3

Inertial Fusion Energy Technologies

This chapter deals with the technologies other than the driver technologies covered in Chapter 2 that are required to produce and utilize the energy from fusion nuclear reactions in an inertial fusion energy (IFE) system. The first sections in this chapter cover the targets, chambers, related materials issues, as well as tritium production and recovery. Subsequent sections cover crosscutting issues of environment, health, and safety as well as balance-of-plant and economic considerations.

In addition to target science, there are challenges for IFE embedded in what is usually labeled “technology” (e.g., chambers): These challenges involve a broad range of scientific disciplines, including nuclear and atomic physics, materials and surface science, and many aspects of engineering science. In the next several years, however, IFE research will be involved not in engineering developments, but rather in science and engineering research aimed at determining whether feasible solutions exist to very challenging “technology” problems.

An effort is needed to determine whether there is any IFE concept (where “concept” means some combination of target type, driver, and chamber) that appears to be feasible. Only certain combinations of targets, drivers, and chambers seem to be workable. While the emphasis today and in the near future should be on target performance, working exclusively on problems associated with target performance could easily lead to solutions that are not compatible with practical driver and chamber options. Such a serial approach could lead to dead ends and could also extend the time it takes to arrive at practical applications of IFE. For each technological approach, the committee identifies a series of critical R&D objectives that



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3 Inertial Fusion Energy Technologies This chapter deals with the technologies other than the driver technologies covered in Chapter 2 that are required to produce and utilize the energy from fusion nuclear reactions in an inertial fusion energy (IFE) system. The first sections in this chapter cover the targets, chambers, related materials issues, as well as tritium production and recovery. Subsequent sections cover crosscutting issues of environ- ment, health, and safety as well as balance-of-plant and economic considerations. In addition to target science, there are challenges for IFE embedded in what is usually labeled “technology” (e.g., chambers): These challenges involve a broad range of scientific disciplines, including nuclear and atomic physics, materials and surface science, and many aspects of engineering science. In the next several years, however, IFE research will be involved not in engineering developments, but rather in science and engineering research aimed at determining whether feasible solu- tions exist to very challenging “technology” problems. An effort is needed to determine whether there is any IFE concept (where “con- cept” means some combination of target type, driver, and chamber) that appears to be feasible. Only certain combinations of targets, drivers, and chambers seem to be workable. While the emphasis today and in the near future should be on target performance, working exclusively on problems associated with target performance could easily lead to solutions that are not compatible with practical driver and chamber options. Such a serial approach could lead to dead ends and could also extend the time it takes to arrive at practical applications of IFE. For each techno- logical approach, the committee identifies a series of critical R&D objectives that 89

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90 An Assessment of the Prospects for Inertial Fusion Energy must be met for that approach to be viable. If these objectives cannot be met, then other approaches will need to be considered. The approach used in the High Average Power Laser (HAPL) program (see Chapter 1) was one in which all the potential feasibility issues of the entire IFE system were studied, and then the most important ones were addressed to try to find basic solutions. It is a good example of how a national IFE program might be structured. HIGH-LEVEL CONCLUSIONS AND RECOMMENDATIONS The main high-level conclusions and recommendations from this chapter are given below. Conclusions Conclusion 3-1: Technology issues—for example, chamber materials dam- age and target fabrication and injection—can have major impacts on the basic feasibility and attractiveness of IFE and thus on the direction of IFE development. Conclusion 3-2: At this time, there appear to be no insurmountable fusion technology barriers to realizing the components of an IFE system, although knowledge gaps and large performance uncertainties remain, including those surrounding the performance of the system as a whole. Conclusion 3-3: Significant IFE technology research and engineering efforts are required to identify and develop solutions for critical technology issues and systems such as targets and target systems; reaction chambers (first wall/blanket/shield); materials development; tritium production, recovery and management systems; environment and safety protection systems; and economic analysis. Recommendations Recommendation 3-1: Fusion technology development should be an impor- tant part of a national IFE program to supplement research in IFE science and engineering.

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Inertial Fusion Energy Technologies 91 Recommendation 3-2: The national inertial fusion energy technology effort should leverage materials and technology development from magnetic fusion energy efforts in the United States and abroad. Examples include ITER’s test blanket module R&D program, materials development, plasma-facing com- ponents, tritium fuel cycle, remote handling, and fusion safety analysis tools. TARGET FABRICATION AND HANDLING FOR INERTIAL FUSION ENERGY Sufficiently rapid fabrication of targets that meet the exacting specifications needed to achieve high gain and an acceptable cost has long been recognized as a key requirement of practical energy application of inertial fusion. All of the earlier National Research Council (NRC) studies on IFE commented on the importance of target fabrication to the success of inertial fusion for energy applications and noted that the prospects for success appear favorable albeit with much work remaining.1 Most of the many IFE power plant design studies have given serious consideration to how the target fabrication requirements could be achieved.2 The consensus of these studies is that with adoption of a limited number of target designs, the selection of mass fabrication techniques, and a development program, the required accuracy and cost goals may be achieved. The R&D needed to make these projections a reality has begun with efforts at General Atomics, the Lawrence Livermore National Laboratory (LLNL) and the University of Rochester. This recent work has focused primarily on laser-driven targets, both direct and indirect drive. Earlier work on ion-beam-driven targets indicates that similar conclusions are expected to hold. Pulsed-power target development is at an early stage, but the 1  “Summary of the Findings and Recommendations of the 1986, 1990, and 1997 National Research Council’s Reviews of the Department of Energy’s Inertial Confinement Fusion Program,” Document prepared by NRC staff member E.E. Boyd and provided to the committee on March 2, 2011. 2 For example, see the following: D.T. Goodin, N.B. Alexander, L.C. Brown, et.al., 2005, Demonstrating a target supply for inertial fusion energy, Fusion Science and Technology 47: 1131-1138; D.T. Frey, N.B. Alexander, A.S. Bozek, D.T. Goodin, R.W. Stemke, T.J. Drake, and D. Bitner, 2007, Mass production methods for fabrication of inertial fusion targets, Fusion Science and Technology 51: 786-790; L.R. Foreman, P. Gobby, J. Bartos, et al., 1994, Hohlraum manufacture for inertial confinement fusion, Fusion Technology 26: 696-701; M.J. Monsler and W.R. Meier, 1994, Automated target production for inertial fusion energy, Fusion Technology 26: 873-880; K.D. Wise, T.N. Jackson, N.A. Masnari, et al., 1979, A method for the mass-production of ICF targets, Journal of Nuclear Materials 85-86: 103-106; B.A. Vermillion, J.T. Bousquet, R.E. Andrews, et al., 2007, Development of a new horizontal rotary GDP coater enabling increased production, Fusion Science and Technology 51: 791-794; J.T. Bousquet, J.F. Hund, D.T. Goodin, and N.B. Alexander, 2009, Advancements in glow discharge polymer coatings for mass production, Fusion Science and Technology 55: 446-449; W.S. Rickman and D.T. Goodin, 2003, Cost modeling for fabrication of direct drive inertial fusion energy targets, Fusion Science and Technology 43: 353-358; K.R. Schultz, 1998, Cost effective steps to fusion power: IFE target fabrication, injection and tracking, Journal of Fusion Energy 17: 237-246.

