Final Report of the Committee on a Strategic Plan for U.S. Burning Plasma Research (2019) / Chapter Skim
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4 Advancing Magnetic Fusion Toward an Economical Energy Source
4 Advancing Magnetic Fusion Toward an Economical Energy Source
Pages 89-133
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From page 89... ...
Additionally, research and innovations are needed to reduce the size and cost of the fusion power system and to attract industries and utilities to pursue fusion energy-based electricity production for the United States. This chapter describes the research needed to advance magnetic fusion toward an economical energy source beyond what will be conducted with the International Thermonuclear Experimental Reactor (ITER)
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From page 90... ...
When ITER operation establishes key burning plasma science and when the accompanying research program has simultaneously advanced burning plasma sci ence, materials science, fusion nuclear science, and engineering science, the design of the compact fusion pilot plant can be finalized and construction commence. As identified in the committee's interim report,2 without the research accompanying ITER aimed to improve and fully enable the fusion system, the United States risks being overtaken as our partners advance the science and technology required to deliver fusion energy.
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From page 91... ...
Fusion Energy Sciences Advisory Committee (FESAC) has recommended research leading to the construction of an FNSF prior to DEMO.3,4 The FNSF would be the first part of a two-step approach to a fusion power plant that would commence in parallel with the study of burning plasma in ITER.
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From page 92... ...
FNSF approaches the characteristics of a power-producing fusion energy device and that vary the shape of the magnets that confine the toroidal burning plasma.5 The pathways considered by Korea and China proceed directly from ITER to DEMO, but the Korean and Chinese DEMO facilities would be designed and oper ated in two phases. Higher-power and longer-duration fusion power would occur in the second phase after the first phase established burning plasma opera ing sce t narios and some fusion nuclear technologies.
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From page 93... ...
Addition ally, fusion nuclear components will need to safely and efficiently fuel, exhaust, breed, confine, extract, and separate unprecedented quantities of tritium.10 The development path and technical missions to progress beyond ITER toward a commercial fusion power plant were recently summarized based on a detailed system engineering study for an FNSF. In addition to the study of burning plasma and control, the development of fusion technology is categorized into three steps.
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From page 94... ...
• In place of two-step approach with a FNSF having a mission limited to fusion component development followed by a second DEMO facility, recent science and technology advances suggest a compact fusion pilot plant might be built at a cost comparable to previous FNSF designs while being ulti mately capable of demonstrating the overall systems efficiency required to produce electricity. Relative to previous pathways to commercial fusion energy, a compact fusion pathway targets smaller device size, lower capital cost, and shorter development steps.
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From page 95... ...
electrical utilities seeking lower capital-cost capacity additions, shorter construction times, and more flexible siting options that result from smaller power-plant footprint.14 FIGURE 4.2 Illustration of the demonstration fusion power plant (DEMO) approach and the pilot plant approach to next-step fusion energy development devices.
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From page 96... ...
The scientific and technical opportunities for developing a compact fusion pilot plant are described below. The important relationship between compact size and high magnetic field is discussed along with the engineering challenges associ ated with high-temperature superconducting magnets and the plasma science and materials science challenges associated with continuous operation and high-power plasma exhaust.
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From page 97... ...
. To reach burning plasma conditions, the ITER super n conducting magnets are the largest ever built, with a total magnetic stored energy of 51 GJ, a nominal mechanical stress of 600 MPa, and a magnetic field strength of B = 5.3 T within the plasma.19 Today's opportunity for compact magnet fusion e nergy results from the potential for high-field superconducting magnets.
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From page 98... ...
The magnetic field strength used for conceptual design studies of compact fusion devices are limited by the high stresses within the materials needed to support the magnets.26 However, DOE's 2018 FESAC report Transformative Enabling Capabilities for Efficient Advance Toward Fusion Energy27 concluded a "consensus within the magnet community that existing high strength stainless steel and superalloy materials are adequate for projected fusion require ments" (p.
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From page 99... ...
Finding: Although additional research, including magnet engineering research, is needed to demonstrate the viability of the compact pathway to fusion power, the combination of new high-field superconducting magnet technology with advanced burning plasma science is a significant opportunity to decrease the size and cost of a magnetic fusion power system. Plasma Power Handing for Compact Fusion Power handling is one of the crucial challenges for magnetic confinement f usion, and the compact pathway to economical fusion path may either heighten or help to mitigate this challenge.
