Global warming is a phenomenon caused mainly by the excessive release of carbon-di-oxide (CO2). CO2 is emitted from coal and oil-fired power plants across the country. There has been lot of debates on the need to develop alternate sources. Nuclear energy is been seen as an effective means of reducing the green house gases. In this paper, the different types of technologies are discussed on how they can contribute to the reduction of global warming.
The recent years have seen a global debate on the issue of global warning. The impact of the increase in CO2 levels around the world on the earth's near surface air temperature has been widely documented. Global surface temperatures have increased by 0.74 ± 0.18 °C (1.33 ± 0.32 °F) during the last century. (David, 2005).
The challenges posed by global warming have led to intergovernmental dialogues culminating in the Kyoto Protocol. This treaty is an international treaty under the United Nations Framework Convention on Climate Change adopted in 1997 and enforced since 2005. It has been ratified by 183 countries and represents the single largest initiative towards combating global climate change. (UN Framework Convention on Climate Change, 2009)
The Kyoto Protocol commits the UK to reduce her greenhouse emissions by 12.5% below the 1990 levels.
UK has been actively promoting the use of gas to fuel its power plants in order to achieve the short term goal of reducing greenhouse gases by 12.5% by 2012. (Pidgeon, Irene, & Wouter, 2008).
It is in this context that nuclear energy has once again found favor among the country's policy makers. The existing nuclear power plants have all been commissioned long ago and by 2025, many of them will have reached the end of their life and will be decommissioned. Unless steps are urgently taken to renew the development of new power plants based on nuclear energy, UK, which is a pioneer in the field of nuclear energy, may lose the capability to develop and run the nuclear power plants for ever.
History of atomic power
The basic process of Nuclear Power is based on nuclear fission of Uranium atoms, which leads to large release of energy. This energy is captured and is used to generate steam in a boiler. The steam from the steam generator drives a steam turbine, which is connected to an electric generator thus producing electricity. The electricity is distributed through a power grid. Nuclear fission was first discovered in 1939 and the world's first chain reaction was achieved by the Manhattan project in 1942 at the University of Chicago. It was only in 1951, after the WWII that electricity was first generated from nuclear power. The experimental reactor EBR-1 produced about 100 kW of electricity.
In the early 1950's, nuclear power research was mainly focused for civilian electricity and submarine propulsions. The efforts of British and French were focused on natural uranium fueled, graphite moderated and gas cooled reactors (GCR).(World Nuclear Association)
Research was carried out since 1954 both for civilian power generation and submarine propulsion with mutual benefits. In 1956 Calder Hall-1, a 50 MW(e) Gas Cooled Reactor, was installed for the first time in UK and it operated till March 2003. The turning point for the spread of nuclear power was in the First Geneva Conference in 1955. The US Atomic Energy Commission predicted 1000 nuclear plants online in the USA by the year 2000. (Cohn, 1997).
By the end of 1970's, there was a total down fall in the development and it not revive. One of the major causes for this downturn was the disastrous accident at a civilian nuclear power station at the Three Mile Island in 1979. Opposition to nuclear power in Europe increased.
Again in 1986, the Chernobyl disaster brought the advancement of nuclear power generation to an abrupt halt. Thousands of people died and many more were affected for life due to the radioactive leakage.
However, the Chernobyl accident was one motivation. It helped in the exchange and promotion of best practices in the nuclear industry. It also brought to focus the need to adopt better safety regulations and the use of innovative solutions.
Another worrisome factor is the disposal of the spent waste from the nuclear reactor. About one third of the spent fuel discharged from power reactors is reused and reprocessed. The rest is in interim storage.
Basics of Nuclear Fission
Nuclear Fission is the process of spontaneous decomposition of nucleus of heavy elements into fragments accompanied by the release of appreciable amount of energy in the form of gamma rays.
Certain substances called nuclear fuels such as Uranium- 235 undergo typical fission when a neutron impinges on a U-235 nucleus to produce an unstable U-236 which further breaks down to generate neutrons. Thus a self-sustaining chain reaction propagates that releases energy at a controlled rate in a nuclear reactor. The fission products and release of three neutrons in a controlled nuclear fission reaction when a slow-moving neutron is absorbed by the nucleus of a U-235 atom is illustrated in Figure 2.
