High Performance Blanket for AriesAT Power Plant

1
High Performance Blanket for Aries-AT Power Plant

• A. R. Raffray1, L. El-Guebaly2, S. Gordeev3, S.
  Malang3,
• E. Mogahed2, F. Najmabadi1, I. Sviatoslavsky2, D.
  K. Sze4,
• M. S. Tillack1, X. Wang1, and the ARIES Team
• 1University of California, San Diego, 460 EBU-II,
  La Jolla, CA 92093-0417, USA
• 2University of Wisconsin, Fusion Technology
  Institute, 1500 Engineering Drive, Madison, WI
  53706-1687, USA
• 3Forschungszentrum Karlsruhe, Postfach 3640,
  D-76021 Karlsruhe, Germany
• 4Argonne National Laboratory, 9700 South Cass
  Avenue, Argonne, IL 60439, USA
• SOFT 2000 Poster Presentation, Madrid, Spain,
  September 2000

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Abstract
The ARIES-AT blanket has been developed with the
overall objective of achieving high performance
while maintaining attractive safety features,
simple design geometry, credible maintenance and
fabrication processes, and reasonable design
margins as an indication of reliability. The
design is based on Pb-17Li as breeder and coolant
and SiCf/SiC composite as structural material.
This paper describes the results of the design
study of this blanket including a discussion of
the major SiC composite parameters and properties
influencing the design, and a description of the
design configuration, analysis results and
reference operating parameters.
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Blanket Metrics for an Attractive Power Plant as
Basis for ARIES-AT Blanket Design

• Blanket Design Measures and Parameters
• High temperature operation
• Heat load accommodation
• Reasonable pressure drop/pumping power
• Configuration and material choice yielding
  acceptable TBR
• Low activation material with no serious
  consequences on blanket and VV from LOFA and LOCA
• Radial segmentation replaceable regions and
  lifetime region
• Design simplicity/Minimization of number of
  components
• Minimization of pressure joints in high
  irradiation area
• Stress limit margin as reliability measure
• Conservative analysis assumptions
• Develop plausible and reasonable-cost fabrication
  scheme in parallel with design evolution
• Maintenance scheme compatible with replacement of
  non-lifetime components

• Metrics
• (not in ranking order)
• High performance
• Tritium self-sufficiency
• Safety
• Waste minimization
• Reliability
• Fabrication
• Maintenance
• Cost

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Brayton Cycle Offers Best Near-Term Possibility
of Power Conversion with High Efficiency

• Maximize potential gain from high-temperature
  operation with SiCf/SiC
• Compatible with liquid metal blanket through use
  of IHX
• High efficiency translates in lower COE and lower
  heat load

5
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) 35C
• 3-stage compression with 2 inter-coolers
• Turbine efficiency 0.93
• Compressor efficiency 0.88
• Recuperator effectiveness (advanced design)
  0.96
• Cycle He fractional DP 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," to be presented at the
14th ANS Topical Meeting on Technology of Fusion
Energy, October 15-19, 2000, Park City Utah
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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
• 1050C
• Total compression ratio 3
• Cycle efficiency 0.585
• Cycle He temp. at HX inlet
• 604C
• Pb-17 Inlet Temp. to Power
• Core 650C

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SiCf/SiC Properties Used for Design Analysis
Consistent with Suggestions from International
Town Meeting on SiCf/SiC Held at Oak Ridge
National Laboratory in January 2000

• Density 3200 kg/m3
• Density Factor 0.95
• Young's Modulus 200-300 GPa
• Poisson's ratio 0.16-0.18
• Thermal Expansion Coefficient 4 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
  1000C
• Maximum Allowable SiC Burnup 3

