November 15, 2000 A. R. Raffray, and the ARIES Team., ARIES-ST and ARIES-AT Blanket Designs, APEX Meeting Summary of Major Features of ARIES-ST and ARIES-AT Blanket Designs Presented by A. René Raffray University of California, San Diego with the Contribution of the ARIES Team and S. Malang APEX Meeting, SNL, Albuquerque November 15, 2000 For more information see:

November 15, 2000 A. R. Raffray, and the ARIES Team., ARIES-ST and ARIES-AT Blanket Designs, APEX Meeting Unique Features of ARIES-ST Power Plant Include: Use of water coolant in the power core (for the Cu centerpost) strongly discourages the use of reactive materials such as Li and Be High power cycle  is needed to offset the effect of high recirculating power in the normal-conducting TF system Relatively high power density results from very high plasma beta The absence of space on the inboard side for a breeding blanket places additional constraints on material selection and dimensions The highly elongated plasma together with an integrated outboard TF shell and vacuum vessel led to a vertical maintenance scheme and toroidally integrated blanket

November 15, 2000 A. R. Raffray, and the ARIES Team., ARIES-ST and ARIES-AT Blanket Designs, APEX Meeting ARIES-ST Power Parameters Fusion Power 2859 MW Neutron Power 2287 MW Alpha Power 572 MW Total Thermal Power3107 MW Ave. FW Surf. Heat Flux0.46 MW/m 2 Max. FW Surf. Heat 0.6 MW/m 2 Average Wall Load4.2 MW/m 2 Maximum O/B Wall Load 6.0 MW/m 2

November 15, 2000 A. R. Raffray, and the ARIES Team., ARIES-ST and ARIES-AT Blanket Designs, APEX Meeting ARIES-ST Utilizes a Dual Coolant Approach to Uncouple Structure Temperature from Main Coolant Temperature Ferritic steel+Pb-17Li+He Flow lower temperature He ( °C) to cool structure and higher temperature Pb-17Li ( °C) for flow through blanket

November 15, 2000 A. R. Raffray, and the ARIES Team., ARIES-ST and ARIES-AT Blanket Designs, APEX Meeting ARIES-ST Blanket Configuration

November 15, 2000 A. R. Raffray, and the ARIES Team., ARIES-ST and ARIES-AT Blanket Designs, APEX Meeting Example Analysis of ARIES-ST First Wall Parameters Used in the Analysis First wall thickness3 mm Second wall thickness3 mm Web thickness4 mm First wall channel depth25 mm Roughness of ribbed surface  m Roughness of smooth surfaces  m Coolant pressure12 MPa Coolant velocity75 m/s Steel properties: Thermal conductivity26.2 W/m-K Young’s modulus207 GPa Poisson’s ratio0.3 Thermal expansion coeff.12x /K First Wall Temperature Distribution

November 15, 2000 A. R. Raffray, and the ARIES Team., ARIES-ST and ARIES-AT Blanket Designs, APEX Meeting Thorough Stress Analysis Confirms Stresses are Within Allowable Values Design conditiontemperaturecalculatedcode limit peak value membrane stress (in web)500˚C68 MPa183 MPa (S mt ) membrane plus bending580˚C148 MPa195 MPa (1.5 S mt ) primary plus secondary575˚C430 MPa464 MPa (3 S m ) First Wall Thermal + Pressure Von Mises Stress

November 15, 2000 A. R. Raffray, and the ARIES Team., ARIES-ST and ARIES-AT Blanket Designs, APEX Meeting ARIES-ST Power Core Coolant Routing (Driving a Brayton Power Cycle) Cycle He used to cool divertor and FW High temperature Pb-17Li from blanket used to heat He through IHX Power Core He temp ˚C He pressure12 MPa Pb-17Li temperature ˚C He flow rate1444 kg/s Pb-17Li flow rate47450 kg/s He temperature to turbine ˚C Power cycle  > 45%

November 15, 2000 A. R. Raffray, and the ARIES Team., ARIES-ST and ARIES-AT Blanket Designs, APEX Meeting ARIES-AT Blanket Design Objective Develop ARIES-AT Blanket Design to Achieve High Performance while Maintaining: Attractive safety features Simple design geometry Reasonable design margins as an indication of reliability Credible maintenance and fabrication processes Design Utilizes High-Temperature Pb-17Li as Breeder and Coolant and SiC f /SiC Composite as Structural Material

November 15, 2000 A. R. Raffray, and the ARIES Team., ARIES-ST and ARIES-AT Blanket Designs, APEX Meeting Brayton Cycle Offers Best Near-Term Possibility of Power Conversion with High Efficiency Maximize potential gain from high- temperature operation with SiC f /SiC Compatible with liquid metal blanket through use of IHX High efficiency translates in lower COE and lower heat load

