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Laser-Driven IFE Power Plants—Initial Results from ARIES-IFE Study
Farrokh NajmabadiFor the ARIES Team
Third US-Japan Workshop onLaser-Driven Inertial Fusion Energy
Jan.25-27, 2001Lawrence Livermore National LaboratoryElectronic copy: http://aries.ucsd.edu/najmabadi/TALKS
ARIES Web Site: http://aries.ucsd.edu/ARIES
Ø ARIES-IFE Goals and Plans
ü Program started in June 2000 at roughly $1M/year level.
Ø Initial Results
ü Accurate target output spectrum
ü Detailed modeling of load on the chamber wall
ü Chamber wall engineering
ü On-going progress on advanced engineered material, target injection and tracking, final optics, and safety
Outline
Ø Analyze & assess integrated and self-consistent IFE chamber concepts
Ø Understand trade-offs and identify design windows for promising concepts. The research is not aimed at developing a point design.
Ø Identify existing data base and extrapolations needed for each promising concept. Identify high-leverage items for R&D:• What data is missing? What are the shortcomings of present tools?• For incomplete database, what is being assumed and why?• For incomplete database, what is the acceptable range of data?
Would it make a difference to zeroth order, i.e., does it make or break the concept?
• Start defining needed experiments and simulation tools.
ARIES Integrated IFE Chamber Analysis and Assessment Research -- Goals
ARIES-IFE Is a Multi-institutional Effort
Program ManagementF. Najmabadi
Les Waganer (Operations)
Mark Tillack (System Integration)
Program ManagementF. Najmabadi
Les Waganer (Operations)
Mark Tillack (System Integration)Advisory/Review
Committees
Advisory/ReviewCommittees
OFESOFESExecutive Committee
(Task Leaders)
Executive Committee(Task Leaders)
FusionLabs
FusionLabs
• Target Fab. (GA, LANL*)
• Target Inj./Tracking (GA)
• Materials (ANL)
• Tritium (ANL, LANL*)
• Drivers* (NRL*, LLNL*, LBL*)
• Chamber Eng. (UCSD, UW)
• CAD (UCSD)
• Target Physics (NRL*, LLNL*, UW)
• Chamber Physics (UW, UCSD)
• Parametric Systems Analysis (UCSD, BA, LLNL)
• Safety & Env. (INEEL, UW, LLNL)
• Neutronics, Shielding (UW, LLNL)
• Final Optics & Transport (UCSD, NRL*,LLNL*, LBL)
Tasks
* voluntary contributions
An Integrated Assessment Defines the R&D Needs
Characterizationof target yield
Characterizationof target yield
Target Designs
ChamberConcepts
Characterizationof chamber response
Characterizationof chamber response
Chamber environment
Chamber environment
Final optics &chamber propagation
Final optics &chamber propagation
Chamber R&D:Data base
Critical issues
Chamber R&D:Data base
Critical issues
DriverDriver
Target fabrication, injection, and tracking
Target fabrication, injection, and tracking
Assess & Iterate
Ø ARIES-IFE Goals and Plans
ü Program started in June 2000 at roughly $1M/year level.
Ø Initial Results
ü Accurate Target Output Spectrum
ü Detailed Modeling of load on the chamber wall
ü Chamber wall engineering
ü On-going progress on advanced engineered material, target injection and tracking, final optics, and safety
Outline
We Use a Structured Approach to Asses Driver/Chamber Combinations
Ø Six classes of target were identified. Advanced target designs from NRL (laser-driven direct drive) and LLNL (Heavy-ion-driven indirect-drive) are used as starting points.
Ø To make progress, we divided the activity based on three classesof chambers:• Dry wall chambers;• Solid wall chambers protected with a “sacrificial zone” (such
as liquid films);• Thick liquid walls.
Ø We plan to research these classes of chambers in series with the entire team focusing on each.
Ø While the initial effort is focused on dry walls, some of the work is generic to all concepts (e.g., characterization of target yield).
• 1992 Sombrero Study highlighted many advantages of dry wall chambers.
• General Atomic calculations indicated that direct-drive targets do not survive injection in Sombrero chamber.
A Year Ago (2nd US/Japan Workshop)Feasibility of Dry Wall Chambers Was in Question
Target injection Design Window Naturally Leads to Certain Research Directions
Chamber-based solutions:Low wall temperature: Decoupling of first wall & blanket temperaturesLow gas pressure: More accurate calculation of wall loading & response
Advanced engineered materialAlternate wall protection Magnetic diversion of ions*
Target-based solutions: Sabot or wake shield, Frost coating* * Not considered in detail
Target injection window(for 6-m Xe-filled chambers):Pressure < 10-50 mTorrTemperature < 700 C
Reference Direct and Indirect Target Designs
NRL Advanced Direct-Drive Targets
DT Vapor0.3 mg/cc
DT Fuel
CH Foam + DT
1 µm CH +300 Å Au
.195 cm
.150 cm
.169 cm
CH foamρ = 20 mg/cc
DT Vapor0.3 mg/cc
DT Fuel
CH Foam + DT
5 µ CH
.122 cm
.144 cm
.162 cm
CH foamρ = 75 mg/cc
1
10
100
1000
0 5 10 15time (ns)
laser power •NRL Direct Drive Target Gain Calculations (1-D) have been corroborated by LLNL and UW.