See http//aries.ucsd.edu/PUBLIC/SiCSiC/,
also A. R. Raffray, et al., Design Material
Issues for SiCf/SiC-Based Fusion Power
Cores, submitted to Fusion Engineering Design,
August 2000 From ARIES-I
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ARIES-AT Machine and Power Parameters
Power and Neutronics Parameters Fusion Power
1719 MW Neutron Power 1375
MW Alpha Power 344 MW Current Drive
Power 25 MW Overall Energy Multiplicat. 1.1 T
otal Thermal Power 1897 MW Ave. FW Surf. Heat
Flux 0.26 MW/m2 Max. FW Surf. Heat 0.34
MW/m2 Average Wall Load 3.2 MW/m2 Maximum
O/B Wall Load 4.8 MW/m2 Maximum I/B Wall Load
3.1 MW/m2
Machine Geometry Major Radius 5.2
m Minor Radius 1.3 m FW Location at O/B
Midplane 6.5 m FW Location at Lower O/B 4.9
m I/B FW Location 3.9 m Toroidal
Magnetic Field On-axis Magnetic Field 5.9
T Magnetic Field at I/B FW 7.9 T Magnetic
Field at O/B FW 4.7 T
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Cross-Section and Plan View of ARIES-AT Showing
Power Core Components
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Coolant Routing Through 5 Circuits Serviced by
Annular Ring Header
Pb-17Li Coolant Inlet Temperature 653 C Outlet
Temperature 1100 C Blanket Inlet Pressure 1
MPa Divertor Inlet Pressure 1.7 MPa Mass Flow
Rate 22,700 kg/s
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
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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 SiCf/SiC box and second pass to superheat
  Pb-17Li
• Maintain blanket SiCf/SiC temperature (1000C) lt
  Pb-17Li outlet temperature (1100C)

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ARIES-AT Outboard Blanket Segment Configuration
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Multi-Dimensional Neutronics Analysis to
Calculate Tritium Breeding Ratio and Heat
Generation Profiles
Latest data and code 3-D tritium breeding
gt 1.1 to account for uncertainties Blanket
configuration and zone thicknesses adjusted
accordingly Blanket volumetric heat
generation profiles used for thermal-hydraulic
analyses
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Poloidal Distribution of Surface Heat Flux and
Neutron Wall Load
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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
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Temperature Distribution in ARIES-AT Blanket
Based on Moving Coordinate Analysis
Max. SiC/PbLi Interf. Temp. 994 C
Pb-17Li Inlet Temp. 764 C
Pb-17Li Outlet Temp. 1100 C
Pb-17Li Inlet Temp. 764 C Pb-17Li Outlet
Temp. 1100 C From Plasma Side - CVD
SiC Thickness 1 mm - SiCf/SiC Thickness 4
mm (SiCf/SiC k 20 W/m-K) - Pb-17Li
Channel Thick. 4 mm - SiC/SiC Separ. Wall
Thick. 5 mm (SiCf/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
FW Max. CVD and SiC/SiC Temp. 1009C and
996C
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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 (ltlt 190 MPa)
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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.
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3-D Thermal Stress Analysis of Toroidal Half of
Module in First Outboard Blanket Region
Example case Eff. h in Pb-17Li channel 15
kW/m2-K Max. thermal stress 113 MPa Max.
thermal stress 114 MPa Max. combined stress
174 MPa (within the 190 MPa limit)
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Develop Plausible Fabrication Procedure and
Minimize Joints in High Irradiation Region
E.g. First Outboard Region Blanket
Segment 1. Manufacture separate halves of the
SiCf/SiC poloidal module by SiCf weaving and SiC
Chemical Vapor Infiltration (CVI) or polymer
process 2. Manufacture curved section of
inner shell in one piece by SiCf 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
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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.
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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
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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 Tinterface at the expense of
additional heat transfer from outlet Pb-17Li to
inlet Pb-17Li and increase in Pb-17Li Tinlet
Very difficult to achieve maximum Pb-17Li /SiC
Tinterface lt Pb-17Li Toutlet However, manifold
flow in region with very low or no radiation
Set manifold annular dimensions to miminimize
DTbulk while maintaining a reasonable DP
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Typical ARIES-AT Blanket Parameters for Design
Point

• E.g. Blanket Outboard Region 1
• Number of Segments 32
• Number of Modules per Segment 6
• Module Poloidal Dimension 6.8 m
• Average Module Toroidal Dimension 0.19 m
• First Wall SiCf/SiC Thickness 4 mm
• First Wall CVD SiC Thickness 1 mm
• First Wall Annular Channel Thickness 4 mm
• Average Pb-17Li Velocity in First Wall 4.2 m/s
• First Wall Channel Re 3.9 x 105
• First Wall Channel Transverse Ha 4340
• MHD Turbulent Transition Re 2.2 x 106
• First Wall MHD Pressure Drop 0.19 MPa
• Maximum SiCf/SiC Temperature 996C
• Maximum CVD SiC Temperature 1009 C
• Maximum Pb-17Li/SiC Interface Temperature 994C
• Average Pb-17Li Velocity in Inner Channel 0.11
  m/s