November 15, 2000 A. R. Raffray, and the ARIES Team., ARIES-ST and ARIES-AT Blanket Designs, APEX Meeting Advanced Brayton Cycle Parameters Based on Present or Near Term Technology Evolved with Expert Input from General Atomics * Min. He Temp. in cycle (heat sink) = 35°C 3-stage compression with 2 inter- coolers Turbine efficiency = 0.93 Compressor efficiency = 0.88 Recuperator effectiveness (advanced design) = 0.96 Cycle He fractional  P = 0.03 Intermediate Heat Exchanger -Effectiveness = 0.9 -(mCp) He /(mCp) Pb-17Li = 1 * R. Schleicher, A. R. Raffray, C. P. Wong, "An Assessment of the Brayton Cycle for High Performance Power Plant," presented at the 14th ANS Topical Meeting on Technology of Fusion Energy, October 15-19, 2000, Park City Utah

November 15, 2000 A. R. Raffray, and the ARIES Team., ARIES-ST and ARIES-AT Blanket Designs, APEX Meeting Compression Ratio is Set for Optimum Efficiency and Reasonable IHX He Inlet Temperature IHX He inlet temperature dictates Pb-17Li inlet temperature to power core Example Design Point: Max. Cycle He Temperature = 1050°C Total compression ratio = 3 Cycle efficiency = Cycle He temp. at HX inlet = 604°C Pb-17 Inlet Temp. to Power Core = 650°C

November 15, 2000 A. R. Raffray, and the ARIES Team., ARIES-ST and ARIES-AT Blanket Designs, APEX Meeting SiC f /SiC Enables High Temperature Operation and its Low Decay Heat Helps Accommodate LOCA and LOFA Events W/O Serious Consequences on In-Reactor Structure 1,2 Properties Used for Design Analysis Consistent with Suggestions from International Town Meeting on SiC f /SiC Held at Oak Ridge National Laboratory in Jan 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 Thermal Conductivity through Thickness ≈ 20 W/m-K Maximum Allowable Combined Stress≈ 190 MPa Maximum Allowable Operating Temperature ≈ 1000 °C Maximum Allowable SiC/LiPb Interface Temperature ≈ 1000°C Maximum Allowable SiC Burnup ≈ 3% 4 1 D. Henderson, et al, and the ARIES Team, ”Activation, Decay Heat, and Waste Disposal Analyses for ARIES-AT Power Plant," 14th TOFE 2 E. Mogahed, et al, and the ARIES Team, ”Loss of Coolant and Loss of Flow Analyses for ARIES-AT Power Plant," 14th ANS T. M. On TOFE 3 See: also A. R. Raffray, et al., “Design Material Issues for SiC f /SiC-Based Fusion Power Cores,” submitted to Fusion Engineering & Design, August 2000 * From ARIES-I

November 15, 2000 A. R. Raffray, and the ARIES Team., ARIES-ST and ARIES-AT Blanket Designs, APEX Meeting ARIES-AT Machine and Power Parameters 1,2 Power and Neutronics Parameters Fusion Power 1719 MW Neutron Power 1375 MW Alpha Power 344 MW Current Drive Power25 MW Overall Energy Multiplicat.1.1 Total Thermal Power1897 MW Ave. FW Surf. Heat Flux0.26 MW/m 2 Max. FW Surf. Heat 0.34 MW/m 2 Average Wall Load3.2 MW/m 2 Maximum O/B Wall Load 4.8 MW/m 2 Maximum I/B Wall Load 3.1 MW/m 2 Machine Geometry Major Radius5.2 m Minor Radius1.3 m FW Location at O/B Midplane 6.5 m FW Location at Lower O/B 4.9 m I/B FW Location3.9 m Toroidal Magnetic Field On-axis Magnetic Field5.9 T Magnetic Field at I/B FW 7.9 T Magnetic Field at O/B FW 4.7 T 1 F. Najmabadi, et al.and the ARIES Team, “Impact of Advanced Technologies on Fusion Power Plant Characteristics,” 14th ANS Top. Meeting.on TOFE 2 R. L. Miller and the ARIES Team, “Systems Context of the ARIES-AT Conceptual Fusion Power Plant,” 14th ANS Top. Meet. On TOFE

November 15, 2000 A. R. Raffray, and the ARIES Team., ARIES-ST and ARIES-AT Blanket Designs, APEX Meeting Cross-Section and Plan View of ARIES-AT Showing Power Core Components