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From page 100... ...
that scale in proportion to qA/B.34 Self-consistent models for detached divertors indicate the impurity fraction required for detachment scales in proportion to the ratio of the escaping fusion power to the poloidal magnetic field. For this reason, a compact pilot plant operating at lower power but higher magnetic field may be preferred to a higher-power fusion system because the compact design allows lower impurity concentration within the detached divertor region.
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From page 101... ...
Achieving Steady Uninterrupted Operation for Compact Fusion A commercial fusion power source will need to produce electricity continu ously for several months at a time. A critical goal for a compact fusion pilot plant is to demonstrate uninterrupted operation and to establish the basic science and technology needed for commercial fusion power.
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From page 102... ...
Ghoniem, P.W. Humrickhouse, et al., 2018, Overview of the fusion nuclear science facility, a credible break-in step on the path to fusion energy, Fusion Engineering and Design 135:236-270, http://dx.doi.org/10.1016/j.fusengdes.2017.05.081.
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From page 103... ...
operation around βN = 3.5, which is twice the normalized pressure in the ITER reference scenario. These high oloidal p beta regimes also have improved energy confinement, making high poloidal beta regimes promising modes to operate a commercial fusion power device and a f sion DEMO.
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From page 104... ...
operating at high magnetic field and within an advanced fusion confinement regime would produce significant fusion power while operating at lower plasma current and full bootstrap current. Similar levels of fusion power were described by the HTS-ST pilot plant design developed by Menard and co-authors.50 As was described in the Chapter 3 section on "Extending ITER Performance," just as recent advances in theory and simulation provide opportunities to signifi cantly extend ITER performance, these advances also improve the prospects for a compact fusion pilot plant.
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From page 105... ...
Taking advantage of these research opportunities would increase the technical readiness needed for the design and construction of a compact fusion pilot plant. High-Critical-Temperature Superconducting Magnets Magnetic fusion energy requires access to the highest possible magnetic fields that can be maintained with superconducting magnets.
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From page 106... ...
Lee, and E.E. Hellstrom, 2014, Isotropic round-wire multifilament cuprate superconductor for generation of magnetic fields above 30 T, Nature Materials 13:375.
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From page 107... ...
The status and future directions of high magnetic field science, including the potential for fusion energy applications, were assessed in 2013.58 Important goals of the Magnet Development Program of the DOE Office of High Energy Physics are to investigate fundamental aspects of magnet design that lead to substantial performance improvements and cost reduction.59 Progress in the use of HTS magnets for fusion energy applications have been reported; however, additional engineering research is needed to gain full-size operating experience with fusion magnets, including magnet quench detection and protection, demountable coil development and testing, conductor stress/strain management, and characteriza tion of radiation resistance. Finding: While additional R&D is needed to establish the technical basis for large high-field HTS magnets, the growing industrial capability to produce HTS conductor, opportunities to partner with industry and other DOE pro gram offices, and the rapid progress in HTS magnets may enable significant reductions in the size of magnetic fusion devices and support the compact lower-cost pathway to fusion development.
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From page 108... ...
Furthermore, significant developments in SiC/SiC composites have been demonstrated in the ceramic gas turbine industry, and have transformative potential for nuclear fusion pilot plant components. The Transformative Enabling Capabilities report also called attention to novel tritium extraction technologies proposed for liquid metal breeding blankets and for plasma-facing components.
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From page 109... ...
Additionally, engineer ing strategies need to be developed for subsystem and component reliability and efficient remote maintenance of fusion nuclear components. Development of a compact fusion pilot plant with higher magnetic field strength will require development of a new generation of higher frequency sources for radio waves and millimeter waves and also technology research to extend the capabili ties and efficiency of higher-power launching apparatus and transmission systems.
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From page 110... ...
Blanket and Tritium Fuel Cycle Research The integrated first wall and breeding blanket of a fusion reactor will need to operate at high temperature to ensure efficient conversion of fusion power into electricity in addition to generating tritium in the blanket. The tritium generated in the blanket, as well as the unburned tritium fuel from the plasma exhaust, will need to be efficiently extracted and processed for re-introduction to the plasma.
