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Use of fusion energy as a heat for various applications
Fusion Engineering and Design 58 – 59 (2001) 1103– 1107 www.elsevier.com/locate/fusengdes
Use of fusion energy as a heat for various applications Satoshi Konishi * Reactor System Laboratory, Department of Fusion Plasma Research, Japan Atomic Energy Research Institute, 801 -1 Mukaiyama, Naka-machi, Naka-gun, Ibaraki-ken 311 -0193, Japan
Abstract The potential use of fusion energy for various applications not limited for electric power generation is considered. The inherent need for periodical replacement of a blanket that converts neutron energy for utilization allows flexibility of use of energy by various coolants. One of the potentially attractive uses is of form of heat, at the temperature of supercritical water or superheated, where temperatures above 400– 600°C will be achieved with a ODS ferritic steel structure. In this temperature range, many of the plants such as petrochemical, paper, gas and other chemical plants can be operated; besides electricity generation is also more efficient than the light water reactor temperature. Under the constraint of the global environment problem, this feature of fusion energy improves its attractiveness by the production of low carbon fuels such as hydrogen or alcohol, as well as electricity. © 2001 Elsevier Science B.V. All rights reserved. Keywords: Fusion energy; Process heat; Synfuel; Supercritical water; Blanket
1. Introduction The utilization of fusion energy has been mostly considered for electricity generation. Previous reactor studies describe the generation process with various coolants, such as pressurized water [1], liquid lithium [2], helium gas [3,4] or superheated vapor [5], and expect them to become a major electricity supplier in the future. However, if fusion is to be a viable energy source in the future, it should fit the entire energy supply system at the time when fusion would be realized, that is the later half of the 21st century. For this purpose, the fusion program must understand the possible * Tel.: +81-292-70-7520; fax: +81-292-70-7468. E-mail address: [email protected] (S. Konishi).
features of the structure of the energy demand and supply in the future, and the utilization of energy from fusion should aim at the most suitable form. At the same time, the unique feature of fusion energy that is less suitable for other energy sources must be considered. The present study considers the utilization of fusion energy from the demand side and proposes a possible option for it, and an approach of development toward it. 2. Perspective of the future energy A number of researches are performed to predict and describe the future energy supply. Although results are strongly dependent on the future political options and broadly spread, the following observations are generally agreed [6]:
0920-3796/01/$ - see front matter © 2001 Elsevier Science B.V. All rights reserved. PII: S 0 9 2 0 - 3 7 9 6 ( 0 1 ) 0 0 5 5 9 - 2
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S. Konishi / Fusion Engineering and Design 58–59 (2001) 1103–1107
1. While the increase of energy demand in advanced nations is slow, developing countries require rapid increase of energy supply. Energy security that is not limited by fuel resource, fuel cycle or location will be expected. 2. Constraint for energy consumption will not be the fossil fuel supply that is no longer regarded to exhaust in the near future, but the global warming effect that generates carbon dioxide. 3. For the above reason, renewable energy is expected to increase. 4. For the same reason, shift of energy consumption from fossil fuel to synthetic fuels such as hydrogen will be expected. 5. Dispersed sources rather than centralized supply will be expected, while the entire supply structure will be networked. It should be noted that although the fission energy, either conventional or unconventional, is expected to play a major role, public acceptance and the nuclear proliferation problem might limit it.