November 15, 2000 A. R. Raffray, and the ARIES Team., ARIES-ST and ARIES-AT Blanket Designs, APEX Meeting Coolant Routing Through 5 Circuits Serviced by Annular Ring Header Circuit Thermal Power Mass Flow Rate 1. Lower Divertor + Inboard Blanket Region 501 MW 6100 kg/s 2. Upper Divertor +1/2 Outboard Blanket Region I 598 MW 7270 kg/s 3. 1/2 Outboard Blanket Region I 450 MW 5470 kg/s 4. Inboard Hot Shield + 1/2 Outboard Blanket II 182 MW 4270 kg/s 5. Outboard Hot Shield + 1/2 Outboard Blanket II 140 MW 1700 kg/s Pb-17Li Coolant Inlet Temperature653 °C Outlet Temperature1100 °C Blanket Inlet Pressure 1 MPa Divertor Inlet Pressure1.7 MPa Mass Flow Rate 22,700 kg/s

November 15, 2000 A. R. Raffray, and the ARIES Team., ARIES-ST and ARIES-AT Blanket Designs, APEX Meeting ARIES-AT Utilizes a 2-Pass Coolant Approach to Uncouple Structure Temperature from Outlet Coolant Temperature ARIES-AT: 2-pass Pb-17Li flow, first pass to cool SiC f /SiC box and second pass to “superheat” Pb-17Li Maintain blanket SiC f /SiC temperature (~1000°C) < Pb-17Li outlet temperature (~1100°C)

November 15, 2000 A. R. Raffray, and the ARIES Team., ARIES-ST and ARIES-AT Blanket Designs, APEX Meeting ARIES-AT Outboard Blanket Segment Configuration

November 15, 2000 A. R. Raffray, and the ARIES Team., ARIES-ST and ARIES-AT Blanket Designs, APEX Meeting Multi-Dimensional Neutronics Analysis to Calculate Tritium Breeding Ratio and Heat Generation Profiles 1 Latest data and code 3-D tritium breeding > 1.1 to account for uncertainties Blanket configuration and zone thicknesses adjusted accordingly Blanket volumetric heat generation profiles used for thermal-hydraulic analyses 1 L. A. El-Guebaly and the ARIES Team, “Nuclear Performance Assessment for ARIES-AT Power Plant,” 14th TOFE

November 15, 2000 A. R. Raffray, and the ARIES Team., ARIES-ST and ARIES-AT Blanket Designs, APEX Meeting Poloidal Distribution of Surface Heat Flux and Neutron Wall Load

November 15, 2000 A. R. Raffray, and the ARIES Team., ARIES-ST and ARIES-AT Blanket Designs, APEX Meeting Moving Coordinate Analysis to Obtain Pb-17Li Temperature Distribution in ARIES-AT First Wall Channel and Inner Channel Assume MHD-flow- laminarization effect Use plasma heat flux poloidal profile Use volumetric heat generation poloidal and radial profiles Iterate for consistent boundary conditions for heat flux between Pb-17Li inner channel zone and first wall zone Calibration with ANSYS 2-D results

November 15, 2000 A. R. Raffray, and the ARIES Team., ARIES-ST and ARIES-AT Blanket Designs, APEX Meeting Temperature Distribution in ARIES-AT Blanket Based on Moving Coordinate Analysis Pb-17Li Inlet Temp. = 764 °C Pb-17Li Outlet Temp. = 1100 °C Max. SiC/PbLi Interf. Temp. = 994 °C FW Max. CVD and SiC/SiC Temp. = 1009°C° and 996°C° Pb-17Li Inlet Temp. = 764 °C Pb-17Li Outlet Temp. = 1100 °C From Plasma Side: - CVD SiC Thickness = 1 mm - SiC f /SiC Thickness = 4 mm (SiC f /SiC k = 20 W/m-K) - Pb-17Li Channel Thick. = 4 mm - SiC/SiC Separ. Wall Thick. = 5 mm (SiC f /SiC k = 6 W/m-K) Pb-17Li Vel. in FW Channel= 4.2 m/s Pb-17Li Vel. in Inner Chan. = 0.1 m/s Plasma heat flux profile assuming no radiation from divertor

November 15, 2000 A. R. Raffray, and the ARIES Team., ARIES-ST and ARIES-AT Blanket Designs, APEX Meeting Pressure Stress Analysis of Inner Shell of Blanket Module Differential pressure stress on blanket module inner shell varies poloidally from ~ 0.25 MPa at the bottom to ~ 0 MPa at the top Maximum pressure stress for 0.25 MPa Case: -218 MPa for 5-mm thickness -116 MPa for 8-mm thickness Use tapered thickness from 7 mm at bottom to ≈ 3 mm at top to maintain comfortable combined stress margin (<< 190 MPa)

November 15, 2000 A. R. Raffray, and the ARIES Team., ARIES-ST and ARIES-AT Blanket Designs, APEX Meeting Pressure Stress Analysis of Outer Shell of Blanket Module at Segment End of First Outboard Region 6 modules per outboard segment Side walls of all inner modules are pressure balanced Side walls of outer modules must be reinforced to accommodate the Pb-17Li pressure (1 MPa) For a 2-cm thick outer module side wall, the maximum pressure stress = 85 MPa The side wall can be tapered radially by tailoring the thickness to maintain a uniform stress. This would reduce the SiC volume fraction and benefit tritium breeding. The thermal stress at this location is small and the sum of the pressure and thermal stresses is well within the 190 MPa limit. The maximum pressure stress at the first wall is quite low, ~60 MPa.