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92 An Assessment of the Prospects for Inertial Fusion Energy slower repetition rate (~0.1 Hz as opposed to 10 Hz) and the simple target design should ease the challenges of target fabrication for pulsed power. However, much remains to be done for IFE target development for all drivers. The committee concurs with the conclusion that suitable target fabrication will be possible at an acceptable cost, so that target fabrication is not an obviously insurmountable obstacle for IFE. However, the committee does not endorse the ­projected target cost numbers any more than it endorses estimates of future costs for any component of IFE technology in the early development stage. The costs could be much higher or lower than estimated in the conceptual studies that have been done. Only a substantial national development effort will provide the validation needed. When and if ignition is reached, it will be necessary to turn more attention and devote greater resources to target fabrication development. Concepts for producing targets at a rate 100,000 times the rate at which targets are produced today have been developed; therefore, if and when ignition is reached, it would be a good time to determine if the target factory components can be validated with real equipment and if a small, complete factory operating at modest production rates can be built and operated successfully. Such a facility should be accompanied by continued development, begun under the inertial confinement fusion (ICF) program, of physics models of the formation of small hollow spheres, subsequent deuterium- tritium (DT) layering, and other fabrication processes. Background and Status3 For direct drive, an inertial fusion target consists of a spherical capsule that contains a smooth layer of DT fuel. For indirect drive, the capsule is contained within a metal “hohlraum” that converts the driver energy into X-rays to drive the capsule. These concepts are shown schematically in Figure 3.1. For pulsed-power, target designs vary from those similar to indirect drive, to cylindrical metal shells containing DT. Several examples of IFE targets are shown in Figure 3.2. Fusion fuel targets must be delivered in a form that meets the stringent require- ments of the particular inertial fusion energy scheme, in sufficient quantity and at a low enough cost to supply affordable electricity to the grid. A fusion power plant will consume as many as 1 million targets per day. The allowable target cost will depend on the maximum marketable cost of electricity and the target yield, with estimates for laser and heavy-ion beam systems of 20-40 cents each, based on conceptual modeling studies. For higher-yield, pulsed-power systems, the cost could be proportionately higher. The cost of raw materials for the targets under 3  Portions of this discussion are taken from Appendix C of the Department of Energy’s (DOE’s) Fusion Energy Sciences Advisory Committee 1999 report Summary of Opportunities in the Fusion Energy Sciences Program.

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Inertial Fusion Energy Technologies 93 Indirect-drive Direct-drive Shield Capsule Laser beams from all directions 0.35 µm laser beam in two cone arrays FIGURE 3.1  Indirect-drive and direct-drive IFE target concepts. SOURCE: LLNL. FIGURE 3.2  Examples of IFE targets used with various driver schemes. NRL, Naval Research Labora- tory; LANL, Los Alamos National Laboratory, LLNL, Lawrence Livermore National Laboratory, LBNL, Lawrence Berkeley National Laboratory. SOURCE: General Atomics. consideration currently is at the few-cents-per-target level. Mass manufacturing experience in other industries suggests that these production cost goals are pos- sible, but a development program is required to validate the conceptual modeling studies. Current target production costs and rates are not useful for estimating the costs of mass-produced targets, although the gap between what can be done today and what is needed indicates that target fabrication for IFE plants is a challenge.

