The dispute involves what happens if we turn to nuclear as the primary global energy source and is caused by evaluations of the amount of CO2 emissions resulting from declining quality of uranium ore. The NREL group considered this and have a brief discussion of their choice of assumptions. I'll wait for Storm van Leeuwen's response before forming an opinion of the NREL results.
Future Uranium Ore Grade Scenario Projections
Many factors that influence nuclear life cycle GHG emissions are expected to improve over time, lowering GHG emissions. For example, the increased use of multipurpose mines reduces the energy required to extract uranium, and the gradual switch to centrifuge uranium enrichment reduces the energy required for this process compared to diffusion enrichment. On the other hand, if the global uranium market-average ore grade decreases over time, life cycle GHG emissions could increase for the average nuclear power plant due to higher energy demand for uranium recovery. Emissions from mining and milling can contribute to a significant portion of life cycle GHG emissions; for example, Dones and colleagues (2007a) estimate approximately 30%. Uranium is a nonrenewable resource and global rates of recovery are highest for the higher-quality ore grades, even though the majority of global recoverable resource consists of lower ore grades (ABARE 2004, IAEA 2008). The potential impact of decreasing uranium ore grades creates a major difference between nuclear and renewable technologies for future GHG mitigation potential6 (Storm van Leeuwen 2007). Here we use a scenario analysis framework similar to Storm van Leeuwen's (2007), but without the influence of the AEI method, with more recent data, and with a more global focus. The present analysis is intended to explore the boundary of the potential impact of decreasing ore grade on life cycle GHG emissions.
Life Cycle Greenhouse Gas Emissions of Nuclear Electricity Generation
Systematic Review and Harmonization
Ethan S. Warner, Garvin A. Heath
http://onlinelibrary.wiley.com/doi/10.1111/j.1530-9290.2012.00472.x/full
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