3. Features of the fusion energy Previously, the features of fusion energy were considered as: unlimited fuel resource, ‘cleanliness’ and safety. They may be true to some extent, but we are now aware that they are not unique for fusion, and fusion actually has some limitations. In fact, renewable energies may be more suitable for such a statement, and practically fission may be equivalent to fusion. On the other hand, from the aspects of energy supply, fusion has the following features that may be obvious, but its implications are not well understood: 1. Fuel resource and fuel cycle are not limited by geographical or geopolitical location, climate or season. Fusion can supply energy at any location or time at the required scale. The low hazard potential of the fusion reactor is expected to allow it to be situated close to the consumers. 2. In the fusion reactors, energy is generated in the blanket by the fast neutron, which is independent from the reaction in plasma, and is
replaced at programmed intervals like fuels in fission reactors. The blanket can therefore generate the energy as heat at various temperature ranges depending on the choice of material and coolants. The first feature suggests the fusion reactor to supply its product energy for not only the grid and the distant customer, but also for closely located industries that require an intense energy source. This is not possible for renewable energies or current fission energy. Also, unlimited location will allow a fusion reactor to be situated near the existing and future consumers, while fuel cycle, particularly reprocessing of spent fuel, ultimate disposal of high level wastes and nuclear proliferation are concerned to limit the growth of fission. The second feature of fusion implies the flexibility of the use of fusion energy as a thermal plant. Unlike in the case of a fission reactor that requires entirely different types of reactors for different coolants, fusion can supply various types of heat from the same plasma. Pressurized water, liquid metal and helium will supply heat, respectively, at around 300, 500 and 900 °C or above. They can be generated from a single plant. Fig. 1 schematically shows this concept. If the plant is adequately designed and prepared, the fusion plant can change the application of energy in the middle of its lifetime, simply by changing types of blanket. This feature gives fusion energy the capability to adapt to the changing energy demands in the future.
Fig. 1. Concept of multiple use of fusion energy.
S. Konishi / Fusion Engineering and Design 58–59 (2001) 1103–1107
1105
Fig. 2. Multiple use of fusion energy and its environmental effects.
4. Use of heat Many kinds of industry use heat between 400 and 800 °C with steam as the preferred media of heat transfer. Most advanced thermal plants such as natural gas or coal fired generation stations also use supercritical water in this temperature range. Temperatures lower than 300 °C have less value as energy with poor efficiency, and limited use. Temperatures above 800 °C are also used in many industries, but in most of the cases heat is generated by the direct reaction or used as radiation from the frame. If the material for the blanket is available, steam at above 500 °C is considered to be the best target for the current development program. Blankets cooled with supercritical water, probably with martensitic steel as tubing material, can provide heat energy for sophisticated thermal generation plants and various industries. Possible customers may include, oil distillation, petrochemical, paper/pulp, and coal liquidization. When a fusion plant is located in the vicinity of these industries, it can supply process energy for both pressure and heat in the form of steam. Steam from a fusion reactor can also be used for electricity generation, and the ratio could be determined according to the needs, or will be changed when the demand changes. Heat can sequentially be used as a ‘cascade’ for efficiency, and the low temperature end can be used for
water desalination or residential heat. It is anticipated that the electricity will be the primary use of fusion energy, but such multipurpose use will increase the business prospects, and particularly moderates the disadvantage of fusion to have minimal possible capacity of approximately 2 GW thermal. Use of heat also enhances the energy efficiency of the entire fusion plant drastically. One of the important uses of heat from fusion will be the production of synfuel. As previously described, methanol or hydrogen is anticipated to become major fuels for dispersed generators such as micro-gas turbine or fuel cell, or transportation because of preferred effects on reduction of carbon dioxide emission. The steam reforming reaction, Cm Hn + H2O= CO2 + H2, is an endothermic reaction that requires a large amount of heat, and can be regarded as a transformation of fusion energy to the form of H2 chemical energy. Carbon monoxide is another possible product of reforming, and the reaction between CO and H2, 2H2 + CO = CH3OH, produces methanol, which is another synthetic fuel expected to be used as a substitute of current liquid fuels. At higher temperatures, vapor electrolysis, another form of conversion of fusion energy to hydrogen, will be possible. Fig. 2 illustrates an example of the use of energy for multiple purposes. A fusion plant will generate electricity, synthetic fuels, and fresh wa-
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S. Konishi / Fusion Engineering and Design 58–59 (2001) 1103–1107
Fig. 3. Multiple use of fusion energy and its environmental effects.
