Energy Management. Future options for nuclear energy. Essay. Marko Krejci. MSc-Degree Program Sustainable Energy Engineering.

Transcription

1 Energy Management Essay Future options for nuclear energy Marko Krejci 18 May 2003 MSc-Degree Program Sustainable Energy Engineering Department of Energy Technology Royal Institute of Technology Stockholm Sweden

2 Abstract As negative impacts of fossil fuel usage are becoming more and more obvious, society is looking for technologically and economically viable solutions. In that light interest for nuclear power is raising. Nuclear energy can be seen as an option for large-scale power production in the short and medium time scale, thus reducing the greenhouse gas emissions while the renewables reach the technological level when they will be capable of satisfying the energy needs of our society. Nevertheless, there are also several drawbacks connected with its usage. The most important ones are costs, waste management and proliferation, whereas safety and resources issues are not so crucial but should not be disregarded. If nuclear power is to stay a viable solution, those issues will have to be dealt with. This essay will give an overview of possible solutions to the problems mentioned that are being offered by the nuclear industry. 1 Introduction Nuclear energy today provides for about 6% of primary energy consumption, which equals for roughly 18% of electricity consumption. Electricity production is the sole usage of nuclear energy usage today. Expansion of nuclear energy predicted in the seventies did not happen for various reasons, which will be described in the text to follow. Strategies involving nuclear energy differ greatly between various countries, where some have chosen to completely abandon their nuclear programs (Austria, Italy), some decided to phase out nuclear power (Sweden, Germany) and some chose to continue their nuclear programmes thus planning and building new reactors (Finland, China). As negative impacts of fossil fuel usage and connected greenhouse gas (GHG) emissions are becoming more and more apparent, nuclear industry hopes that this could lead to revival of nuclear as an future energy option. Nuclear lobby 1

3 stresses practically no GHG emissions from nuclear power plants as their big advantage and a possible powerful tool for reducing the effects of fossil fuels. In this aspect, nuclear energy has an obvious advantage over fossil fuels and can be seen as a partial substitute for their usage. Furthermore the advanced state of nuclear technology compared to renewables allows for large-scale power production with competitive prices thus not affecting the economical aspect of sustainable development concept. Remaining issue is the social aspect of nuclear power. It has extremely negative reputation in the overall public, which should not be disregarded when looking at future of nuclear power. The reasons for this are several: its origin from the military nuclear programs (and with that connected proliferation issue) and the fear of possible consequences resulting from uncontrolled release of radioactive materials. If nuclear power is to represent a significant energy source in the future many of the issues still open will have to be dealt with in order to keep its comparative advantages and to diminish its disadvantages. 2 Issues of nuclear power 2.1 Waste management Nuclear power cycle produces extremely radiotoxic materials. Amount of these materials is low, but their nature requires handling with significant protective measures and long-term repositories. Even though public is more concerned about the Chernobyl-type accidents, nuclear waste is far more serious problem of nuclear power generation. Various solutions have been proposed to safely store these materials, but deep geological repositories have been chosen as a most suitable solution. Main concern generates from the fact that waste produced remains radiotoxic for extremely long time periods (~10 6 years). This makes it somewhat difficult to predict the safe containing of radioactive materials within the repository in distant future. Main concerns arise from two possible paths of radioactive materials: natural 2

