One of the main selling points in the push to expand nuclear power is the claim that it is "low-carbon" and well suited to fight climate change caused by carbon dioxide emissions coming from fossil fuel power plants and fossil fuel engines. Many state and national governments are currently adopting quotas for low-carbon energy sources and nuclear power proponents are pushing for nuclear power to be classified as low-carbon along with such sources as hydro, solar, wind and biogas. While it definitely emits less carbon dioxide than a coal or natural gas power plant, a nuclear power reactor is not quite as low-carbon as many think.
The Committee on Climate Change of the government of the United Kingdom has called for less than fifty grams of carbon dioxide (CO2) to be emitted in the generation of each kilowatt hour of electricity by the year 2030. It has been suggested that any new nuclear power plants that are constructed in the U.K. starting now should have to follow the fifty gram CO2 limit.Due to the long lead time required for the licensing and construction of a nuclear power plant, it is quite possible that even power plants that are under construction or just starting construction may not be generating power for the grid before 2030.
When considering the entire life cycle of a power source, there are five main areas to analyze. Construction, operation, fuel production, dismantling and waste disposal. Although many analyses of carbon generation by nuclear power plants have been carried out, there is no universally accepted scientifically agreement on how much CO2 is emitted by a nuclear power plant in its lifetime.
Starting in chronological order, construction of a nuclear power plant consumes an enormous amount of concrete which generate CO2 as it cures.
Next, the production of uranium fuel also generates CO2 as fossil fuels are consumed in digging, milling and transportation. As the high grade deposits of uranium are exhausted, the use of fossil fuels and the generation of CO2 will increase because of the greater energy cost of fuel production for deposits with lower percentages of recoverable uranium.
Operations of a nuclear power plant produce little CO2.
Since the problem of nuclear waste disposal has not be solved as yet, it is hard to estimate CO2 emissions associated with waste disposal. Underground repositories will have to dug which will consume fossil fuels. And waste will have to be transported to the repositories which will also consume fossil fuels.
Finally, the costs that will be associated with the decommissioning of nuclear power plants is not well defined so estimates of CO2 generation are difficult but there will be fossil fuels needed for the equipment that dismantles retired nuclear power plants and fossil fuels consumed in the transportation of the debris from the dismantling. This will generate CO2.
A recent meta-study of the most thorough analyses of CO2 emission of nuclear power plants found that over half of the studies said that nuclear power plants generated more than the fifty grams of CO2 limit called for by the CCC. Some studies claimed that CO2 generation of nuclear power plants during their life cycles were under fifty grams but close analysis of those studies showed that they failed to adequately consider the possible contribution of decommissioning and/or waste disposal to the total CO2 emitted.
With respect to renewable power sources, a recent study found that a life cycle analysis of hydropower, biogas, wind and solar all fell under the fifty grams limit for CO2 generation. The cost and efficiency of some renewable energy sources such as photovoltaic solar are rapidly evolving and their CO2 emission should fall even further.
Whatever positive arguments can be made for the construction of nuclear power plants, it appears that lowering CO2 emissions to help mitigate climate change is not one of them.
