Survey of Energy Resources 2007
Uranium - Resources
Uranium is a metal approximately as common as tin or zinc, and it is a constituent of most rocks and even of the sea (WNA, 2007). The economically-producible occurrences of any mineral are a function of concentration, exploration and production technology, demand and market price. Hence resource availability changes dynamically with improved geological knowledge, advances in production technology and increased price expectations. At higher prices, lower-concentration occurrences may become economically attractive, while innovative production methods may enable production from deposits previously beyond reach. Low prices may reduce previously economic resources to easy-to-produce high-concentration sources. This does not mean that the physical occurrence of the mineral no longer exists - it just delineates the economically recoverable portion of that resource at a given point in time (Rogner, 2000). Thus, assessment of the future availability of any mineral, including uranium, which is based (a) on current production costs and price data and (b) on state-of-the-art technology and existing geological knowledge (as most resource assessments do) is erring on the conservative side.
Recent and detailed information on uranium resources is reported in the publication Uranium 2005: Resources, Production and Demand (Red Book), a joint report of the OECD Nuclear Energy Agency and the International Atomic Energy Agency (NEA/IAEA, 2006). (Fig. 6-4 ) The resources reported by 44 countries are classified by the level of confidence in the estimates, and by production cost-categories. The 2005 Red Book deviates somewhat from the resource categorisation used in former Red Book editions. Identified Resources consist of two categories (a) Reasonably Assured Resources (RAR) and (b) Inferred Resources (both reported in terms of recoverable uranium for three production cost-ranges, i.e., less than US$ 40/kgU, less than US$ 80/kgU and less than US$ 130/kgU - Fig. 6-5 ).
Total Reasonably Assured Resources increased by 4% between 2003 and 2005 to 3.297 mtU (Table 6-1) and Inferred Resources by 1.9% over the same period (Table 6-2). Total Identified Resources amounted to 4.743 mtU (an increase of 3.3% over the 2003 resource levels). What is more important is the significant increase in the Identified Resources' lowest cost-category (production costs of less than US$ 40/kgU) of 13% compared to 2003. Given the much lower growth of Total Identified Resources of 3.3% over the period, this increase in the lowest cost-category is not the result of new discoveries but the effect of re-evaluations of already-known resources prompted by the drastically changed market conditions. Given the limited maturity and geographical coverage of uranium exploration worldwide there is considerable potential for the discovery of new resources of economic interest.
Undiscovered Resources (Prognosticated Resources and Speculative Resources) add another estimated 7.1 mtU at costs less than US$ 130/kgU (Table 6-3). This includes both resources that are expected to occur either in or near known deposits, and more speculative resources that are thought to exist in geologically favourable, yet unexplored areas. There are also an estimated further 3.0 mtU of speculative resources for which production costs have not been specified. Given the rather limited economic relevance of these occurrences in the short to medium run, the resource quantities have remained essentially unchanged since 2003.
Resource totals, on balance, increased between 2003 and 2005, indicating that increased uranium prices and demand expectations have triggered a re-evaluation of known resources, especially abandoned deposits where production costs exceeded revenues during the low-price era, and have dramatically accelerated exploration expenditures. Continuing efforts in both areas can be expected to lead to further additions to the identified uranium resource base, just as during past periods of heightened exploration efforts.
Unconventional uranium resources and thorium further expand the resource base. Unconventional resources are occurrences that require novel technologies for their exploitation and/or use and often represent low-concentration occurrences. Some typical uranium concentrations are shown in Fig. 6-6.
Unconventional uranium resources include about 22 mtU that occur in phosphate deposits and up to 4 000 mtU contained in sea water. The technology to recover uranium from phosphates is mature, with estimated costs of US$ 60-100/kgU. The technology to extract uranium from sea water has only been demonstrated at the laboratory scale, and extraction costs were estimated in the mid-1990s at US$ 260/kgU (Nobukawa, et al., 1994) but scaling up laboratory-level production to thousands of tonnes is unproven and may encounter unforeseen difficulties.
Thorium is three times as abundant in the Earth's crust as uranium. Although existing estimates of thorium reserves plus additional resources total more than 4.5 mt, such estimates are considered still conservative. They do not cover all regions of the world and the historically weak market demand has limited thorium exploration (IAEA, 2007).
The exploitation of unconventional uranium occurrences would require additional research and development efforts for which there is no imminent economic necessity, given the large conventional resource base and the option of reprocessing and recycling spent fuel. However, niche opportunities may be explored in greater detail in the not-so-distant future. For example, an international consortium has set out to explore the commercial extraction of uranium from uraniferous coal ash from coal power stations located in Yunnan province, China.
Fig. 6-7 summarises the potential longevity of the world's conventional uranium resources. For both the current light water reactors (LWR) once-through fuel cycle and a pure fast reactor fuel cycle, the estimates demonstrate how long conventional uranium resources would last, assuming electricity generation from nuclear power remains at its 2005 level. Identified uranium resources used in once-through mode with current reactor technology and enrichment practices would last 85 years. Closed fuel-cycles and pure fast breeder reactor technology extend the uranium resource reach to several thousand years.
Exploitation of undiscovered resources would increase these timelines to several hundreds of years (once-through) and tens of thousands of years (closed-fuel cycle and fast breeders), although significant exploration and development would be required to move these resources to more definitive categories.