March 16-17, 2000ARIES-AT Blanket Design and Power Conversion, US/Japan Workshop/ARR ARIES-AT Blanket Design and Power Conversion The ARIES Team Presented by A. René Raffray US/Japan Workshop on Fusion Power Plant Studies and Advanced Technologies University of California, San Diego March 16-17, 2000

ARIES-AT Blanket Design and Power Conversion, US/Japan Workshop/ARR Presentation Outline Design Process Power Cycle –Benefit of high-temperature operation Blanket –MHD flow considerations –Coolant routing –Performance and margins for given constraints Divertor –Possibility of LiPb as coolant Summary of SiC/SiC International Town Meeting

March 16-17, 2000ARIES-AT Blanket Design and Power Conversion, US/Japan Workshop/ARR Design Process Minimize COE while maintaining reasonable margins, credible fabrication and maintenance processes, and attractive safety features

March 16-17, 2000ARIES-AT Blanket Design and Power Conversion, US/Japan Workshop/ARR Brayton Power Cycle Best near-term possibility of power conversion with high efficiency –Maximize potential gain from high- temperature operation with SiC/SiC Compatible with liquid metal blanket through use of HX

March 16-17, 2000ARIES-AT Blanket Design and Power Conversion, US/Japan Workshop/ARR Power Cycle Parameters Brayton Cycle Parameters: Min. T He in cycle (heat sink) = 35°C 3-stage compression with 2 inter-coolers Turbine efficiency = 0.93 Compressor efficiency = 0.88 Recuperator effectiven. = 0.96 Cycle He fractional  P = 0.03 Total compression ratio set to maximize efficiency (=2-2.5) Intermediate Heat Exchanger Effectiveness = 0.9 (mCp) He /(mCp) LiPb = 1

March 16-17, 2000ARIES-AT Blanket Design and Power Conversion, US/Japan Workshop/ARR Brayton Cycle Efficiency, He HX Inlet Temp. and LiPb HX Outlet Temp. as a Function of Total Compression Ratio Max. Cycle He Temp. = 1050°C Example Design Point: Total compression ratio = 3 Cycle efficiency = Cycle He temp. at HX inlet = 604°C LiPb Inlet Temp. to Divertor = 650°C

March 16-17, 2000ARIES-AT Blanket Design and Power Conversion, US/Japan Workshop/ARR ARIES-AT Machine and Power Parameters Used for Analysis Power and Neutronics Parameters Fusion Power 1737 MW Neutron Power 1390 MW Alpha Power 347 MW Current Drive Power41 MW Transport Power to Divertor 289 MW Fraction of Divertor Power Radiated Back to FW0.2 Overall Energy Multiplication1.1 Total Thermal Power1927 MW Average FW Surface Heat Flux0.5 MW/m 2 Max. FW Surface Heat Flux0.7 MW/m 2 Max. Divertor Surf. Heat Flux5 MW/m 2 Average Wall Load4.3 MW/m 2 Maximum O/B Wall Load 6.1 MW/m 2 Maximum I/B Wall Load 4.0 MW/m 2 Machine Geometry Major Radius4.8 m Minor Radius1.2 m FW Location at O/B Midplane 6 m FW Location at Lower O/B 4.8 I/B FW Location3.6 m Toroidal Magnetic Field On-axis Magnetic Field7.5 T Magnetic Field at I/B FW 10 T Magnetic Field at O/B FW 6 T

March 16-17, 2000ARIES-AT Blanket Design and Power Conversion, US/Japan Workshop/ARR Cross-Section of ARIES-AT Showing Power Core Components and Coolant Routing (Preliminary) LiPb Coolant –Inlet/Outlet Temperatures653/1100 °C –Inlet Pressure ~2.5 MPa (Divertor- dependent) Circuit 1 - Lower Divertor + I/B Blkt Region –Thermal Power535 MW –Mass Flow Rate 6500 kg/s Circuit 2 - Upper Divertor + 1st O/B Blkt Region –Thermal Power1040 MW –Mass Flow Rate 12,700 kg/s Circuit 3 - Hot Shield + 2nd O/B Blkt Region –Thermal Power352 MW –Mass Flow Rate 4270 kg/s

