The Special Case of Nuclear Power

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Mitigating climate change is not a "one size fits all" affair. Local conditions are diverse, the menu of technology options is broad, and all have a role to play. Each option must be evaluated on its climate change merits relative to alternatives on a case by case basis.

This article focuses on electricity while recognizing that mitigation opportunities exist throughout the entire energy system. In particular, energy efficiency has increased substantially since the early 1970s, and opportunities for further improvements are huge.

Electricity generation accounts for 40% of total carbon emissions, but only 16% of the world's final energy consumption. It will therefore remain a prime target for greenhouse gas (GHG) emission controls.

Technology options for electricity generation
More efficient conversion of fossil fuels. Technology improvements have the potential to increase average power generation efficiencies by about 50% over the next half century.

Switching to less carbon intensive fossil fuels. Particularly when used in high efficiency combined cycle power plants, natural gas has substantially lower GHG emissions than coal.

Carbon dioxide capture and disposal (CCS). CCS involves separating CO2 before or after combustion and isolating it from the atmosphere, e.g., in geological formations or the ocean. CCS would allow the continued use of fossil fuels with drastically reduced carbon emissions.

Increased use of renewable sources. Technological advances and technology learning offer new opportunities and lower costs for renewable technologies for both off-grid and grid applications.

Increased use of nuclear power. Nuclear energy could replace fossil fueled electricity generation in many parts of the world.

Special treatment for nuclear power
Nuclear power is the only technology explicitly excluded from Article 6 projects, i.e. joint implementation (JI), and the clean development mechanism (CDM) . Yet it has substantial climate benefits. The complete nuclear power chain, from resource extraction to waste disposal including reactor and facility construction, emits only 2-6 grams of carbon per kilowatt-hour, about the same as wind and solar power (see Figure 1).

Figure 1: GHG Emissions of different electricity generating options

How much less carbon is there in the atmosphere because of nuclear power? That depends of what you think would have replaced the missing nuclear plants. If one assumes replacement entirely by conservation, hydropower and new renewables, the answer is zero - nuclear power would not have reduced carbon emissions at all relative to that possible alternative history. If one assumes replacement by other sources proportional to their role is today's electricity generating mix, the answer is 500 MtC per year.

If one assumes that a more realistic replacement in the high-growth 1960s, 1970s and 1980s would have been a proportional increase of all fossil fuels, the answer is 630 MtC per year. Finally, if one assumes replacement entirely by coal, the answer is 740 MtC per year. For comparison, the Kyoto Protocol's aggregate reduction requirement of 5.2% relative to 1990 equals 195 MtC per year. Without the USA and Australia it equals 120 MtC per year. At 500 MtC per year (i.e. the case above of purely proportional replacement) nuclear power would already be reducing the world's carbon emissions significantly more than will the Kyoto Protocol in the first commitment period.

Looking ahead, the Third Assessment Report of the Intergovernmental Panel on Climate Change estimates simply that nuclear power has the greatest greenhouse gas mitigation potential of all electricity supply options.

One size does not fit all
In reducing GHG emissions different countries face different demands and opportunities. The best strategy generally involves a mix of reductions, and for nearly all countries that mix is different. It depends on the opportunities available - countries with untapped wind or hydropower resources, for example, have more possibilities than those with none, and countries that are heavy coal users can consider CCS. It depends on specific energy needs and how fast a country is growing. In developing countries, the best promise for the rural poor may be off-grid renewables, while in growing mega-cities the mix needs to include large centralized power generation to match large centralized power demand. And it depends on national preferences and priorities. How countries trade off among environmental quality, jobs, occupational hazards, energy security and energy costs is at least partly a matter of national preference, and thus an area of legitimate disagreement even where there is agreement on relevant facts. A country sufficiently averse to nuclear risks might rationally prefer a nonnuclear route to GHG emission reductions, even if it were more expensive.

Leveling the playing field
One question for CoP-11/MoP-1 is whether to end the special treatment of nuclear power. Nuclear power can and is used by Annex I countries to help meet their Kyoto Protocol commitments. But it cannot be used by non- Annex I countries to help reduce emissions through the CDM. The exclusion of any technology limits options, flexibility, and costeffectiveness. The alternative is to limit only what matters - carbon emissions - and let countries fulfill those obligations cleverly, innovatively, and in ways tailored to their own situations.

For more information: H.H.Rogner@iaea.org