Transcript ARIES: Fusion Power Core and Power Cycle Engineering

IFE Dry Chamber Wall Designs
A. R. Raffray and F. Najmabadi
University of California, San Diego
Laser IFE Materials Working Group Meeting
University of California, Santa Barbara
August 30, 2001
For more info, please visit the ARIES web site:
http://aries.ucsd.edu/ARIES/
August 30, 2001
A. R. Raffray, IFE Dry Chamber Wall Designs
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Outline of Presentation
• Dry Chamber Wall Design
– Must satisfy conflicting requirements set by operation and performance of different
components
• Dry Chamber Wall Options
– Armor is Key Region - Blanket design can be adapted from MFE blankets
– Candidate Armor Materials and Configurations
• C, W, Engineered surface (fibrous surface), others
• Example thermal analyses
– Key Material Issues
• Use of very thin armor on structural material to separate energy accommodation function from
structural function
• Surface and near-surface properties under pulsed conditions (ion and neutron fluxes and fluence)
• Armor fabrication and bonding
• Erosion
– Armor lifetime and need for in-situ repair
• Tritium retention issues
– Must consider other armor options besides C
• Must prioritize material R&D - make the most of information from MFE and focus on key IFE issues
August 30, 2001
A. R. Raffray, IFE Dry Chamber Wall Designs
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Requirements from Several Components and Processes
Must be Balanced in Evolving IFE Chamber Design
Tout
• Power production
Laser Energy,
Gain,
Rep. Rate
Laser
Driver
• Material temperature
constraint
• Chamber clearing
Target
Injection
HX to
Power
Cycle
• Wall lifetime
Chamber
Size
• Capital cost
• Cycle efficiency
• Wall lifetime
Coolant
Temperature
Chamber
Gas
Pressure
• Target thermal control
• Laser breakdown
• Chamber clearing
• Target thermal control
• Wall lifetime
Tin
August 30, 2001
A. R. Raffray, IFE Dry Chamber Wall Designs
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Target Thermal Control Requirements on Wall Temperature and
Chamber Gas Pressure
• Analysis of design window for successful injection of direct and indirect
drive targets in a gas-filled chamber (e.g., Xe)
• No major constraints for indirect-drive targets.
• Narrow design window for direct-drive targets
(Pressure < ~50 mTorr, Wall temperature < 700 °C)
August 30, 2001
A. R. Raffray, IFE Dry Chamber Wall Designs
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Laser Beam Propagation and Breakdown Sets Requirement on the
Chamber Gas Pressure for a Given Laser Intensity
•
The chamber environment
following a target
explosion contains a hot,
turbulent gas which will
interact with subsequent
laser pulses.
• Gas breakdown may occur
in the vicinity of the target
where the beam is focused.
•
A better understanding of
the degree of gas
ionization and the effects
on beam propagation is
needed (under study at
UCSD).
August 30, 2001
A. R. Raffray, IFE Dry Chamber Wall Designs
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Outline of Presentation
• Dry Chamber Wall Design
– Must satisfy conflicting requirements set by operation and performance of different
components
• Dry Chamber Wall Options
– Armor is Key Region - Blanket design can be adapted from MFE blankets
– Candidate Armor Materials and Configurations
• C, W, Engineered surface (fibrous surface), others
• Example thermal analyses
– Key Material Issues
• Use of very thin armor on structural material to separate energy accommodation function from
structural function
• Surface and near-surface properties under pulsed conditions (ion and neutron fluxes and fluence)
• Armor fabrication and bonding
• Erosion
– Armor lifetime and need for in-situ repair
• Tritium retention issues
– Must consider other armor options besides C
• Must prioritize material R&D - make the most of information from MFE and focus on key IFE issues
August 30, 2001
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Armor is Key Region
All the Action Takes Place within 0.1-0.2 mm of Surface
Photon and Ion Attenuations in C and W Slabs
from NRL Direct Drive Target Spectra (154 MJ)
•
•
•
Depth (mm):
0
0.02
1
3
Typical T Swing (°C): ~1000 ~300 ~10 ~1
•
~ 0.1 mm Armor
•
Structural
Material
August 30, 2001
3-5 mm
Photon and ion energy deposition
falls by 1-2 orders of magnitude
within 0.1 mm of surface
Because of thermal capacity of
armor, FW structure experiences
much more uniform q’’ and quasi
steady-state temperature
Most of neutrons deposited in the
back where blanket and coolant
temperature will be at quasi steady
state due to thermal capacity effect
Focus IFE effort on armor design
and material issues
Blanket design can be adapted from
MFE blankets
Coolant
A. R. Raffray, IFE Dry Chamber Wall Designs
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Example of Adapting an MFE Blanket Design to IFE
• Variation of ARIES-AT blanket
• High performance blanket with possibility
of adjusting wall temperature to satisfy
target thermal control requirement
Blanket & First Wall Segment
• Simple, low pressure design with SiCf/SiC
structure and Pb-17Li coolant and breeder.
