Fusion Energy Power for future generations

Transcription

1 Fusion Energy Power for future generations this fraction will increase to 70% in the next twenty years, unless action is taken. The uneven distribution of energy sources around the world holds great potential for international conflict. Recent international tensions have again highlighted the importance of this energysecurity issue. Plasma image from the START experiment at UKAEA, Culham. With an increasing world population and a growing economy, the demand for energy is certain to grow. To bring the standard of living of the world population up to western standards by the year 2100 will require up to five times as much energy as we use today. New solutions will be required for providing an answer to both the energy demand and the emission problems associated with our present energy system. Fusion energy, the energy source of the sun and the stars, has seen remarkable progress over the last decades, and is now ready to move out of the laboratory. Background Energy supply must be geared to ensuring the uninterrupted physical availability of energy products, at a price that is affordable for all consumers, while respecting environmental concerns and looking towards sustainable development. Environmental concerns have highlighted the weaknesses of present energy sources. Sustained economic growth and the increasing use of energy services are contributing to the increase in greenhouse gas emissions. Climate change is a major challenge and a longterm battle for the international community. Apart from climate change mitigation, another important issue is the need felt by many countries to generate their energy independent of foreign fuel supply. A recent green paper of the European Commission points out that Europe imports about 50% of its energy, and that The need for new non-polluting and sustainable forms of energy to reduce the energy dependency of developed countries and to contribute to climate change minimisation is therefore becoming urgent. To meet this challenge, all energy options have to be considered that can contribute to an optimised future energy mix. Fusion, which would be particularly suited for the centralised supply of baseload electricity, appears as one of the most attractive long-term energy options because of the widespread and abundant distribution at low cost of its fuel supplies and because of its favourable safety and environmental features. Fusion energy would ideally complement intermittent renewable energy sources in the future energy mix. In a fusion reactor, light atoms (isotopes of hydrogen) fuse together and release a very large amount of energy. The fusion process takes place at an extremely high temperature of 150 million degrees Celsius. At this temperature, matter forms a plasma, a hot gas of charged particles. The energy released in the fusion reaction is used to generate electricity. Fusion research started some decades ago, but only at the end of the 1960s did major scientific events, such as the use of tokamak machines for the confinement of hot plasmas, enhance the level of knowledge sufficiently to put fusion on the path towards a future energy source. The fuels of a fusion reactor are 1

2 A look inside the Joint European Torus (), the largest fusion experiment in the world. is located in Culham, GB. widely distributed around the world, cheaply available, and inexhaustible. The long-term objective of fusion programmes in the international community is the creation of prototype plants for power stations to meet the needs of society: operational safety, environmental compatibility, economic viability. During the last years, very important results have been achieved, confirming that fusion should now be considered as a credible energy option having the potential for clean, large-scale power generation. Safety and Environmental Issues The safety and environmental aspects of possible future fusion power stations have been assessed in many and extensive studies, all of which have confirmed the attractive characteristics of fusion power. The operation of fusion power stations will make no adverse contribution to global climate change as no greenhouse gases are produced. There is no possibility of uncontrolled power runaway since inherent physical processes limit power excursions of the fusion plasma. Moreover, the plasma vessel of a fusion reactor will only contain enough fuel for a relatively short burning time less than a minute. The fusion process can therefore be stopped without problem and with no consequences. Even in the case of a total loss of active cooling, melting of the reactor structures is excluded due to the low density of decay heat of the materials present in the reactor. Even in the worst possible inplant driven accident scenario, the risk to the general public would be below the level at which evacuation of the area aournd the power plant is required. The fusion fuel cycle does not involve any input of radioactive material and there is no radioactive waste associated with spent fuel. Radioactivity is present in the intermediate fuel, tritium, but there is no radioactive fuel cycle outside the power station as the tritium is made inside the plant. Fusion power stations will not make use of uranium, plutonium or other fissile materials; none of the materials required are subject to the non-proliferation treaties, so the presence of illicit fertile or fissile materials could be easily detected. The radiotoxicity of the activated structural materials generated by a fusion reactor during its lifetime will only last for approximately one hundred years, after which the activity is comparable to that of the ash from coal power stations. After this cooling-down period almost all the materials in a fusion power station could be disposed of as non-active waste, recycled, or given shallow-land disposal. Therefore, fusion waste would 2