ter at the same time. In the future energy systems, fusion can provide stable electricity for base load, fuels for transportation and dispersed generators, and heat for industry. From the aspects of the contribution to the global environment, the effect of fusion energy is expected to be fourfold: 1. generating electricity without emission of carbon dioxide; 2. providing low (possibly no) carbon fuels for generators and transportation; 3. providing energy for recovery or sequestration of CO2; and 4. generating fresh water for irrigation that produces a sink of CO2. These effects are summarized in Fig. 3. It should be noted that such use of heat is impossible, or at least ineffective for renewable energies such as photovoltaic or wind, or conventional light water reactors.
gests a different approach. There will be multiple possible options of blanket coolants and the corresponding materials. For instance, a combination of ferritic steel– water, vanadium alloy–liquid lithium, SiC/SiC composite–He are well known concepts. They are in different phases of development, and probably do not fit well to the demo– prototype–commercial increment steps. These different blankets, however, can be adapted to any point of the steps of plasma devices, because they are independent of the plasma confinement device. Fig. 4 illustrates the steps of the plasma device and blankets. For instance, the demo reactor that initially has a water-cooled blanket can
5. Development strategy for blanket technology Although strategy for the development of a fusion reactor is different in each case, it is generally considered that the development will proceed by large increment of steps, such as demo reactor, prototype, and commercial reactor, each taking approximately two decades. However, the above understanding of the nature of the blanket sug-
Fig. 4. Development of plasma device and blankets.
S. Konishi / Fusion Engineering and Design 58–59 (2001) 1103–1107
replace it with a gas-cooled blanket when it is technically mature during periodical blanket replacement. This feature will provide the material and blanket development program more flexibility, and the capability to keenly reflect the commercial demands in the future. It will be important to consider the utilization of fusion energy that will be more attractive and advantageous in the future, by responding to the market. In order to do so, various types of blanket must be developed for such various purposes.
6. Conclusions As described above, periodical replacement of the blanket that has been considered as a drawback of a fusion reactor, from the view point of cost, can be regarded as an advantage to flexibly reflect the future demand. Since fusion will be a future energy source that will have to respond to unknown requirements, flexibility of the development program will be important. It should be noted that many kinds of fission reactors with different coolants, CO2, liquid metal, heavy water, molten salt, light water and helium gas, have been developed in the past, simply because a nuclear reaction is dependent on coolants. And yet, high temperature steam, which is the most effective and extensively used heat transfer media in industry, has not been generated from fission reactors. As a conclusion, it is suggested that various kinds
1107
of blankets with different coolants would be developed; in particular, the ferritic steel–steam coolant seems to be one of the most attractive options for near-term targets. Use of heat not only for power generation but also for various industrial applications will provide fusion a better chance to contribute to future energy systems. It should be further noted that the use of heat will be suitable for markets in developing countries where industrial energy will be needed and where electricity needs are not very large. Use in countries where a major part of the increase of energy consumption anticipated in the next century will be effective, and fusion is free from the limitation of nuclear fuel supply, processing and ultimate disposal of spent fuel, and proliferation control. References [1] M. Kikuchi, Steady state tokamak reactor based on the bootstrap current, Nucl. Fusion 30 (1990) 265. [2] F. Najimabadi, et al., Overview of ARIES-RS tokamak fusion power plant, Fusion Eng. Des. 41 (1998) 365. [3] S. Nisho, et al., Improved tokamak concept focusing on easy maintenance, Fusion Eng. Des. 41 (1998) 357. [4] I. Cook, J. Raeder, W. Gulden, Overview of the SEAFT and SEAL studies, J. Fusion Energy 16 (3) (1997) 245. [5] K. Okano, et al., Compact reversed shear tokamak reactor with super-heated steam cycle, Nucl. Fusion 40 (2000) 635. [6] A. Grubler, M. Jefferson, N. Nakicenovic, Global energy perspectives, a summary of the joint study by IIASA and World Energy Council, International Institute for Applied Systems Analysis Report, RR-96-10, July 1996.