• Innovative design leads to high Pb-17Li
outlet temperature (~1100oC) while
keeping SiCf/SiC structure temperature
below 1000oC leading to a high thermal
efficiency of ~ 55%.
• Plausible manufacturing technique.
• Very low afterheat.
• Class C waste by a wide margin.
• Modular blanket for ease of replacement.
August 30, 2001
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Candidate Dry Chamber Armor Materials
•
Carbon (considered for SOMBRERO)
-
•
Tungsten & Other Refractories
-
•
August 30, 2001
Melting concern
Fabrication/bonding and integrity under IFE conditions
Engineered Surface to Increase Effective Incident Area
-
•
High temperature capability
Key tritium retention issue (in particular co-deposition)
Radiation effects on properties
Erosion (several mechanisms; effects of IFE conditions - pulsed operation,
radiation...)
Fabrication - Bonded layer or integrated with structural material?
Safety
e.g. C fibrous carpet
With C, still tritium retention issue
Possibility of coating fiber with W
Requirement on fiber thermal conductivity - negative effect of neutron irradiation
Others?
A. R. Raffray, IFE Dry Chamber Wall Designs
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Example Temperature History for Tungsten Flat Wall Under
Energy Deposition from NRL Direct-Drive Spectra Including
Time-of-Flight Effects
•
•
•
•
Temp. variation mostly in thin armor
region
Key issue for tungsten is to avoid
reaching the melting point = 3410°C
Significant margin for design
optimization
Similar margin for C slab
•
•
•
Coolant temperature = 500°C
Chamber radius = 6.5 m
Maximum temperature = 1438 °C
Armor surface
3-mm thick W
Chamber Wall
Coolant at 500°C
Energy
Front
Evaporation heat
flux B.C at incident
wall
August 30, 2001
20mm depth
Coolant
Convection B.C. at
coolant wall:
h= 10 kW/m2-K
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Consider Engineered Surface Configuration for
Improved Thermal Performance
• Porous Media
- Carbon considered as example but
could also be coated with W
- Fiber diameter ~ diffusion
characteristic length for 1 ms
- Increase incident surface area per
unit cell seeing energy deposition
jincident
L
Q
jfiber= jincident sin q
ESLI Fiber-Infiltrated Substrate
Large fiber L/d ratio ~100
August 30, 2001
A. R. Raffray, IFE Dry Chamber Wall Designs
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Example Thermal Analysis for Fiber Case
•
•
•
•
Incidence angle = 30°
Porosity = 0.9
Effective fiber separation = 54 mm
Sublimation effect not included
Single Carbon
Fiber
1 mm
Convection B.C.
at coolant wall:
h= 10 kW/m2-K
Temperature
Distribution in
Fiber Tip at 2.5 ms
10mm
Coolant at 500°C
Max. Temp.
= 1318°C
August 30, 2001
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Summary of Thermal Results for Carbon Fibrous
Wall without Protective Gas
Coolant temperature = 500 °C; Energy deposition multiplier = 1
Porosity
Fiber Effective
Separation (mm)
0.8
29.6
0.8
29.6
0.8
29.6
0.9
54
C flat wall as comparison:
Incidence
Angle (°)
5
30
45
30
Maximum Temp.