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From page 111... ...
A sig nificant enhancement of research activities is needed to validate blanket concepts and the science and technologies of the tritium fuel cycle prior to constructing a compact fusion pilot plant. The 2018 Transformative Enabling Capabilities report64 highlighted a number of technologies that show tremendous potential for fusion power development.
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From page 112... ...
These concepts, along with innovations and promising new methods to separate and process tritium, will be essential to the development of a compact, lower cost fusion reactor. PRE-PILOT-PLANT RESEARCH PROGRAM FOR THE COMPACT FUSION PATHWAY Conceptual design studies for various compact fusion pilot plants have con cluded that in addition to a burning plasma experiment research is needed to understand the interconnected science and technology for the high-field super conducting magnets and for the fusion components that surround the plasma, convert fusion power into useful heat, and breed and recover tritium.
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From page 113... ...
Humrickhouse, et al., 2018, Overview of the fusion nuclear science facility, a credible break-in step on the path to fusion energy, Fusion Engineering and Design 135:236-270, http://dx.doi.org/10.1016/j.fusengdes.2017.05.081.
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From page 114... ...
This two-stage approach reduces the cost and accelerates fusion demonstration in the compact fusion pathway. The key elements of the pre-pilot-plant research strategy, in addition to the burning plasma science and technology that will be learned from ITER operation, are the following: • Systems engineering for a compact fusion pilot plant, • Advanced materials modeling for fusion technology, • Testing of large-bore, high-field HTS magnets for magnetic fusion, • Developing long-lifetime materials for fusion, • Advancing tritium science and blanket technologies, • A fusion neutron irradiation facility for prototypical materials qualification, • Demonstrating sustained high-power-density fusion plasmas with opti mized plasma exhaust configuration for compact fusion, and • Continued development of fusion-enabling technologies needed to heat, measure, and control the burning plasma and to safely maintain the com ponents within the compact fusion pilot plant.
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From page 115... ...
Industrial experience could be developed by industrial participation in testing of component prototypes prior to the decision to construct a compact fusion pilot plant. Advanced Materials Modeling for Fusion Technology The United States has made significant advances in multi-scale modeling of plasma materials interactions and high-energy neutron induced degradation of structural materials.66,67,68 These multi-scale models attack the complex materi als degradation issues from both a "bottom-up" atomistic-based approach and a "top-down" continuum perspective, and they focus on the hierarchical integration of kinetic processes for species reactions and diffusion to model microstructure evolution over experimental timescales.
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From page 116... ...
On March 9, 2018, MIT and a newly formed private company, Common wealth Fusion Systems, announced the start of a staged research effort for fusion experiments and fusion power systems based on advances in high-temperature superconductors.69 Other efforts to develop large HTS magnets include the Magnet Development Program sponsored by the DOE Office of High Energy Physics, the National Institute for Fusion Science at Toki, Japan, the National High Magnetic Field Laboratory (Tallahassee, Florida) , which announced the world's largest mag netic field generated with superconducting solenoid in December 2017, and several European efforts including CERN, CEA (FR)
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From page 117... ...
superconducting magnet researchers. It would be much less costly than a full coil test facility, and research use may include non-fusion applications of HTS magnets including those for high energy physics.
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From page 118... ...
Virtually all of the technologies related to the tritium fuel cycle are at low technical readiness, with uncertain parameters that describe tritium migration through materials and across interfaces, its retention in bulk solids and liquids, and its retention and behavior in plasma-facing materials. Building technical readiness for fusion power requires a program of materials testing and component performance when exposed to fusion neutrons.72,73 In a fusion power system, the breeding blanket is a critical component that con sists of a set of modules covering the interior of the fusion vacuum vessel, capable of supporting a high heat load and an intense neutron flux.74 The breeding blanket will need to (1)
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From page 119... ...
demonstrate TBM performance for an extended period of time. At the ITER Organization, the ITER TBM program will provide an oppor tunity for testing tritium breeding blanket concepts that would result in tritium self-sufficiency, an extraction of high-grade heat and net electricity production in future fusion reactors.
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From page 120... ...
