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Japanese perspective of fusion nuclear technology from ITER to DEMO
Fusion Engineering and Design 83 (2008) 865–869
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Fusion Engineering and Design journal homepage: www.elsevier.com/locate/fusengdes
Japanese perspective of fusion nuclear technology from ITER to DEMO Satoru Tanaka a , Hideyuki Takatsu b,∗ a b
University of Tokyo, Hongo 7-3-1, Bunkyo-ku, Tokyo 113-8656 Japan Division of Fusion Energy Technology, Fusion Research and Development Directorate, Atomic Energy Agency, Japan
a r t i c l e
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Article history: Available online 22 August 2008 Keywords: Fusion nuclear technology ITER project Broader Approach activities Test blanket module DEMO
a b s t r a c t The world fusion community is now launching the construction of ITER, the first nuclear-grade fusion machine in the world. In parallel with the ITER Program, Broader Approach (BA) activities also started this year with the collaboration of Japan and EURATOM, mainly at the Rokkasho BA site in Japan, as complementary activities toward DEMO. The Atomic Energy Commission of Japan reviewed the ongoing ‘Third Phase Basic Program of Fusion Research and Development’, and then issued the results of the review, ‘National Policy of Future Fusion Research and Development’, in November 2005. In this report, it was anticipated that ITER will be made operational in a decade and that its programmatic objective can be met in the following seven or eight years. Under this assumption, the report presented a road map toward DEMO and beyond and identified R&D items in fusion nuclear technology that are indispensable for fusion energy utilization. In the present paper, Japanese view and policy on fusion nuclear technology in ITER and beyond will be summarized, and an overview is given of a minimum set of R&D items in fusion nuclear technology toward DEMO that are essential for fusion energy utilization. © 2008 Published by Elsevier B.V.
1. Introduction In 1992, the Atomic Energy Commission of Japan laid down the ‘Third Phase Basic Program of Fusion Research and Development’ [1], whose central element was ITER. Over the next ten years, significant research progress was made; also, the world fusion program began shifting into a new stage. Taking into account these changes, in June 2003, the Atomic Energy Commission of Japan set up an ad hoc committee on basic issues on fusion research and development and charged it to check and review the progress of fusion R&D and to investigate future basic programs. In response, the ad hoc committee thoroughly reviewed the ongoing activities and achievements obtained so far under the Third Phase Basic Program and discussed a possible road map and portfolio so as to enable Japan to initiate the Fourth Phase Basic Program, where construction and operation of DEMO will be the central element. The ad hoc committee issued in November 2005 a report entitled ‘National Policy of Future Fusion Research and Development’ [2], which was endorsed by the Atomic Energy Commission of Japan. In this report, it was anticipated that ITER will be made operational in a decade, and that its programmatic objective can be
∗ Corresponding author at: Mukouyama 801-1, Naka-shi, Ibaraki-ken 311-0193, Japan. Tel.: +81 29 270 7500; fax: +81 29 270 7468. E-mail address: [email protected] (H. Takatsu). 0920-3796/$ – see front matter © 2008 Published by Elsevier B.V. doi:10.1016/j.fusengdes.2008.06.028
met in the following seven or eight years. Under this assumption, the report presented a road map toward the DEMO and identified R&D items on fusion nuclear technology indispensable for fusion energy utilization. The ITER Organization Establishment Agreement and related documents were signed on 21 November 2006 and are expected to enter into force in the autumn of 2007. The BA Agreement also entered into force on 1 June 2007. As such, these two large international projects on fusion program will embark in the year 2007, and world fusion program is entering into a new ‘ITER era’. These projects are central elements in the world fusion program along the pathway toward DEMO and essential for an early realization of fusion energy utilization. The present paper provides an overview of the Japanese view and policy on fusion nuclear technology in ITER and beyond, and presents a minimum set of R&D items in fusion nuclear technology toward DEMO, which is essential for fusion energy utilization. 2. Fusion energy strategy from ITER to DEMO and beyond Early realization of fusion energy utilization is important in order to contribute to the resolution of global environmental problems and provide energy security. In order to put fusion power into practical use, it is necessary to make fusion systems technically practical as a power generation system, as well as to be economically competitive against other energy systems. To this end, it is
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necessary to ensure economical competitiveness, and to demonstrate safety and operation reliability for the commercialization of the fusion energy. Japan considers ITER a core program in the road map toward DEMO, in which the scientific and technological feasibility of fusion energy will be demonstrated, namely: demonstration of techniques for the control of extended burning plasmas; demonstration of essential reactor technologies in an integrated system; and proofof-principle integrated performance of DEMO blankets through the ITER Test Blanket Program. Through active participation in the ITER Project, including the areas of component fabrication, construction and assembly, commissioning, operation, exploitation and decommissioning phases, the technology basis for the design and construction of DEMO will be established. The next step beyond ITER is DEMO, whose mission is to simultaneously realize steady-state fusion core plasmas with high Q values and power generation on a practical scale. The economic