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94 An Assessment of the Prospects for Inertial Fusion Energy The fabrication techniques currently used for inertial confinement fusion (ICF) research targets must meet exacting specifications, have maximum flexibility to accommodate changes in target designs, and provide thorough characterization for each target. Current ICF target fabrication techniques for research targets may not be well suited to economical mass production of IFE targets. Because of the large number of designs and the thorough characterization required for each target, an ICF research target can currently cost thousands of dollars apiece. However, IFE target mass-fabrication studies are encouraging. Fabrication techniques are pro- posed that are well suited for economic mass production and promise the precision, reliability, and economy needed. However, work has just begun on these techniques. • Fuel capsules. The capsules must meet stringent specifications including out- of-round (dmax – dmin < 1 µm), wall thickness uniformity (∆w < 0.5 µm), and surface smoothness (<200 Å rms).4 The microencapsulation process, by which tiny particles or droplets are surrounded by a coating, appears well-suited to IFE target production if sphericity and uniformity can be maintained as the capsule size is increased from current 0.5- to 2-mm cap- sules to the ~5-mm-diameter capsule needed for IFE. Microencapsulation also appears to be suited to the production of foam shells, which are needed for several IFE target designs. Capsule designs for OMEGA experiments and direct-drive IFE power plants are shown in Figure 3.3. • Hohlraums. ICF hohlraums are currently made by electroplating the h ­ ohlraum material, generally gold, onto a mandrel that is then dissolved, leaving the empty hohlraum shell. This technique does not scale up for mass production. Stamping, die-casting, and injection molding, however, do hold promise for IFE hohlraum production.5 • Target assembly. ICF research targets are currently assembled manually using micromanipulators under a microscope. Placement of the capsule at the center of the hohlraum must be accurate to within 25 µm. For IFE, this process must be fully automated, which appears possible. Initial efforts with robotic target assembly and snap-together alignment techniques have shown promising results.6 • Target characterization. Precise target characterization of every research target is needed to prepare the complete “pedigree” required by the ICF experimentalists. Characterization for current research targets is largely 4  D. Goodin, General Atomics, “Target Fabrication and Injection Challenges in Developing an IFE Reactor,” Presentation to the committee on January 30, 2011. 5  A. Nikroo, General Atomics, “Technical Feasibility of Target Manufacturing,” Presentation to the committee on July 7, 2011. 6  A. Nikroo, during a site visit to General Atomics on February 22, 2012.

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Inertial Fusion Energy Technologies 95 ICF target IFE target OMEGA 5 m m CH + 5 m m CH 0.08 m m Pd CH (DT)64 CH (DT)64 45 m m 176 m m Fuel DT Fuel DT 20 m m 334 m m Gas Gas 330 m m 1780 m m D2/DT FIGURE 3.3  Direct-drive target capsules. SOURCE: University of Rochester. done manually and is laborious. For IFE the target production processes must be sufficiently repeatable and accurate that characterization can be fully automated and used only with statistical sampling of key parameters for process control. • DT filling and layering. Targets for ICF experiments are filled by perme- ation, and a uniform DT ice layer is formed by “beta layering.” Using very precise temperature control, excellent layer thickness uniformity and sur- face smoothness of about 1 µm rms can be achieved.7 These processes are suited to IFE, although the long fill and layering times needed may result in large (up to ~10 kg) tritium inventories. Advanced techniques, such as liquid wicking into a foam shell, could greatly reduce this amount. These processes are improving but remain far short of the level of reproducibility that a reactor would require. If IFE targets need DT ice smoothness of better than ~1 µm to achieve high gain, new layering techniques will be needed. • Target handling and injection. IFE targets will be injected into the target chamber at rates as high as ~10-20 Hz. The targets must have adequate 7  D. Goodin, General Atomics, “Target Fabrication and Injection Challenges in Developing an IFE Reactor,” Presentation to the committee on January 30, 2011.

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96 An Assessment of the Prospects for Inertial Fusion Energy thermal and mechanical robustness and protection, such as hohlraums or sabots, to survive the injection and in-chamber flight. This solution must also be compatible with the chamber protection and energy recovery schemes (see the next section, “Scientific and Engineering Challenges and R&D Priorities.”). ICF research targets that meet all current specifications for both laser direct and indirect drive have been fabricated and fielded in small quantities, including the uniform, smooth DT ice layer. ICF research targets currently cost thousands of dollars apiece on average, but the costs vary widely; simple production targets can cost many times less, and targets requiring significant development effort could cost many times more than that amount. For a power plant, a significant transition needs to be undertaken using low-cost, high-throughput manufacturing techniques, along with large batch sizes for any chemical processes, as well as likely use of statistical characterization. Many of the processes used for current target fabrication do not scale well to mass production and will need to be replaced. Examples are die-casting arrays of hohlraum parts instead of diamond turning a mandrel for gold plating, and the use of large-batch chemical vapor deposition (CVD) diamond coaters for the ablators and membranes instead of the small size bounce-pan ­ oaters now used. The HAPL program, led by the Naval Research c Laboratory (NRL), which went well beyond laser drivers to consider all aspects of IFE power by laser direct drive, and the Laser Inertial Fusion Energy (LIFE) program, led by LLNL, which focuses on IFE by laser indirect drive, have begun evaluation and selection of mass production methods that can meet IFE require- ments. The termination of the HAPL program has slowed this effort. There have been successful efforts to develop several IFE target mass produc- tion techniques. To make thick-walled polymer capsules, a poly-alpha-methyl- styrene (PAMS) mandrel is made by microencapsulation and then coated with glow discharge polymer (GDP). A rotary kiln version of the GDP coater has been made that is capable of mass production, but it has not been used enough to demonstrate that it can meet the surface roughness specification.8 In the HAPL program,9 foam shells were made that met the HAPL target specification with appreciable yield using microencapsulation droplet generators. Applying a smooth, gastight over- coat to these foam shells was the focus of development at the time that the HAPL program ended. A cryogenic fluidized bed for layering deuterium in direct-drive targets was built in the HAPL program. It was successfully operated at cryogenic 8  A. Nikroo, General Atomics, “Technical Feasibility of Target Manufacturing,” Presentation to the committee on July 7, 2011. 9  J.D. Sethian, D.G. Colombant, J.L. Giuliani, et al., 2010, The science and technologies for fusion energy with lasers and direct-drive targets, IEEE Transactions on Plasma Science 38 (4): 690-703.

