Thorium reserves

This reaction offers the advantage of a superior neutron yield of in a thermal reactor system. The abiHty to breed fissile from naturally occurring Th allows the world s thorium reserves to be added to its uranium reserves as a potential source of fission power. However, the Th/ U cycle is unlikely to be developed in the 1990s owing both to the more advanced state of the / Pu cycle and to the avadabiHty of uranium. Thorium is also used in the production of the cx-emitting radiotherapeutic agent, Bi, via the production of Th and subsequent decay through Ac (20). 

Figure 5.47. Proven thorium reserves given as kg of thorium oxide per m averaged over each country (source Hedrick, 1998 GIS layout Sorensen, 1999).

In April 2008, a research group from the Hebrew University in Jerusalem, under the direction of Amnon Marinov, reported the discovery of a few individual atoms of unbibium in natural thorium reserves. That report has been strongly criticized and no supporting evidence has been produced yet. If true, the results would be astounding. It would be the first time that a transfermium element had been found as a natural product. 

The U.S. Geological Survey was scheduled to publish a revised study of U.S. thorium resources in August 1979. Partial results of this study, which cover most of these resources but do not include the beach placers of Florida, Georgia, and the Carolinas, were presented orally by Staatz [S5] of the U.S. Geological Survey in 1978. Table 6.14 lists the types of deposit, the principal districts in which potentially economic thorium-bearing deposits have been found, the principal thorium minerals, and estimates of thorium reserves and resources. Thorium from the vein deposits, the first type, could be produced for less than 30/lb. Thorium is the principal salable product in these deposits. Thorium could be coproduced with other elements from disseminated deposits, massive carbonatites, and placers the amount of thorium that might be produced from them, and its cost, depends on the marketability of the other minerals that occur with the thorium. 

Thorium makeup requirements for one reactor system, the HTGR (high-temperature gas-cooled reactor), may be estimated from Fig. 3.33. A 1000-MWe HTGR requires 7.4 MT of thorium as feed pet year. Reprocessing recovers 6.8 MT, which can be recycled after storage for 20 to 30 years to permit excess Th to decay. The net thorium consumption of a 1000-MWe reactor then is 0.6 MT/year. Thus, the 441,000 MT of U.S. ThOa thorium reserves listed in Table 6.14 would provide thorium fuel for... 

Thorium-232 can be used in specially designed nuclear reactors that use or Pu j,. But the World Thorium reserves also stand around 6 million tons. 

This restudy made it apparent that, for the long-term benefit of the country, and indeed of the whole world, it was time we placed relatively more emphasis on the longer-range and more difficult problem of breeder reactors, which can make use of nearly all of our uranium and thorium reserves, instead of the less than one per cent of the uranium and very little of the thorium utilized in the present types of reactors. Only by the use of breeders would we really solve the problem of adequate energy supply for future generations. (Seaborg, 1962)... 

The abimdance of thorium in the earth s crust is about three times that of uranium. Hence, the thoriiun fuel cycle ensures a long-term nuclear fuel supply. For countries with abundant thorium reserves, the thorium fuel cycle in HWRs would enhance the sustainability of nuclear power and the degree of energy independence using a single reactor type. 

More than 400 nuclear power stations are in operation worldwide. Based on the current rate of use, the known low-cost uranium reserves will last for 50 year, but lower-grade sources could be used in future. An alternative could be thorium, which is three times more abundant than uranium. For example, India, which has large thorium reserves, may develop this technology. 

This timescale is fuUy sufficient to start, transition to, and implement a full Pu— Th232 u233 cycle facility not just in Canada, but globally with India and China, who both possess ample thorium reserves, including fuel manufacturing, plutonium destruction, and actinide separations. 

Several components are required in the practical appHcation of nuclear reactors (1 5). The first and most vital component of a nuclear reactor is the fuel, which is usually uranium slightly enriched in uranium-235 [15117-96-1] to approximately 3%, in contrast to natural uranium which has 0.72% Less commonly, reactors are fueled with plutonium produced by neutron absorption in uranium-238 [24678-82-8]. Even more rare are reactors fueled with uranium-233 [13968-55-3] produced by neutron absorption in thorium-232 (see Nuclear reactors, nuclear fuel reserves). The chemical form of the reactor fuel typically is uranium dioxide, UO2, but uranium metal and other compounds have been used, including sulfates, siUcides, nitrates, carbides, and molten salts. 

Total reserves of thorium at commercial price in 1995 was estimated to be >2 x 10 metric tons of Th02 (H)- Thorium is a potential fuel for nuclear power reactors. It has a 3—4 times higher natural abundance than U and the separation of the product from Th is both technically easier and less expensive than the enrichment of in However, side-reaction products, such as and the intense a- and y-active decay products lead to a high... 

Gadolinite and bastnasite fron Sweden served at first as raw material for the rare earth eloivents and thorium. Later it was necessary to seek new raw materials and the so-called "Carolina sand" was found in the USA, a monazite v ch oociorred there in certain gold-panning areas. Finally a nearly ine diaustible reserve of monazite was discovered in Brazil v ch guaranteed raw material supplies far into the future. 

In 1898 Mme. Curie in Paris and Professor G. C. Schmidt at the University of Munster, working independently, found that thorium, like uranium, is radioactive (43). This discovery opened up a vast new field of research as a result of which thorium is now known to be the parent substance of an entire series of radioactive elements. The story of their discovery will be reserved, however, for a later chapter. 

Current estimates of the available reserves and further resources of uranium and thorium, and their global distribution, are shown in Figs. 5.44-5.50. The uraruum proven reserves indicated in Fig. 5.44 can be extracted at costs below 130 US /t, as can the probable additional reserves indicated in Fig. 5.45. Figure 5.46 shows new and unconventional resources that may later become reserves. They are inferred on the basis of geological modelling or other indirect information (OECD and IAEA, 1993 World Energy Council, 1995). The thorium resource estimates are from the US Geological Survey (Hedrick, 1998) and are similarly divided into reserves (Eig. 5.47), additional reserves (Fig. 5.48) and more speculative resources (Fig. 5.49). The thorium situation is less well explored than that of uranium the reserves cannot be said to be "economical", as they are presently mined for other purposes (rare earth metals), and thorium is only a byproduct with currently very limited areas of use. The "speculative" Th-resources may well have a similar status to some of the additional U-reserves. 

The different levels of reserves and resources are summed up in Figs. 5.50 and 5.51, giving a probable magnitude of total exploitable resources. The one for thorium will be used as a basis for the nuclear scenario below. 

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