aspect is understood to be an important factor in the development of DEMO, and should be duly taken into account. DEMO is intended to be the final integrated tokamak facility before the development of commercial fusion reactors, and will be upgraded during its operational phase so as to demonstrate to the utility industry and the public its attractiveness as a power generation system, mainly in terms of foreseeable economic competitiveness, safety, reliability and timeliness. Japan’s planned Tokamak type DEMO will have a core dimension similar to that of ITER with a power generation capability on the gigawatt (GW) scale. DEMO needs to operate continuously for about one year with high plant efficiency, high output stability at the transmission end, and with an overall tritium breeding ratio greater than 1. Major technical requirements for DEMO are outlined below: 1. For the fusion core plasma, high plasma pressure operation is required to increase fusion power density to several times that of ITER, so as to realize thermal output of 3–4 GW. It also requires non-inductive, steady-state operation and the control of heat and particles to enable continuous operation over at least one year. 2. The first wall and blanket structure must withstand a neutron fluence of about 10–20 MW/m2 and heat flux of 1 MW/m2 . The blanket must achieve tritium fuel self-sufficiency with high reliability. The divertor must withstand higher heat and particle fluxes than the first wall, and it must accommodate these load conditions and stay operational for several years. Scheduled maintenance of the first wall and divertor is expected once per three to five years, and down-time for maintenance should be minimized so as not to jeopardize plant availability. Continuous and reliable operation of the heating and current drive system up to one year should be established. 3. DEMO is the first plant system which supplies its own tritium fuel by means of an in situ tritium-breeding blanket and which drives a high-temperature and high-pressure medium containing tritium. Safe and reliable systems to process, handle and monitor a large amount of tritium fuel should be incorporated in DEMO. 4. In view of the economic competitiveness of fusion power generation system, construction cost of DEMO should be suppressed to an acceptable level, taking future commercialization into account. Two types of DEMO designs are under development in Japan: the SlimCS, led by JAEA, and the Demo-CREST, by CRIEPI (Central Research Institute of Electric Power Industry). The SlimCS features a low-aspect-ratio (A = 2.6) design with a reduced-size central solenoid and a thin toroidal field coil system, resulting in a reduced weight of the machine and eventually a minimiz-
ing construction cost [3]. In addition, the low aspect ratio has the merits of achieving vertical stability for high elongation and high normalized-beta plasma, which leads to a high power density device with reasonable physics requirements. The Demo-CREST design envisages two-staged operations: a demonstration and a development phases. In the first phase, the design will operate with plasma performances extrapolated from the early stages of ITER operation; will be constructed using materials and technologies proven on, or extrapolated from, ITER, and will demonstrate power generation up to 500 MW. In the latter phase, it will show the possibility for economic competitiveness by introducing advanced plasma performances and high performance blankets [4]. It should be underlined that, in the process of fusion energy system development, collaborations with fission areas are becoming more important. The expertise and knowledge available in the fission areas are deemed of significant value in the development of fusion nuclear systems, such as safety and licensing, treatment and disposal of radwaste, neutron irradiation damage of materials, nuclear data, computational science, and so on. Therefore, these collaborations should be further strengthened. 3. Roles of ITER project 3.1. Construction Much R&D progress has been made during the ITER Engineering Design Phase by the Japanese ITER Implementing Agency (IA), the former JAERI (now re-structured as JAEA) in collaboration with domestic universities and industries, particularly in the areas of fabrication technologies development for key ITER components, and in demonstrating of their performance. On the basis of these achievements, JAEA, now the Japanese ITER Domestic Agency (DA), is partly responsible for procurement, during the construction phase, of the following critical fusion technology components: superconducting magnets; in-vessel components (blanket/first wall and divertor); heating/current drive systems; blanket remote handling system; tritium safety system; and diagnostics system. Procurement activities will be launched shortly for some long-lead-time components such as the magnet, while procurement of the other components will follow, subject to the ITER project schedule. These procurement activities are essential to construct a technology knowledge base within the domestic research body and industries for the design and fabrication of DEMO components. 3.2. Operation Commissioning of the ITER facility is planned to start in the year 2014 and first plasma is planned for 2016. The Japanese DA plans to engage heavily during the commissioning and operation phases to contribute to the successful operations of ITER. It is understood that performance of the ITER components and their safe and reliable operation will be evaluated, demonstrated, and enhanced step-bystep during the commissioning and operation phases proceeding from hydrogen to full non-inductive current drive high duty DT phase. Operational experiences and knowledge gained during these phases are essential to the construction of a technology basis for a fusion reactor and for the design of DEMO. In these phases, technologies essential to a fusion reactor will be demonstrated in an integrated fashion under real fusion environments. In this sense, the following aspects are deemed of high importance: (1) demonstration of superconducting magnet performance under plasma discharges and radiation environments; (2) demonstration and improvements of remote maintenance technologies for components which exposed to radiation environments and subjected to operational deformations; (3) demonstration of
