Thorium

Description

Three times more abundant than uranium and a potential reactor fuel that cannot easily be weaponised.

Physical Properties

Atomic Properties

Discovery & History

Jöns Jacob Berzelius Discovery

Thorium was discovered in 1828 by Swedish chemist Jöns Jacob Berzelius , one of the founding fathers of modern chemistry. Berzelius identified the new element while analyzing a black mineral sample sent to him by Norwegian mineralogist Morten Thrane Esmark, who had found it near Løvøya island in Norway.

The Norwegian Connection

The original sample was discovered by Morten Thrane Esmark in 1828 on the island of Løvøya in the Langesundsfjord region of Norway. Esmark passed the mineral to his father, the mineralogist Jens Esmark, who sent a sample to Berzelius in Stockholm. This collaboration between Norwegian field work and Swedish analytical chemistry led to the element's discovery.

Chemical Analysis

Berzelius used his advanced analytical techniques to isolate and characterize the new element. He reused the name "thorium", which he had given in 1817 to a supposed element (oxide "thorina") that turned out to be yttrium phosphate. The name "thorium" was chosen after Thor, the Norse god of thunder .

19th Century Chemistry

The discovery occurred during the golden age of element discovery, when chemists were systematically analyzing new minerals using improved analytical methods. Berzelius's work with thorium contributed to the development of atomic weight determination and helped establish principles of chemical analysis that remain important today.

Radioactivity Discovery

Thorium's radioactive properties weren't discovered until 1898 by Gerhard Carl Schmidt and Marie Curie independently. This discovery came shortly after Becquerel's discovery of radioactivity and established thorium as only the second known radioactive element after uranium, launching the field of nuclear chemistry.

Scientific Legacy

The discovery of thorium exemplified 19th-century collaborative chemistry and established the foundation for understanding actinide elements. Berzelius's methodical approach to isolating and characterizing thorium became a model for discovering and studying other heavy elements.

Isotopes

Data: IAEA Nuclear Data Section, LiveChart of Nuclides, ground-state evaluations, retrieved October 10, 2026. Abundance is the share of atoms in the natural element; a dash means the isotope has no standard natural abundance.

Applications & Uses

Nuclear Fuel Applications

Thorium is increasingly recognized as a next-generation nuclear fuel with significant advantages over uranium-based fuels. Thorium-232, when bombarded with neutrons, converts to uranium-233, which is an excellent fissile material for nuclear reactors. This thorium fuel cycle produces less long-lived radioactive waste and cannot easily be weaponized, making it an attractive option for peaceful nuclear energy.

Molten Salt Reactors

Thorium is the preferred fuel for molten salt reactor (MSR) technology, where thorium fluoride is dissolved in molten salt that serves as both fuel and coolant. These reactors can operate at atmospheric pressure, have inherent safety features, and can consume existing nuclear waste. Countries like China and India are investing heavily in thorium MSR development.

Gas Mantles and High-Temperature Applications

Historically, thorium's most common use was in gas lantern mantles , where thorium dioxide provided intense, bright light when heated. Although largely phased out due to radioactivity concerns, thorium compounds are still used in specialized high-temperature applications, including refractory materials for crucibles and furnace linings that must withstand intense heat.

Specialty Alloys and Materials

Thorium is used to create specialized magnesium-thorium alloys for aerospace applications, where high strength-to-weight ratios are critical. These alloys maintain their properties at elevated temperatures, making them valuable for jet engine components and missile applications. The addition of small amounts of thorium significantly improves the creep resistance of magnesium alloys.

Scientific and Research Applications

Research institutions use thorium in various applications, including neutron sources , radiation detection equipment calibration, and fundamental nuclear physics research. Thorium compounds serve as reference standards for radiation measurements and are used in studying heavy element chemistry and nuclear decay processes.

Future Energy Applications

Advanced nuclear technologies are exploring thorium's potential in accelerator-driven systems (ADS) and small modular reactors (SMRs). These systems could provide clean, safe nuclear power with reduced waste production and enhanced proliferation resistance, making thorium a key element in future sustainable energy strategies.

Abundance