Nuclear energy: life cycle analysis of energy and greenhouse gas intensities

200702051123Summary: greenhouse gas [GHG] intensities correlate closely with energy intensities. During their entire life cycle, conventional nuclear reactors generate about 20 times less GHGs than typical brown coal plants, and about half as much GHG as photovoltaics. Wind turbines and hydroelectric generate roughly three times less GHG than conventional nuclear.

The final reports prepared by Australia’s Prime Ministerial task force on Uranium Mining, Processing and Nuclear Energy are now available. All of the reports are indexed here. My first area of interest is to review the latest complete nuclear life-cycle figures. In particular, we need to know the total greenhouse gas impact of the nuclear fuel cycle, plant construction, operation, decommissioning, waste storage and electricity generation.

The key report was prepared by the University of Sydney, titled Life-Cycle Energy Balance and Greenhouse Gas Emissions of Nuclear Energy in Australia [PDF]. The results are summarized in the table at left:

A comparable analysis has been undertaken for a number of conventional fossil-fuel and renewable electricity technologies. As with the methodology for the nuclear case, a range of literature values and current estimates have been used to examine the performance of these technologies in an Australian context, assuming new capacity is installed at close to world’s best practice. These results, together with a summary of the nuclear energy results, are presented in the table below. The figures in parentheses represent the likely range of values.

Hybrid input-output-based life-cycle assessment (IO-LCA) is a complex process. When applied to a complex industrial cycle like nuclear the complexities compound. The cascading of assumed-value ranges leads to the wide ranges of estimated intensities. I’ve reviewed the report fairly carefully – I think the authors have diligently attempted to choose conservative assumed values as they processed the literature review. They have also done a thorough sensitivity analysis [see page 115 for the conclusions]. If you wish, you can download the IO-LCA spreadsheet models and run your own cases.

In particular, I think the energy intensity of the future nuclear industry is better than depicted because I anticipate significant process economies from such new technologies as high temperature, modular pebble-bed reactors. Such modular reactors will be series-manufactured, pre-approved and pre-licensed. New fourth-generation plant construction will bear no resemblance to our experience of custom-designed, custom-built plants with 15 year commissioning spans. Similarly, the greenhouse gas intensity of the new plants should improve roughly proportionate to the resultant energy intensity.

Nuclear vs. advanced coal generation: We don’t yet know the cost of GHG sequestration for either conventional “dirty coal” generation or for advanced coal technologies such as IGCC. But we can anticipate that the GHG intensity advantage of nuclear will be less than 20:1 when compared to a coal plant + sequestration.

Long-term storage risks: I’ve not seen an objective analysis of the relative long-term risks of GHG sequestration and nuclear waste storage. My personal guesstimate is I would rather be responsible for the small volumes of nuclear waste as I expect the storage technology to advance radically once it is actually undertaken [don't think of storing radioactive waste for 10,000 years - think of storing for 50 to 100 years in one [or a very few] federally operated storage facilities]. Periodically, advancing technology, economics and safety will dictate upgrading the waste storage scheme – thus the relative short planning horizon. At some point the technology might support a 10,000 year scheme – but it is not required nor even advisable at this point.

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