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Inertial Fusion Energy Technologies 97 FIGURE 3.4 Electric-field-mediated microfluidics (“lab-on-a-chip”) wicking of cryogenic D 2 into a foam capsule target. ITO, indium tin oxide. SOURCE: University of Rochester. temperatures using empty capsules but has yet to be operated with deuterium- filled capsules. General Atomics has built a robotic target assembly station based on commercially available industrial robots. This station has glued together cone- in-shell targets suitable for fast ignition experiments10 such that the virtual cone tip coincides with the capsule center to within the specification of 10 µm. LLNL is developing target assembly techniques for the National Ignition Facility’s (NIF’s) National Ignition Campaign (NIC) that facilitate target component self-alignment (“snap-together” assembly), which will be useful for IFE target assembly. Devel- opment of the process for manufacturing hohlraum parts made of lead by cold forging (or stamping) started recently. Some development of die-casting hohlraum parts is also expected to begin soon.11 Innovative concepts such as the University of Rochester’s use of electric-field mediated microfluidics (lab-on-a-chip),12 shown in Figure 3.4, may allow higher quality at lower cost. In summary, progress has been made on IFE target fabrication, creating many opportunities for improved materials and technologies, but much remains to be done. 10  A.Nikroo, during a site visit to General Atomics on February 22, 2012. 11  A. Nikroo, General Atomics, “Technical Feasibility of Target Manufacturing,” Presentation to the committee on July 7, 2011. 12  D.R. Harding, T.B. Jones, Z. Bei, W. Wang, S.H. Chen, R.Q. Gram, M. Moynihan, and G. Randall, 2010, Microfluidic Methods for Producing Millimeter-Size Fuel Capsules for Inertial Fusion, Materials Research Society Fall Meeting, Boston, Mass.

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98 An Assessment of the Prospects for Inertial Fusion Energy FIGURE 3.5  Cost breakout for target mass manufacture, based on a representative factory model (example shown for LIFE targets). SOURCE: R. Miles, J. Biener, S. Kucheyev, et al., 2008, “LIFE Target Fabrication Research Plan,” LLNL-TR-408722. To estimate possible costs, factory models have been constructed based on experience from the chemical batch processing industry combined with in-house expertise at General Atomics and LLNL. These models considered likely man- ufacturing and assembly equipment types, factory build costs, personnel and operational costs, and in-process volumes, among other things, and amortized the integrated costs over the volume of targets produced. Predictions ranged from 17 to 35 cents per target.13 A breakout of projected target costs based on a target factory economics model is shown in Figure 3.5. Conclusion 3-4: Target fabrication at the quality and production rate needed appears possible with continued development. 13  See,for example, D.T. Goodin, A. Nobile, J. Hoffer, et al., 2003, Addressing the issues of target fabrication and injection of inertial fusion energy, Fusion Engineering and Design 69: 803-806; R. Miles, et al., 2009, “LIFE Target Fabrication Costs,” LLNL-TR-416932; and R. Miles, J. Biener, S. Kucheyev, et al., 2008, “LIFE Target Fabrication Research Plan,” LLNL-TR-408722.

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Inertial Fusion Energy Technologies 99 Scientific and Engineering Challenges and R&D Priorities Target Fabrication The scientific challenges to IFE target fabrication lie primarily in understand- ing the physics behind the specifications for inertial fusion target requirements: sphericity, uniformity and smoothness (How good is good enough?), and under- standing the physics and chemistry behind the ability to achieve those requirements (Which physical processes control sphericity, uniformity, and smoothness?) Experi- ments with IFE targets at the NIF can help provide the physics understanding. The engineering challenges lie in selecting and developing materials that can achieve these requirements and in developing the processes and equipment needed to do so reliably and repeatedly with very high yield at reasonable cost. The specific requirements appear at present to include these: • The ability to fabricate IFE targets that meet specifications such as those for indirect drive: —  apsules with 4 mm diameter, <1 µm sphericity, ~100 µm wall with C <0.5 µm Δw, <200 Å rms surface smoothness, and a surface power spectrum below the NIF capsule profile. — Hohlraums fabricated to ≤10 µm accuracy. Targets assembled to ≤10 µm accuracy. and those for direct drive: —  oam shell capsules with ~150 µm thick with <0.5 µm Δw and ~4 mm F diameter with <1 µm sphericity. Foam density ≤100 mg/cm3 with cell size <1 µm. A seal coat14 on top of the capsule having a 1-5 µm wall with <0.5 µm Δw, <200 Å rms surface smoothness, and a surface power spectrum meeting the NIF/NIC required profile. • A projected cost of mass-producing IFE targets for a power plant of ≤$0.50 each. The objectives of IFE target fabrication R&D must be to understand the physics behind the specifications for inertial fusion target requirements and understand the physics behind the ability to achieve those requirements to such a depth that 14  The seal coat surface for the direct drive capsule both seals the capsule and facilitates its injection into the target chamber without going out of specification by the time it reaches the center.

