Climate change: The case for nuclear energy

Radovan Stoklasa/Reuters

Reducing greenhouse gas (GHG) emissions is a key objective of energy policies in many countries. As energy consumption will continue to increase in the medium and long term, even if the recent financial crisis might curtail this rise momentarily, there is a general consensus on the need to foster the development and use of all carbon-free options for energy supply. What role can nuclear energy play?

The Intergovernmental Panel on Climate Change (IPCC) has estimated that to stabilise global temperatures at 2ºC above pre-industrial levels–the cut required to avoid catastrophic consequences for the planet–global GHG emissions in 2050 should be reduced by at least 50% below 2000 levels. This could imply reductions of up to 80% by 2050 for OECD countries.

With expected population and energy demand growth, this means reducing the carbon intensity of the world energy system by a factor of four. This is an enormous challenge, and it cannot be faced without mobilising all the available options, including energy conservation and the large-scale deployment of low-carbon energy sources.

No surprise therefore that policy makers from many countries should be expressing a new (or renewed) interest in nuclear energy as a means to address climate change issues. This is because countries producing electricity with nuclear clearly feel they would benefit from carbon emissions savings as nuclear energy substitutes fossil sources. However, nuclear energy was excluded from the two international flexibility mechanisms of the Kyoto Protocol, i.e., the Clean Development Mechanism (CDM) and the Joint Implementation (JI). The upcoming 15th Conference of the Parties (COP-15) to the United Nations Framework Convention on Climate Change (UNFCCC), which will be held on 7-18 December in Copenhagen, will have to discuss in particular the post-Kyoto design of the CDM. This mechanism allows developing countries to receive the benefits for greenhouse gas reductions they achieve on behalf of developed countries with commitments to reductions. It also plays an important role in facilitating foreign direct investment and technology transfer. Given the challenges, this is surely the right moment to take a closer look at the role nuclear energy can play in this context.

Consider greenhouse gas emissions first of all. Throughout the entire nuclear energy chain, from construction to operation and decommissioning, these emissions are negligible compared to their fossil-fuel equivalents, and are comparable with renewable sources such as solar or wind. Furthermore, the GHG emissions of the nuclear chain are mainly due to fossil fuel consumption associated with construction of nuclear power plants, including the likes of cement production, as well as with uranium enrichment. But even these sources are expected to decrease with technological progress. In particular, the deployment of centrifuge technology for enrichment will cut greenhouse gas emissions per unit of nuclear energy produced.

Looked at in terms of equivalent CO2 emissions per kilowatt hour of energy output, the nuclear chain emits an average of some 8 g CO2-eq./kWh,  while the gas chain (assuming use of the combined-cycle technology) emits around 400 g CO2-eq./kWh and the coal chain with state-of-the-art power plants emits around 1,000 g CO2-eq./kWh. Carbon capture and sequestration could drastically reduce the emissions of coal-fired power plants; however, this is not yet a mature and competitive technology. Most renewable energy chains for electricity generation emit between 5 and 60 g CO2-eq./kWh, hydropower being on the lower side of the range and photovoltaic sources on the higher side.

Nuclear energy already contributes to lower carbon emissions in the world’s economies, especially in OECD countries where it provides more than 20% of total electricity supply. It has been estimated that, since the commercial development of nuclear electricity generation, the cumulative savings of CO2 emissions as a result of nuclear power plants substituting for coal-fired units is around 60 Gt CO2-eq., representing some 20% of the cumulated emissions of the power sector during that period. At present, the emissions avoided thanks to nuclear electricity generation are around 2 Gt CO2-eq. per year assuming that electricity from nuclear energy would be substituted by other technologies in proportion to their current share in the energy mix. That means nuclear energy helps “decarbonise” the economy. In fact, in OECD countries, the GHG emissions from the energy sector would increase by one-third if nuclear power plants are shut down and replaced by fossil-fuelled power plants.

With the ongoing process of plant life extension, the existing global fleet–439 reactors as of June 2008­–will continue producing carbon-free electricity for several decades and the reactors under construction–around 50 at present around the world–will add scores of gigawatts to installed nuclear capacity by 2015. In many OECD countries, however, concrete steps towards ordering and building new nuclear power plants have not yet been taken. In short, most energy scenarios show only a moderate increase in installed nuclear capacity worldwide in spite of the repeated announcements of a nuclear revival.

The Nuclear Energy Agency projects that in 2050, nuclear capacity worldwide could range between 540 and 1400 GWe, compared with 370 GWe today. Under the high scenario, the share of nuclear energy in total electricity generation would reach 22%, i.e., 7% more than in 2008, but in the low scenario it would be only 9%, i.e., 6% less than in 2008. The annual savings of CO2 emissions that would result from these low and high nuclear scenarios amount to some 4.5 and 11.5 Gt CO2-eq. respectively. These quantities are not at all negligible and, in the high scenario, would contribute massively to reaching CO2 reductions identified by the IPCC in its business as usual scenarios.  

More rapid deployment of nuclear energy could improve on this scenario, and is achievable from the technical, industrial and financial viewpoints, but would require stronger political and social support.

This also means overcoming some of the main challenges to its further development. It is high time the nuclear industry and governments addressed the legitimate public concerns about radioactive waste disposal for instance, as well as reinforcing safeguards in non-proliferation agreements. In addition, the financial risks of nuclear projects need to be discussed openly. Like other low-carbon technologies such as renewables, the cost structure of nuclear energy is characterised by high capital costs and low variable costs, which can be a disadvantage in liberalised power markets with volatile prices. On the other hand, nuclear energy has the advantage that its average costs over the full life cycle of the plant are highly competitive.  Suitable financing models and government support can address the question of capital costs for nuclear as well as for other low-carbon technologies.

The challenge to reduce carbon emissions cannot be overstated. It is now time to recognise the value of nuclear energy for reducing greenhouse gas emissions in the legal and institutional framework to be developed at Copenhagen and beyond. This would provide the impetus needed to deal with the challenges and realise the full potential of nuclear energy as a reliable part of our energy and environmental future.

NEA (2008), Nuclear Energy Outlook


NEA (2009) “Addressing Climate Change” in Nuclear Energy in Perspective, available at

©OECD Observer N° 278 March 2010

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