Sovacool in 2008 reported on a survey he conducted in Singapore screening 103 lifecycle studies of greenhouse gas-equivalent emissions for nuclear power plants to identify a subset of the most current, original, and transparent studies. The article begins by briefly opining on the separate components of the nuclear fuel cycle before explaining the methodology of the survey and exploring the variance of lifecycle estimates. It calculates that while the range of emissions for nuclear energy over the lifetime of a plant, reported from qualified studies examined, is from 1.4 g of carbon dioxide equivalent per kWh (g CO2e/kWh) to 288 g CO2e/kWh, the mean value is 66 g CO2e/kWh.
The article then opines on some of the factors responsible for the disparity in lifecycle estimates, in particular identifying errors in both the lowest estimates (not comprehensive) and the highest estimates (failure to consider co-products). It should be noted that nuclear power is not directly emitting greenhouse gas emissions, but rather that lifecycle emissions occur through plant construction, operation, uranium mining and milling, and plant decommissioning.
Of the remaining 19% of studies that were relatively up to date, accessible, and methodologically explicit, they varied greatly in their comprehensiveness, some counting just construction and decommissioning as part of the fuel cycle, and others including mining, milling, enrichment, conversion, construction, operation, processing, waste storage, and decommissioning. Adding even more variation, studies differed in whether they assessed future emissions for a few individual reactors or past emissions for the
global nuclear fleet; assumed existing technologies or those under development; and presumed whether the electricity needed for mining and enrichment came from fossil fuels, other nuclear plants, renewable energy technologies, or a combination thereof. Furthermore, the specific reactors studied differ greatly themselves. Some utilize relatively high-quality uranium ore located close to the reactor site; others require the importation of low-quality ore from thousands of kilometers away.
A nuclear plant in Canada may receive its fuel from open-pit uranium mines enriched at a gaseous diffusion facility, whereas a reactor in Egypt may receive its fuel from an underground mine enriched through centrifuge. A nuclear facility in France may operate with a load factor of 83% for 40 years on a closed fuel cycle relying on reprocessed fuel, whereas a light water reactor in the United States may operate with a load factor of 81% for 25 years on a once-through fuel cycle that generates significant amounts of spent nuclear fuel. Rather than detail the complexity and variation inherent in the greenhouse gas emissions associated with the nuclear lifecycle, most studies obscure it; especially those motivated on both sides of the nuclear debate attempting to make nuclear energy look cleaner or dirtier than it really is.
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