It has been estimated that the fission of 1 kg of U-235 liberates as much as heat as produced by burning 2000 tonnes of coal.
Nuclear Power Technologies
Nuclear power plants convert the energy (released from nuclear fission) and generate electricity in a method similar to thermal power stations which generate electricity from the thermal energy released from burning of fossil fuels.
U-235 or P-239 (plutonium) is commonly used as nuclear fuels in nuclear power plants. The nuclear chain reaction is controlled by using cadmium rods as moderators. These have the ability to absorb neutrons and thus control the rate of the chain reaction. The energy released from this reaction appears mainly as heat and can be removed by circulating a coolant around the reactor. Automatic and manual systems are implemented to put a check on fission reaction if unsafe conditions are detected. The heat so released and cooled is then transferred to an area where thermal energy can be utilized to produce electricity. The resultant hot coolant is used as a heat source for a boiler from which the pressurized steam generated is used to run turbines that are connected to electrical generators.
There are various reactor designs which include:
Graphite moderated reactor -This incorporates Chernobyl Reactor RBMK with unusual reactor configuration.
Light water reactor- This utilizes the commonly used Pressurized Water Reactor (PWR) and the Boiling Water Reactor (BWR).
Heavy water reactor - This uses heavy water (D2O) or water enriched with deuterium (an isotope of hydrogen). Canada's CANDU reactor is an example of heavy water reactor.
Molten salt reactor – Here special organic coolants like MSBR is used.
Liquid metal cooled reactor – Here liquid metals such as sodium or lead-bismuth alloy is used to cool the reactor core.
Gas cooled thermal reactor – This consists of the Advanced Gas cooled Reactor (AGR), the Gas Cooled Fast Breeder Reactor (GCBR) and the High Temperature Gas Cooled Reactor (HTGR). British Magnox is an example of Gas Cooled Reactor.
Safety, Health and Environment issues in Nuclear Power Plants
Maximum safety in nuclear plants as discussed in the “World Nuclear Association” can be achieved by ensuring high quality in design and construction, by making a provision to restrict the dangerous effects of fuel damage to the plant as a whole, by using high engineered equipment capable of preventing operational disturbances, by equipping problem detecting systems and radioactive leakage systems.
Challenges for the UK industry
The UK Government is committed to achieving the targets set by Kyoto Protocol and has come out with a white paper for nuclear power. However, there are challenges ahead as any resumption of nuclear investment would mean substantial investments in establishing nuclear power plants, which are expensive. There is a grounswell of opposition to the use of nuclear power itself by NGO groups such as Greenpeace. The White Paper on new-build nuclear power, in 2003 has clearly identified the lack of preparedness and the possibility of postponement of deliveries of power from nuclear sources by many years. The Government is also keenly studying the impact of disposal of hazardous nuclear waste, which is a major concern. As nuclear power plants require at least 5 years for construction, even if the approval is obtained by 2013, the earliest a plant can be put in operation is 2018. (Gordon MacKerron, 2004)
The global warming has brought a new urgency to the development of nuclear energy. Numerous technologies are available for harnessing the nuclear power. Some of the obsolete technologies being used in the British nuclear industry need to be upgraded to the next Generation IV type of nuclear reactors. The Government is in the process of finalizing the guidelines for the coming decades. Technologies such as nuclear fusion and use of nuclear power for hydrogen generation are being discussed as the possible future.
Cohn, M. S. (1997). Too Cheap to Meter: An economic and philosophical Analysis of the Nuclear Dream. Albany,NY: State University of New York Press.
David, A. (2005). Fate of fossil fuel CO2 in geologic time. Retrieved from Journal of Geophysical Research: http://geosci.uchicago.edu
Pidgeon, N. F., Irene, L., & Wouter, P. (2008). Climate change or nuclear power—No thanks! A quantitative study of public perceptions and risk framing in Britain. Global Environmental Change 18 , 69-85.
UN Framework Convention on Climate Change. (2009). Kyoto Protocol: Status of Ratification.
World Nuclear Association. (n.d.). World Nuclear Association. Retrieved from http://www.world-nuclear.org