4 movement of materials either by underground waters or as a result of geological processes, and the unaware intrusion of humans into the repository. On the other hand, nuclear industry claims that the actual risk (probability x consequence) posed by these repositories is relatively small, as repositories are to be built in geologically stable formations with no or very little contact with water. Also the probability of unaware intrusion is considered to be low. There are some other indicators that show this might be true: radioactive material coming from the OKLO natural reactor did not migrate significantly in around one billion years since the reactor was in operation. Very long time spans involved introduce certain uncertainty in all these predictions but also raise some other issues as if the repositories should be built in a manner that the materials reposited are reversible or not. This issue arises from the fact that the materials produced in the nuclear fuel cycle might be useful in technologies to be developed, or could be made harmless with future transmutation technologies. Tansmutation is a technology currently developed that could significantly reduce the problems mentioned. Transmutation has a potential to significantly decrease the radiotoxicity of the nuclear waste (10 3 to 10 4 years). This would not abolish the need for deep geological repositories, but would significantly reduce the volume of the waste and would make the predictions of the future behaviour of the repository far more reliable. Accelerator driven transmutation reactors, also called actinide burners, are the plants with dual purpose: burning radioactive waste from spent fuel and producing energy. Burning radioactive waste is a process that changes its composition into either short-lived or stable isotopes. Therefore transmutation technology changes the composition of radioactive waste in such a manner that its radiotoxicity falls below the level of natural uranium ore in timescale of ten thousand of years or less, instead of couple of hundred thousands of years. This might still seem as a long time, but it is a decrease by almost factor of 100, which might significantly increase the possibility to design an appropriate repository and predict its behaviour. 3

5 2.2 Economical issues Electricity coming from nuclear power plants today is one of the cheapest. Nevertheless in some countries nuclear power has proven to be uneconomical solution. The problem of nuclear energy is that it is very capital oriented and therefore very dependent on the capital costs. Costs of the fuel are representing only minor fraction of the nuclear electricity costs. In respect to that, a parallel can be drawn with the hydropower, which require large capital investments but afterwards have very low operation costs. Feasibility of nuclear power is particularly questioned by liberalisation of the energy markets. This trend favours investments with short construction periods and relatively low initial investment costs. Economical feasibility of nuclear power will mainly depend on the cost of capital and on the costs of competing technologies. Fossil fuels are seen as a competitive technology. With today s, volatile, prices of fossil fuels nuclear option might prove a very competitive option. In addition to that, introducing the carbon taxes or CO 2 sequestration technologies, which would increase the price of fossil fuel electricity, would even more enhance possible positive economical impacts of nuclear power. 2.3 Nuclear materials proliferation Civilian use of nuclear power makes nuclear materials relatively easily available to various parties, some of which might attempt to use them for terror purposes. This issue is particularly stressed in current global political situations. Materials on the front end of nuclear cycle are not very appropriate for these purposes, as the materials would require extensive infrastructure for making them useful for any kind of terrorist attack. This makes the materials on the front end of nuclear fuel cycle inappropriate for small organisations. Materials on the back end of the nuclear fuel cycle might pose a significant threat in certain circumstances. When the radioactive fuel exits the reactor it is extremely radioactive and therefore very difficult to handle without extensive equipment. After exiting the reactor the fuel may be reprocessed for extraction of plutonium for subsequent reactor fuel cycles. This plutonium 4

6 is quite appropriate for producing a nuclear weapon, even of a small scale. For this reason reprocessing of the fuel is not used in many countries having nuclear power, even though its usage in the nuclear fuel cycle is advantageous from the fuel economy point of view. Various technical solutions have been proposed to tackle these issues and the concept of Integral fast reactor is one of them. These installations would incorporate a fast breeder nuclear reactor and the fuel reprocessing plant. This would allow for on-site reprocessing of fissile material (uranium and plutonium) and reintroducing them in the fuel cycle, thus decreasing the possibility for proliferation (as no fissile material would exit the plant). The reactor would also have the possibility to burn trans-uranic elements from the waste. This feature would significantly reduce the radiotoxicity of nuclear waste as well as its amount. 2.4 Safety of installations After Chernobyl and TMI accidents, public and scientific concern has raised on the safety of nuclear installations. This has resulted in extensive research that has been conducted. As a consequence of that, today s safety of nuclear reactors is pretty high resulting in very low actual risk for the public and personnel, in comparison to the conventional power generation technologies. In that manner nuclear power plant accidents can be compared to the airplane crashes. Risk coming form airplane transportation is much lower then the one from road transportation. Despite of that fear of airplanes and public sensitivity on airplane crashes is much higher then to car crashes. Similar situation is with nuclear power plants and conventional, fossil fuelled, power plants. Nevertheless the research is continuing to increase the safety even more, as many believe that if a large-scale nuclear accident would occur now it would pose very serious problems to nuclear industry revival aspirations. Development of future nuclear reactors aims at developing passively safe installations. This means that the natural occurring forces would prevent any kind of serious accident. 5