Use of fusion energy as a heat for various applications Satoshi Konishi * Reactor System Laboratory, Department of Fusion Plasma Research, Japan Atomic Energy Research Institute, 801 -1 Mukaiyama, Naka-machi, Naka-gun, Ibaraki-ken 311 -0193, Japan
Abstract The potential use of fusion energy for various applications not limited for electric power generation is considered. The inherent need for periodical replacement of a blanket that converts neutron energy for utilization allows flexibility of use of energy by various coolants. One of the potentially attractive uses is of form of heat, at the temperature of supercritical water or superheated, where temperatures above 400– 600°C will be achieved with a ODS ferritic steel structure. In this temperature range, many of the plants such as petrochemical, paper, gas and other chemical plants can be operated; besides electricity generation is also more efficient than the light water reactor temperature. Under the constraint of the global environment problem, this feature of fusion energy improves its attractiveness by the production of low carbon fuels such as hydrogen or alcohol, as well as electricity. © 2001 Elsevier Science B.V. All rights reserved. Keywords: Fusion energy; Process heat; Synfuel; Supercritical water; Blanket
1. Introduction The utilization of fusion energy has been mostly considered for electricity generation. Previous reactor studies describe the generation process with various coolants, such as pressurized water [1], liquid lithium [2], helium gas [3,4] or superheated vapor [5], and expect them to become a major electricity supplier in the future. However, if fusion is to be a viable energy source in the future, it should fit the entire energy supply system at the time when fusion would be realized, that is the later half of the 21st century. For this purpose, the fusion program must understand the possible * Tel.: +81-292-70-7520; fax: +81-292-70-7468. E-mail address: [email protected] (S. Konishi).
features of the structure of the energy demand and supply in the future, and the utilization of energy from fusion should aim at the most suitable form. At the same time, the unique feature of fusion energy that is less suitable for other energy sources must be considered. The present study considers the utilization of fusion energy from the demand side and proposes a possible option for it, and an approach of development toward it. 2. Perspective of the future energy A number of researches are performed to predict and describe the future energy supply. Although results are strongly dependent on the future political options and broadly spread, the following observations are generally agreed [6]:
0920-3796/01/$ - see front matter © 2001 Elsevier Science B.V. All rights reserved. PII: S 0 9 2 0 - 3 7 9 6 ( 0 1 ) 0 0 5 5 9 - 2
1104
S. Konishi / Fusion Engineering and Design 58–59 (2001) 1103–1107
1. While the increase of energy demand in advanced nations is slow, developing countries require rapid increase of energy supply. Energy security that is not limited by fuel resource, fuel cycle or location will be expected. 2. Constraint for energy consumption will not be the fossil fuel supply that is no longer regarded to exhaust in the near future, but the global warming effect that generates carbon dioxide. 3. For the above reason, renewable energy is expected to increase. 4. For the same reason, shift of energy consumption from fossil fuel to synthetic fuels such as hydrogen will be expected. 5. Dispersed sources rather than centralized supply will be expected, while the entire supply structure will be networked. It should be noted that although the fission energy, either conventional or unconventional, is expected to play a major role, public acceptance and the nuclear proliferation problem might limit it.
