Field-Reversed Configuration Fusion Power Plants

1. Field-Reversed Configuration Fusion Power Plants John F. Santarius University of Wisconsin Workshop on Status and Promising Directions for FRC Research PPPL June 8-9, 1999

2. Collaborators • University of Wisconsin • Canh Nguyen Laila El-Guebaly • Gil Emmert Doug Henderson • Hesham Khater Jerry Kulcinski • Elsayed Mogahed Sergei Ryzhkov • Mohamed Sawan • University of Washington • Loren Steinhauer • University of Illinois • George Miley JFS 1999

3. FRC Power Plant Applications JFS 1999

4. Field-Reversed Mirror (D-T, Condit, et al., LLNL, 1976) University of Wisconsin JFS 1999

5. SAFFIRE Field-Reversed Mirror(D-3He, Miley, et al., Univ. of Illinois, 1978) JFS 1999

6. ARTEMIS Field-Reversed Configuration(D-3He, Momota, et al., NIFS, 1992) JFS 1999

7. A D-T FRC Engineering Scoping StudyIs In Progress • Collaboration of Universities of Wisconsin, Washington, and Illinois. • Objective: To investigate critical engineering issues for D-T FRC Power Plants. • Systems analysis • Tritium-breeding blanket design • Radiation shielding and damage • Activation, safety, and environment • Plasma modeling • Current drive • Plasma-surface interactions JFS 1999

8. FRC Plasma Power Flows Differ Significantly from Tokamak Power Flows • Power density can be very high due to its b2B4 scaling, but this does not necessarily imply an unmanageable first-wall heat flux. • Charged-particle power transports from internal plasmoid to edge region and then out ends of fusion core. • Expanded flux tube in end chamber reduces heat and particle fluxes, so charged-particle transport power only slightly impacts the first wall. • Mainly bremsstrahlung power contributes to first-wall surface heat. • Relatively small peaking factor along axis for bremsstrahlung and neutrons. JFS 1999

9. Linear Geometry Greatly Facilitates Engineering • Flow of charged particles to end plate reduces first-wall surface heat flux. • Modules containing blanket, shield, and magnet can be replaced as single units due to their moderate mass. • Maintenance should be easier and improve reliability and availability. • Considerable flexibility exists for placement of pipes, manifolds, etc. • Direct conversion of transport power to electricity could increase net efficiency. University of Wisconsin JFS 1999

10. FRC Geometry Greatly Reduces the ‘Divertor’ Problem • MHD tilt instability, probably the closest FRC analogue to a tokamak disruption, will send the plasma along the axis and into the end chamber, where measures can be more easily taken to mitigate and localize the effects. • Steady-state heat flux is broadly spread and due almost exclusively to bremsstrahlung radiation power. • Edge region vacuum pumps well and should shield the core plasma from most impurities.. JFS 1999

11. Compact Toroids Might Provide both Fueling and Current Drive for FRC’s • Compact toroids carry particles and current at 100’s of km/s. • Small spheromaks merging with a large FRC will relax to an FRC with a slightly larger current. • Added helicity must balance resistive decay of the plasma current. • Added particles should balance particle transport losses. • Spheromaks would be injected at ~1 Hz. • Either vertical or horizontal geometry should work. • Key question is power required for self-consistent fueling and current drive. JFS 1999

12. D-T FRC Engineering Scoping StudyKey Assumptions • Rotating magnetic field (RMF) current drive. • Steady-state operation. • He/Li20/SiC for coolant/breeder/structure of first wall and blanket. • Superconducting magnets, possibly high-Tc. • Thermal energy conversion only. • Horizontal (radial) maintenance of blanket/shield/magnet modules (~5 m length). • ARIES economic model assumptions. JFS 1999

13. Liquid-Walled FRC Power Plants Might Achieve Extremely High Power Densities • The APEX study uses the FRC as a key alternate to the tokamak. • Thick liquid walls (Li, Flibe, LiPb, LiSn) would attenuate neutrons and serve as • Tritium breeder • Radiation shield • Heat transfer medium JFS 1999

14. FRC Magnets Fit Well within Superconducting State-of-the-Art • Magnetic fields for both D-T and D-3He FRC power-plant coils are usually projected to be <6 T. • Externally generated field within fusion core nearly equals the field on the coils  increased power density (B4). • MHD pressure drop for liquid-metal coolants will require less pumping power than in tokamaks. • High-temperature superconductors presently operate at relevant current densities at 5 T in short lengths. • High-temperature superconductors should be more resistant to quenching and may, therefore, reduce the required radiation shield. JFS 1999

15. Pulsed FRC Power Plants • High FRC power density gives flexibility that would help accommodate changes necessitated by pulsing. • High-temperature superconductors would facilitate a pulsed design. • Neutron-fluence limited, therefore unaffected by pulsing, rather than heat-flux limited. • More robust against quenching due to pulsed fields. • Might be fueled by periodic CT injection for fueling and current drive. • Also potentially for inducing instability for ash removal and plasma MHD conversion? • Transport implications? JFS 1999

16. D-3He Fuel Could Make Good Use of theHigh Power Density Capability of FRC’s • D-T fueled innovative concepts become limited by first-wall neutron or surface heat loads well before they reach b or B-field limits. • D-T fueled FRC’s optimize at B  3 T. • D-3He needs a factor of ~80 above D-T fusion power densities. • Fusion power density scales as b2B4. • Superconducting magnets can reach at least 20 T. • Potential power-density improvement by increasing B-field to limits is (20/3)^4 ~ 2000 ! JFS 1999

17. Proliferation-Resistant FRC Power PlantMay Be Possible (Probably Requires D-3He) JFS 1999

18. Conclusions • From a fusion energy development perspective, FRC’s occupy the important position of leading the b-driven, engineering-attractiveness route. • The cylindrical geometry and disruption-free operation of D-T FRC’s should allow them to overcome the major engineering obstacles facing D-T tokamaks. • FRC’s match D-3He fuel well, and the combination potentially could outperform D-T. JFS 1999