1. Fusion Power Plants: Visions and Development Pathway Farrokh Najmabadi UC San Diego 15 th ICENES May 15 – 19, 2011 San Francisco, CA You can download a copy of the paper and the presentation from the ARIES Web Site: ARIES Web Site: http://aries.ucsd.edu/ARIES/

2. The ARIES Team Has Examined Many Fusion Concepts As Power Plants Focus of the talk is on Tokamak studies:  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)  Starlite study (1995) (goals & technical requirements for power plants & Demo)  ARIES-RS reversed-shear tokamak (1996)  ARIES-AT advanced technology and advanced tokamak (2000) Focus of the talk is on Tokamak studies:  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)  Starlite study (1995) (goals & technical requirements for power plants & Demo)  ARIES-RS reversed-shear tokamak (1996)  ARIES-AT advanced technology and advanced tokamak (2000) Criteria for power plant attractiveness were developed in consultation with Electric Utilities and Industry

3. Nature of Power Plant Studies has evolved in time.  Concept Exploration (< 1990)  Limited physics/engineering trade-offs due to lack of physic understanding.  The only credible vision was a large, expensive pulsed tokamak with many engineering challenges (e.g., thermal energy storage).  Concept Definition ( ~ 1990-2005)  Finding credible embodiments (Credible in a “global” sense).  Better physics understanding allowed optimization of steady- state plasma operation and physics/engineering trade-offs.  Concept Feasibility and Optimization (> 2010)  Detailed analysis of subsystems to resolve feasibility issues.  Trade-offs among extrapolation and attractiveness.  Concept Exploration (< 1990)  Limited physics/engineering trade-offs due to lack of physic understanding.  The only credible vision was a large, expensive pulsed tokamak with many engineering challenges (e.g., thermal energy storage).  Concept Definition ( ~ 1990-2005)  Finding credible embodiments (Credible in a “global” sense).  Better physics understanding allowed optimization of steady- state plasma operation and physics/engineering trade-offs.  Concept Feasibility and Optimization (> 2010)  Detailed analysis of subsystems to resolve feasibility issues.  Trade-offs among extrapolation and attractiveness.

4. For the same physics and technology basis, steady-state devices outperform pulsed tokamaks * Many engineering challenges such as thermal energy storage, lower performance of fusion core due to thermal cycling, etc.

5. Improving Economic Competitiveness Reducing life-cycle cost:  80s goals:  Low recirculating power;  High power density;  Later Additions  High thermal conversion efficiency;  Less-expensive systems. Reducing life-cycle cost:  80s goals:  Low recirculating power;  High power density;  Later Additions  High thermal conversion efficiency;  Less-expensive systems. Mass power density= net electric output / mass of fusion core Q E = net electric output / recirculating electric power

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

7. ARIES-AT 5.2 9.2% (5.4) 11.5 3.3 36 0.14 0.59 5 COE insensitive of current drive COE insensitive of power density Evolution of ARIES Tokamak Designs 1 st Stability, Nb 3 Sn Tech. ARIES-I’ Major radius (m)8.0   ) 2% (2.9) Peak field (T)16 Avg. Wall Load (MW/m 2 )1.5 Current-driver power (MW)237 Recirculating Power Fraction0.29 Thermal efficiency0.46 Cost of Electricity (c/kWh)10 Reverse Shear Option High-Field Option ARIES-I 6.75 2% (3.0) 19 2.5 202 0.28 0.49 8.2 ARIES-RS 5.5 5% (4.8) 16 4 81 0.17 0.46 7.5

8. A range of attractive tokamak power plants is available. Estimated Cost of Electricity (1992 c/kWh) Major radius (m) Approaching COE insensitive of power density High Thermal Efficiency High  is used to lower magnetic field

9. Fusion Technologies Have a Dramatic Impact of Attractiveness of Fusion

10. ARIES-I Introduced SiC Composites as A High-Performance Structural Material for Fusion SiC composites are attractive structural material for fusion  Excellent safety & environmental characteristics (very low activation and very low afterheat).  High performance due to high strength at high temperatures (>1000 o C).  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. SiC composites are attractive structural material for fusion  Excellent safety & environmental characteristics (very low activation and very low afterheat).  High performance due to high strength at high temperatures (>1000 o C).  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.

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

12. Outboard blanket & first wall ARIES-AT features a high-performance blanket  Simple, low pressure design with SiC structure and LiPb coolant and breeder.  Innovative design leads to high LiPb outlet temperature (~1,100 o C) while keeping SiC structure temperature below 1,000 o C leading to a high thermal efficiency of ~ 60%.  Simple manufacturing technique.  Very low afterheat.  Class C waste by a wide margin.  Simple, low pressure design with SiC structure and LiPb coolant and breeder.  Innovative design leads to high LiPb outlet temperature (~1,100 o C) while keeping SiC structure temperature below 1,000 o C leading to a high thermal efficiency of ~ 60%.  Simple manufacturing technique.  Very low afterheat.  Class C waste by a wide margin.