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plant-scale tritium-fuel processing and safe handling technologies; (4) control technology of tokamak components and plant system compatible with plasma operations; and (5) demonstration of invessel components performance compatible with heat, particle and electromagnetic loads, and with fuel injection, vacuum pumping and heat removal systems. 3.3. Exploitation Tests of DEMO-relevant breeding blankets are an important mission of ITER. The Test Blanket Module (TBM) program is therefore central to the development of simultaneous tritium breeding and power extraction technology. The ITER Parties plan to install and test their TBMs from the first day of ITER operation. Three equatorial ports are available for TBM testing, and with two TBMs per port, six TBMs can be simultaneously installed and tested [5]. Experimental data from TBM is essential for demonstration of the principles of tritium self-sufficiency in an integrated blanket system; development of the technology necessary to install breeding capabilities in DEMO; and for providing integrated experimental results on reliability, safety, environmental impact, and efficiency of fusion energy extraction systems. Successful TBM experiments in ITER represent an essential step on the path to DEMO in all the ITER Parties’ fusion development plans. The Japanese plan to take a leading role in development, design, fabrication and testing in ITER of a water-cooled ceramic breeder TBM concept and to participate as a partner for the other three TBM concepts: a He-cooled ceramic breeder concept; a He-cooled liquid LiPb concept; and a liquid lithium concept. For the water-cooled ceramic breeder TBM, led by JAEA, the materials to be used are well qualified and fabrication technologies of the TBM elements have been well developed [6]. Structural and functional irradiation data
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for the blanket materials has been accumulated mainly on fission reactors, and the engineering database for use in the TBM design is sufficiently mature, including that for the tritium recovery system. Neutronics performance of the design concept was validated on a 14-MeV neutron source, the FNS device located at/operated by JAEA. Recently, the main thrust of R&D efforts are being placed on thermal and mechanical performance testing of the TBM by using large-scale mock-ups and on development of advanced breeding/multiplying materials. On the other three TBM concepts, mainly led by universities, technological bases have shown good progress, and discussions toward international collaborations will be started. 4. Roles of accompanying programs 4.1. Broader Approach (BA) activities The BA activities were started as collaborative activities between Japan and EURATOM in the field of fusion energy research, either in support of or complementary to the ITER Project along the pathway toward DEMO, with the ultimate objective of an early realization of fusion energy for peaceful purposes [7]. The BA Agreement was signed on 5 February 2007 and entered into force on 1 June 2007. The BA Activities comprise the following three projects: (1) the Engineering Validation and Engineering Design Activities for the International Fusion Materials Irradiation Facility (IFMIF/EVEDA); (2) the International Fusion Energy Research Center (IFERC); and (3) the Satellite Tokamak Program. Projects are shown in Fig. 1. The first two projects will be implemented in Rokkasho and the third in Naka, both located in Japan. The duration of the projects is ten years (six years for IFMIF/EVEDA). An implementing organization has been established and technical activities have begun.
Fig. 1. Three projects to be implemented in the BA Activities: (1) the Engineering Validation and Engineering Design Activities for the International Fusion Materials Irradiation Facility (IFMIF/EVEDA); (2) the International Fusion Energy Research Center (IFERC); and (3) the Satellite Tokamak Program. Inter-relations among the three Projects and with the ITER Projects are illustrated.
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IFMIF is an accelerator-driven, intense neutron irradiation facility based on d-Li stripping reactions, capable of producing neutron irradiation environments similar to those in a fusion reactor, and is an essential facility to validate candidate materials for the DEMO. The main objective of the EVEDA phase is to complete engineering design of the facility and to implement validating R&Ds, eventually to prepare for the future construction of the facility. IFERC serves the function, inter alia, of DEMO design and R&D coordination center with the mission of coordinating scientific and technological activities toward DEMO. The expected outcomes include conceptual designs of DEMO, where progress in complementary technology R&D will be incorporated. Technology R&D will be implemented on issues of mutual interest, including: advanced structural materials (reduced-activation ferritic–martensitic steels and SiCf /SiC composites), advanced blanket materials (breeders and multipliers), and tritium technologies [8]. These activities will be carried out over the next ten years and will contribute either to the construction of technology bases for materials standards and structural design codes, or to the development of advanced blankets and tritium technologies, for DEMO. The Satellite Tokamak Program concerns the upgrade of the existing JT-60 facility to an advanced superconducting tokamak (JT-60SA) and subsequent joint exploitation. From the technology viewpoint, construction and operation experience from JT-60SA will be of high value both for ITER and for DEMO.