3 Progress Fusion: figure-of-merit (the 'triple product') doubles every 1.8 years T3 ST 4004 Alcator A TFR 8080 not constitute a permanent burden for future generations. Progress in Fusion Research PLT TFTR Alcator C 8086 Target ITER PDX DIII TFTR DIII-D Pentium 4 Merced P7 Pentium Pro P6 Pentium P5 Moore's Law: number of transistors doubles every 2 years Year The progress of fusion research through the years measured by the triple product, which is an indication of the performance of a fusion plasma. For comparison, the development of computer chips is indicated. entific programme has started, and now serves as a research facility hosting a large number of international research efforts. has produced significant fusion power in deuterium/tritium plasmas (up to 16 MW) in the short pulses characteristic of existing experimental devices. Break-even conditions, where the fusion output power equals the external input power required to heat the plasma, have almost been reached. Moreover, has demonstrated that fusion devices can be operated safely with tritium fuel and that radioactive structures can be maintenanced and modified using remote handling techniques. Thanks to the success of and other experiments, the world fusion community is ready to take the Next Step of constructing a larger device, which will produce plasmas under reactor conditions of high power gain and provide a reliable basis for proceeding to a demonstration reactor, capable of producing electricity. This project, under the name of ITER, is a collaboration between EU, Japan, Russia, Canada, China and the USA. ITER will produce ten times more power than is needed as input. There has been great scientific and technological progress in developing fusion over the last decade. The figure above shows the progress of the so-called triple product, a figure-of-merit which measures the performance of a fusion plasma. The triple product has seen an increase of a factor of in the last thirty years, and another factor of 6 is needed to arrive at the level required for a power plant. In the figure, the progress is compared to that of computer chips. The central research facility of the European Fusion Programme is the Joint European Torus (), in Culham, Great Brittain. The focusing of significant European fusion research funding on has made it the pre-eminent fusion facility in the world and allowed Europe to take major strides in fusion research. is complemented by a number of specialized smaller devices run by more than 20 individual member states. was approved in 1974, began operations in 1983, and met its planned operational goals on schedule in Since then, a new sci- An artist s impression of the Joint European Torus, 3

4 The next step fusion experiment: ITER external costs are substantial. Appreciation of the importance of external costs has become widespread in recent years. Studies show that fusion, along with wind, belongs in the class of low external cost sources 1. The current ITER design is a cost-effective tokamak, which allows the study of burning plasmas under physics conditions which can be extrapolated to a reactor and in which important reactor technologies will be integrated. The ITER participants now have to approve the construction of the machine and select the site where this international project should come to life. A decision about how to proceed with ITER is expected in the course of In parallel to the realisation of ITER, the Fusion Programme will need to come with further technology developments in order to build a commercial electricity-producing reactor. Technological progress is required in several areas, especially in the development of plasma-facing materials sustaining high heat loads and of low activation structural materials. Economics of Fusion Electricity To be a viable commercial option, fusion must be competitive with other mid-21 st century electricity-generation technologies. As in nuclear fission, the investment cost dominates in assessing the cost of electricity (equivalent to more than 70%). The cost of fuel would represent a negligible percentage. Many studies have been conducted within the framework of the fusion programme to evaluate electricity costs for fusion and compare them with those of other advanced or renewable energy sources. Comparing the projected costs of electricity from energy sources producing steady power, the projected fusion costs are roughly comparable to those from clean (pollution abated) coal plants and about fifty percent larger than those from fission. The projected fusion costs are also comparable to the projected costs of electricity from typical renewables 1. In comparison to renewables, fusion has the advantage of being able to provide continous base load electricity, without additional cost for storage. The direct costs of electricity generation do not include costs such as those associated with environmental damage or adverse impacts upon health. In the case of some present sources of electricity, these For comparison: the external costs of electricity from present European coal-fired plants are high, twenty times greater than the estimated external costs of fusion electricity. About one half of the estimated external costs of the coal-fired stations is attributed to climate change. Fusion in the Future Energy Mix In the future, fusion will be part of an energy system in which several energy sources complement each other. The evolution of the energy mix is investigated using energy scenario s, which describe the use and production of energy for a certain period in the future. These scenario s can be modeled on a computer. In studies using this approach, fusion power was incorporated into existing economic modelling of energy scenarios for Europe 2, up to the end of this century. The most important constraints applied in these studies were on carbon dioxide production. The important constraints applied to fusion were assumed limits to the speed with which it could be deployed. These studies show, broadly, that fusion could bring a contribution of at least twenty percent of the electricity supply by the end of this century, mainly constrained by the assumed rate at which it could be deployed. However, fusion would capture little or none of the market if there were no environmental constraints or little economic development. Since the environmentally-constrained scenarios were constructed to have minimal cost, satisfying the demand without fusion would be more expensive: the sums involved are huge, dwarfing the costs of fusion development. Fusion is currently not considered an immediately helpful CO2-mitigation technology, because it will not be economically available in the coming decades. Intermediate solutions, like the substitution of coal by natural gas and CO2-seques- 4