7 2.5 Fuel resources If nuclear power is to experience a revival in the future, the fuel reserves issue would become an issue. Currently estimated conventional reserves of uranium are estimated to be somewhere between 10 and 30 million tonnes. In case of 10 million tonnes, this would cover today s demand for next 200 years. As the uranium prices are currently low there is no need for extraction of more expensive uranium or for extensive exploration of new sources. Experience with the conventional fuels has shown that the increased prices would most probably lead to extensive exploration and discovery of new uranium deposits. There is also the possibility of extraction of uranium from seawater, shales and marine phosphates. These would impose higher costs on the uranium fuel and in some cases require very large amounts of material to be handled. As the fuel cost is contributing only with around 10% in the total electricity cost of today s nuclear power generation, even using significantly more expensive uranium would not drastically increase the price of electricity produced. Nevertheless, if large-scale expansion of nuclear industry would take place, new fuel cycles would have to be considered. This would involve breeding cycles and introducing of thorium as a fertile fuel. Reserves of thorium are about two orders of magnitude larger then the uranium ones. Breeding technology is not jet developed enough for power production purposes. Several demonstration facilities have been constructed but closed down because experiencing serious technical difficulties. If breeding technology would be developed, extractable energy from uranium resources would increase for a factor of roughly 100. It can be concluded that the nuclear fuel resources are abundant at the time and have the potential to cover the demand for very long time span, even in the case of significant expansion of the nuclear industry. 6

8 3 Future scenarios Scenarios for the future usage of nuclear power vary significantly; from complete abandoning of the nuclear power, as seen by its critics, to seeing the nuclear power as the only available technology with the realistic large scale potential to reduce the greenhouse gas emissions and replace limited reserves of fossil fuels, as claimed by its advocates. Following paragraphs will try to give a rough estimation of nuclear energy potential to reduce CO 2 emissions. Current global energy demand is about 400 EJ/year (commercial primary energy). In the future this amount is expected to grow by a factor two to three in the next 50 years, both due to increase of population and energy consumption per capita. Factor of two assumes introducing significant energy efficiency measures and savings. Renewables (wind, solar, biomass) currently contribute with around 1% to the total primary energy consumption. The most optimistic predictions hope for renewables contributing with 22% to the total energy demand by the year This would in fact mean that renewables should experience the expansion by a factor of 44 within next 50 years. In addition to this optimistic assumption let us make an additional optimistic assumption that future fossil fuel energy consumption will change in a way that the percentage of natural gas used would be increased and sequestration measures introduced. According to that we can assume that the C emissions from fossil fuels would drop from today s 18 gc/mj to 12 gc/mj in In addition to this we assume that the hydropower production will grow by a factor of two, thus keeping its share in total energy production constant. The reason for not assuming more significant increase in hydro-production is already high percentage of used technically viable resources. Under these assumptions, if we would want to maintain the same carbon emissions as they are today (with no decrease), nuclear power production would have to be increased from 24 EJ to roughly 48 EJ, thus pertaining the same energy share of 6% as today. 7

