel; however, it’s not the only element that can be used for nuclear power. Thorium has also been explored as a nuclear fuel. A number of countries have been researching or developing thorium reactors; some scientists have speculated that, despite the concept of thorium as a nuclear fuel being suggested as long ago as 1942, it was not pursued due to thorium’s lack of weapons applications in comparison to uranium. Others have pointed to the high start-up costs of thorium reactors as the reason they have yet to take off.

Before it was being talked about as a potential means of generating electricity, thorium was being used in the forerunners to electric lights. Thorium dioxide glows when heated, and was used in the gaslights that lit streets. Thorium gas mantles are still produced in camping lanterns by camping suppliers, although some suppliers switched to other elements due to thorium’s radioactivity. Though it’s radioactive, thorium is safe to use in these lanterns as the glass is sufficient to block the radiation produced.

Thorium dioxide also has the distinction of having the highest melting point of any oxide. It’s used in high-temperature crucibles due to this property.

Remember, you can keep track of all of the previous entries in this series on the site here, or on the Royal Society of Chemistry’s dedicated page.