RECENT RESULTS FROM USA MAGNETIC FUSION POWER PLANTS

1. RECENT RESULTS FROM USA MAGNETIC FUSION POWER PLANTS Farrokh Najmabadi University of California, San Diego, La Jolla, CA, United States of America German Nuclear Society Annual Meeting on Nuclear Technology 2004 25-27 May 2004, Düsseldorf, You can download a copy of this presentation from ARIES Web Site: http://aries.ucsd.edu/ARIES/

2. The ARIES Team Has Examined Several Magnetic Fusion Concept as Power Plants in the Past 15 Years • 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) • Fusion neutron source study (2000) • ARIES-AT advanced technology and advanced tokamak (2000) • ARIES-IFE assessment of IFE chambers (2003) • ARIES-CS Compact Stellarator Study (Current Research)

3. Scientific & Technical Achievements Goals and Requirements Periodic Input from Energy Industry Projections and Design Options R&D Needs and Development Plan Analysis of Conceptual Fusion Power Plants Identifies Key R&D Issues and Provides a Vision for Fusion Research Evaluation Based on Customer Attributes Attractiveness Characterization of Critical Issues Feasibility No: Redesign Yes Balanced Assessment of Attractiveness & Feasibility

4. Scientific & Technical Achievements Projections and Design Options R&D Needs and Development Plan Analysis of Conceptual Fusion Power Plants Identifies Key R&D Issues and Provides a Vision for Fusion Research Goals and Requirements Periodic Input from Energy Industry • Conceptual Design of Magnetic Fusion Power Systems Are Developed Based on a Reasonable Extrapolation of Physics & Technology • Plasma regimes of operation are optimized based on latest experimental achievements and theoretical predictions. • Engineering system is based on “evolution” of present-day technologies, i.e., they should be available at least in small samples now. Only learning-curve cost credits are assumed in costing the system components. Evaluation Based on Customer Attributes Attractiveness Characterization of Critical Issues Feasibility No: Redesign Yes Balanced Assessment of Attractiveness & Feasibility

5. Scientific & Technical Achievements Projections and Design Options R&D Needs and Development Plan Analysis of Conceptual Fusion Power Plants Identifies Key R&D Issues and Provides a Vision for Fusion Research 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

6. Customer Requirements

7. Top-Level Requirements for Fusion Power Plants Was Developed in Consultation with US Industry Public Acceptance: • No public evacuation plan is required: total dose < 1 rem at site boundary; • Generated waste can be returned to environment or recycled in less than a few hundred years (not geological time-scale); • No disturbance of public’s day-to-day activities; • No exposure of workers to a higher risk than other power plants; Reliable Power Source: • Closed tritium fuel cycle on site; • Ability to operate at partial load conditions (50% of full power); • Ability to maintain power core (avilability > 80%); • Ability to operate reliably with < 0.1 major unscheduled shut-down per year. • Economic Competitiveness: Above requirements must be achieved simultaneously and consistent with a competitive life-cycle cost of electricity.

8. Top-Level Requirements Translate into Directions for System Optimization Top –Level Requirements for Commercial Fusion Power • Have an economically competitive life-cycle cost of electricity: • Low recirculating power; • High power density; • High thermal conversion efficiency; • Less-expensive systems. • 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.

9. Fusion Plasma

10. Portfolio of MFE Configurations Externally ControlledSelf Organized Example: Field-reversed Configuration • Confinement field generated mainly by currents in the plasma • Poloidal field >> Toroidal field • Small aspect ratio • Simpler geometry Example: Stellarator • Confinement field generated by mainly external coils • Toroidal field >> Poloidal field • Large aspect ratio • More stable, better confinement

11. Optimization involves trade-off among various parameters • Trade-off between bootstrap current fraction and b • Advanced Tokamak Regime • Trade-off between vertical stability and plasma shape • Trade-off between plasma edge condition and plasma facing components capabilities, • … Important Parameters of a Fusion Plasma • Fusion power density, Pf ~ b2BT4 and b  bN(I/aB) • High magnetic field • Higher performance plasma (bN ) • Recirculating power is dominated by the power to drive and maintain plasma current. • Maximize self-driven bootstrap current • Confinement is not a major issue for a power plant size plasma.

12. Approaching COE insensitive of power density Approaching COE insensitive of current drive Evolution of ARIES Designs

13. High accuracy equilibria; Large ideal MHD database over profiles, shape and aspect ratio; RWM stable with wall/rotation or wall/feedback control; NTM stable with LHCD; Bootstrap current consistency using advanced bootstrap models; External current drive; Vertically stable and controllable with modest power (reactive); Rough kinetic profile consistency with RS /ITB experiments, as well GLF23 transport code; Modest core radiation with radiative SOL/divertor; Accessible fueling; No ripple losses; 0-D consistent startup; Detailed Physics Modeling Has Been Performed for ARIES-AT

14. Fusion Technologies

15. ARIES-AT Fusion Core

16. The ARIES-RS Utilizes An Efficient Superconducting Magnet Design TF Coil Design • 4 grades of superconductor using Nb3Sn and NbTi; • Structural Plates with grooves for winding only the conductor. TF Structure • Caps and straps support loads without inter-coil structure; • TF cross section is flattened from constant-tension shape to ease PF design.

