National Fusion Power Plant Studies Program Achievements and Recent Results

1. National Fusion Power Plant Studies Program Achievements and Recent Results Prepared for Bill Dove OFES Headquarters June, 1999

2. National Power Plant Studies Program Provides a Vision for the Fusion Program • Establish Goals and Requirements for Fusion Power: • Economics (power density, recirculating power, thermal efficiency, availability, etc.); • Safety (no need for evacuation); • Environmental (low-level waste, minimize waste); • Provides a common basis for comparative assessment. • Perform Self-Consistent Design & Analysis (both plasma core & engineering components), for example: • Detailed analysis of MHD equilibrium and stability and current drive subject to constraints on k (vertical stability shell and coils), d (divertor geometry), location of kink shell (blanket design), current-driver launcher (first wall design), core-plasma radiation (first wall and divertor design), etc.

3. National Power Plant Studies Program Provides a Vision for the Fusion Program • Determine Potential of Confinement Concepts: • Concept potential as a power plant or a fusion development device (benefits); • Degree of extrapolation from present data base (risk); • Identification of key issues for R&D program; • Identification of innovative solution to improve the concept. • Determine Potential of Enabling and Power Technologies: • As a candidate for a power plant; • As a vehicle to help fusion development;

4. Scientific & Technical Achievements Projections and Design Options R&D Needs and Development Plan Framework:Assessment Based on Attractiveness & Feasibility Goals and Requirements Periodic Input from Energy Industry Evaluation Based on Customer Attributes Attractiveness Characterization of Critical Issues Feasibility No: Redesign Yes Balanced Assessment of Attractiveness & Feasibility

5. GOAL: Demonstrate that Fusion Power Can Be a Safe, Clean, & Economically Attractive Option Requirements: • Have an economically competitive life-cycle cost of electricity: • Low recirculating power; • High power density; • High thermal conversion efficiency. • Gain Public acceptance by having excellent safety and environmental characteristics: • Use low-activation and low toxicity materials and care in design. • Have operational reliability and high availability: • Ease of maintenance, design margins, and extensive R&D. • Acceptable cost of development.

6. Conceptual Design of Magnetic Fusion Power Systems Are Developed Based on a Reasonable Extrapolation of Physics & Technology What has been achieved: Credibility R & D Program Power Plant Design and Analysis What is important: Attractiveness • Visions for Fusion Power Systems Provide Essential Guidance to Fusion Science & Technology R&D.

7. The ARIES Team Has Examined Several Magnetic Fusion Concept as Power Plants in the Past 10 Years • TITAN reversed-field pinch (1988) • ARIES-I first-stability tokamak (1990) • ARIES-III D-3He-fueled tokamak (1991) • ARIES-II and -IV second-stability tokamaks (1992) • Pulsar pulsed-plasma tokamak (1993) • SPPS stellarator (1994) • Starlite study (1995) (goals & technical requirements for power plants & Demo) • ARIES-RS reversed-shear tokamak (1996) • ARIES-ST spherical torus (1999)

8. Power Plant Studies Program Has Identified Key R&D Directions (selected physics areas) Trade-off of b and bootstrap fraction (recirculating power) which resulted in a fundamental shift in the direction of tokamak research and significantly influenced TPX design. Continuous interaction with tokamak program, resulting in the ARIES-RS design which represents the goal of the advanced tokamak program. The need to operate RFP with a highly radiative core and an efficient current drive system so that a compact RFP can be realized. Development of new stellarator magnetic configuration to address the critical issue of large size. Directions for optimization of spherical tokamak concept. Assessment of potential advanced fuels and pulsed-tokamak operation.

9. Power Plant Studies Program Has Identified Key R&D Directions for Tokamak Optimization • ARIES-I First Stability Steady-State: • Demonstrated the trade-off of b (power density) and bootstrap fraction (recirculating power) which resulted in a fundamental shift in the direction of tokamak research. • High aspect ratio, low current with a high bootstrap current fraction and intermediate elongation is optimum. • ARIES-II Second Stability Steady-State: • Found that the true benefit of second-stability is to reduce current drive requirement. • High-b equilibria are not optimum because of bootstrap misalignment and overdrive.

10. Power Plant Studies Program Has Identified Key R&D Directions for Tokamak Optimization • Pulsar, Pulsed Tokamak: • Demonstrated that plasma b is limited by ohmic profile constraint. • Feasibility issue of large and costly thermal energy storage was removed by an innovative thermal storage design. • Long pulse (1 hour or more) is essential for feasibility. • High cost of current-drive system (PF coils) leads to optimum plasmas with high aspect ratio, low current, and high bootstrap fraction (same as first-stability steady state). • Demonstrated that for the same physics and technology extrapolation, pulsed tokamaks are substantially more costly than steady-state one. • Pulsed Tokamak Operation is Not Attractive

11. Power Plant Studies Program Has Identified Key R&D Directions for Tokamak Optimization • ARIES-RS Reversed-Shear, Steady-State: • Excellent potential for power plant because of high bootstrap fraction and high plasma beta. • The tokamak program uses ARIES-RS parameters as the R&D goals. • Starlite assessment: • Reversed-shear tokamak plasmas lead to attractive power plant embodiments. • First-stability steady-state tokamak plasmas (specially with high-field magnets) are acceptable fall back positions. • Pulsed-tokamak plasmas are not attractive.

12. ARIES-RS is an attractive vision for fusion with a reasonable extrapolation in physics & technology • Competitive cost of electricity; • Steady-state operation; • Low level waste; • Public & worker safety; • High availability.

