Van Gosen reports that historically, uranium and thorium deposits worldwide have been classified and reported according to the resource reporting scheme developed by the Nuclear Energy Agency (NEA) of the Organisation for Economic Co-operation and Development and the International Atomic Energy Agency (IAEA) [3]. This system consists of a biaxial classification that considers the degree of geological assurance and the production costs of uranium concentrate and (where applicable) thorium concentrate.
Thorium, similar to uranium, has the potential to be utilized as a nuclear fuel. Despite numerous projects and several pilot test reactors in several countries designed to evaluate thorium as a viable reactor fuel, thorium-based nuclear power has yet to be fully commercialized. Currently, research and development is being carried out on several concepts for advanced reactors using thorium, including: high-temperature gas-cooled reactors; molten salt reactors; Candu type reactors; advanced heavy water reactors; and fast breeder reactors [49]. Federal government-supported projects, particularly in India and China, are focused on the development of thorium-based nuclear
power [3, 49]. Based on these activities, utilization of thorium as fuel in a commercial reactor is not expected until at least 2020 [3].
Because of the low demand for thorium, it has not been a primary target of exploration in the past. The research and development efforts mentioned above may increase the demands for thorium and likewise increase national and global evaluations of thorium deposits. Mineral deposits that are rich in the rare earth elements (REEs) also typically contain anomalous enrichments in thorium. Because deposits rich in REEs are currently being exploited, the most likely sources of thorium in the immediate future will come from the recovery of thorium as a co-product of the mining and processing of REE deposits.
Production of REEs during the 1950s to the late 1980s came primarily from the United States, India, South Africa, and Brazil. In 1927, Chinese geologists discovered REE deposits at Bayan Obo in the Inner Mongolia autonomous region. Mines and processing plants built at Bayan Obo began to produce REE concentrates in 1957 [50]. By 2002, China became the dominant producer of REEs in the world [50]. During the more than 80 years following the discovery of Bayan Obo, REE deposits were found in 21 of China’s Provinces and autonomous regions [50]. In 2009, China reported its domestic extractable quantities of REEs as 18.6 Mt of REE oxide [51, p. 410]. China introduced a production quota on their REE industry in 2008 [50], which triggered a worldwide look for REE deposits in other countries. In recent years, deposits of REE resources have been assessed in Australia, Brazil, Canada, China, Finland, Greenland, India, Kyrgyzstan, Madagascar, Malawi, Mozambique, South Africa, Sweden, Tanzania, Turkey, the United States and Viet Nam [52, 53, 54].
The majority of the actively mined REE ore deposits are mined and processed only to produce REEs. Coexisting thorium-rich minerals could be evaluated as sources of by-product or co-product thorium if a market develops for thorium in the future. For now, the production of thorium as the primary product is uneconomic [3]. In the context of production, a by-product can be defined as product(s) derived from a joint production process that is minor in quantity and/or has minor net realizable value (NRV) when compared to the principal products [55]. By convention, by-products also are not inventoried, but the NRV from by-products is typically recognized as “other income” or as a reduction of joint production processing costs when the by-product is produced. Co-product on the other hand is a major output from a joint production process that is significant in quantity and/or in NRV.
Co-products play an important role in the economic analysis of a mineral project. In most REE-thorium-rich deposits, the most common thorium-bearing mineral is monazite, a REE-thorium-phosphate mineral. Thus, most of the thorium content in the majority of REE deposits is due to monazite, and only occasionally due to other thorium-rich minerals, such as thorite (thorium silicate). Monazite can contain as much as 20 per cent thorium oxide [56] and future production would most likely come from those REE deposits that contain monazite.
See pages 42 to 47 of the report.
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