National Fusion Power Plant Studies Program Achievements and Recent Results Farrokh Najmabadi University of California, San Diego FESAC Meeting March 4-5, 1999 UC San Diego Electronic copy: ARIES Web Site:

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- 3 He-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 tokamak (1999)

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  (vertical stability shell and coils),  (divertor geometry), location of kink shell (blanket design), current-driver launcher (first wall design), core-plasma radiation (first wall and divertor design), etc.

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;

Power Plant Studies Program Has Identified Key R&D Directions (selected physics areas) Trade-off of  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.

ARIES-RS is a conceptual 1000MWe power plant based on a Reversed-Shear tokamak plasma ARIES-RS represents an attractive vision for fusion with a reasonable extrapolation in physics and technology:  Minimum cost of electricity  Low level waste  Public and worker safety  High availability

Our Vision of Tokamaks Has Improved Drastically in the Last Decade

The ARIES-ST Study Has Identified Key Directions for Spherical Tokamak Research Substantial progress is made towards optimization of ST equilibria with >95% bootstrap fraction:  = 54%,  = 3; A feasible center-post design has been developed; Several methods for start-up has been identified; Current-drive options are limited; 1000-MWe ST power plants are comparable in size and cost to advanced tokamak power plants.

Spherical Tokamak Geometry Offers Some Unique Design features (e.g., Single-Piece Maintenance)

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.

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.

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 (1000 o C) Excellent candidate for coupling to a closed gas cycle drastically simplifying balance of plant.

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

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. Laser or Plasma Arc Forming

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

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

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.

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.