Thorium: Extraction

How beach sands yield a radioactive by-product

The world's main thorium source is monazite, a rare-earth and thorium phosphate found in heavy-mineral beach and river sands. Thorium also occurs in carbonatites and veins, in minerals such as thorianite and thorite. Monazite is separated from ilmenite, rutile and zircon during mineral-sands mining, then cracked chemically to recover rare earths. Thorium ends up in the residue. About 95% of supply comes as a companion of mineral-sands mining. USGS says monazite would likely not be recovered for thorium alone.

Thorium is produced only because rare earths are. Its main source is monazite, a rare-earth and thorium phosphate found in heavy-mineral beach and river sands in India, Australia, Brazil, the US and parts of Africa and Southeast Asia. Monazite is separated during mineral-sand mining, then cracked to recover rare earths, leaving thorium in a residue. USGS says that without rare-earth demand, monazite would likely not be recovered for thorium. Only a small fraction of the thorium mined is refined and used; the rest is stored under radiation rules. India's IREL is one of the few companies that mines monazite at scale outside China's supply chain.

Methods compared

How each method works

Sands are mined by dredge or dry methods and concentrated into heavy minerals on site. Dry plants then use magnetic and electrostatic separators to split ilmenite, rutile, zircon and monazite. India's 2019 rules for beach-sand minerals use a threshold of 250 ppm ThO2 for thorium (IBM 2022).

Uses existing mineral-sand mines, but monazite is radioactive and needs licensed handling.

Ground monazite is digested with hot caustic soda, which turns phosphate into trisodium phosphate and leaves rare-earth, thorium and uranium hydroxides. Acid leaching then dissolves rare earths selectively, leaving thorium-rich residue. IREL's OSCOM plant in Odisha makes mixed rare-earth chloride and recovers uranium as ammonium diuranate.

Proven process; thorium accumulates as a residue that must be stored and monitored.

Thorium hydroxide residue is dissolved in nitric acid and purified by solvent extraction, then precipitated and calcined to thorium dioxide or kept as nitrate. Volumes are small and tied to research and fuel programmes.

Makes usable thorium; demand is too small to justify large plants.

Stage 1 pressurised heavy water reactors burn natural uranium and make plutonium. Stage 2 fast breeders, starting with the 500 MWe PFBR, use that plutonium and can breed uranium-233 from thorium blankets. Stage 3 reactors would run on thorium and uranium-233.

Could tap India's huge thorium resource; the full cycle is decades from commercial scale.

By-product supply

Companionality is about 95%: thorium comes from monazite in mineral sands mined for titanium, zircon and rare earths (Nassar et al. 2015). Supply is set by rare-earth and mineral-sand economics, not by any thorium price. Far more thorium is mined than used, so stored residues grow each year (Nassar et al.; Pitron 2020). If thorium reactors become commercial, the first supply would come from these stockpiles rather than new mines.

Share produced as a by-product

Who does it: global

Who does it: India

India holds the world's largest identified thorium resource, about 850,000 t (World Nuclear Association via USGS), in 13.15 Mt of monazite (Jan 2026). Monazite mining and processing are reserved for state entities, chiefly IREL under the Department of Atomic Energy. India supplied 47% of US thorium compound imports in 2021-24 (USGS). The PFBR's criticality in April 2026 moves India into stage 2 of the programme that is meant to end in thorium-fuelled reactors.