13. Key Performance Parameters of ARIES-RS

14. Our Vision of Magnetic Fusion Power Systems Has Improved Dramatically in the Last Decade, and Is Directly Tied to Advances in Fusion Science & Technology Estimated Cost of Electricity (c/kWh) Volume of Fusion Core (m3)

15. Alternative Confinement Systems • No current-drive (low recirculating power): • Stellarators (SPPS): recent advances bring the size in-line with advanced tokamaks. Needs coils and components with complicated geometry. • No superconducting TF coils • Spherical tokamaks (ARIES-ST): Potential for high performance and small size devices for fusion research but requires high beta and perfect bootstrap alignment. Center-post is a challenge. • RFP (TITAN): Simple magnets and potential for high performance. Steady-state operation requires resolution of the conflict between current-drive and confinement.

16. Stellarator Power Plant Study focused the US Stellarator Activity on Compact Stellarators • Modular MHH configuration represented a factor of two improvement on previous stellarator configuration with attractive features for power plants. • Many critical physics and technology areas were identified.

17. The ARIES-ST Study Has Identified Key Directions for Spherical Torus Research • Substantial progress is made towards optimization of high-performance ST equilibria, providing guidance for physics research. Assessment: • 1000-MWe ST power plants are comparable in size and cost to advanced tokamak power plants. • Spherical Torus geometry offers unique design features such as single-piece maintenance. • Modest size machines can produce significant fusion power, leading to low-cost development pathway for fusion.

18. Power Plant Studies Program Has Identified Key R&D Directions (selected technology areas) Introduction of SiC composites and associated blanket design (one of three low-activation material under development world-wide); The emphasis on RF systems (especially fast waves) for current drive and the respective launchers (e.g., folded wave-guides); Innovative superconducting magnet designs using plates and a structural cap (later used in ITER); Segmentation of fusion core for ease of maintenance and reduction of waste. Innovative high-performance blanket design with ferritic steels; Introduction of advanced manufacturing techniques which reduce the unit costs of components drastically.

19. SiC Composites as High-performance Structural Material • Excellent safety & environmental characteristics (very low activation and very low afterheat) • High performance due to high strength at high temperatures (1000oC) • Excellent candidate for coupling to a closed gas cycle drastically simplifying balance of plant.

20. High-Performance Ferritic Steels Blanket Typically, the coolant outlet temperature is limited to the max. operating temperature of structural material (550oC for ferritic steels) By using a coolant/breeder (LiPb), cooling the structure by He gas, and SiC insulators, a coolant outlet temperature of 700oC is achieved for ARIES-ST increasing the thermal conversion efficiency substantially.

21. Laser or Plasma Arc Forming • A laser or plasma-arc deposits a layer of metal (from powder) on a blank to begin the material buildup • The laser head is directed to lay down the material in accordance with a CAD part specification AeroMet has produced a variety of titanium parts as seen in attached photo. Some are in as-built condition and others machined to final shape. Also see Penn State for additional information.

22. Schematic of Spray Casting Process Molten Metal Furnace, Courtesy of SECO/WARWICK, Inc

23. National Power Plant Studies ProgramIs a High-Leverage Research Effort High-quality scientific research Unique in the world Community input and consensus Maximize use of resources Visions for the national fusion program A high-leverage niche on the international program

24. National Power Plant Studies Program Is a High-Leverage Research Effort High-quality scientific research through in-depth analysis and integration ensures that innovation, assessment, and design solutions are credible, meet all applicable requirements and accepted by the scientific community. Maximize use of resources by focusing on high-leverage issues, continuity of team core groups, and benefiting from the participation of team members in national or international projects. Community input and consensus are actively sought. The team comprises key members from major fusion centers. Decisions are made by consensus in order to obtain the best technical solution without institutional bias. Team is flexible and expert groups and advocates are brought in as needed. Workshop and “Town meeting” are held for direct discussion and dissemination of the results.

25. National Power Plant Studies Program Is a High-Leverage Research Effort • Unique in the world in the ability to provide a fully integrated analysis of power plant options including plasma physics, fusion technology, economics, safety, etc. • A high-leverage niche on the international fusion program. US power plant studies program has provided visions of safe, environmentally benign, and economically competitive power plant for the international fusion program. • It is recognized internationally as a credible driving force towards an attractive end product (goal of US program); • As such, our vision is having an impact on international fusion program plans and scientists; • This is witnessed by the number of international collaborations in this area, especially long-term visits ( a few months to a year) by international scientists to work with us.

26. Advances in Physics and Technology Are Helping to Reduce the Cost of Fusion Systems Substantially.Continued Improvements Can Reasonably Be Expected. Examples: • Higher performance plasmas (e.g, advanced tokamak, ST); • High-Temperature Superconductors: • Operation at higher fields; • Operation at higher temperatures and decreased sensitivity to nuclear heating simplifies cryogenics. • Advanced Manufacturing Techniques: • Manufacturing cost can be more than 20 times the raw material costs; • New “Rapid Prototyping” techniques aim at producing near-finished products directly from raw material (powder or bars). Results: low-cost, accurate, and reliable components. • Advance ARIES-RS study is exploring the impact of improved physics and advanced technologies.

27. Summary Marketplace and customer requirements establish design requirements and attractive features for a competitive commercial fusion power product. Progress in plasma physics understanding and engineering and technology are the key elements in achieving the goals of fusion. Power plant studies marry the marketplace and customer requirements (attractiveness) to R&D (credibility) in order to provide essential guidance to R&D directions of the program. The National US power plant studies program has been very successful in shaping future R&D. The key ingredient of this success is detailed and self-consistent design work which underlines the credibility of this activity for the fusion scientists.