Energie en klimaat

Nuclear power and greenhouse gas emissions

Nuclear Energy and
Climate Change

Myth 1: the generation of electricity by nuclear fission does not lead to greenhouse gas emissions.

Even if this were the case, switching the entire world's electricity production to nuclear would still not solve the problem because the production of electricity is only one of many human activities that release greenhouse gases.

Other sources of greenhouse gases include transport and heating, agriculture, the production of cement and deforestation. The CO2 released worldwide through electricity production accounts for only 9% of total annual human greenhouse gas emissions (UIC, 2001b).

This section discusses:

Greenhouse gas emissions from nuclear power production

It is true that the actual fission process whereby electricity is generated does not release greenhouse gases. However, in various stages of the nuclear process (e.g. mining, uranium enrichment, building and decommissioning of power plants, processing and storing radioactive waste) huge amounts of energy are needed, much more than for less complex forms of electricity production. Most of this energy comes in the form of fossil fuels, and therefore nuclear power indirectly generates a relatively high amount of greenhouse gas emissions.

How much greenhouse gas is emitted compared to the amount of electricity produced?

In order to establish the magnitude of these emissions compared to emissions from other forms of electricity production, it is necessary to carry out comparative lifecycle assessment of the various energy supply options. In these assessments the total emissions over the whole lifecycle are added together and divided by the total electricity produced over the lifetime of the power plant: the result shows the total greenhouse gas emissions per kWh electricity.

A number of lifecycle assessments for various electricity production processes have been carried out in the past. One of the most comprehensive of these was carried out by the ÷ko Institute in Germany. It is based on 10 years of research in the GEMIS (Global Emission Model for Integrated Systems) database. A number of the results are shown in the following table.

Generation MethodGreenhouse Gas Emissions (CO2-eq. /kWh)
Wind 20
Hydroelectric 33
Nuclear 35
Gas Combined Cycle Ca.400
Coal Ca.1000

Table 1: Greenhouse gas emissions per generation method in Germany (÷ko Institute, 1997).

From the data above it can be concluded that nuclear power emits about the same quantity of greenhouse gases as electricity produced from a number of renewable sources, but much less than fossil fuel sources: 12 times less than gas power stations and almost 30 times less than coal power stations.

Much of these emissions occur when energy is used for the mining of uranium, during transports and in the enrichment process that makes uranium usable as reactor fuel. The emissions during decommissioning of a nuclear reactor are probably underestimated in these analyses, because in practice these emissions turn out to be much higher than was assumed theoretically.

In a number of other studies similar emissions data are reported, where nuclear power emissions are calculated in the range of 30-60 g CO2-eq. /kWh (IAE, 1994; CRIEPI, 1995). A more recent study by Storm van Leeuwen & Smith (2004) estimated the difference in emissions between nuclear and gas power plants to be much smaller than the assessments described above. According to their data, nuclear power production causes the emission of just 3 times fewer greenhouse gases than modern natural gas power stations. This figure is based on rich ores with over 0.1% uranium content. Moreover they expect a dramatic decrease of the percentage of uranium content in ores, which will make the extraction of the uranium much more energy consuming.

The emissions from the nuclear industry are strongly dependent on the percentage of uranium in the ores used to fuel the nuclear process. The global average uranium content in ores is currently about 0.15% (Canadian Nuclear, 2002, cited in Slingerland et al, 2004).

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How many nuclear power plants are needed to reduce emissions?

Can we reduce the emissions of the public energy sector (electricity and combined heat/ electricity) by replacing fossil fuels with nuclear power on a large scale? And if so, how many new power plants would we need?

Makhijani (2002) estimates that, in order to produce a noticeable reduction in global CO2 emissions, it would be necessary to build 2000 large new nuclear reactors of 1000 MW each. The U.S. National Commission on Energy estimates that U.S. reactors would have to double or triple over the next 30-50 years. This means about 300-400 new reactors, including those to replace reactors which will be retiring during that period (National Commission on Energy, 2004).

We have calculated the number of new nuclear power stations that would be needed to reduce the emissions of the public energy sector by 2012 according to the targets of the Kyoto Protocol in the EU-15 (EU prior to the expansion).