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Inertial Fusion Energy Technologies 135 Some licensing and regulatory-related work has been done for the ITER pro- gram, and much of that work provides insights into IFE licensing processes and issues. The LIFE program has considered licensing issues more than any other IFE program; however, much more effort would be needed if IFE were to seri- ously pursue an NRC license. The Next Generation Nuclear Plant (NGNP) fission ­reactor project plans to license and build a high-temperature gas fission reactor. Gas reactors have been built and operated previously in the United States and Europe, although at lower operating temperatures than are envisioned for the NGNP. The licensing strategy developed for the NGNP provides a good picture of the chal- lenges associated with licensing a relatively standard technology.65 The licensing of fission power plants is moving toward a risk-informed approach, whereas in the past it took primarily a deterministic approach. The LIFE program is developing a similar approach.66 The favorable safety characteristics of the IFE and MFE fusion plants should simplify the licensing process; however, the burden of proof for IFE plants will be no different than for fission plants. One of the safety-related goals for fusion is to demonstrate that there would never be a need for public evacuation under any event. This is a clear example of the favorable safety characteristics of a fusion plant. Conclusion 3-20: Some licensing/regulatory-related research has been car- ried out for the ITER (magnetic fusion energy) program, and much of that work provides insights into the licensing process and issues for inertial fusion energy. The laser inertial fusion energy (LIFE) program at Lawrence Livermore National Laboratory has considered licensing issues more than any other IFE approach; however, much more effort would be required when a Nuclear Regulatory Commission license is pursued for inertial fusion energy. Safety analysis has been an important part of the IFE design studies cited earlier. Early analyses were relatively simple. They often looked at total inventories of radioactive material and determining how much material could be released based on total system energy. These analyses have given way to more sophisticated analyses, sometimes employing tools originally developed for the fission industry and adapted to fusion.67 Tritium inventory and release mitigation is an important part of the fusion safety case. Tritium can be highly mobile under certain condi- 65  Next Generation Nuclear Plant Licensing Strategy—A Report to Congress, www.ne.doe.gov/ pdfFiles/NGNP_report toCongress.pdf, August 2008. 66  M. Dunne, E.I. Moses, P. Amendt, et al., 2011, Timely delivery of laser inertial fusion energy (LIFE), Fusion Science and Technology 60: 19-27. 67  B.J. Merrill, A lithium-air reaction model for the MELCOR code for analyzing lithium fires in fusion reactors, Fusion Engineering and Design 54: 485-493.

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136 An Assessment of the Prospects for Inertial Fusion Energy tions, so minimizing its inventory in fusion facilities is a first step (see the section on tritium management above). Other radioactive material present in the IFE plant must also be considered, together with possible release scenarios. Overall, the IFE source term is significantly smaller than its fission counterpart, which should ben- efit the licensing process. Analysis done for systems studies shows acceptable safety performance; however, in the absence of experimental results to validate models, the actual performance remains highly uncertain. Validation and verification of models is extremely important to the NRC and will be an important factor in the licensing process. Recommendation 3-9: Validation and verification of models is extremely important to the Nuclear Regulatory Commission and will be an important factor in the licensing process. Development of models, including validation and verification, should be pursued early. Working with the NRC early and often will be important, as well as looking to other programs (e.g., ITER and fission) for successful licensing strategies. Scientific and Engineering Challenges and Future R&D Objectives The environmental, safety, and health aspects of the IFE facilities should con- tinue to be an important point of discussion in any program. The IFE community should continue to analyze and bring attention to the favorable characteristics of these plants. Continued development of sophisticated models, together with data for validation of the models, is important in the preparation for licensing of an IFE plant. The IFE program should continue to keep abreast of NRC licensing activities and keep the lines of communication with the NRC open. Path Forward Near Term (<5 Years) Needed R&D activities include systems studies with a focus on realistic assump- tions and schedules. Radioactive waste management should be an area of particular focus given recent activities by the Blue Ribbon Commission on America’s Nuclear Future (BRC).68 The development of a safety model, with an eye towards future licensing, and the development of experiments to validate models will be critical. 68  The BRC was created under the authority of DOE and tasked with devising a new strategy for managing the back end of the nation’s inventory of nuclear fuel cyclewaste; it issued its final report in January 2012. A copy of the report and other information on the commission can be obtained at http://tinyurl.com/bvsshko; accessed on May 16, 2013.

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Inertial Fusion Energy Technologies 137 Medium Term (5-15 Years) Concepts for recycling IFE target and chamber materials need to be studied experimentally, possibly using only nonradioactive elements. Experiments would be done to benchmark accident analysis codes with materials and configurations typical of fusion power plant designs. Success would be experimental validation of safety models. Long Term (>15 Years) The long-term objective would be to begin development of the licensing case for an IFE demonstration plant. BALANCE-OF-PLANT CONSIDERATIONS The purpose of an IFE power plant is to produce useful energy in the form of electricity or high-temperature process heat, or chemical energy in the form of hydrogen. To do this, the power plant must convert the energetic products of fusion reactions—high-energy neutrons and charged particles—into the desired useful forms. To become a practical source of energy, IFE must produce and convert the fusion energy in a manner that is technically feasible, environmentally acceptable, and economically attractive compared to other long-term, sustainable sources of energy. The high-energy neutrons and charged particles from the fusion reactions deposit their thermal energy on the walls of the reaction chamber and in the tritium-breeding blanket surrounding the chamber. Everything outside the cham- ber and blanket, excluding the laser or particle beam drivers or the pulsed power system, is considered the “balance of plant” (BOP). The BOP includes the systems for conversion of thermal energy to electricity, the buildings and structures for the power plant, and all the conventional services. While schemes have been proposed to convert some of the charged-particle energy directly into electricity by electro- static or magnetohydrodynamic processes, first-generation IFE power plants will most likely utilize fairly conventional thermal power conversion systems to convert the energy contained in the hot coolant from the chamber wall and blanket into electricity. Similar “heat engine” thermal power conversion systems are widely used on nuclear fission power plants and on fossil-fired power plants around the world. The Rankine cycle, or steam cycle, and the Brayton cycle, or gas-turbine cycle, are widely used heat engines that appear well suited for application to the conversion of thermal energy from fusion into electricity. There appears to be little need for power conversion system development that would be unique to fusion or IFE, although IFE-specific BOP designs will need to be developed, and opportunities for innovation should always be welcome.