handling are important for application toward DEMO, and will be pursued in parallel with ITER and BA activities. High fluence neutron irradiation testing of candidate reduced activation structural materials in fission reactors or other facilities and companied post irradiation evaluations should be continued so as to better understand irradiation effects on material properties, to examine their feasibility in DEMO and to narrow down candidates for future testing on IFMIF. To this end, it is encouraged to obtain irradiation data at greater than 80 dpa in the near future. Advancements in developing several key components in ITER are essential toward the realization of economically competitive DEMO. For example, higher magnetic field strength is indispensable to create a compact DEMO, and thus R&D efforts along this line are highly encouraged. Moreover, higher beam energy for the neutral beam (NB) system and higher system efficiencies, higher reliabilities, and CW compatibility for the NB and Electron Cyclotron systems are necessary for compliance with DEMO design. A particular challenge for DEMO is tritium fuel self-sufficiency, including controlled handling of a high-temperature and highpressure medium that contains a large amount of tritium. The amount of tritium in DEMO is much greater than that in ITER. Tremendous R&D efforts are required to process, manage, monitor and control a large amount of tritium inside and outside the reactor core.
4.2. Other activities complementary to ITER toward DEMO
According to the ITER Final Design Report [9], major basic performances with regard to the technical objectives are expected to be achieved, at shortest, in about seven years (in the early 2020s) after the start of ITER operation. For early realization of fusion energy, it is desirable to proceed to the construction of DEMO after the achievement of basic performance in ITER.
In addition to the BA activities, R&D on neutron irradiation effects on reduced activation structural materials, high performance of superconducting magnet and heating/current drive systems beyond ITER capabilities, and tritium processing and safe
5. Road map to DEMO
Fig. 2. A possible road map toward DEMO with a minimum set of R&D items.
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Therefore, it is necessary to implement an integrated R&D program in addition to, and in parallel with, the ITER Project, so that the decision to move on to the DEMO phase can be made in a timely manner. A road map from ITER to DEMO and a minimum set of transitional R&D items are illustrated in Fig. 2. If the DEMO engineering design can be initiated in the early 2020s, followed by the smooth initiation of DEMO construction, it will be possible to begin operation of DEMO in the 2030s, with the mission to demonstrate continuous power generation, safety, operational reliability and economic competitiveness. In this scenario, it is foreseeable to commercialize fusion energy by the middle of this century. By realizing this challenging and meaningful road map, fusion energy could contribute to global nuclear energy supply in the latter half of this century. 6. Summary In June 2007, the BA Activities were formally initiated. The ITER project follows shortly. The world fusion program is entering into a new ‘ITER era’, and these two projects are central in the world fusion program along the pathway toward DEMO, as well as for an early realization of commercial fusion energy utilization. With these new developments in the world fusion program, and against the background of significant research progress achieved so far in Japan, an overview of Japanese view and policy on ITER and beyond was presented, mainly from the viewpoint of fusion nuclear technology, including a possible road map and a minimum set of fusion nuclear technology R&D items toward DEMO that are essential for fusion energy utilization. The view and policy shown are largely based on the report issued in November 2005 by the ad hoc
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committee on basic issues on fusion research and development, entitled ‘National Policy of Future Nuclear Fusion Research and Development’, and endorsed by the Atomic Energy Commission of Japan. As far as fusion nuclear technologies are concerned, active participation in the ITER Project through the component fabrication, construction and assembly, commissioning, operation, exploitation and decommissioning phases is essential to achieve a sound technology basis for the design and construction of DEMO. In particular, Japanese leadership and participation in the TBM testing are of the highest priority. The BA Activities are designed to be complementary to ITER and to DEMO, and smooth and effective implementation of the three BA Projects are important for a timely start-up of the DEMO phase. The other key R&Ds on reduced activation structural materials, high performance of superconducting magnet and heating/current drive systems and tritium processing and safe handling should be pursued in parallel in a consistent manner with the development of DEMO design studies. References [1] HP of the Atomic Energy Commission of Japan, http://www.aec.go.jp/ jicst/NC/senmon/kakuyugo2/siryo/kettei/kettei920609.htm. [2] HP of the Atomic Energy Commission of Japan, http://www.aec.go.jp/jicst/NC/ senmon/kakuyugo2/siryo/kettei/houkoku051026 e/index.htm. [3] K. Tobita, et al., Nucl. Fusion 47 (2007) 892–899. [4] R. Hiwatari, et al., Nucl. Fusion 47 (2007) 387–394. [5] L. Giancarli, et al., Fusion Eng. Des. 81 (2006) 393–406. [6] M. Enoeda, et al., Fusion Eng. Des. 81 (2006) 415–424. [7] S. Matsuda, in: Presented at the 24th SOFT, Warsaw, Fusion Eng. Des., in press. [8] T. Nishitani et al., ICFRM-13, Nice (2007). [9] ITER Final Design Report, ITER EDA Documentation Series No. 14, IAEA (1999).