(°C)
654
1317
1624
1318
1530
• Initial results indicate that for shallow angle of incidence the fiber configuration
perform better than a flat plate and would provide more margin
(confirmed by initial results from RHEPP/MAP facility on ESLI sample)
• Optimization study is under way
August 30, 2001
A. R. Raffray, IFE Dry Chamber Wall Designs
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Outline of Presentation
• Dry Chamber Wall Design
– Must satisfy conflicting requirements set by operation and performance of different
components
• Dry Chamber Wall Options
– Armor is Key Region - Blanket design can be adapted from MFE blankets
– Candidate Armor Materials and Configurations
• C, W, Engineered surface (fibrous surface), others
• Example thermal analyses
– Key Material Issues
• Use of very thin armor on structural material to separate energy accommodation function from
structural function
• Surface and near-surface properties under pulsed conditions (ion and neutron fluxes and fluence)
• Armor fabrication and bonding
• Erosion
– Armor lifetime and need for in-situ repair
• Tritium retention issues
– Must consider other armor options besides C
• Must prioritize material R&D - make the most of information from MFE and focus on key IFE issues
August 30, 2001
A. R. Raffray, IFE Dry Chamber Wall Designs
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Armor Material Issues
• Armor material does not need to be the same as structural
material
-
Actually, separating energy accommodation function from structural
function is beneficial
Focus on surface and near-surface properties under pulsed conditions (ion
and neutron fluxes and fluence)
• Armor fabrication and bonding
-
August 30, 2001
Integrity
Ability to accommodate pulsed operation
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Armor Erosion
• Lifetime is a Key issue for Armor
-
Even erosion of one atomic layer per shot results in ~ cm erosion per year
-
Need to better understand molecular surface processes
-
Need to evolve in-situ repair process
-
Several erosion mechanisms in particular for carbon
-
August 30, 2001
Major uncertainties in estimating sublimation based on vapor pressure for
carbon because of difficulty of predicting atomic cluster size of sublimating
carbon
A. R. Raffray, IFE Dry Chamber Wall Designs
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1. Several Erosion Mechanisms Must Be Considered for the Armor
2. Tritium Co-Deposition is a Major Concern for Carbon Because of Cold
Surfaces (Penetration Lines)
Erosion:
Melting
Subli mation/
evaporation
Physical Sputtering
Chemical Sputtering
Radiation Enhanced
Subli mation
Macroscopic
(Brittle) Erosion
Splashing Erosion
Tritium Retention:
Co-deposition
Carbon
Tungsten
No
Yes (SP ~3367 °C)
Yes (MP = 3410°C )
Yes
Yes (peaks at ~ 1
keV)
Yes (peaks at ~ 0.5
keV and 800 K))
Yes (increases
dramatically with T,
peaks at ~ 1 keV)
Yes (thermal stress +
vapor formation)
No
Yes, high threshold
energy
No
Yes (with cold
surfaces with H/C
ratio of up to 1)
No
No
No
Yes (melt layer)
From the ARIES Tritium Town
Meeting (March 6–7, 2001, Livermore
(IFE/MFE Discussion Session):
(http://joy.ucsd.edu/MEETINGS/0103-ARIES-TTM/)
• Carbon erosion could lead to tritium codeposition, raising both tritium inventory
and lifetime issues for IFE with a carbon
wall. Redeposition/co-deposition requires
cold surfaces which would exist in the
beam penetration lines and pumping
ducts.
(For H/C=1, 60 g T per 1mm C for R=6.5 m)
• Macroscopic erosion might be a more
important lifetime issue than sputtering
and sublimation for IFE operating
conditions for high energy ions (>>1 keV)
• R&D effort should be prioritized
• Must Consider Alternate Options for Armor (e.g. W)
August 30, 2001
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Conditions Assumed for ITER ELM’s, VDE’s and
Disruptions Compared to Conditions Associated with a
Typical Direct Drive Target IFE (latest NRL target)
ITER T ype-I
ELM’s
Energy
Locat ion
Time
Max.
Temperature
Frequency
Base
Temperature
ITER VDE’s
<1 MJ/m2
~ 50 MJ/m2
Surface near div. surface
st rike point s
100-1000 µs
~ 0.3 s
melt ing/
melt ing/
sublimat ion
sublimat ion
points
points
Few Hz
~ 1 per 100
cycles
200-1000°C
~ 100°C
ITER
Disrupt ions
~ 10 MJ/m2
surface
~ 1 ms
melt ing/
sublimat ion
points
~ 1 per 10
cycles
~ 100°C
Typical IFE
Operat ion
(direct-drive
NRL target )
~ 0.1 MJ/m2
bulk (~mm’s)
~ 1-3 ms
~ 1500-2000°C
(for dry wall)
~ 10 Hz
~ >500°C
•
We should make the most of existing R&D in MFE area (and other areas) since
conditions can be similar within ~1-1.5 order of magnitude (ELM’s vs IFE)
•
Contact established and initial meeting with Dr. G. Federici (ITER, Garching),
Prof. H. Bolt (IPP, Garching (ASDEX)) and Dr. B. Schedler (Plansee, Austria)
August 30, 2001
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Summary of some key points from discussion with Plansee
(Austrian manufacturer of refractory-based material) to discuss
their experience from MFE and its possible application to IFE
Contact person: Dr. Bertram Schedler
I. Testing of W and W/Rhenium Samples
•
Fatigue tests of 107 cycles at a maximum temperature of ~1000°C with a 150Hz rotating
anode were performed on W and W/rhenium alloy samples. Microcracks induced by
stress relief were observed on the surface.