5 Inside the TEXTOR tokamak, located in Jülich, Germany The upward trend in future energy demands is a reality that needs to be faced. Emission of greenhouse gasses affecting the climate, the adverse health effects caused by the present energy system, and the energy-security issue all demand radical changes in the way we produce our energy. We need a full range of safe and environmentally-friendly energy options applicable to the near-term, medium-term and long-term. With its inherent environmental and safety advantages fusion should be seen as an important element in any global strategy designed to allow sustainable economic growth. As fusion is particularly suited for base load electricity production, it is the ideal complement of other renewable sources in the future energy mix. Fusion technology, brought to fruition, will be an asset of the utmost value to give to our descendants. tration could, however, help to reduce the greenhouse gas emissions in the short and medium term and fusion could then be available when a replacement of these technologies is necessary because of the exhaustion of resources and issues of energy security. With these long-term prospects in mind, it is clear that public funding is still needed for further fusion energy development. Since the relevant industries are oriented towards short-term profit, their early participation in fusion funding cannot be expected. However, industry will readily benefit from spin-off emerging from pioneering projects such as the large scale superconducting coils required for a fusion reactor. A Roadmap to Fusion Energy In a report to the EU Council Presidency published mid 2001, a group of independent experts chaired by David King (Chief Scientific Advisor to UK Prime Minister Tony Blair) advocate a fast track approach towards the development of commercial fusion energy. The fast track roadmap consists of two generations of devices, first the next step ITER, and second a prototype power plant DEMO/ PROTO. This development should be combined with the parallel testing of appropriate plasma-facing materials. The second device should demonstrate the technical feasibility, potential reliability of operation and economic attractiveness of fusion energy, and should serve as a credible prototype for a commercial power plant. DEMO/PROTO could achieve net electricity production about 35 years after the decision to construct ITER, after which commercial deployment of fusion energy could start. Whether the fast track roadmap can be followed strongly depends on political will. If the development steps that are performed in parallel in the fast track scenario are instead performed sequentially, the time to net electricity production will be extended to about fifty years. The fast track scenario could substantially reduce the total amount of funding to reach the long-term objective, but this does require increased short-term funding. The fast-track timescale has found resonance outside of Europe as well: following a request by the Department of Energy of the USA, the American FESAC advisory committee published a report January this year, detailing the requirements for achieving fusion-powered electricity to the grid in 35 years. A Need for Fusion? Notes 1) G. Borelli et al., Socio-Economic Research on Fusion, Summary of EU Research , EFDA RE RE-1, July ) P. Lako, J.R. Ybema, and A.J. Seebregts, Long-term Scenarios and the Role of Fusion Power, ECN-C , Petten, February Contact Prof. N.J. Lopes Cardozo, FOM-institute for plasma physics, P.O. Box 1207, 3430 BE Nieuwegein, The Netherlands, Tel. +31 (0) , Fax: +31 (0) , cardozo@rijnh.nl. On the Internet Starting point for the European Fusion Program The next step fusion experiment ITER The largest fusion experiment in the world, in Culham, GB General information on fusion FOM - Institute for Plasma Physics Rijnhuizen 5