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Impact of Advances in Fusion Physics & Technology on the Attractiveness of Tokamak Power Plants

Impact of Advances in Fusion Physics & Technology on the Attractiveness of Tokamak Power Plants. Farrokh Najmabadi University of California San Diego 22th annual meeting of Japan Society of Plasma Science & Nuclear Fusion Research December 1, 2005

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Impact of Advances in Fusion Physics & Technology on the Attractiveness of Tokamak Power Plants

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  1. Impact of Advances in Fusion Physics & Technology on the Attractiveness of Tokamak Power Plants Farrokh Najmabadi University of California San Diego 22th annual meeting of Japan Society of Plasma Science & Nuclear Fusion Research December 1, 2005 Electronic copy: http://aries.ucsd.edu/najmabadi/ ARIES Web Site: http:/aries.ucsd.edu/ARIES

  2. 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

  3. Fusion physics & technology Low-activation material Elements of the Case for Fusion Power Were Developed through Interaction with Representatives of U.S. Electric Utilities and Energy Industry • Have an economically competitive life-cycle cost of electricity • Gain Public acceptance by having excellent safety and environmental characteristics • No disturbance of public’s day-to-day activities • No local or global atmospheric impact • No need for evacuation plan • No high-level waste • Ease of licensing • Reliable, available, and stable as an electrical power source • Have operational reliability and high availability • Closed, on-site fuel cycle • High fuel availability • Capable of partial load operation • Available in a range of unit sizes

  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. Last decade: Reverse Shear Regime • Excellent match between bootstrap & equilibrium current profile at high b. • Requires wall stabilization (Resistive-wall modes). • Internal transport barrier. A dramatic change occurred in 1990: Introduction of Advanced Tokamak • Our vision of a fusion system in 1980s was a large pulsed device. • Non-inductive current drive is inefficient. • Some important achievements in 1980s: • Experimental demonstration of bootstrap current; • Development of ideal MHD codes that agreed with experimental results. • Development of steady-state power plant concepts (ARIES-I and SSTR) based on the trade-off of bootstrap current fraction and plasma b (1990) • ARIES-I: bN= 2.9, b=2%, Pcd=230 MW

  6. 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

  7. Increase Power Density Power density, 1/Vp What we pay for,VFPC High-Field Magnets • Little Gain Big Win • ARIES-I with 19 T at the coil (cryogenic). • Advanced SSTR-2 with 21 T at the coil (HTS). D r r > D r ~ D r < D High bootstrap, High b • 2nd Stability: ARIES-II/IV • Reverse-shear: ARIES-RS, ARIES-AT, A-SSRT2 Decrease Recirculating Power Fraction • Improvement “saturates” about Q ~ 40. • A steady-state, first stability device with Nb3Sn Tech. has a recirculating fraction about 1/2 of this goal. Directions for Improvement • Improvement “saturates” at ~5 MW/m2 peak wall loading (for a 1GWe plant). • A steady-state, first stability device with Nb3Sn technology has a power density about 1/3 of this goal.

  8. Approaching COE insensitive of power density Reduced COE mainly due to advanced technology Evolution of ARIES Designs

  9. ARIES-I Introduced SiC Composites as A High-Performance Structural Material for Fusion • Excellent safety & environmental characteristics (very low activation and very low afterheat). • High performance due to high strength at high temperatures (>1000oC). • Large world-wide program in SiC: • New SiC composite fibers with proper stoichiometry and small O content. • New manufacturing techniques based on polymer infiltration or CVI result in much improved performance and cheaper components. • Recent results show composite thermal conductivity (under irradiation) close to 15 W/mK which was used for ARIES-I.

  10. ARIES-I: • SiC composite with solid breeders • Advanced Rankine cycle Many issues with solid breeders; Rankine cycle efficiency saturated at high temperature Max. coolant temperature limited by maximum structure temperature High efficiency with Brayton cycle at high temperature Continuity of ARIES research has led to the progressive refinement of research • Starlite & ARIES-RS: • Li-cooled vanadium • Insulating coating • ARIES-ST: • Dual-cooled ferritic steel with SiC inserts • Advanced Brayton Cycle at  650 oC • ARIES-AT: • LiPb-cooled SiC composite • Advanced Brayton cycle with h = 59%

  11. 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.

  12. ARIES-ST Featured a High-Performance Ferritic Steel Blanket • Originally developed for ARIES-ST, further developed by EU (FZK). • Typically, the coolant outlet temperature is limited to the max. operating temperature of structural material (550oC for ferritic steels). • A coolant outlet temperature of 700oC is achieved by using a coolant/breeder (LiPb), cooling the structure by He gas, and SiC insulator lining PbLi channel for thermal and electrical insulation.

  13. 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%.

  14. 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

  15. The ARIES-AT Utilizes An Efficient Superconducting Magnet Design • On-axis toroidal field: 6 T • Peak field at TF coil: 11.4 T • TF Structure: Caps and straps support loads without inter-coil structure; Superconducting Material • Either LTC superconductor (Nb3Sn and NbTi) or HTC • Structural Plates with grooves for winding only the conductor.

  16. YBCO Superconductor Strip Packs (20 layers each) CeO2 + YSZ insulating coating (on slot & between YBCO layers) Inconel strip 430mm 8.5 • Epitaxial YBCO • Inexpensive manufacturing would consist of layering HTS on structural shells with minimal winding! Use of High-Temperature Superconductors Simplifies the Magnet Systems • 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

  17. Modular sector maintenance enables high availability • Full sectors removed horizontally on rails • Transport through maintenance corridors to hot cells • Estimated maintenance time < 4 weeks ARIES-AT elevation view

  18. 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

  19. 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

  20. SiC composites lead to a very low activation and afterheat. • All components of ARIES-AT qualify for Class-C disposal under NRC and Fetter Limits. 90% of components qualify for Class-A waste. 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 Ferritic Steel Vanadium

  21. Blanket 1 (replaceable) Blanket 2 (lifetime) Shield (lifetime) • Only “blanket-1” and divertors are replaced every 5 years Fusion Core Is Segmented to Minimize the Rad-Waste

  22. 90% of waste qualifies for Class A disposal Generated radioactivity waste is reasonable • 1270 m3 of Waste is generated after 40 full-power year (FPY) of operation (~50 years) • Coolant is reused in other power plants • 29 m3 every 4 years (component replacement) • 993 m3 at end of service • Equivalent to ~ 30 m3 of waste per FPY • Effective annual waste can be reduced by increasing plant service life.

  23. 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

  24. Advances in plasma physics has led to a dramatic improvement in our vision of fusion systems • Attractive visions for tokamak exist. • The main question is to what extent the advanced tokamak modes can be achieved in a burning plasma (e.g., ITER): • What is the achievable bN (macroscopic stability) • Can the necessary pressure profiles realized in the presence of strong a heating (microturbulence & transport) • Pace of “Technology” research has been considerably slower than progress in plasma physics. • Advanced technologies have a dramatic impact on attractiveness of fusion. Considerable more technology R&D is needed.

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