Engineering Input to System Code and TradeOff Studies to Assess Sensitivities of Major Functions to

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Engineering Input to System Code and Trade-Off
Studies to Assess Sensitivities of Major
Functions to Engineering Parameters

• Presented by
• A. René Raffray
• University of California, San Diego
• With contribution from S. Malang
• ARIES Meeting
• UCSD, La Jolla, CA
• April 3-4, 2007

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Schematic of ARIES Next Step Study as I
Understand It(TBD)
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Outline

• Engineering Input to System Code
• - Components
• Trade-off studies at the function level in
  conjunction with providing input to system code
• - Assessing high-leverage engineering parameters
  to guide integrated trade-off studies to be
  performed by the system code in the future
• - Help provide info on RD direction

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Engineering Input to System Code

• Blanket definitions for different concepts
• - Materials
• - Radial Build
• - Algorithm for performance parameters (nuclear
  analysis, thermal- hydraulic, stress, coupling
  to power cycle, etc)
• Input configurations already developed as part
  of ARIES (recent studies)
• - Self-cooled Pb-17Li SiCf/SiC (ARIES-AT)
• - DCLL (ARIES-CS)
• - He-Cooled Ceramic Breeder (ARIES-CS)
• - Flibe?
• This would help trade-off runs in system code,
  with the understanding that the input parameters
  would have to be refined once a configuration is
  chosen for more detailed design studies.
• (UCSD/UW?)