March 16-17, 2000ARIES-AT Blanket Design and Power Conversion, US/Japan Workshop/ARR ARIES-AT Outboard Blanket Configuration

March 16-17, 2000ARIES-AT Blanket Design and Power Conversion, US/Japan Workshop/ARR Cross-Section of First Outboard Region of ARIES-AT Blanket Simple poloidal box structure and coolant routing Floating inner shell separating 2 flow passes 1st pass flow through annular region to maintain SiC/SiC structure < 1000°C -MHD flow control by adjusting channel toroidal dimension -Possibility of using swirl flow as an alternative Slow 2nd pass flow through central region to superheat LiPb to ~1100°C Central inner rib to accommodate differential LiPb pressure

March 16-17, 2000ARIES-AT Blanket Design and Power Conversion, US/Japan Workshop/ARR Blanket Module Pressure Stress Analysis Differential Pressure Stress on Blanket Module Inner Shell Pressure Stress on Blanket End Module Outer Shell

March 16-17, 2000ARIES-AT Blanket Design and Power Conversion, US/Japan Workshop/ARR LiPb Temperature Distribution in FW Poloidal Channel under MHD-Laminarization Effect

March 16-17, 2000ARIES-AT Blanket Design and Power Conversion, US/Japan Workshop/ARR Flow and Thermal Parameters for LiPb-Cooled FW of Outboard Region 1 as a Function of FW Channel Thickness

March 16-17, 2000ARIES-AT Blanket Design and Power Conversion, US/Japan Workshop/ARR Divertor Design Considerations Compatibility with Blanket Configuration Structural Material SiC/SiC thickness < 1mm (  th ~ 235 MPa and  T SiC = 250°C for q’’= 5 MW/m 2 ) W with thin SiC insert with or without structural function Possible Concepts Dry Wall –LiPb as coolant (Preferable to avoid in-reactor high pressure He but needs innovative scheme because of poor heat transfer removal capabilities)\ –Porous W HX concept with He coolant as in ARIES-ST –Phase-change liquid metal (Li) Liquid Wall (Sn-Li)

March 16-17, 2000ARIES-AT Blanket Design and Power Conversion, US/Japan Workshop/ARR LiPb Cooling Scheme for ARIES-AT Divertor

March 16-17, 2000ARIES-AT Blanket Design and Power Conversion, US/Japan Workshop/ARR Velocity,  P, Re, and Interaction Parameter as a Function of Divertor Channel Inlet/Outlet Slot Dimension High inertia regime (low interaction parameter) to overcome MHD-induced slanted velocity profile

March 16-17, 2000ARIES-AT Blanket Design and Power Conversion, US/Japan Workshop/ARR Typical Blanket and Divertor Parameters for Example Design Point Blanket Outboard Region 1 No. of Segments32 No. of Modules per Segment6 Module Poloidal Dimension6 m Avg. Module Toroidal Dimen.0.18 m FW SiC/SiC Thickness 4 mm FW CVD SiC Thickness 1 mm FW Annular Channel Thickness5 mm Avg. LiPb Velocity in FW 5.8 m/s FW Channel Re6.2 x 10 5 FW Channel Transverse Ha3540 MHD Turbulent Transition Re1.8x10 6 FW MHD Pressure Drop 0.49 MPa Maximum SiC/SiC Temp. 997°C Maximum CVD SiC Temp. (°C)1030 °C Lower Outer/Inner Divertor Poloidal Dimension1.5/1.0 m Divertor Channel Toroidal Dimension3.8 cm Divertor Channel Radial Dimension3.75 cm Number of Divertor Channels 744/595 SiC Insert Thickness 0.5 mm W Thickness 3 mm PFC Channel Thickness 2 mm Number of Toroidal Passes3/2 Velocity in PFC Channel 1/ 1.2 m/s Maximum SiC Temperature 1000/1040°C Maximum W Temperature 1150/1180°C W (1-D) Thermal Stress 162 MPa Toroidal Dimension of Inlet and Outlet Slot1 mm Vel. in Inlet & Outlet Slot to PFC Channel 2.5/3.1 m/s Interaction Parameter in Inlet/Outlet Slot0.34/0.42 Pressure Drop 0.47/0.5 MPa