•
These tests indicated that adding 5-10% of rhenium to W would provide better resistance
against cracking, but at the expense of lower thermal conductivity.
•
Also, rhenium can be added to W to increase thermal expansion coefficient if required by
thermal expansion mismatch at bond with CFC (or SiC but SiC thermal expansion
coefficient is close to that of W).
•
A porous structure (5-20% porosity) might help diffuse the stresses by small propagation
of micro cracks without catastrophic damage.
August 30, 2001
A. R. Raffray, IFE Dry Chamber Wall Designs
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Summary of some key points from discussion with Plansee
(Austrian manufacturer of refractory-based material) to discuss
their experience from MFE and its possible application to IFE
II. Fabrication procedures
•
Physical Vapor Deposition (atomic deposition from sputtering) provides a highly dense
non-columnar deposit of pure W and pure rhenium on CFC. Typical thicknesses would be
about 25-120 microns. Higher thicknesses are possible but takes a long time and are not
attractive economically.
•
PVD process could also be used for W and rhenium on SiC/SiC (CVD could also be used
at ~650°C)
•
Vacuum plasma spraying could be used for higher thicknesses (200-500 microns).
•
PVD coating survived up to 12 MW/m2 at the Jülich facility (sweeping e-beam)
August 30, 2001
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Summary of some key points from discussion with Plansee
(Austrian manufacturer of refractory-based material) to discuss
their experience from MFE and its possible application to IFE
III. W Bonding to C and/or SiC
•
A key problem with W bonding to C (or SiC) is carbide formation at interface between W
and C (or SiC). It would lower the thermal conductivity and reduce ductility. For example
at 1400°C over 5 hours, 10-20 microns of WC was formed at the interface.
•
One improvement is to avoid carbide formation by using a thick W layer to maintain low
enough temperature at the interface (<900°C), or by multilayer coating (about 5 microns
of rhenium/W multilayers) to prevent diffusion of carbon to W interface (patented process
from Plansee)
•
SiCf/SiC is preferred to CFC mostly based on its oxidation protection as compared to CFC
(~700°C)
•
SiC and W are not stable at high temperature. They form a WSi eutectic with 10% W in
Si which melts at 1400°C (much lower than pure W ~ 3410°C). 0.7-22% of C in W also
reduces the melting point to ~2710°C.
•
To avoid eutectic melting the interface SiC/W temperature should be maintained
< ~1300°C. However, diffusion reaction forming brittle intermetallic phase of WSi and
possible carbide formation would still occur, necessating the use of a diffusion barrier.
August 30, 2001
A. R. Raffray, IFE Dry Chamber Wall Designs
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Summary of some key points from discussion with Plansee
(Austrian manufacturer of refractory-based material) to discuss
their experience from MFE and its possible application to IFE
IV. Behavior under IFE Conditions
•
It is very difficult to predict the thermo-mechanical behavior of a thin tungsten layer on
SiCf/SiC or CFC under the cyclic nature of IFE operation (~1500-2000°C peak
temperature, ~10Hz) and under the high energy (~ 100 keV) ion flux and neutron fluence
expected.
•
General interest in follow-on meetings on an ad-hoc basis
August 30, 2001
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Concluding Remarks
• HAPL material R&D should focus on issues specific to inertial fusion
- Final Optics
- Armor
- Pulsed neutron-irradiation effects
• Developing a dry wall chamber requires a coordinated effort
- Engineering
- Design integration
- Material
• Armor R&D
- Maximize information from and synergy with MFE effort on PFC armor
- Also use MFE data base on blanket and structural material
- Prioritize R&D
-
Focus on feasibility issues first
Develop in-situ repair processes
C: tritium retention issue (if this cannot be solved, other issues are irrelevant)
W armor: Fabrication/bonding of W layer on structural material; cyclic testing of mock up
August 30, 2001
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