3. Features of the fusion energy Previously, the features of fusion energy were considered as: unlimited fuel resource, ‘cleanliness’ and safety. They may be true to some extent, but we are now aware that they are not unique for fusion, and fusion actually has some limitations. In fact, renewable energies may be more suitable for such a statement, and practically fission may be equivalent to fusion. On the other hand, from the aspects of energy supply, fusion has the following features that may be obvious, but its implications are not well understood: 1. Fuel resource and fuel cycle are not limited by geographical or geopolitical location, climate or season. Fusion can supply energy at any location or time at the required scale. The low hazard potential of the fusion reactor is expected to allow it to be situated close to the consumers. 2. In the fusion reactors, energy is generated in the blanket by the fast neutron, which is independent from the reaction in plasma, and is
replaced at programmed intervals like fuels in fission reactors. The blanket can therefore generate the energy as heat at various temperature ranges depending on the choice of material and coolants. The first feature suggests the fusion reactor to supply its product energy for not only the grid and the distant customer, but also for closely located industries that require an intense energy source. This is not possible for renewable energies or current fission energy. Also, unlimited location will allow a fusion reactor to be situated near the existing and future consumers, while fuel cycle, particularly reprocessing of spent fuel, ultimate disposal of high level wastes and nuclear proliferation are concerned to limit the growth of fission. The second feature of fusion implies the flexibility of the use of fusion energy as a thermal plant. Unlike in the case of a fission reactor that requires entirely different types of reactors for different coolants, fusion can supply various types of heat from the same plasma. Pressurized water, liquid metal and helium will supply heat, respectively, at around 300, 500 and 900 °C or above. They can be generated from a single plant. Fig. 1 schematically shows this concept. If the plant is adequately designed and prepared, the fusion plant can change the application of energy in the middle of its lifetime, simply by changing types of blanket. This feature gives fusion energy the capability to adapt to the changing energy demands in the future.
Fig. 1. Concept of multiple use of fusion energy.
S. Konishi / Fusion Engineering and Design 58–59 (2001) 1103–1107
1105
Fig. 2. Multiple use of fusion energy and its environmental effects.
4. Use of heat Many kinds of industry use heat between 400 and 800 °C with steam as the preferred media of heat transfer. Most advanced thermal plants such as natural gas or coal fired generation stations also use supercritical water in this temperature range. Temperatures lower than 300 °C have less value as energy with poor efficiency, and limited use. Temperatures above 800 °C are also used in many industries, but in most of the cases heat is generated by the direct reaction or used as radiation from the frame. If the material for the blanket is available, steam at above 500 °C is considered to be the best target for the current development program. Blankets cooled with supercritical water, probably with martensitic steel as tubing material, can provide heat energy for sophisticated thermal generation plants and various industries. Possible customers may include, oil distillation, petrochemical, paper/pulp, and coal liquidization. When a fusion plant is located in the vicinity of these industries, it can supply process energy for both pressure and heat in the form of steam. Steam from a fusion reactor can also be used for electricity generation, and the ratio could be determined according to the needs, or will be changed when the demand changes. Heat can sequentially be used as a ‘cascade’ for efficiency, and the low temperature end can be used for
water desalination or residential heat. It is anticipated that the electricity will be the primary use of fusion energy, but such multipurpose use will increase the business prospects, and particularly moderates the disadvantage of fusion to have minimal possible capacity of approximately 2 GW thermal. Use of heat also enhances the energy efficiency of the entire fusion plant drastically. One of the important uses of heat from fusion will be the production of synfuel. As previously described, methanol or hydrogen is anticipated to become major fuels for dispersed generators such as micro-gas turbine or fuel cell, or transportation because of preferred effects on reduction of carbon dioxide emission. The steam reforming reaction, Cm Hn + H2O= CO2 + H2, is an endothermic reaction that requires a large amount of heat, and can be regarded as a transformation of fusion energy to the form of H2 chemical energy. Carbon monoxide is another possible product of reforming, and the reaction between CO and H2, 2H2 + CO = CH3OH, produces methanol, which is another synthetic fuel expected to be used as a substitute of current liquid fuels. At higher temperatures, vapor electrolysis, another form of conversion of fusion energy to hydrogen, will be possible. Fig. 2 illustrates an example of the use of energy for multiple purposes. A fusion plant will generate electricity, synthetic fuels, and fresh wa-
1106
S. Konishi / Fusion Engineering and Design 58–59 (2001) 1103–1107
Fig. 3. Multiple use of fusion energy and its environmental effects.
