Estimates of available uranium stocks at different price compared to the present uranium demand for existing reactors. (EWG, 2006) 

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... patterns, with huge consequences on its national and worldwide economic systems. If nuclear energy becomes difficult or impossible to implement, then fossil fuels may become once again the main choice of industrialized and developing economies (with coal as the cheapest option). The likely increase of fossil fuels prices, hard competition for their supply as well as related environmental concerns, call for urgent, worldwide rethinking of standards of life, degrowth policies, and larger reliance on energy conservation and renewables. This is the major challenge that the whole planet is facing and nobody can predict at present if and to what extent this is likely to happen in the short or medium run. About 440 reactors are presently in operation in 30 countries with a total installed capacity of 372 GW el . Compared to fossil fuels, used in power generation, residential, commercial, industrial and transport sectors, nuclear energy is only used for electricity generation. Electricity from all sources has a market share of about 17.1% worldwide and 21.1% in OECD countries, in terms of final energy consumption. The nuclear share of world electricity supply during the period 1973-2008 increased from 3,3% (1973) to about 18% (1990), then decreased to 13.5% (2008) (De Paoli, 2008; IEA, 2010). Oil powered electricity declined its share from 24.7% (1973) to 5.5% (2008). Natural gas and to a lesser extent coal expanded their share in the same period (IEA, 2010). Nuclear energy supplies about 34% of the total electricity produced in the European Union. Italy does not have nuclear plants in operation but imports about 15% of its electricity mainly from France, where 77% of electricity comes instead from nuclear (ENEA, 2009). The global nuclear electricity generation (except for China and India) was projected - even before the Japanese accident - to increase at rates lower than the overall electricity generation by 2030 (Lenzen, 2010). IEA (2008) foresees an installed capacity increase to 415-519 GW el in 2030, EIA (2010) predicts an increase to 481 GW el , and OECD-NEA projections predict up to 600 GW el (Lenzen, 2010). Such a lower growth rate can be attributed to public concerns about safety, proliferation risks, restrictions in supply chains due to skilled labor shortage and insufficient enrichment capacity, lack of experienced contractors, lack of solutions for spent fuel disposal. According to Lenzen (2010) promises of performance improvement (higher resources sustainability, inherent safety, substantial reductions in radioactive waste volumes and lifetime) rely on the new generation-IV reactor and fuel cycle technology, foreseen by 2030. How these forecasts of nuclear development will be affected by the Fukushima accident and the need for increased safety devices and strategies is still to be seen, thus adding uncertainty to uncertainty. The annual world uranium production has been around 50,772 t U in 2009 covering about the 77.5% of annual demand (that is around 65,500 t U ) (WNA, 2010a). The gap between demand and production has been (and still is) met by secondary sources such as low enriched uranium (LEU) from the dismantling of nuclear warheads, re-enrichment of depleted uranium tails and spent fuel reprocessing (NEA, 2010). Two main periods of high uranium exploration can be identified. The first one, in the 1950s, was driven by the demand of weapon industry while the second one, in the 1970s, was due to the fast development of nuclear civil programs as a reaction to the 1973 oil embargo (Remme et al , 2007). Prices have been recently rising after about twenty years of decreasing trend (WNA, 2010a), thus stimulating new exploration activities and leading to an increased resource supply (Lenzen, 2010). World uranium Reasonably Assured Resources (RAR) and inferred resources were 3.2 Mt U in 2003, increasing to 4.7 Mt U in 2005, 5.5 Mt U in 2007 (Lenzen, 2010) and finally 6.3 Mt U in 2009 (D’Urso, 2010). RAR and inferred resources should provide uranium for the next 100 years at current production rates (Lenzen, 2010). Mudd and Diesendorf (2008) highlight that, despite perceived resource scarcity, the last two nuclear programs (nuclear weapon race in the 1940s and civil nuclear development in the 1960s) have been followed by new resource discovery. As with all fossil fuels, it is expected that the new deposits explored in the future will be deeper compared to most of the presently exploited deposits. The average ore grade mined is also expected to be lower as far as the best deposits are exploited, although Canadian newly discovered deposits show an increasing trend (Mudd and Diesendorf, 2008; Heinberg, 2009). A summary of world uranium producers is provided in Figure 1. It clearly appears that the uranium market is dominated by very few countries, similarly to the market of fossil fuels (and maybe even more). The