Additionally, international collaboration on the various aspects of the tritium fuel cycle and the accompanying areas of fusion nuclear materials, plasma-facing materials, fusion nuclear science, and enabling technologies requires serious consideration. These objectives are critical steps toward developing working breeding blankets for future fusion concepts.
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From page 121... ...
In particular, determining whether construction of a volumetric fusion neutron irradiation f acility using a magnetic mirror device, or an alternate configuration, would more rapidly advance the technology readiness and lower the cost of the compact fusion pathway needs to be answered as part of the systems engineering studies. Sustaining High-Power Density Fusion Plasmas with Optimized Plasma Exhaust The United States has made significant contributions to the development and understanding of high-performance, steady-state burning plasma operating sce narios that will be used in ITER to demonstrate fusion power gain for pulses of several minutes.
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From page 122... ...
High βN reduces the size of the fusion device and increases the bootstrap current fraction, thereby reducing the current drive power and improving the overall efficiency of the pilot plant. While ITER and JT-60SA will provide some information about performance improvements with increasing βN, plasma edge pedestal models pre dict that the highest performance, and hence highest fusion power density, will be achieved with optimal shaping of the plasma, including aspect ratio, triangularity, and elongation.
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From page 123... ...
Fusion performance achieved with the tokamak configuration is superior to other magnetic configurations; however, theory, simulation, and experiments with the stellarator configuration is strongly related to the tokamak and can contribute to the integrated science and technology needed to design the compact fusion pilot plant. The stellarator concept was invented in the United States, and, in some configu rations, the confinement field can be produced entirely by the external magnetic coils.
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From page 124... ...
Quasi-symmetric stellarators might help validate m odels to predict fusion performance and improved optimization of a compact fusion pilot plant. Because the only operating quasi-symmetric stellarator is located in the United States and, more importantly, because quasi-symmetric stellarators might lead to improved designs for a compact fusion confinement system, oppor tunities exist to explore this configuration and validate the physics of 3D magnetic fields and quasi-symmetry for toroidal magnetic confinement.
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From page 125... ...
This progress combined with opportunities to develop technologies for fusion, such as high-temperature superconducting magnets and advanced materials, now make a compact device technically possible, affordable, and at tractive for industrial participation. This finding is supported by the following: • Although additional research, including magnet engineering research, is needed to demonstrate the viability of the compact pathway to fusion power, the combination of new high-field superconducting magnet tech nology with advanced burning plasma science is a significant opportunity to decrease the size and cost of a magnetic fusion power system.
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From page 126... ...
S . B u r n i n g P l as m a R e s e a r c h • While significant progress needs to be demonstrated to achieve uninter rupted operation of a high-performance fusion confinement device, the higher magnetic field in the compact fusion pathway appears to allow op eration at high fusion power density, high poloidal beta, and high bootstrap current fraction more easily than other pathways to commercial fusion power.
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From page 127... ...
Recommendation: In recognition of the significant challenges that need to be addressed for the construction of a compact fusion pilot plant facility capable of electricity production, the U.S. DOE Office of Fusion Energy Sci ences plan for a pilot plant should have a two-phase approach.
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From page 128... ...
al., 1992, "Pilot Plant: A Shortened Path to Fusion Power," IAEA Fusion Conference, IAEA-CN 56/G-1-5, International Atomic Energy Agency, Vienna, Austria, pp.
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From page 129... ...
as Fusion Power Plans -- The Starlite Study," p. 383 in Proceedings of 16th IAEA International Conference on Fusion Energy, Volume 3, International Atomic Energy Agency, Vienna, Austria.
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From page 130... ...
usion nuclear science facilities and pilot plants based on the spherical tokamak, Nuclear Fusion F 56:106023.
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From page 131... ...
usion nuclear science facilities and pilot plants based on the spherical tokamak, Nuclear Fusion F 56:106023.
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From page 132... ...
Radel, and A Davis, 2017, An improved near term 14 MeV neutron test facil ity for fusion power plant materials, Fusion Science and Technology 72:248, https://doi.org/10.1 080/15361055.2017.1333861.
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From page 133... ...
McInnes, 2015, Report on the Workshop on Integrated Simulations for Magnetic Fusion Energy Sciences, U.S. Department of Energy, Office of Science, Washington, DC.
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