1. March 3-4, 2005 HAPL meeting, NRL 1 Assessment of Blanket Options for Magnetic Diversion Concept A. René Raffray UCSD With contributions from M. Sawan (UW), I. Sviatoslavsky (UW) and X. Wang (UCSD) HAPL Meeting NRL Washington, DC March 3-4, 2005

2. HAPL meeting, NRL 2 Outline Impact of magnetic diversion on blanket design requirements Magnetic field impact on liquid breeders Reduced FW heat flux impact on He-cooled ceramic breeder option Summary

3. March 3-4, 2005 HAPL meeting, NRL 3 Magnetic Diversion Impact on Blanket Design Requirements Geometry results in a split blanket, the lower part being serviced from the bottom and the top part supported by a bridge spanning over the ion collector plate location and serviced from the top. Reduced heat flux on FW (only X-ray energy deposition) eases FW coolant requirements and opens up possibility of blanket options -Liquid breeder (Li, Pb-17Li, Flibe molten salt) -Perhaps He-cooled ceramic breeder However, MHD effects introduced Example 60-Beams Illumination Configuration

4. March 3-4, 2005 HAPL meeting, NRL 4 B v a b Conducting side walls From: M. A. Hoffman and G. A. Carlson, “Magnetic Field Effects in Fusion Reactor Blankets, Proceedings of the 13th Intersociety Energy Conversion Energy Conference, SAE P-75, IEEE 78-CH1372, San Diego (Aug. 20-25, 1978) 1096-1108. MHD Effects in Conducting Liquid Flow in a Magnetic Field Depends on Hartmann Number, Wall Conductance Ratio and Relative Directions of Liquid Flow and Magnetic Field Hartmann Number, H (ratio of magnetic to ordinary viscosity): Wall Conductance Ratio: Simple Estimate of MHD Pressure Drop in a Channel: Normal laminar flow pressure gradient Induced eddy current results in retarding force on flow (j x B)

5. March 3-4, 2005 HAPL meeting, NRL 5 MHD Effects Include Flow Laminarization (and reduced heat transfer at the wall) and Increased Pressure Drop Laminar-to-Turbulent Transition Re as a Function of Hartmann No. Non-dimensionalized Hartmann pressure gradient as a function of Hartmann No. and wall conductance ratio for circular pipe From: M. A. Hoffman and G. A. Carlson, “Magnetic Field Effects in Fusion Reactor Blankets,” Proceedings of the 13th Intersociety Energy Conversion Energy Conference, SAE P-75, IEEE 78-CH1372, San Diego, (Aug. 20-25, 1978), 1096-1108. Non-MHD transition Re ~ 2300 Non-MHD laminar flow non- dimensionalized pressure gradient ~ 8 for circular pipes Transverse magnetic field Parallel magnetic field

6. March 3-4, 2005 HAPL meeting, NRL 6 Simple Liquid Breeder Blanket Options for Preliminary Analysis Low FW heat flux: simple annular module design with liquid breeder slowly flowing in a 2-pass configuration: first through the annular region and then through the inner channel. Simple estimate of MHD pressure drop for annular channel configuration - R chamb = 6.5 m; fusion power = 1750 MW - Magnetic field from cusp magnets will be at variable orientation to coolant flow but transverse B assumed to be conservative (larger effect). -However, additional losses due to the flow turning and also to entry and outlet effect in annular manifold not included. -Constant annular channel dimensions are assumed; d hyd,outer = 9.5 cm; d hyd,inner = 23 cm (geometry effects would result in smaller channels at each end and higher pressure drop). -Li, Pb-17Li and flibe molten salt considered with and without an insulating layer. Illustration of Possible Liquid Breeder Concept for Upper and Lower Blanket Units Annular submodule concept with a first-pass in the annular region and a second pass in the inner channel (insulation layer could be used to reduce MHD effects) ~0.35 m ~6 m ~0.3 m First pass Second pass B

7. March 3-4, 2005 HAPL meeting, NRL 7 Simple MHD  P Comparison of Liquid Breeder Blanket Options Results indicate possible need for insulation for Li and Pb-17Li (in particular for B>1 T and smaller channels). Flibe looks attractive based on the low MHD pressure drop but a significant R&D program would be required to address other material issues since it is not being much considered elsewhere.

8. March 3-4, 2005 HAPL meeting, NRL 8 Ceramic Breeder Blanket Module Configuration (revisited with very low FW heat flux) Initial number and thicknesses of Be and CB regions optimized for TBR=1.1 based on: -T max,Be < 750°C -T max,CB < 950°C -k Be =8 W/m-K -k CB =1.2 W/m-K -  CB region > 0.8 cm 6 Be regions + 10 CB regions for a total module radial thickness of 0.65 m Preferable to couple to a Brayton cycle to avoid accident scenario that could result in Be/steam reaction and would require designing the module box to accommodate high pressure Li 4 SiO 4 or Li 2 TiO 3 as possible CB

9. March 3-4, 2005 HAPL meeting, NRL 9 Magnetic Diversion Results in Major Reduction in FW Heat Flux (photons only v. ions+photons) -Much reduced demand on first wall cooling

10. March 3-4, 2005 HAPL meeting, NRL 10 Brayton Cycle Configuration Considered in Combination with CB Blanket + Intermediate HX to Provide Flexibility for Separately Setting Cycle He Fractional Pressure Drop 3 Compressor stages (with 2 intercoolers) + 1 turbine stage;  P/P~0.05; 1.5 < r p < 3.0 -  T HX ~ 30°C -  comp = 0.89 -  turb = 0.93 -Effect. recup = 0.95

11. March 3-4, 2005 HAPL meeting, NRL 11 Example Optimization Study of CB Blanket and Brayton Cycle For Cases With and Without Magnetic Diversion Maximum cycle efficiency (  ) as a function of chamber radius (R) under the following assumed constraints: Be and CB: -T max,Be < 750°C -T max,CB < 950°C -  blkt = 0.65 m for breeding FS: 1.T max,ODS-FS < 700°C Fusion Power: 1.1800 MW w/o magnetic diversion; and 2.1750 MW w magnetic diversion Coolant: -  T HX = 30°C -P pump /P thermal < 0.05 Magnetic diversion results in substantial increase ion  which peaks at ~ 45% as compared to ~ 36% for case w/o magnetic diversion FW cooling while maintaining the ODS-FS < 700°C imposes a major constraint in the case w/o magnetic diversion

12. March 3-4, 2005 HAPL meeting, NRL 12 Corresponding He Coolant Inlet and Outlet Temperatures Maximum allowable temperature of FS limits the combination of outlet and inlet He coolant temperatures for case w/o magnetic diversion For case with magnetic diversion, limits on coolant plate FS, CB and Be interplay to limit the combination of outlet and inlet He coolant temperatures

13. March 3-4, 2005 HAPL meeting, NRL 13 Summary Results indicate possible need for insulation for Li and Pb-17Li (in particular for B>1 T and smaller channels) -Lose traditional advantage of magnet-less IFE over MFE Flibe looks attractive based on the low MHD pressure drop but a significant R&D program would be required to address other material issues since it is not being muchconsidered elsewhere. Magnetic diversion results in substantial increase in  which peaks at ~ 45% as compared to ~ 36% for case w/o magnetic diversion -FW cooling while maintaining the ODS-FS < 700°C imposes a major constraint in the case w/o magnetic diversion Future effort will focus on: - Finishing scoping study of different options for original configuration (large chamber) and showing comparative assessment and selection for more detailed study -Development and more detailed study of blanket options and design for magnetic diversion case -How to balance the effort between the two?