Miloš René

Additional information is available at the end of the chapter

http://dx.doi.org/10.5772/intechopen.68304

#### **Abstract**

Thorium is a naturally occurring, slightly radioactive element. It is widely distributed in nature with an average concentration of 10.5 ppm Th in the upper earth's crust. In general, thorium occurs in relatively small number in Th-enriched minerals: thorite, thorianite, monazite, bastnaesite, and thorogummite. However, the main world resources of thorium are coupled with monazite and bastnaesite. Monazite-enriched placer deposits occurring mainly in India, Brazil, Australia, and the USA form the recently available resources of thorium. Other commercially interested concentrations of thorium are coupled with bastnaesite mined from carbonatite deposits, especially from Bayan Obo deposit in China. Currently, the worldwide thorium resources by major deposit types are estimated to total about 6.2 million tons of Th. Issues associated with thorium's natural radioactivity are a significant deterrent to its commercial use. The monazite concentrates are recently produced only in India, Brazil, Malaysia, Thailand, and Vietnam, with a total amount of about 7000 tons. Consequently, experimental nuclear reactors based on thorium fuel cycle are operated recently only in India. In the long term, consumption of thorium could increase substantially if its use as a nuclear fuel becomes commercialized.

**Keywords:** thorium, geochemistry, mineralogy, monazite, thorium fuel cycle