March 16-17, 2000ARIES-AT Blanket Design and Power Conversion, US/Japan Workshop/ARR Conclusions High Performance SiC/SiC + LiPb Blanket -Major impact in lowering COE -Attractive safety features Balanced Design Approach -High performance but credible fabrication, reliability, maintenance -Maintain reasonable margins as a measure of reliability For LiPb to be Used as Coolant in the Divertor -Inlet and toroidal flow in PFC channel under low interaction parameter must be verified by detailed MHD analysis and testing Specific SiC/SiC Issues Need to be Addressed -Fabrication/joining procedures and cost -Better definition of key properties at temperature and under irradiation, including: -Thermal conductivity -Compatibility with flowing LiPb -Operating temperature limit (swelling) -Strength degradation -Lifetime

March 16-17, 2000ARIES-AT Blanket Design and Power Conversion, US/Japan Workshop/ARR Summary of International Town Meeting on SiC/SiC Design and Material Issues for Fusion Systems (1) Held at Oak Ridge National Laboratory on January 18-19, The main objective was to bring together the SiC/SiC design and material communities from Japan, the EU and the US to: –exchange information –identify the design-related critical issues –discuss them in light of the latest material R&D results –provide guidelines to help focus future effort. About 30 participants attended the meeting, including 9 from Japan and 5 from the EU. Final discussion session centered on: –the current status of the SiC/SiC parameters and properties –their desirable evolution to increase the performance and attractiveness of SiC/SiC-based fusion power plant designs –reasonable projections that could be used presently in long-term design studies and that would help focus the development of a SiC/SiC material R&D roadmap. See the meeting web site for more detailed information (

March 16-17, 2000ARIES-AT Blanket Design and Power Conversion, US/Japan Workshop/ARR Summary of International Town Meeting on SiC/SiC Design and Material Issues for Fusion Systems (2) Example of some of the interesting and useful information emerging from the meeting: –Trend is to go towards stoichiometry for improved performance (e.g. Tyranno-SA and Hi Nicalon-S fibers) –Low porosity can be achieved (<5%) by non-orthogonal 3-D weaving for enhanced infiltration (CVI) –Based on current cost, it seems reasonable to use $400 per kg for power plant studies looking at 20 years or more in the future. Possibility of lower cost for manufacturing techinque starting with cheapercarbon fiber and CVR (~$100/kg for MER material) but requires further development. –Conventional primary and secondary stress limits do not apply for ceramics; instead, the imposed limit should cover the total stress (thermal + pressure +bending). –A number of irradiation tests have been planned for the next couple of years or two and should provide key data to help better understand many of the thermomechanical issues. –Key properties such as thermal conductivity, and processes influencing the allowable operating temperature window were also discussed. Based on the discussion, the following properties and parameters are suggested for design analysis of SiC/SiC-based power plant for the long term (20-30 years in the future, or more).

March 16-17, 2000ARIES-AT Blanket Design and Power Conversion, US/Japan Workshop/ARR Suggested SiC/SiC Properties for Design Analysis (Assumed here for ARIES-AT Analysis) Density ~3200 kg/m 3 Density Factor0.95 Young's Modulus ~ GPa Poisson's ratio Thermal Expansion Coefficient4 ppm/°C Thermal Conductivity in Plane ~20 W/m-K Therm. Conductivity through Thickness ~20 W/m-K Maximum Allowable Combined Stress~190 MPa Maximum Allowable Operating Temperature ~1000 °C Max. Allowable SiC/LiPb Interface Temperature ~1000°C Min. Allowable Temp. (thermal conductivity basis) ~600°C Maximum Allowable SiC Burnup (ARIES: ~ 3%)Design Dependent Cost ≤$400/kg