9 More realistic assumptions about increase of renewables and success of partial coal phasing out and sequestration technologies, would give even higher rise of nuclear energy portion if at least today s carbon emissions want to be pertained. Results of different scenarios are shown on the table Today Primary energy [EJ] % [EJ] % [EJ] % [EJ] % Fossil fuels Hydro Nuclear Renawables Total Rel. CO 2 emmisions Today Current global energy consumption and with it connected carbon emissions from fossil fuels (average from fossil fuels ~ 18gC/MJ). 1- Nuclear energy is phased out, extremely optimistic assumptions about the growth of renewables (by factor 44 in 50 years), increased role of gas and CO 2 sequestration methods (carbon emissions from fossil fuels are roughly equal to natural gas emissions ~12gC/MJ). 2- Carbon emissions kept constant, assumptions about renewables and fossil as in scenario Moderately optimistic scenario. Expansion of renewables for a factor of 30. Somewhat lower natural gas and sequestration introduction (total carbon emissions from fossil fuels are between those of oil and those of natural gas ~15gC/MJ). Nuclear expansion to retain today s carbon emissions. Calculations presented in the table above are just rough estimations of future energy supply options. They are given to show that it will be extremely difficult to maintain carbon emissions at the present level without the nuclear 8

10 power expansion, even with very optimistic assumptions regarding the energy demand, renewables and natural gas expansion and CO 2 sequestration. In order to achieve the desired reduction of CO 2 emissions, nuclear energy contribution should be achieved by its greater expansion. In case nuclear energy would experience significant expansion in the future its role should not be limited to electricity production only. There is a potential to introduce it in the transport sector as a hydrogen-producing source. By its technical characteristics nuclear power plants are suitable for producing hydrogen. Therefore nuclear power has indirect potential to reduce GHG emissions in a transport sector as well. 4 Conclusion Nuclear power is one of the rare technologies used today, which brings up so many emotions into people. This is the reason why the decisions concerning the nuclear power in the past couple of decades were mainly politically, not scientifically driven. Nuclear energy is capable of providing a reliable, sufficient, cheap and comparably environmentally friendly energy source. It is far from being an ideal energy source, but its obvious advantages, particularly over traditional energy sources should not be neglected. In the ideal world we would have an inexhaustible, cheap and environmentally harmless energy sources, but in the real world several technical, environmental and economical issues exist. Combination of various measures and technologies as expanding renewables and nuclear, reducing coal and expanding natural gas usage, introducing sequestration of CO 2 and energy efficiency could solve today s environmental concerns. Keeping those in mind, nuclear energy seems to be one of the favourable solutions for large-scale energy supply in the future. 9

11 5 References 1. Waclaw Gudowski, Reactor Physics course, Lectures material, KTH, Stockholm, J.U. Knebel, G. Heusener, Research on Transmutation and Accelerator- Driven Systems at the Forschungszentrum Karlsruhe. Forschungszentrum Karlsruhe GMBH, Karlsruhe, Germany. Online: 2. Bob C.C. van der Zwaan, Nuclear energy: Tenfold expansion or phaseout?, IVM, Technological Forecasting and Social Change 69, Amsterdam, Netherlands, M. Lung, O. Gremm, Perspectives f the Thorium fuel cycle, Nuclear Engineering and Design 180, Elsevier, C. Pereira, E.M. Leite, Non-proliferating reprocessed nuclear fuels in pressurized water reactors: Fuel Cycle options, Ann. Nuclear Energy, Vol. 25, No 12, Pergamon, Turan Ünak, What is the potential use of Thor ium in the future energy production technology?, Progress In Nuclear Energy, Vol 37, No 1-4, Pergamon, Great Britain, Jacques Percebois, The peaceful uses of nuclear energy: technologies o f the front and back-ends of the fuel cycle, Energy Policy 31, Elsevier, I. Kimura, Review of cooperative research on Thorium fuel cycle as a promising energy source in the next century, Progress in nuclear energy, Vol 29, Elsevier, Great Britain B. Armory, L.H. Lovins, The Nuclear Option Revisited, Los Angeles Times, 8 July C. W. Forsberg, Hydrogen, nuclear energy, and the advanced high- temperature reactor, International Journal of Hydrogen Energy, Pergamon, article in press (available online at

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