Contents lists available at ScienceDirect
Fusion Engineering and Design journal homepage: www.elsevier.com/locate/fusengdes
Japanese perspective of fusion nuclear technology from ITER to DEMO Satoru Tanaka a , Hideyuki Takatsu b,∗ a b
University of Tokyo, Hongo 7-3-1, Bunkyo-ku, Tokyo 113-8656 Japan Division of Fusion Energy Technology, Fusion Research and Development Directorate, Atomic Energy Agency, Japan
a r t i c l e
i n f o
Article history: Available online 22 August 2008 Keywords: Fusion nuclear technology ITER project Broader Approach activities Test blanket module DEMO
a b s t r a c t The world fusion community is now launching the construction of ITER, the first nuclear-grade fusion machine in the world. In parallel with the ITER Program, Broader Approach (BA) activities also started this year with the collaboration of Japan and EURATOM, mainly at the Rokkasho BA site in Japan, as complementary activities toward DEMO. The Atomic Energy Commission of Japan reviewed the ongoing ‘Third Phase Basic Program of Fusion Research and Development’, and then issued the results of the review, ‘National Policy of Future Fusion Research and Development’, in November 2005. In this report, it was anticipated that ITER will be made operational in a decade and that its programmatic objective can be met in the following seven or eight years. Under this assumption, the report presented a road map toward DEMO and beyond and identified R&D items in fusion nuclear technology that are indispensable for fusion energy utilization. In the present paper, Japanese view and policy on fusion nuclear technology in ITER and beyond will be summarized, and an overview is given of a minimum set of R&D items in fusion nuclear technology toward DEMO that are essential for fusion energy utilization. © 2008 Published by Elsevier B.V.
1. Introduction In 1992, the Atomic Energy Commission of Japan laid down the ‘Third Phase Basic Program of Fusion Research and Development’ [1], whose central element was ITER. Over the next ten years, significant research progress was made; also, the world fusion program began shifting into a new stage. Taking into account these changes, in June 2003, the Atomic Energy Commission of Japan set up an ad hoc committee on basic issues on fusion research and development and charged it to check and review the progress of fusion R&D and to investigate future basic programs. In response, the ad hoc committee thoroughly reviewed the ongoing activities and achievements obtained so far under the Third Phase Basic Program and discussed a possible road map and portfolio so as to enable Japan to initiate the Fourth Phase Basic Program, where construction and operation of DEMO will be the central element. The ad hoc committee issued in November 2005 a report entitled ‘National Policy of Future Fusion Research and Development’ [2], which was endorsed by the Atomic Energy Commission of Japan. In this report, it was anticipated that ITER will be made operational in a decade, and that its programmatic objective can be
∗ Corresponding author at: Mukouyama 801-1, Naka-shi, Ibaraki-ken 311-0193, Japan. Tel.: +81 29 270 7500; fax: +81 29 270 7468. E-mail address: [email protected] (H. Takatsu). 0920-3796/$ – see front matter © 2008 Published by Elsevier B.V. doi:10.1016/j.fusengdes.2008.06.028
met in the following seven or eight years. Under this assumption, the report presented a road map toward the DEMO and identified R&D items on fusion nuclear technology indispensable for fusion energy utilization. The ITER Organization Establishment Agreement and related documents were signed on 21 November 2006 and are expected to enter into force in the autumn of 2007. The BA Agreement also entered into force on 1 June 2007. As such, these two large international projects on fusion program will embark in the year 2007, and world fusion program is entering into a new ‘ITER era’. These projects are central elements in the world fusion program along the pathway toward DEMO and essential for an early realization of fusion energy utilization. The present paper provides an overview of the Japanese view and policy on fusion nuclear technology in ITER and beyond, and presents a minimum set of R&D items in fusion nuclear technology toward DEMO, which is essential for fusion energy utilization. 2. Fusion energy strategy from ITER to DEMO and beyond Early realization of fusion energy utilization is important in order to contribute to the resolution of global environmental problems and provide energy security. In order to put fusion power into practical use, it is necessary to make fusion systems technically practical as a power generation system, as well as to be economically competitive against other energy systems. To this end, it is
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necessary to ensure economical competitiveness, and to demonstrate safety and operation reliability for the commercialization of the fusion energy. Japan considers ITER a core program in the road map toward DEMO, in which the scientific and technological feasibility of fusion energy will be demonstrated, namely: demonstration of techniques for the control of extended burning plasmas; demonstration of essential reactor technologies in an integrated system; and proofof-principle integrated performance of DEMO blankets through the ITER Test Blanket Program. Through active participation in the ITER Project, including the areas of component fabrication, construction and assembly, commissioning, operation, exploitation and decommissioning phases, the technology basis for the design and construction of DEMO will be established. The next step beyond ITER is DEMO, whose mission is to simultaneously realize steady-state fusion core plasmas with high Q values and power generation on a practical scale. The economic aspect is understood to be an important factor in the development of DEMO, and should be duly taken into account. DEMO is intended to be the final