Difference between revisions of "Talk:Expert assessments of nuclear energy"
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7.4.3 Nuclear energy
The average uranium (U) concentration in the continental Earth’s crust is about 2.8 ppm, while the average concentration in ocean water is 3 to 4 ppb (Bunn et al., 2003). The theoretically available uranium in the Earth’s crust is estimated at 100 teratonnes (Tt) U, of which 25 Tt U occur within 1.6 km of the surface (Lewis, 1972). The amount of uranium dissolved in seawater is estimated at 4.5 Gt (Bunn et al., 2003). Without substantial research and develop- ment (R&D) efforts to develop vastly improved and less expensive extraction technologies, these occurrences do not represent practi- cally extractable uranium. Current market and technology conditions limit extraction of conventional uranium resources to concentrations above 100 ppm U. Altogether, there are 4200 EJ (or 7.1 MtU) of identified conven- tional uranium resources available at extraction costs of less than USD 260/kgU (current consumption amounts to about 53,760 tU per year). Additional conventional uranium resources (yet to be discov- ered) estimated at some 4400 EJ can be mobilized at costs larger than USD 260 / kgU (NEA and IAEA, 2012). Present uranium resources are sufficient to fuel existing demand for more than 130 years, and if all conventional uranium occurrences are considered, for more than 250 years. Reprocessing of spent fuel and recycling of uranium and plu- tonium in used fuel would double the reach of each category (IAEA, 2009). Fast breeder reactor technology can theoretically increase ura- nium utilization 50-fold or even more with corresponding reductions in high-level waste (HLW) generation and disposal requirements (IAEA, 2004). However, reprocessing of spent fuel and recycling is not eco- nomically competitive below uranium prices of USD2010 425 / kgU (Bunn et al., 2003). Thorium is a widely distributed slightly radioactive metal. Although the present knowledge of the world’s thorium resource base is poor and incomplete, it is three to four times more abundant than uranium in the Earth’s outer crust (NEA, 2006). Identified thorium resource availability is estimated at more than 2.5 Mt at production costs of less than USD2010 82/kgTh (NEA, 2008). Further information concerning reactor technologies, costs, risks, co- benefits, deployment barriers and policy aspects can be found in Sec- tions 7.5.4, 7.8.2, 7.9, 7.10, and 7.12, respectively.
7.5.4 Nuclear energy
Nuclear energy is utilized for electricity generation in 30 countries around the world (IAEA, 2013a). There are 434 operational nuclear reactors with a total installed capacity of 371 GWe as of Septem- ber 2013 (IAEA, 2013a). Nuclear electricity represented 11 % of the world’s electricity generation in 2012, with a total generation of 2346 TWh (IAEA, 2013b). The 2012 share of global nuclear electricity gen- eration is down from a high of 17 % in 1993 (IEA, 2012b; BP, 2013). The United States, France, Japan, Russia, and Korea (Rep. of)—with 99, 63, 44, 24, and 21 GWe of nuclear power, respectively—are the top five countries in installed nuclear capacity and together represent 68 % of total global nuclear capacity as of September 2013 (IAEA, 2013a). The majority of the world’s reactors are based on light-water technol- ogy of similar concept, design, and fuel cycle. Of the reactors world- wide, 354 are light-water reactors (LWR), of which 270 are pressurized water reactors (PWR) and 84 are boiling water reactors (BWR) (IAEA, 2013a). The remaining reactor types consist of 48 heavy-water reactors (PHWR), 15 gas-cooled reactors (GCR), 15 graphite-moderated reac- tors (RBMK/LWGR), and 2 fast breeder reactors (FBR) (IAEA, 2013a). The choice of reactor technologies has implications for safety, cost, and nuclear fuel cycle issues. Growing demand for electricity, energy diversification, and climate change mitigation motivate the construction of new nuclear reactors.
The electricity from nuclear power does not contribute to direct GHG emissions. There are 69 reactors, representing 67 GWe of capacity, cur- rently under construction in 14 countries (IAEA, 2013a). The bulk of the new builds are in China, Russia, India, Korea (Rep. of), and the United States — with 28, 10, 7, 5, and 3 reactors under construction, respectively (IAEA, 2013a). New reactors consist of 57 PWR, 5 PHWR, 4 BWR, 2 FBR, and one high-temperature gas-cooled reactor (HTGR) (IAEA, 2013a). Commercial reactors currently under construction—such as the Advanced Passive-1000 (AP-1000, USA-Japan), Advanced Boiling Water Reactor (ABWR, USA-Japan), European Pressurized Reactor (EPR, France), Water-Water Energetic Reactor-1200 (VVER-1200, Russia), and Advanced Power Reactor-1400 (APR-1400, Rep. of Korea)— are Gen III and Gen III+ reactors that have evolutionary designs with improved active and passive safety features over the previous generation of reactors (Cummins et al., 2003; IAEA, 2006; Kim, 2009; Goldberg and Rosner, 2011). Other more revolutionary small modular reactors (SMR) with additional passive safety features are under development (Rosner and Goldberg, 2011; IAEA, 2012a; Vujic et al., 2012; World Nuclear Association, 2013). The size of these reactors is typically less than 300 MWe, much smaller than the 1000 MWe or larger size of current LWRs. The idea of a smaller reactor is not new, but recent SMR designs with low power density, large heat capacity, and heat removal through natural means have the potential for enhanced safety (IAEA, 2005a, 2012a). Additional motiva- tions for the interest in SMRs are economies of manufacturing from modular construction techniques, shorter construction periods, incre- mental power capacity additions, and potential for improved financing (Rosner and Goldberg, 2011; Vujic et al., 2012; World Nuclear Associa- tion, 2013). Several SMR designs are under consideration. Light-water SMRs are intended to rely on the substantial experience with current LWRs and utilize existing fuel-cycle infrastructure. Gas-cooled SMRs that operate at higher temperatures have the potential for increased electricity generation efficiencies relative to LWRs and industrial appli- cations as a source of high-temperature process heat (EPRI, 2003; Zhang et al., 2009). A 210 MWe demonstration high-temperature peb- ble-bed reactor (HTR-PM) is under construction in China (Zhang et al., 2009). While several countries have interest in the development of SMRs, their widespread adoption remains uncertain. The choice of the nuclear fuel cycle has a direct impact on uranium resource utilization, nuclear proliferation, and waste management. The use of enriched uranium fuels for LWRs in a once-through fuel cycle dominates the current nuclear energy system. In this fuel cycle, only a small portion of the uranium in the fuel is utilized for energy produc- tion, while most of the uranium remains unused. The composition of spent or used LWR fuel is approximately 94 % uranium, 1 % plutonium, and 5 % waste products (ORNL, 2012). The uranium and converted plu- tonium in the spent fuel can be used as new fuel through reprocessing. While the ultimate availability of natural uranium resources is uncer- tain (see Section 7.4.3), dependence on LWRs and the once-through fuel cycle implies greater demand for natural uranium. Transition to