Accelerated growth of nuclear power in different countries foreseen in future, due to increased demand of carbon-free energy, has made the sustainable use of fuel metals such as uranium and thorium important. While uranium is the main-stay of the present generation of NPPs, with the anticipated steep growth in nuclear energy in future, it will be necessary to introduce thorium too as a fuel.
It is generally believed that thorium resources should be 3 to 4 times larger than uranium resources because the Clarke concentration of thorium is 3 to 4 times larger than that of uranium. However, such a statement does not take into account the differences of chemical properties between uranium and thorium. Uranium has two valence states U4+ and U6+, and is very soluble, as UO22+ under oxidized state. Thorium has only one valence state, Th4+, and has a low solubility at low to intermediate temperature. This property has several major consequences:
- Thorium minerals can be concentrated physically in placer type deposits as resistates;
- Most other thorium deposit types are formed in magmatic and high temperature hydrothermal environments; and
- Metallurgical extraction of thorium from ores requires more costly processes than for U.
Accelerated growth of nuclear power in different countries foreseen in future, due to increased demand of carbon-free energy, has made the sustainable use of fuel metals such as uranium and thorium important. While uranium is the main-stay of the present generation of NPPs, with the anticipated steep growth in nuclear energy in future, it will be necessary to introduce thorium too as a fuel.
It is generally believed that thorium resources should be 3 to 4 times larger than uranium resources because the Clarke concentration of thorium is 3 to 4 times larger than that of uranium. However, such a statement does not take into account the differences of chemical properties between uranium and thorium. Uranium has two valence states U4+ and U6+, and is very soluble, as UO2+2 under oxidized state. Thorium has only one valence state, Th4+, and has a low solubility at low to intermediate temperature. This property has several major consequences:
- Thorium minerals can be concentrated physically in placer type deposits as resistates;
- Most other thorium deposit types are formed in magmatic and high temperature hydrothermal environments; and
- Metallurgical extraction of thorium from ores requires more costly processes than for U.
Most thorium resource estimations correspond to potential resources, because specific exploration and comprehensive resource estimation of thorium deposits have been undertaken randomly or never been really undertaken. Published estimates of thorium resources date mainly from exploration made in the 1950s -1980s for uranium and other commodities, thus are not always certain. Hence, detailed investigations of the resources, as well as ore processing tests are necessary before decision on their economic relevancies can be made.
Recognizing the importance of thorium resources, IAEA has in 2010 initiated this activity to compile data on thorium deposits, occurrences and resources and make it available in an online information system. Based on historical data, and in few cases recent re-evaluations, and data published in different sources it is estimated that the total thorium resources are approximately 6.55 million tonnes Th not considering any resource category or cost class. This estimate is based on preliminary data as in IAEA (2013) World Thorium Occurrences, Deposits and Resources (under preparation).
Details of individual deposits and occurrences as presented in ThDEPO are incomplete in many respects due to non-availability of data. More details will be included as they are made available in future.
Original working URL: https://infcis.iaea.org/THDEPO/About
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