Nuclear Power versus the Greenhouse Effect Nuclear fission

Since the use of fossil fuels has to be reduced significantly within the coming decades, zero-carbon energy sources are required. One option is nuclear power. Here, we distinguish between nuclear fusion and nuclear fission.

All operational nuclear power stations utilize nuclear fission for electricity generation. Here, neutrons bombard the uranium isotope 235U and cause the fission of the uranium. Among others, krypton 90Kr and barium 143Ba are fission by-products. Furthermore, this fission reaction generates new free neutrons xn that can initiate further fission reactions. The mass of the atomic particles after the fission is reduced compared to the original uranium atom. This so-called mass defect is converted to energy AE in the form of heat. The following nuclear reaction equation describes the fission process:

Since nature does not provide uranium in the form that is needed for technical utilization, it must be extracted from uranium ore. Rock with a uranium oxide content of more than 0.1 per cent is a workable uranium ore. Uranium mining produces huge amounts of waste that contains, in addition to some non-toxic components, a lot of radioactive residues. Uranium oxide from uranium ore contains only 0.7 per cent uranium-235. The largest portion is uranium-238, which is not usable for nuclear fission. Therefore, processing plants must enrich the uranium, i.e. the uranium-235 concentration must be increased to 2-3 per cent. In 2002, worldwide uranium production was about 34,000 metric tonnes.

Altogether, 428 nuclear power stations were in operation at the beginning of 2003, with an overall capacity of 353,505 MW. The average nuclear power station power was about 825 MW. Currently, nuclear power's share of the global primary energy demand is below 10 per cent. Figure 1.8 shows that nuclear power has a different contribution to electricity supply in different countries.

Nuclear power dominates the French electricity supply, whereas industrial nations such as Australia, Austria, Denmark, Norway or Portugal do not operate any nuclear power stations at all. Italy decided to abort nuclear power utilization after the Chernobyl disaster; Austria's decision pre-dated it. However, an electricity industry without nuclear power does not necessarily mean higher carbon dioxide emissions. For instance, hydro-electricity produces nearly 100 per cent of Norway's electricity. Iceland's electricity supply is nearly carbon dioxide free as a result of hydro and geothermal power.

If all fossil energy sources used today were replaced by nuclear power, about 10,000 new nuclear power stations would have to be built worldwide. The lifetime of a nuclear reactor is about 30 years, thus all these power stations














ZU 40


H 38

South Korea

H 38


H 38


1 32











United Kingdom




Czech Republic





□ 12



South Africa


Argentina Netherlands Mexico India Brazil China







Source: DOE, 2003

Figure 1.8 Nuclear Power's Share of Electricity Generation in 2000

would have to be renewed after this time. Therefore, a new power plant would have to go on-line every day. In this scenario, politically unstable nations would also acquire, as an unwanted side effect, access to nuclear technology. This would increase the risk of nuclear accidents, sabotage or military use of nuclear energy, resulting in unforeseeable associated costs which make this option increasingly expensive.

As described above, Earth has limited uranium reserves. If the majority of fossil energy sources were to be replaced by nuclear power, the uranium reserves would be depleted in a short time, depending on the nuclear technology employed. Therefore, nuclear fission can only be an alternative to fossil fuels in the medium term.

Nuclear fission does not emit any carbon dioxide directly, but the building of the power plant, uranium mining, transport and disposal result in the emission of significant amounts of carbon dioxide. These indirect carbon dioxide emissions are much lower than those associated with the operation of a coal-fired power plant but higher than the indirect carbon dioxide emission of, for example, wind turbines.

Transport and storage of radioactive materials bear further risks: uranium and fuel rods must be transported to different processing plants and power stations, and radioactive waste must be transported for further treatment and to intermediate and final storage sites. Toxic and highly radioactive waste such as spent fuel rods is already produced during normal operation of a nuclear power station. Besides other radioactive substances, they also contain about 1 per cent plutonium. One microgram of plutonium, i.e. one millionth part of a gram, is considered to be lethal when breathed in; it will cause death by lung cancer. Hence, one gram of plutonium could theoretically wipe out a whole city. There is no absolute safety guarantee with such nuclear material; the possibility of transport accidents and the emission of radioactive material is very real. Final storage of radioactive waste is also very problematic, because this waste will retain its lethal properties over thousands of years.

The normal operation of nuclear power plants also bears risks. Nuclear power stations continuously emit a very small amount of radioactivity. An increased rate of leukaemia in children living near a nuclear power plant has been reported. However, accepted scientific correlations do not exist at present.

The highest risk of nuclear fission is an MCA (maximum credible accident) in a power station. Such an accident would affect millions of people and the emitted radioactivity would make large regions uninhabitable. Many humans and animals would die from radiation or fall ill with cancer. An MCA can never be totally excluded. Nuclear accidents in Harrisburg and Chernobyl have made this clear. In recent years the risk of terrorist attacks has also increased the risk of an MCA.

The first big reactor accident happened on 28 March 1979 at Three Mile Island near Harrisburg, the capital of the US state of Pennsylvania. Large amounts of radioactivity escaped. Numerous animals and plants were harmed and the number of human stillbirths in the neighbourhood of the power plant increased after the accident and cancer rates increased drastically.

On 26 April 1986, another severe nuclear reactor accident happened in the city of Chernobyl in the Ukraine, which had about 30,000 inhabitants. The escaped radioactivity not only affected the vicinity of the plant but also affected Central Europe. Many workers who tried to stop further damage at the plant paid for their efforts with their lives. The number of stillbirths and the incidence of cancer due to exposure to radiation increased significantly in the following years.

As has already been noted, civilian use of nuclear power stations is not their only potential use; they can also be used for military applications. This is one reason why civilian nuclear power has been promoted in some countries. The use of nuclear power in politically unstable countries can provoke international crises. Countries such as Iran, Iraq and North Korea have promoted nuclear power, probably also to exploit its military potential. If the use of civilian nuclear power is encouraged, the risk of nuclear crises and the risk that terrorists will come into possession of nuclear material will rise significantly.

The number of incalculable risks is balanced by the undisputed benefits of civilian use of nuclear power. Other cleaner technologies than nuclear power exist and the potentially enormous costs associated with nuclear accidents suggest that the insistence on withdrawal from the nuclear programme is perfectly justified.

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