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138 An Assessment of the Prospects for Inertial Fusion Energy Conclusion 3-21: Existing balance-of-plant technologies should be suitable for IFE power plants. The thermal conditions—inlet and outlet coolant temperatures—proposed for IFE power plants are similar to those used by fission and fossil power plants today, so that the BOP for an IFE power plant should likewise be very similar to those used today. An area of concern is that of system interfaces and the possibility of hazardous material transport across those interfaces. The IFE reaction chamber will contain quantities of radioactive tritium, radioactive target debris, and some radioactive material sputtered from the first wall. In addition, it will operate at elevated temperatures. Tritium may migrate through the chamber walls and into the primary coolant stream. The coolant will pass through heat exchangers, and tritium may migrate through the heat exchangers into the secondary coolant and eventually into the rest of the power plant and even into the environment. These issues are part of the larger tritium control issue discussed in the section on tritium management, above. These interface concerns may require R&D to develop coat- ings for BOP components and heat exchangers that are resistant to permeation by tritium and tritium removal systems for the various chamber, blanket, and power conversion system coolants. Path Forward Near Term (<5 Years) The design and analysis of BOP systems will continue to be included in IFE system studies and design studies, with emphasis on identification and evaluation of critical issues. Medium Term (5-15 Years) As favored design concepts begin to emerge, R&D into critical issues that have been identified—such as tritium permeation and control—will need to be carried out. Long Term (>15 Years) BOP systems will need to be developed and deployed as part of demonstration IFE systems.

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Inertial Fusion Energy Technologies 139 ECONOMIC CONSIDERATIONS An essential requirement for any new energy system to compete in future markets is to offer a product at a competitive price. For an IFE power plant, the main measure is the cost of electricity (COE). The formula for the COE is typi- cally given by: COE = (Ccap × FCR + Cfuel + COM)/(Penet × 8,760 (hr) × Fcap) + Decom where Ccap, construction costs including interest charges during construction; FCR, fixed charge rate; Cfuel, fuel costs including targets; COM, operations and mainte- nance; Penet, net electric power; Fcap, capacity factor; and Decom, annual decom- missioning charge in mills per kilowatt-hour or $/MWh, which can be calculated as the cost of decommissioning, times the appropriate annual sinking fund factor to accumulate those funds, divided by the amount of electricity produced per year (Penet × 8,760 (hr) × Fcap). Conclusion 3-22: An essential requirement for any new energy system to compete in future markets is to offer a product at a competitive price. For an IFE power plant, the main measures are the cost of electricity generation and, in particular, the capital cost. The capacity (or sometimes called the availability) factor (Fcap) has a large influence on the COE. It is the crucial number in converting capital costs to COE. IFE power systems will be very capital-intensive systems with perhaps relatively modest fuel costs, provided the goals of low-cost targets can be met (discussed further below). Such plants will likely operate as base-load power plants where a premium is placed on operating at the maximum capacity factor. IFE power plant studies typically assign a value of 70 percent to 80 percent to Fcap. These values cannot be achieved today given the early stages of IFE technology development, so really they represent a goal. By way of comparison, the current fleet of fission power plants in the United States routinely achieves an average capacity factor of about 90 percent. Achieving high capacity factors requires two basic features of the system: high component reliability (usually measured by the mean-time-to-failure for each component) and acceptable maintenance or downtimes (usually measured by the mean-time-to-repair for each component). There is a strong relationship between the allowed values of the mean-time-to-failure and the mean-time-to-repair for a given component. The longer mean-time-to-repair, the longer must be the mean- time-to-failure. In other words, the harder it will be to replace the component, the higher must be the degree of reliability. Defining the acceptable values for the

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140 An Assessment of the Prospects for Inertial Fusion Energy mean-time-to-failure and mean-time-to-repair for all the components in a com- plex IFE power plant will require a comprehensive systems engineering approach. Achieving high levels of component reliability requires substantial testing and qualification of fusion components, far beyond what is available today. For example, no fusion reaction chamber has ever been built and certainly none has been tested to the extent needed to establish failure modes and a reliability database. Given the large number of components and systems in an IFE power plant (and an MFE power plant), a substantial investment of time and money will be required to conduct those tests and they will have an enormous impact on the overall time horizon for developing commercial IFE systems. Although much useful testing can and will be done in simulation facilities, at some time, testing in an actual fusion environment will be needed. These very large investments with long timescales will thus have a profound impact on the roadmap for realizing fusion power systems. While ITER and a future IFE demonstration plant are very different, it should be possible to take advantage of some of the experience with ITER—for example, the hardware and procedures developed for remote maintenance—to reduce the implementation time for an IFE demonstration plant. Achieving high capacity factors (availability) in light of an IFE system’s com- ponents is an equally challenging task. Some of these components will necessitate using remote handling systems. While the technology and experience in other fields (e.g., fission reactors and space systems) can be adapted to fusion needs, there exists today very limited experience with remote maintenance in fusion systems. ITER is one very important source of such information. Developing the maintenance systems for an IFE power plant will entail a significant effort, but there is very little work under way today in the United States to support those efforts. For these reasons, the capacity factor is probably the most unpredictable of all the factors that affect the COE. This is true of both fusion concepts, inertial and magnetic. Conclusion 3-23: As presently understood, an inertial fusion energy power plant would have a high capital cost and would therefore have to operate with a high availability. Achieving high availabilities is a major challenge for fusion energy systems. It would involve substantial testing of IFE plant components and the development of sophisticated remote maintenance approaches. Of special concern for the economics of IFE is the cost of the targets. The feasibility of developing successful fabrication and injection methodologies at the low cost required for energy production—about $0.25 to $0.30/target,69 or about 69  W.S. Rickman and D.T. Goodin, 2003, Cost modeling for fabrication of direct drive inertial fusion energy targets, Fusion Science and Technology 43(3): 353-358.