integrated tokamak facility before the development of commercial fusion reactors, and will be upgraded during its operational phase so as to demonstrate to the utility industry and the public its attractiveness as a power generation system, mainly in terms of foreseeable economic competitiveness, safety, reliability and timeliness. Japan’s planned Tokamak type DEMO will have a core dimension similar to that of ITER with a power generation capability on the gigawatt (GW) scale. DEMO needs to operate continuously for about one year with high plant efficiency, high output stability at the transmission end, and with an overall tritium breeding ratio greater than 1. Major technical requirements for DEMO are outlined below: 1. For the fusion core plasma, high plasma pressure operation is required to increase fusion power density to several times that of ITER, so as to realize thermal output of 3–4 GW. It also requires non-inductive, steady-state operation and the control of heat and particles to enable continuous operation over at least one year. 2. The first wall and blanket structure must withstand a neutron fluence of about 10–20 MW/m2 and heat flux of 1 MW/m2 . The blanket must achieve tritium fuel self-sufficiency with high reliability. The divertor must withstand higher heat and particle fluxes than the first wall, and it must accommodate these load conditions and stay operational for several years. Scheduled maintenance of the first wall and divertor is expected once per three to five years, and down-time for maintenance should be minimized so as not to jeopardize plant availability. Continuous and reliable operation of the heating and current drive system up to one year should be established. 3. DEMO is the first plant system which supplies its own tritium fuel by means of an in situ tritium-breeding blanket and which drives a high-temperature and high-pressure medium containing tritium. Safe and reliable systems to process, handle and monitor a large amount of tritium fuel should be incorporated in DEMO. 4. In view of the economic competitiveness of fusion power generation system, construction cost of DEMO should be suppressed to an acceptable level, taking future commercialization into account. Two types of DEMO designs are under development in Japan: the SlimCS, led by JAEA, and the Demo-CREST, by CRIEPI (Central Research Institute of Electric Power Industry). The SlimCS features a low-aspect-ratio (A = 2.6) design with a reduced-size central solenoid and a thin toroidal field coil system, resulting in a reduced weight of the machine and eventually a minimiz-
ing construction cost [3]. In addition, the low aspect ratio has the merits of achieving vertical stability for high elongation and high normalized-beta plasma, which leads to a high power density device with reasonable physics requirements. The Demo-CREST design envisages two-staged operations: a demonstration and a development phases. In the first phase, the design will operate with plasma performances extrapolated from the early stages of ITER operation; will be constructed using materials and technologies proven on, or extrapolated from, ITER, and will demonstrate power generation up to 500 MW. In the latter phase, it will show the possibility for economic competitiveness by introducing advanced plasma performances and high performance blankets [4]. It should be underlined that, in the process of fusion energy system development, collaborations with fission areas are becoming more important. The expertise and knowledge available in the fission areas are deemed of significant value in the development of fusion nuclear systems, such as safety and licensing, treatment and disposal of radwaste, neutron irradiation damage of materials, nuclear data, computational science, and so on. Therefore, these collaborations should be further strengthened. 3. Roles of ITER project 3.1. Construction Much R&D progress has been made during the ITER Engineering Design Phase by the Japanese ITER Implementing Agency (IA), the former JAERI (now re-structured as JAEA) in collaboration with domestic universities and industries, particularly in the areas of fabrication technologies development for key ITER components, and in demonstrating of their performance. On the basis of these achievements, JAEA, now the Japanese ITER Domestic Agency (DA), is partly responsible for procurement, during the construction phase, of the following critical fusion technology components: superconducting magnets; in-vessel components (blanket/first wall and divertor); heating/current drive systems; blanket remote handling system; tritium safety system; and diagnostics system. Procurement activities will be launched shortly for some long-lead-time components such as the magnet, while procurement of the other components will follow, subject to the ITER project schedule. These procurement activities are essential to construct a technology knowledge base within the domestic research body and industries for the design and fabrication of DEMO components. 3.2. Operation Commissioning of the ITER facility is planned to start in the year 2014 and first plasma is planned for 2016. The Japanese DA plans to engage heavily during the commissioning and operation phases to contribute to the successful operations of ITER. It is understood that performance of the ITER components and their safe and reliable operation will be evaluated, demonstrated, and enhanced step-bystep during the commissioning and operation phases proceeding from hydrogen to full non-inductive current drive high duty DT phase. Operational experiences and knowledge gained during these phases are essential to the construction of a technology basis for a fusion reactor and for the design of DEMO. In these phases, technologies essential to a fusion reactor will be demonstrated in an integrated fashion under real fusion environments. In this sense, the following aspects are deemed of high importance: (1) demonstration of superconducting magnet performance under plasma discharges and radiation environments; (2) demonstration and improvements of remote maintenance technologies for components which exposed to radiation environments and subjected to operational deformations; (3) demonstration of