17. YBCO Superconductor Strip Packs (20 layers each) CeO2 + YSZ insulating coating (on slot & between YBCO layers) Inconel strip 430mm 8.5 Use of High-Temperature Superconductors Simplifies the Magnet Systems • HTS does not offer significant superconducting property advantages over low temperature superconductors due to the low field and low overall current density in ARIES-AT • HTS does offer operational advantages: • Higher temperature operation (even 77K), or dry magnets • Wide tapes deposited directly on the structure (less chance of energy dissipating events) • Reduced magnet protection concerns • and potential significant cost advantages Because of ease of fabrication using advanced manufacturing techniques

18. T 1 11 He Divertor 2' 10 Coolant 2 9' Blanket Divertor 9 5' 7' 3 8 LiPb 6 4 Blanket S 11 Coolant 9 10 Intermediate Intercooler 1 Intercooler 2 HX Recuperator 3 1 Compressor 1 8 6 7 5 W net Compressor 3 Turbine Compressor 2 2 4 Heat Rejection HX Advanced Brayton Cycle Parameters Based on Present or Near Term Technology Evolved with Expert Input from General Atomics* • Key improvement is the development of cheap, high-efficiency recuperators.

19. OB Blanket thickness 1.35 m • OB Shield thickness 0.42 m • Overall TBR 1.1 ARIES-ST Features a High-Performance Ferritic Steel 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 leading to 45% thermal conversion efficiency.

20. Simple, low pressure design with SiC structure and LiPb coolant and breeder. ARIES-AT2: SiC Composite Blankets Outboard blanket & first wall • Simple manufacturing technique. • Very low afterheat. • Class C waste by a wide margin. • LiPb-cooled SiC composite divertor is capable of 5 MW/m2 of heat load. • Innovative design leads to high LiPb outlet temperature (~1,100oC) while keeping SiC structure temperature below 1,000oC leading to a high thermal efficiency of ~ 60%.

21. PbLi Inlet Temp. = 764 °C Max. SiC/SiC Temp. = 996°C Max. SiC/PbLi Interf. Temp. = 994 °C Bottom Top PbLi Outlet Temp. = 1100 °C Innovative Design Results in a LiPb Outlet Temperature of 1,100oC While Keeping SiC Temperature Below 1,000oC • Two-pass PbLi flow, first pass to cool SiCf/SiC box second pass to superheat PbLi

22. The divertor is part of the replacement module, and consists of 3 plates, coolant and vacuum manifolds, and the strongback support structure The divertor structures fulfill several essential functions: 1) Mechanical attachment of the plates; 2) Shielding of the magnets; 3) Coolant routing paths for the plates and inboard blanket;

23. Attractiveness:Evaluation Based on Customer Requirements

24. Estimated Cost of Electricity (c/kWh) Major radius (m) High Thermal Efficiency High b is used to lower magnetic field Approaching COE insensitive of power density Our Vision of Magnetic Fusion Power Systems Has Improved Dramatically in the Last Decade, and Is Directly Tied to Advances in Fusion Science & Technology

25. Estimated range of COE (c/kWh) for 2020* AT 1000 (1 GWe) AT 1500 (1.5 GWe) EPRI Electric Supply Roadmap (1/99): Business as usual Impact of $100/ton Carbon Tax. Estimates from Energy Information Agency Annual Energy Outlook 1999 (No Carbon tax). ARIES-AT is Competitive with Other Future Energy Sources * Data from Snowmass Energy Working Group Summary.

26. After 100 years, only 10,000 Curies of radioactivity remain in the 585 tonne ARIES-RS fusion core. Radioactivity Levels in Fusion Power PlantsAre Very Low and Decay Rapidly after Shutdown ARIES-RS: V Structure, Li Coolant; ARIES-ST: Ferritic Steel Structure, He coolant, LiPb Breeder; Designs with SiC composites will have even lower activation levels. • Low afterheat results in excellent safety characteristics • Low specific activity leads to low-level waste that decays away in a few hundreds years.

27. Multi-Dimensional Neutronics Analysis was Performed to Calculate TBR, activities, & Heat Generation Profiles • Very low activation and afterheat Lead to excellent safety and environmental characteristics. • All components qualify for Class-C disposal under NRC and Fetter Limits. 90% of components qualify for Class-A waste. • On-line removal of Po and Hg from LiPb coolant greatly improves the safety aspect of the system and is relatively straight forward.

28. ARIES-AT Also Uses A Full-Sector Maintenance Scheme

29. Feasibility:Fusion Development Path

30. The development path to realize fusion as a practical energy source includes: • Demonstration of high performance, steady-state burning plasmas. • Fusion power technologies are a pace setting element of fusion development. Development of fusion power technologies requires: • Strong base program including testing of components in non-nuclear environment as well as fission reactors. • Material program including an intense neutron source to develop and qualify low-activation material. • A Component Test Facility for integration and test of power technologies in fusion environment.

31. Base Plasma physics Theory & Simulation ST, stellarator, RFP, other ICCs ICC ETR DEMO Tokamak physics Major Facilities Decision point ITER DEMO 14-MeV neutron source Component Test Facility Base Technologies Fusion power technologies Plasma support technologies ITER-Based Development Path