13. Design leads to a LiPb Outlet Temperature of 1,100 o C While Keeping SiC Temperature Below 1,000 o C Two -pass PbLi flow, first pass to cool SiC f /SiC box second pass to superheat PbLi Bottom Top PbLi Outlet Temp. = 1100 °C Max. SiC/PbLi Interf. Temp. = 994 °C Max. SiC/SiC Temp. = 996°C PbLi Inlet Temp. = 764 °C

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

15. After 100 years, only 10,000 Curies of radioactivity remain in the 585 tonne ARIES-RS fusion core. After 100 years, only 10,000 Curies of radioactivity remain in the 585 tonne ARIES-RS fusion core.  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.  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. Ferritic Steel Vanadium Radioactivity levels in fusion power plants are very low and decay rapidly after shutdown Level in Coal Ash

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

17. Waste volume is not large  1270 m 3 of Waste is generated after 40 full-power year (FPY) of operation. Coolant is reused in other power plants 29 m 3 every 4 years (component replacement), 993 m 3 at end of service  Equivalent to ~ 30 m 3 of waste per FPY Effective annual waste can be reduced by increasing plant service life.  1270 m 3 of Waste is generated after 40 full-power year (FPY) of operation. Coolant is reused in other power plants 29 m 3 every 4 years (component replacement), 993 m 3 at end of service  Equivalent to ~ 30 m 3 of waste per FPY Effective annual waste can be reduced by increasing plant service life.  90% of waste qualifies for Class A disposal

18. Some thoughts on Fusion Development

19. Nature of Power Plant Studies has evolved in time.  Concept Exploration (< 1990)  Limited physics/engineering trade-offs due to lack of physic understanding.  The only credible vision was a large, expensive pulsed tokamak with many engineering challenges (e.g., thermal energy storage).  Concept Definition ( ~ 1990-2005)  Finding credible embodiments (Credible in a “global” sense).  Better physics understanding allowed optimization of steady- state plasma operation and physics/engineering trade-offs.  Concept Feasibility and Optimization (> 2010)  Detailed analysis of subsystems to resolve feasibility issues.  Trade-offs among extrapolation and attractiveness.  Concept Exploration (< 1990)  Limited physics/engineering trade-offs due to lack of physic understanding.  The only credible vision was a large, expensive pulsed tokamak with many engineering challenges (e.g., thermal energy storage).  Concept Definition ( ~ 1990-2005)  Finding credible embodiments (Credible in a “global” sense).  Better physics understanding allowed optimization of steady- state plasma operation and physics/engineering trade-offs.  Concept Feasibility and Optimization (> 2010)  Detailed analysis of subsystems to resolve feasibility issues.  Trade-offs among extrapolation and attractiveness.

20. ITER has changed the magnetic fusion landscape  ITER has heightened understanding of many subsystem issues:  New sets of physics information/correlations has been developed to define design requirements for many subsystems (e.g., in-vessel components, transients).  Realities of designing practical systems to be built.  Increased interest in fusion nuclear engineering and material  Realization that new material and technologies have to be developed now.  ITER has heightened understanding of many subsystem issues:  New sets of physics information/correlations has been developed to define design requirements for many subsystems (e.g., in-vessel components, transients).  Realities of designing practical systems to be built.  Increased interest in fusion nuclear engineering and material  Realization that new material and technologies have to be developed now.

21. New Paradigms for Power Plant Studies in the ITER area  Detailed design of subsystems in context of a power plant environment and constraints  Can only be done one system at a time.  Parametric surveys to understand physics/engineering trade-offs.  Sophisticated computational tools are now widely available.  Interaction with material and R&D community to indentify material properties and R&D needs.  Current ARIES project is focusing on detailed design of in- vessel components.  System Tools to analyze trade-offs among R&D risks and benefits.  A new System approach based on the survey of parameter space as opposed to optimizing to a design point.  Detailed design of subsystems in context of a power plant environment and constraints  Can only be done one system at a time.  Parametric surveys to understand physics/engineering trade-offs.  Sophisticated computational tools are now widely available.  Interaction with material and R&D community to indentify material properties and R&D needs.  Current ARIES project is focusing on detailed design of in- vessel components.  System Tools to analyze trade-offs among R&D risks and benefits.  A new System approach based on the survey of parameter space as opposed to optimizing to a design point.

22. Thank you!