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plant-scale tritium-fuel processing and safe handling technologies; (4) control technology of tokamak components and plant system compatible with plasma operations; and (5) demonstration of invessel components performance compatible with heat, particle and electromagnetic loads, and with fuel injection, vacuum pumping and heat removal systems. 3.3. Exploitation Tests of DEMO-relevant breeding blankets are an important mission of ITER. The Test Blanket Module (TBM) program is therefore central to the development of simultaneous tritium breeding and power extraction technology. The ITER Parties plan to install and test their TBMs from the first day of ITER operation. Three equatorial ports are available for TBM testing, and with two TBMs per port, six TBMs can be simultaneously installed and tested [5]. Experimental data from TBM is essential for demonstration of the principles of tritium self-sufficiency in an integrated blanket system; development of the technology necessary to install breeding capabilities in DEMO; and for providing integrated experimental results on reliability, safety, environmental impact, and efficiency of fusion energy extraction systems. Successful TBM experiments in ITER represent an essential step on the path to DEMO in all the ITER Parties’ fusion development plans. The Japanese plan to take a leading role in development, design, fabrication and testing in ITER of a water-cooled ceramic breeder TBM concept and to participate as a partner for the other three TBM concepts: a He-cooled ceramic breeder concept; a He-cooled liquid LiPb concept; and a liquid lithium concept. For the water-cooled ceramic breeder TBM, led by JAEA, the materials to be used are well qualified and fabrication technologies of the TBM elements have been well developed [6]. Structural and functional irradiation data
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for the blanket materials has been accumulated mainly on fission reactors, and the engineering database for use in the TBM design is sufficiently mature, including that for the tritium recovery system. Neutronics performance of the design concept was validated on a 14-MeV neutron source, the FNS device located at/operated by JAEA. Recently, the main thrust of R&D efforts are being placed on thermal and mechanical performance testing of the TBM by using large-scale mock-ups and on development of advanced breeding/multiplying materials. On the other three TBM concepts, mainly led by universities, technological bases have shown good progress, and discussions toward international collaborations will be started. 4. Roles of accompanying programs 4.1. Broader Approach (BA) activities The BA activities were started as collaborative activities between Japan and EURATOM in the field of fusion energy research, either in support of or complementary to the ITER Project along the pathway toward DEMO, with the ultimate objective of an early realization of fusion energy for peaceful purposes [7]. The BA Agreement was signed on 5 February 2007 and entered into force on 1 June 2007. The BA Activities comprise the following three projects: (1) the Engineering Validation and Engineering Design Activities for the International Fusion Materials Irradiation Facility (IFMIF/EVEDA); (2) the International Fusion Energy Research Center (IFERC); and (3) the Satellite Tokamak Program. Projects are shown in Fig. 1. The first two projects will be implemented in Rokkasho and the third in Naka, both located in Japan. The duration of the projects is ten years (six years for IFMIF/EVEDA). An implementing organization has been established and technical activities have begun.
Fig. 1. Three projects to be implemented in the BA Activities: (1) the Engineering Validation and Engineering Design Activities for the International Fusion Materials Irradiation Facility (IFMIF/EVEDA); (2) the International Fusion Energy Research Center (IFERC); and (3) the Satellite Tokamak Program. Inter-relations among the three Projects and with the ITER Projects are illustrated.
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IFMIF is an accelerator-driven, intense neutron irradiation facility based on d-Li stripping reactions, capable of producing neutron irradiation environments similar to those in a fusion reactor, and is an essential facility to validate candidate materials for the DEMO. The main objective of the EVEDA phase is to complete engineering design of the facility and to implement validating R&Ds, eventually to prepare for the future construction of the facility. IFERC serves the function, inter alia, of DEMO design and R&D coordination center with the mission of coordinating scientific and technological activities toward DEMO. The expected outcomes include conceptual designs of DEMO, where progress in complementary technology R&D will be incorporated. Technology R&D will be implemented on issues of mutual interest, including: advanced structural materials (reduced-activation ferritic–martensitic steels and SiCf /SiC composites), advanced blanket materials (breeders and multipliers), and tritium technologies [8]. These activities will be carried out over the next ten years and will contribute either to the construction of technology bases for materials standards and structural design codes, or to the development of advanced blankets and tritium technologies, for DEMO. The Satellite Tokamak Program concerns the upgrade of the existing JT-60 facility to an advanced superconducting tokamak (JT-60SA) and subsequent joint exploitation. From the technology viewpoint, construction and operation experience from JT-60SA will be of high value both for ITER and for DEMO.