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Divertor Input to System Code and Trade-Off
Studies at the Function Level
Impact of heat flux accommodation on choice of
materials and grade level of heat extraction
Heat flux (MW/m2) 5 10 15 20
Divertor Pb-17Li He-cooled Water-cooled con
figuration SiCf/SiC W-alloy Cu
alloy (or refractory)
Coolant temperature and power cycle efficiency
(UCSD/GIT?)
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Impact of Heat Flux Requirements on Choice of
Divertor Configuration
q lt 5 MW/m2 (a) Pb-17Li SiCf/SiC -
Negligible pumping power - W-tiles with
sacrificial layer 5 mm - Advanced design,
needs substantial RD - SiCf/SiC temperature lt
1000C - High-grade heat extraction (b)
He-cooled ODS-FS - low pumping power -
robust and relatively simple plate design -
W-tiles with sacrificial layer 10 mm -
conservative design, modest RD - ODS FS
temperature lt 700C - Medium-to-high-grade
heat extraction
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Impact of Heat Flux Requirements on Choice of
Divertor Configuration (II)
q 5-10 MW/m2 He-cooled W-alloy (or
other refractory, e.g. Ta) - high pumping
power - more complex plate design, e.g
100,000 T-tubes or 400,000 finger-like
units - W temperature 700C (embrittlement)
-1300C (recrystallization) - reliability of
plates impacted by limited material choice and
large number of difficult joints (impact on
availability also) - W-tiles with sacrificial
layer 5 mm - Medium-to-high-grade heat
extraction - Substantial RD q gt 10
MW/m2 He-cooling and liquid metal cooling
increasingly difficult as q is increased past
10 MW/m2 and not feasible at or just above this
heat flux level Low-temperature water with
sub-cooled boiling (ITER-like) - heat sink
material with high thermal conductivity and large
ductility required (e.g. Cu-alloy) -
sufficient lifetime under neutron irradiation
questionable - activation of heat sink
material - W-tiles with sacrificial layer 5
mm - Low-grade heat extraction (divertor power
not usable for power conversion system) -
modest RD
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Changes in Physics and Engineering Parameters Can
Substantially Affect Divertor Configuration,
Material Choices, Performance, Reliability and
RD Requirements
For example - Impact of increasing
radiation fractions from the core and from the
edge - Impact of reducing fusion power for given
electric power by utilizing advanced power core
design with high power cycle efficiency
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Power Conversion Trade-Off Studies and Input to
System Code
Impact of coolant temperature on choice of
materials and grade level of heat extraction
Coolant Exit temperature (C) 420 500 620 800
1000
Power Cycle Low-Perf. High-
Perf. Brayton configuration Rankine Rankin
e W-alloy Possibility of
H2 production
Cycle Efficiency 35 40 45 50 60
(UCSD/Others?)
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Choice of Power Conversion System and Impact of
High-Temperature Coolant in Advanced Power Core
Design Configurations
Coolant exit temperature 420C-500C - Low
performance Rankine cycle - low or no steam
superheating,
- potential for chemical
reactions between water and LM or Be - Cycle
efficiency 32-40 Coolant exit temperature
500C-620C - High performance Rankine
cycle - high steam superheating - 2 or 3
stage steam re-heating, requiring large HXs
(tritium permeation issue) - water/steam
pressure gt comparable He pressure high potential
for chemical reactions between water and LM
or Be - Cycle efficiency 42-46 Coolant
exit temperature gt620C - Brayton
cycle - 2-3 compression stages - highly
effective recuperator needed for high perfromance
- Cycle efficiency 45-60 Coolant exit
temperature gt800-900C - H2 production
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Example Rankine Cycle with a Steam Generator
Superheat, single reheat and regeneration
(not optimized) For example calculations,
set - Turbine isentropic efficiency
0.9 - Compressor isentropic efficiency
0.8 - Min.(TcoolTsteam,cycle)gt 10C - Pmin
0.15 bar
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Example Brayton Cycle Considered
Set parameters for example calculations - Blanket
He coolant used to drive power cycle - Minimum
He temperature in cycle (heat sink) 35C -
3-stage compression - Optimize cycle
compression ratio (but lt 3.5 not limiting for
cases considered) - Cycle fractional DP
0.07 - Turbine efficiency 0.93 - Compressor
eff. 0.89 - Recuperator effectiv. 0.95
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Comparison of Brayton and Rankine Cycle
Efficiencies as a Function of Blanket Coolant
Temperature (for example cases)
For this example, 650C is the temperature
level where it becomes advantageous to choose
the Brayton cycle over the Rankine cycle based
on cycle efficiency The choice of cycle needs
to be made based on the specific design and
including other considerations - materials -
reliabilty - safety - partial power
production? - others?
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For Combination of Power Core Coolant(s) and
Cycle, Provide Input to System Code on Efficiency
and Pumping Power as a Function of Fusion Power
Density
E.g., from ARIES-CS study, for DCLL blanket and
Brayton cycle
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For a Given Power Core Configuration, Increasing
the Neutron Wall Load has an Impact on Different
Functions
Higher NWL -gt shorter life time -gt relatively
longer replacement time -gt lower
availability Higher NWL -gt lower coolant exit
temperature -gt lower gross efficiency in the
power conversion system Higher NWL -gt higher
pumping power -gt lower net efficiency in the
power conversion system Higher NWL -gt thicker
shielding -gt larger radial build in inboard -gt
larger machine
These trade-offs to be done for each power core
configuration choice and use as input in system
code (UW?)
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Implications of Waste Treatment on Power Plant
Design Requirements
Blanket modules have to be replaced every 3 to
5 years, depending on the maximum
NWL Potential waste treatment methods for the
different materials used in the blankets
are - re-use (typical example liquid metal
breeder) - re-cycling (typical example ceramic
breeder, beryllium multiplier) - shallow land
burial (typical example steel structure) Waste
treatments of the different materials requires
separating them. Were should this separation
be performed, and, for re-cycling, where will the
ceramic breeder or the beryllium pebbles be
transferred for re-processing? - on the power
plant site? - a number of small reprocessing
plants would be required. At what cost? - at a
central location for a number of power
plants? - frequent and difficult shipments of
highly activated components with possibly high
tritium inventories would be
required. (UW?)
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Implications of Magnetic Field Level on Coil
System
Choice of superconducting material - Nb3Sn
(lt16 T) - NbTi (lt 8-9 T) - HTS (higher
temperature) Cooling requirements Coil
design Coil fabrication and assembly Mechani
cal support Nuclear shielding Need input from
MIT to include in system code
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Impact of Power Core Component Design Choice on
Reliability and Availability
Number of design units Number of parts in
each unit Number of welds and joints Length
of welds Coolant pressure Maximum stresses
compared to allowable limits Can we use a
semi-quantitative method as metric for this
function when evaluating different design
choices? (Boeing/INL?)
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Impact of Design Choices on Maintenance
Number of cuts and rewelding Possibility of
avoiding cutting/rewelding of coolant
lines Implication on replacement time and
power plant availability Can we use a
semi-quantitative method as metric for this
function when evaluating different design
choices? (Boeing?)
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Impact of Tritium Breeding and Recovery on Fuel
Management, Safety and Cost
Tritium breeding - Importance of being able to
adjust TBR to meet any operation or
uncertainties in design predictions
(active knob) - How practical is proposed method
(e.g. adjusting 6Li) Tritium
recovery - Maximizing efficiency of the tritium
extraction system from the breeder - Implication
on tritium inventory - Implication on cost
savings in the tritium control system
(INL/UW?)