ter at the same time. In the future energy systems, fusion can provide stable electricity for base load, fuels for transportation and dispersed generators, and heat for industry. From the aspects of the contribution to the global environment, the effect of fusion energy is expected to be fourfold: 1. generating electricity without emission of carbon dioxide; 2. providing low (possibly no) carbon fuels for generators and transportation; 3. providing energy for recovery or sequestration of CO2; and 4. generating fresh water for irrigation that produces a sink of CO2. These effects are summarized in Fig. 3. It should be noted that such use of heat is impossible, or at least ineffective for renewable energies such as photovoltaic or wind, or conventional light water reactors.
gests a different approach. There will be multiple possible options of blanket coolants and the corresponding materials. For instance, a combination of ferritic steel– water, vanadium alloy–liquid lithium, SiC/SiC composite–He are well known concepts. They are in different phases of development, and probably do not fit well to the demo– prototype–commercial increment steps. These different blankets, however, can be adapted to any point of the steps of plasma devices, because they are independent of the plasma confinement device. Fig. 4 illustrates the steps of the plasma device and blankets. For instance, the demo reactor that initially has a water-cooled blanket can
5. Development strategy for blanket technology Although strategy for the development of a fusion reactor is different in each case, it is generally considered that the development will proceed by large increment of steps, such as demo reactor, prototype, and commercial reactor, each taking approximately two decades. However, the above understanding of the nature of the blanket sug-
Fig. 4. Development of plasma device and blankets.
S. Konishi / Fusion Engineering and Design 58–59 (2001) 1103–1107
replace it with a gas-cooled blanket when it is technically mature during periodical blanket replacement. This feature will provide the material and blanket development program more flexibility, and the capability to keenly reflect the commercial demands in the future. It will be important to consider the utilization of fusion energy that will be more attractive and advantageous in the future, by responding to the market. In order to do so, various types of blanket must be developed for such various purposes.
6. Conclusions As described above, periodical replacement of the blanket that has been considered as a drawback of a fusion reactor, from the view point of cost, can be regarded as an advantage to flexibly reflect the future demand. Since fusion will be a future energy source that will have to respond to unknown requirements, flexibility of the development program will be important. It should be noted that many kinds of fission reactors with different coolants, CO2, liquid metal, heavy water, molten salt, light water and helium gas, have been developed in the past, simply because a nuclear reaction is dependent on coolants. And yet, high temperature steam, which is the most effective and extensively used heat transfer media in industry, has not been generated from fission reactors. As a conclusion, it is suggested that various kinds
1107
of blankets with different coolants would be developed; in particular, the ferritic steel–steam coolant seems to be one of the most attractive options for near-term targets. Use of heat not only for power generation but also for various industrial applications will provide fusion a better chance to contribute to future energy systems. It should be further noted that the use of heat will be suitable for markets in developing countries where industrial energy will be needed and where electricity needs are not very large. Use in countries where a major part of the increase of energy consumption anticipated in the next century will be effective, and fusion is free from the limitation of nuclear fuel supply, processing and ultimate disposal of spent fuel, and proliferation control. References [1] M. Kikuchi, Steady state tokamak reactor based on the bootstrap current, Nucl. Fusion 30 (1990) 265. [2] F. Najimabadi, et al., Overview of ARIES-RS tokamak fusion power plant, Fusion Eng. Des. 41 (1998) 365. [3] S. Nisho, et al., Improved tokamak concept focusing on easy maintenance, Fusion Eng. Des. 41 (1998) 357. [4] I. Cook, J. Raeder, W. Gulden, Overview of the SEAFT and SEAL studies, J. Fusion Energy 16 (3) (1997) 245. [5] K. Okano, et al., Compact reversed shear tokamak reactor with super-heated steam cycle, Nucl. Fusion 40 (2000) 635. [6] A. Grubler, M. Jefferson, N. Nakicenovic, Global energy perspectives, a summary of the joint study by IIASA and World Energy Council, International Institute for Applied Systems Analysis Report, RR-96-10, July 1996.