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Inertial Fusion Energy Technologies 141 one ten thousandth of current costs, and at a production rate that is 100,000 times faster than current rates—is a critical issue for inertial fusion. IFE researchers working on target capsule costs argue that between increased yields and batch-size increases, cost reductions of two orders of magnitude are possible with significant development programs.70 It appears that the target-cost numbers may be possible, although challenging, considering the number of assumptions and judgments that are needed to get to the desired reduction of a factor of 10,000. Conclusion 3-24: The cost of targets has a major impact on the economics of inertial fusion energy power plants. Very large extrapolations are required from the current state-of-the-art for fabricating targets for inertial confine- ment fusion research to the ability to mass-produce inexpensive targets for inertial fusion energy systems. Construction or capital costs are typically divided into fusion-specific com- ponents (e.g., laser or particle-beam drivers, chambers, and target fabrication and injection) and the BOP. The BOP was discussed in the preceding section and will likely rely on existing concepts with cost estimates that are relatively well known. Cost estimates for the fusion components necessarily entail more uncertainty because in some instances (e.g., chambers and high-capacity target fabrication) they are still in the very early stages of development. Nevertheless, the construction costs have less uncertainty than the capacity factor. In fission electricity experience, standard project costs (e.g., owner’s cost and engineering during construction) are typically taken as a percentage of the basic capital cost. Escalation and inflation factors may also be incorporated. The IFE COE estimated in various studies falls between 5 and 10 cents/kWh in current dollars.71 These estimated COEs for IFE power plants are in the same general range as COEs for other energy options, but because of the relatively early phase of the development of IFE components and systems, much uncertainty sur- rounds them. It appears that the COE numbers obtained in past studies are pos- 70  D.T.Goodin, N.B. Alexander, L.C. Brown, D.T. Frey, R. Gallix, C.R. Gibson, et al., 2004, A cost- effective target supply for inertial fusion energy, Nuclear Fusion 44(12): S254-265. 71  DOE, 1992, OSIRIS and SOMBRERO Inertial Fusion Power Plant Designs, DOE/ER-54100-1, Volume 1. Executive Summary and Overview; T. Anklam, LLNL, “Life Delivery Plan,” Presentation to committee on March 30, 2011; B. Badger, D. Bruggink, P. Cousseau, et al., 1995, LIBRA-SP, A Light Ion Fusion Power Reactor Design Study Utilizing a Self-Pinched Mode of Ion Propagation—Report for the period ending June 30, UWFDM-982 University of Wisconsin Fusion Technology Institute; J.T. Cook, G.E.Rochau, B.B. Cipiti, C.W. Morrow, S.B. Rodriguez, C.O. Farnum, et al., 2006, Z-Inertial Fusion Energy: Power Plant, SAND2006-7148, SNL; M. Dunne, LLNL, “Overview of the LIFE Power Plant,” Presentation to the committee on January 29, 2011; I.N. Sviatoslavsky, et al., 1993, “SIRIUS-P, An Inertially Confined Direct Drive Laser Fusion Power Reactor,” UWFDM-950, University of Wisconsin Fusion Technology Institute.

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142 An Assessment of the Prospects for Inertial Fusion Energy sible, but they contain uncertain components owing to the untested assumptions that must be made when making estimates for new technology. Financing and business considerations, such as the fixed charge rate (capital charge rate), will have an important influence on the COE. Usually this is made up of two parts: a charge rate for the share held by equity investors and a (lower) charge rate for the debt-investor share. These terms can vary based on the con- fidence investors have in the readiness and cost-effectiveness of the technology and the extent to which the investment is protected. Investment can be protected in some states by a decision of the public utility commission. Debt investment can be protected by federal loan guarantees or by direct federal assumption of the debt. The charge rate for IFE will be determined by the entire history of the technology. The more complex the technology, the more prone it is to delays and bumps along the road to implementation and the bigger the effect on investor and guarantor psychology. For example, most past IFE cost of electricity studies did not carry individual uncertainty ranges. Some of the difficulties in using estimates of electricity costs for IFE in comparison with other energy technologies or among IFE options could be overcome, in part, if uncertainty ranges were a required component of cost estimates. It is not clear to what extent the COE studies for IFE are “forward” estimates (made without looking at a cost goal) or “backward” estimates (made with an eye on a cost goal), or a mixture of the two. Certainly, the BOP estimates can be based on conventional databases of cost elements and would qualify as forward cost esti- mates. They can be compared to cost estimates made for other, traditional energy technologies, with the caveat that future estimates for all technologies may be low when compared to actual as-built and as-operated facilities. Hence, cost estimates for fusion, even were they to be based totally on forward calculations, should be compared to estimates of future COEs for other technologies, not current-day market prices. Cost estimates for the purely fusion components of the COE may have been, to some degree, backward estimates, starting from values based on views of future prices of the alternatives. Analysts taking this approach would determine if it was possible to reach such targets for the fusion components of the COE and then use those possible numbers to compute a total COE. In such cases, the fusion COEs might be better labeled “possible values” rather than COE estimates. In addition to predicting possible COE values, cost analysis can help to identify where R&D dollars should be targeted. The sensitivity of total cost-to-cost varia- tions in system components helps to identify where a reduction in cost (via R&D, for example) would have the greatest impact. The effectiveness of such analyses depends critically on having a well-developed system engineering capability. Similarly, the technology readiness level (TRL) process is another useful tool