Although the Protocol does not actually stipulate the sectors in which emissions reductions are to be made, we have made the calculations assuming that each sector contributes according to the levels of its current contribution to total emissions. This means that while this sector accounts for 39% of emissions it should be responsible for 39% of emissions reductions (EarthTrends, 2003).

Assuming that electricity generation from nuclear power plants does indeed cause the indirect emission of 35g CO2-eq./kWh (÷ko, 1997), 72 new medium sized plants of 500MW each would be required in the EU-15. (For an explanation of the calculations and assumptions please refer to appendix 1). These would have to be built before the end of the first commitment period 2008- 2012. Leaving aside the huge costs this would involve, it is unlikely that it is technically feasible to build so many new plants in such a short time, given that only 15 new reactors have been built in the last 20 years (WISE, 2003). Furthermore, with so many new reactors, the world supply of uranium would be exhausted very quickly.

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Nuclear power and heat production

Society does not just require energy in the form of electricity: heat is also essential. In the average French household for example, two thirds of the energy used is heat and one-third is electricity (WWF, 2000). When fossil fuels are burnt to produce electricity, a by-product of the process is heat.

Traditionally this heat energy has been lost as waste and therefore the efficiency of fossil fuel burning power plants has been low. However, in the last few decades huge advances have been made in fossil fuel cogeneration plants where most of this 'waste heat' is recovered and used in industrial heating or urban heating systems. The efficiency in these plants can reach as high as 90%, compared to 35-55% in conventional plants (Field, 2000; WWF, 2000).

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How efficient is a nuclear power plant compared to a modern natural gas fired cogeneration plant?

The ÷ko Institute has calculated the total greenhouse gas emissions of producing 1kWh electricity and 2kWh heat by various energy systems.

A natural-gas fired cogeneration plant typically generates about one-third electricity and two-thirds heat, so all of the emissions in this system would stem from the cogeneration plant.

In the case of a conventional nuclear plant power, the heat would have to be generated from another source: the ÷ko study chose an oil-fired central heating system. (Oil was chosen because the associated emissions fall between those of coal and gas.) The total emissions in this case would be as for 1kWh electricity generation in the nuclear plant, and 2 kWh heat production by the oil-fired central heating system. The results reveal that the total emissions from the gas cogeneration plant are of the same order of magnitude as those produced in the nuclear + oil example.

Therefore, if we were to replace older fossil-fuel burning power stations with new cogeneration systems, for the same amount of electricity and heat generation the total greenhouse gas emissions would be similar to those in a system based on electricity from nuclear power and heating from fossil fuels.

A number of nuclear cogeneration power plants have been built in Russia, Slovakia, Switzerland and Canada amongst others (Federation of Electric Power Companies of Japan, 2000). However, these are the exception rather than the rule.

While nuclear cogeneration is technically feasible, there is much less experience with this method than with fossil-fuel powered cogeneration plants mainly because nuclear power plants are built far from urban areas. Therefore the transport of the heat from the nuclear power station to the consumer would lead to a lot of heat loss.

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Greenhouse gas emissions in France

In 2003 France generated 75% of its electricity in nuclear power plants. The nuclear industry likes to use France as a shining example of the advantages of nuclear power. However, France's greenhouse gas emissions in 2000 were still increasing, largely because it has lost control of energy consumption in other sectors, e.g. transport.

Furthermore, studies of future energy scenarios carried out by the French Government Central Planning Agency show no evident correlation between CO2 emissions and nuclear power.

In fact, the scenario with the lowest emissions was the one in which the growth in demand was minimised, not the one with the greatest use of nuclear power (Boisson, 1998 & Charpin et al., 2000). In another study, a comparison was made between the results of investments in wind energy and the same amount of investment in nuclear energy. The results were clearly favourable for wind energy. With the same investment much more energy could be generated with wind. Moreover, with investments in wind energy more new jobs were generated than with investments in nuclear energy (Bonduelle & Levevre, 2003).

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Friends of the Earth Vlaanderen & Brussel (voorheen Voor Moeder Aarde) is lid van Friends of the Earth International