gap between demand and supply of uranium raises concerns for a possible peak of world uranium (Figure 2). Compared to oil, uranium is relatively abundant but difficult to find at economically attractive concentration grades. The trend of production and the increase in price are signals of the gradual depletion of the best deposits and the need for exploiting new deposits that could require higher investments and extraction costs. Uranium is having the same trend as oil, where scarcity and increasing extraction costs are causing the so-called “oil peak”. Some authors suggest that uranium is also near to or has already passed its peak (Bardi, 2006; Heinberg, 2009), although this trend is not easy to be confirmed because of the irregular production activities. The future of nuclear power will be heavily affected by either the scarcity of uranium resources and the increase of extraction costs, so that it might be very difficult to keep the promises of cheap nuclear energy, even without taking into account the cost increase determined by the demand for better technologies. Nuclear electricity is the final product of several upstream activities from mining to processing and finally converting the nuclear fuel. These activities, together with downstream disposal and processing of used fuel, constitute the nuclear fuel cycle (WNA, 2010b). A fuel cycle can, in turn, be classified into two types: “once-through” (open) and “closed”. The latter types “reuse the nuclear materials extracted from irradiated fuel” (IAEA, 2009) while the former ones do not reuse nuclear materials and discharge them directly into disposal sites (Sovacool, 2008a). The choice between “open” or “closed” cycles is an important national policy decision (IAEA, 2009). At present most of the nuclear reactors operate adopting the “once-through” cycle (Owen, 2006; Sovacool, 2008a). Reactors operating with closed cycles, separate waste products from the still fissionable material, that is reprocessed and re-used. The reprocessing activity has the double advantage to reduce both the upstream demand for natural uranium and the downstream waste that must be disposed of (Lenzen, 2008; Sovacool, 2008a). Closed-cycle reactors have however disadvantages linked to the reprocessing costs, proliferation risks and problems with fuel cycle safety (Sovacool, 2008a). The two nuclear cycle types share at least five interconnected stages (Figure 3): (1) upstream or “front-end” activities, in which uranium is extracted from ore (open pit, underground mining or in situ leaching), milled, converted to uranium hexafluoride, enriched and finally used to make the fuel element; (2) power plant construction; (3) plant operation and maintenance; (4) downstream or “back-end” activities, in which the spent fuel is conditioned, reprocessed and disposed in final repositories (if any); (5) plant decommissioning and mine site reclamation (Sovacool, 2008a). Other related activities (heavy water and zirconium alloy production) and transport of the materials among the different steps must also be taken into account (Owen, 2006; IAEA, 2009). The present review is based on 9 LCA studies published since 2000, dealing with the nuclear fuel cycle at a different level of detail and scope. Four of them are actual LCAs of specific cycles (Lee et al , 2000, 2002; Dones et al , 2005; Wissel and Spohn, 2008), while the other five are in turn reviews of the existing literature (Gagnon et al , 2002; Fthenakis and Kim, 2007; Sovacool, 2008a; Lenzen, 2008; Fthenakis and Kim, 2009), making up for more than one hundred of cases compared and summarized. Most of the reviewed studies are focused on greenhouse gas emissions over the nuclear fuel cycle (Lenzen, 2008; Sovacool, 2008a) or on the comparison with other fossil or renewable energy cycles (Gagnon et al , 2002; Dones et al , 2005; Fthenakis and Kim, 2007). The latter also include indicators different than greenhouse gas emission, such as radioactive emissions (noble gases, H 3 , C 14 , aerosols, Actinides; Dones et al , 2005); SO 2 , and NO x emissions, and direct land requirements (Gagnon et al , 2002; Fthenakis and Kim, 2009), indirect land requirements (Fthenakis and Kim, 2009), energy payback ratio (Gagnon et al , 2002; Lenzen, 2008), and energy requirements (Lenzen, 2008). A comparison of the average CO 2 emissions from different types of power plants powered by either renewable and nonrenewable sources (Table 1) shows a very large range of options, with nuclear ranking low compared to fossil fuels and still high compared with wind, hydro and other renewables. The most surprising aspect in the reviewed studies is the large spread of estimates of CO 2 emissions from nuclear. Sovacool (2008a) calculates an average emission of 66 g CO 2 /kWh el , but due to the spread based on very different assumptions the real meaning of such an average is questionable and therefore scarcely useful for nuclear policy planning. Some authors (Fthenakis and Kim, 2007; Sovacool, 2008a; Lenzen, 2008) investigated the causes that contribute to the ...