November 15, 2000 A. R. Raffray, and the ARIES Team., ARIES-ST and ARIES-AT Blanket Designs, APEX Meeting 3-D Thermal Stress Analysis of Toroidal Half of Module in First Outboard Blanket Region Example case: Effective h in Pb-17Li channel = 15 kW/m 2 -K Max. thermal stress = 113 MPa Max. thermal stress = 114 MPa Max. combined stress = 174 MPa (within the 190 MPa limit)

November 15, 2000 A. R. Raffray, and the ARIES Team., ARIES-ST and ARIES-AT Blanket Designs, APEX Meeting Develop Plausible Fabrication Procedure and Minimize Joints in High Irradiation Region E.g. First Outboard Region Blanket Segment 1.Manufacture separate halves of the SiC f /SiC poloidal module by SiC f weaving and SiC Chemical Vapor Infiltration (CVI) or polymer process; 2. Manufacture curved section of inner shell in one piece by SiC f weaving and SiC Chemical Vapor Infiltration (CVI) or polymer process; 3.Slide each outer shell half over the free- floating inner shell; 4.Braze the two half outer shells together at the midplane; 5.Insert short straight sections of inner shell at each end; Brazing procedure selected for reliable joint contact area

November 15, 2000 A. R. Raffray, and the ARIES Team., ARIES-ST and ARIES-AT Blanket Designs, APEX Meeting ARIES-AT First Outboard Region Blanket Segment Fabrication Procedure (cont.) 6.Form a segment by brazing six modules together (this is a bond which is not in contact with the coolant; and 7.Braze caps at upper end and annular manifold connections at lower end of the segment.

November 15, 2000 A. R. Raffray, and the ARIES Team., ARIES-ST and ARIES-AT Blanket Designs, APEX Meeting Maintenance Methods Allow for End-of-Life Replacement of Individual Components * *L. M. Waganer, “Comparing Maintenance Approaches for Tokamak Fusion Power Plants,” 14th ANS Topical Meeting on Technology of Fusion Energy, October 15-19, 2000, Park City Utah

November 15, 2000 A. R. Raffray, and the ARIES Team., ARIES-ST and ARIES-AT Blanket Designs, APEX Meeting Annular Manifold Configuration with Low Temp. Inlet Pb-17Li in Outer Channel and High Temp. Outlet Pb-17Li in Inner Channel (e.g manifold between ring header and outboard blanket I ) Reduction in T interface at the expense of additional heat transfer from outlet Pb-17Li to inlet Pb-17Li and increase in Pb-17Li T inlet Very difficult to achieve maximum Pb-17Li /SiC T interface < Pb-17Li T outlet However, manifold flow in region with very low or no radiation Set manifold annular dimensions to miminimize  T bulk while maintaining a reasonable  P

November 15, 2000 A. R. Raffray, and the ARIES Team., ARIES-ST and ARIES-AT Blanket Designs, APEX Meeting Typical ARIES-AT Blanket Parameters for Design Point E.g. Blanket Outboard Region 1 Number of Segments32 Number of Modules per Segment6 Module Poloidal Dimension6.8 m Average Module Toroidal Dimension0.19 m First Wall SiC f /SiC Thickness 4 mm First Wall CVD SiC Thickness 1 mm First Wall Annular Channel Thickness4 mm Average Pb-17Li Velocity in First Wall 4.2 m/s First Wall Channel Re3.9 x 10 5 First Wall Channel Transverse Ha4340 MHD Turbulent Transition Re2.2 x 10 6 First Wall MHD Pressure Drop 0.19 MPa Maximum SiC f /SiC Temperature996°C Maximum CVD SiC Temperature 1009 °C Maximum Pb-17Li/SiC Interface Temperature994°C Average Pb-17Li Velocity in Inner Channel 0.11 m/s

November 15, 2000 A. R. Raffray, and the ARIES Team., ARIES-ST and ARIES-AT Blanket Designs, APEX Meeting ARIES-AT Blanket Design - Conclusions The Blanket Design Utilizes High-Temperature Pb-17Li as Breeder and Coolant and SiC f /SiC Composite as Structural Material –High performance (Brayton cycle efficiency ~59%) –Attractive safety features (low activation SiC f /SiC) –Simple design geometry –Reasonable design margins as an indication of reliability –Credible maintenance and fabrication processes Key R&D Issues Have Been Identified, Including –SiC f /SiC fabrication/joining, and material properties at high temperature and under irradiation, in particular: Thermal conductivity, maximum temperature limits, lifetime