handling are important for application toward DEMO, and will be pursued in parallel with ITER and BA activities. High fluence neutron irradiation testing of candidate reduced activation structural materials in fission reactors or other facilities and companied post irradiation evaluations should be continued so as to better understand irradiation effects on material properties, to examine their feasibility in DEMO and to narrow down candidates for future testing on IFMIF. To this end, it is encouraged to obtain irradiation data at greater than 80 dpa in the near future. Advancements in developing several key components in ITER are essential toward the realization of economically competitive DEMO. For example, higher magnetic field strength is indispensable to create a compact DEMO, and thus R&D efforts along this line are highly encouraged. Moreover, higher beam energy for the neutral beam (NB) system and higher system efficiencies, higher reliabilities, and CW compatibility for the NB and Electron Cyclotron systems are necessary for compliance with DEMO design. A particular challenge for DEMO is tritium fuel self-sufficiency, including controlled handling of a high-temperature and highpressure medium that contains a large amount of tritium. The amount of tritium in DEMO is much greater than that in ITER. Tremendous R&D efforts are required to process, manage, monitor and control a large amount of tritium inside and outside the reactor core.
4.2. Other activities complementary to ITER toward DEMO
According to the ITER Final Design Report [9], major basic performances with regard to the technical objectives are expected to be achieved, at shortest, in about seven years (in the early 2020s) after the start of ITER operation. For early realization of fusion energy, it is desirable to proceed to the construction of DEMO after the achievement of basic performance in ITER.
In addition to the BA activities, R&D on neutron irradiation effects on reduced activation structural materials, high performance of superconducting magnet and heating/current drive systems beyond ITER capabilities, and tritium processing and safe
5. Road map to DEMO
Fig. 2. A possible road map toward DEMO with a minimum set of R&D items.
S. Tanaka, H. Takatsu / Fusion Engineering and Design 83 (2008) 865–869
Therefore, it is necessary to implement an integrated R&D program in addition to, and in parallel with, the ITER Project, so that the decision to move on to the DEMO phase can be made in a timely manner. A road map from ITER to DEMO and a minimum set of transitional R&D items are illustrated in Fig. 2. If the DEMO engineering design can be initiated in the early 2020s, followed by the smooth initiation of DEMO construction, it will be possible to begin operation of DEMO in the 2030s, with the mission to demonstrate continuous power generation, safety, operational reliability and economic competitiveness. In this scenario, it is foreseeable to commercialize fusion energy by the middle of this century. By realizing this challenging and meaningful road map, fusion energy could contribute to global nuclear energy supply in the latter half of this century. 6. Summary In June 2007, the BA Activities were formally initiated. The ITER project follows shortly. The world fusion program is entering into a new ‘ITER era’, and these two projects are central in the world fusion program along the pathway toward DEMO, as well as for an early realization of commercial fusion energy utilization. With these new developments in the world fusion program, and against the background of significant research progress achieved so far in Japan, an overview of Japanese view and policy on ITER and beyond was presented, mainly from the viewpoint of fusion nuclear technology, including a possible road map and a minimum set of fusion nuclear technology R&D items toward DEMO that are essential for fusion energy utilization. The view and policy shown are largely based on the report issued in November 2005 by the ad hoc
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committee on basic issues on fusion research and development, entitled ‘National Policy of Future Nuclear Fusion Research and Development’, and endorsed by the Atomic Energy Commission of Japan. As far as fusion nuclear technologies are concerned, active participation in the ITER Project through the component fabrication, construction and assembly, commissioning, operation, exploitation and decommissioning phases is essential to achieve a sound technology basis for the design and construction of DEMO. In particular, Japanese leadership and participation in the TBM testing are of the highest priority. The BA Activities are designed to be complementary to ITER and to DEMO, and smooth and effective implementation of the three BA Projects are important for a timely start-up of the DEMO phase. The other key R&Ds on reduced activation structural materials, high performance of superconducting magnet and heating/current drive systems and tritium processing and safe handling should be pursued in parallel in a consistent manner with the development of DEMO design studies. References [1] HP of the Atomic Energy Commission of Japan, http://www.aec.go.jp/ jicst/NC/senmon/kakuyugo2/siryo/kettei/kettei920609.htm. [2] HP of the Atomic Energy Commission of Japan, http://www.aec.go.jp/jicst/NC/ senmon/kakuyugo2/siryo/kettei/houkoku051026 e/index.htm. [3] K. Tobita, et al., Nucl. Fusion 47 (2007) 892–899. [4] R. Hiwatari, et al., Nucl. Fusion 47 (2007) 387–394. [5] L. Giancarli, et al., Fusion Eng. Des. 81 (2006) 393–406. [6] M. Enoeda, et al., Fusion Eng. Des. 81 (2006) 415–424. [7] S. Matsuda, in: Presented at the 24th SOFT, Warsaw, Fusion Eng. Des., in press. [8] T. Nishitani et al., ICFRM-13, Nice (2007). [9] ITER Final Design Report, ITER EDA Documentation Series No. 14, IAEA (1999).