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Inertial Fusion Energy Technologies 143 that is also discussed in Chapter 4.72 In dealing with uncertainty ranges, the use of TRLs for each component, with separate uncertainty ranges on the component COE appropriate for different TRLs, could help planners decide on where in order to allocate resources to lower costs. Such a methodology would help to standardize cost and uncertainty estimates across different fusion technologies; it is discussed further in Chapter 4. Use of TRLs and other readiness concepts, such as “integration readiness levels,”73 also provide structure for keeping costs under control. There have been problems historically with cost escalation in government/industry partnerships from which useful lessons for IFE can be drawn. For instance, many large DOE pro- grams/projects did not proceed as planned. Although there are many reasons why projects may fail technically or not meet their cost objectives, two stand out and are worth special consideration given the charge to this committee: (1) the breakdown of large, multiowner projects, and (2) significant cost increases in large, first-of- a-kind demonstration or prototype plants. The committee believes that the TRL methodology should be required for all major components of the IFE program. It is important to note that the COE for IFE may not be the most immediate obstacle to successful development. At the size currently envisioned in most studies, the total cost of an IFE plant may be the biggest obstacle to IFE development, when looked at through the prism of current-day electricity company concerns. Given the rapid escalation in capital costs over the last decade, projected costs of gigawatt facilities for all capital-intensive electricity plants have reached the point where they represent a significant fraction of company capitalizations, making investments a “bet-the-company” decision. Efforts are under way to downsize electricity plants to reduce the sticker shock. A national IFE program should explore a range of plant sizes given the uncertain market and financial situation in this country in the com- ing decades. In particular, it is very important to understand the lower bound for an IFE plant output in terms of key physics constraints (e.g., target energy gain) and engineering constraints. Conclusion 3-25: The financing of large, capital-intensive energy options such as an IFE power plant will be a major challenge. R&D can attempt to address the two major economic obstacles confronting IFE—namely, skepticism about reaching cost/kWh targets and the high cost per 72  DOE, 2011, Technology Readiness Assessment Guide, DOE G 413.3-4A, Washington D.C.: Department of Energy. 73  See J.C. Mankins, 2002, Approaches to strategic research and technology (R&T) analysis and road mapping, Acta Astronautica 51(1-9): 3-21 and B. Sauser, J.E. Ramirez-Marquez, R. Magnaye, and W. Tan, 2008, A systems approach to expanding the technology readiness level within defense acquisition, International Journal of Defense Acquisition Management 1: 39-58.

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144 An Assessment of the Prospects for Inertial Fusion Energy plant. R&D can also attempt to reduce investor risk, whether for government or private investors, by encouraging innovation in IFE components and designs, improving TRLs through engineering advances, and by laying the ground for spin- offs of private companies. Systems analysis—in this context, the purely technical quantitative assess- ment of the expected performance of various interconnected technologies—is an important tool in the development of any complex system.74 Systems analysis can also identify outcomes of various implementation scenarios based on various assumptions. It is primarily concerned with the performance of various technolo- gies and does not address the pathways or nontechnical constraints in achieving the implementation of those technologies. However, it does enable assessing the ­sensitivity of the system to nontechnical constraints translated into system impacts. Cost assessment is one of the outcomes of a systems analysis, as discussed earlier. As already mentioned, the cost of a plant generating 1 GW or more of electric- ity represents a considerable portion of the book value of any U.S. company likely to build a fusion reactor: this is in and of itself a huge barrier to entry. There is another problem specific to those high-capitalization facilities that might be built in the many states in the United States in which competitive, short-term electric- ity markets have been established. A fusion facility, like a nuclear fission facility, will not pay off its investors for a long time. In the absence of long-term contracts, these facilities would endure an extended period of vulnerability to market prices dropping, forcing bankruptcy and massive losses. While it could be that long- term contracts will be established in such markets in the years ahead, until that time, investments in expensive, capital-intensive projects are risky in competitive m ­ arkets. Investors would therefore be looking for a high rate of return, driving up the per-kilowatt-hour cost. The fission industry is working to modularize and downsize electricity plants to reduce the high costs and impact on the grid. Fusion R&D might want to fol- low that example. One goal of R&D could be to design IFE power plants that are naturally smaller or radically cheaper or to improve existing designs. Designers might explore modular systems in which relatively small fusion devices—built in sequence as finances allow—share common driver facilities. The assignment of an “investor readiness level” to a design, including differentiated levels of readiness to venture capitalists, equity investors, and debt investors, could prove a useful discipline for planning. Even though the COE might be higher, a smaller plant might be more viable in the United States because its total cost is more attractive to potential investors. 74  K.A. McCarthy and K.O. Pasamehmetoglu, “Using Systems Analysis to Guide Fuel Cycle Development” (Paper 9477, INL/CON-09-15764). In: Global 2009, Paris, 2009.

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Inertial Fusion Energy Technologies 145 Because it is not possible to anticipate which business model will be the most successful decades from now, a long-range technology should have an eye on supporting multiple business models. These models range from those in which the U.S. government stands behind the technology, maintains a high percentage of the ownership of the construction, and even operates the plant, to a model in which venture capitalists support small companies and obtain key patents on IFE components, to a model where the government builds a few facilities with the idea that private companies will step in afterward to improve and market the by then proven technology. Government support for R&D, as part of or in addition to systematic engi- neering approaches, could greatly benefit IFE under all of these business models. Rewarding innovation as part of engineering could provide a stronger base from which spinoff companies could arise. Encouraging ideas from a larger community than is now involved in IFE efforts could contribute to increased innovation and could also increase the number of patents likely to be developed, which is a pre- requisite for the venture capital model. Based on the information in this section and its conclusions, the committee makes three recommendations: Recommendation 3-10: Economic analyses of inertial fusion energy power systems should be an integral part of national program planning efforts, particularly as more cost data become available. Recommendation 3-11: A comprehensive systems engineering approach should be used to assess the performance of IFE systems. Such analysis should also include the use of a technology readiness levels (TRLs) meth- odology to help guide the allocation of R&D funds. Recommendation 3-12: Further efforts are needed to explore how best to minimize the capital cost of IFE power plants even if this means some increase in the cost of electricity. Innovation will be a critical aspect of this effort. ­ ossible options include use of a smaller fusion module, even P at higher specific capital cost per megawatt of electricity, and the use of a fusion module for which capital cost is reduced by accepting a higher oper- ating cost.