LLNL/LBNL HIF Target
Energy output and X-ray Spectra from Reference Direct and Indirect Target Designs
0.570.013Residual thermal energy
458154Total
18.1 (4%) 24.9 (16%)Debris ions kinetic energy
8.43 (2%) 18.1 (12%)Burn product fast ions
0.36 (0.1%) 0.0046 (0.003%)Gammas
316 (69%) 109 (71%)Neutrons
115 (25%) 2.14 (1%)X-rays
HI Indirect Drive Target (MJ)
NRL Direct Drive Target (MJ)
X-ray spectrum is much harderfor NRL direct-drive target
Ion Spectra from Reference NRL Laser-Driven Direct –Drive Target
Slow Ions
Fast Ions
The Spectrum Is Coupled With BUCKY Code to Establish Operating Windows for the First Wall
• Chamber gas pressure can be reduced substantially specially at lower wall temperatures.
• Dec. 2000 results• Time of flight spread in
ion-debris energy flux on the wall was not included.
Vaporization Threshold for NRL target in 6.5m graphite chamber:
LLNL target specturm + knock-ons
600
700
800
900
1000
1100
1200
1300
1400
1500
0 0.05 0.1 0.15 0.2 0.25 0.3
Xe Density (Torr)
Initi
al W
all T
empe
ratu
re (
C)
Wallsurvives
Wallvaporizes
Sombrero >>
Temporal Distribution of Ion-Debris Energy Flux Allows Operation at 700 C and Vacuum
Ion thermal power on the chamber wall including time-of-flight
(6.5-m radius chamber in vacuum)
• NRL advanced direct-drive targets with output spectra from LLNL & NRL target codes.
• Most of heat flux due to fusion fuel and fusion products.
• Chamber wall with C armor and initial temperature of 700 C survives.
• Results confirmed by Bucky(see talk by Peterson)
An Efficient Dry-laser IFE Blanket With Low Wall Temperature Is Possible
Ø Simple, low pressure design with SiC structure and LiPb coolant and breeder.
Ø Innovative design leads to high LiPb outlet temperature (~1100oC) while keeping SiCstructure temperature below 1000oC leading to a high thermal efficiency of ~ 60%.
Ø Simple manufacturing technique.
Ø Very low afterheat.
Ø Class C waste by a wide margin.
Outboard blanket & first wallØ As an example, we considered a variation of ARIES-AT blanket as shown:
An Efficient Dry-laser IFE Blanket With Low Wall Temperature Is PossibleØ IFE dry-wall blanket example: ARIES-AT blanket. First wall
coated with C armor and is cooled by He. Coupled to advanced Brayton Cycle
Ø Power loadings based on NRL targets injected at 6 Hz.
Ø 30% of power is in the first wall.
Blanket(e.g.
ARIES-AT)
Sep.FW
Pb-17Lioutin
He
BlanketPb-17Li (70% of Thermal Power)
He
FW (30% of Thermal Power)
~50°CIHX
Example Case:Ø For a ∆TFW of ~100-150°C, the
average surface Twall at target injection can be lowered to ~600°C while maintaining a cycle efficiency of 50%
Initial Results from ARIES-IFE have Removed Major Feasibility Issues of Dry Wall Chambers
Ø Research is now focused on Optimization And Attractiveness
Ø Trade-off studies are continuing to fully characterize the design window. We are analyzing response of the chamber to∗ Higher target yields∗ Smaller chamber sizes∗ Different chamber wall armor
Ø Un-going activities in:∗ Engineered Material,∗ Effect of chamber environment on target trajectory∗ Final optics∗ Safety
• Good parallel heat transfer, compliant to thermal shock
• Tailorable fiber geometry, composition, matrix
• Already demonstrated for high-power laser beam dumps and ion erosion tests
• Fibers can be thinner than the x-ray attenuation length.
Advanced Engineered Materials May Provide Superior Damage Resistance
Carbon fiber velvet in carbonizable substrate7–10 µm fiber diameter1.5-2.5-mm length1-2% packing fraction
Variations in the Chamber Environment Affects the Target Trajectory in an Unpredictable Way
• Forces on target calculated by DSMC Code
•“Correction Factor” for 0.5 Torr Xepressure is large (~20 cm)
• Repeatability of correction factor requires constant conditions or precise measurements
• 1% density variation causes a change in predicted position of 1000 µm (at 0.5 Torr)
• For manageable effect at 50 mTorr, density variability must be <0.01%.
• Leads to in-chamber tracking
Ex-chamber tracking system
• MIRROR R 50 m
• TRACKING, GAS, &• SABOT REMOVAL • 7m
• STAND-OFF • 2.5 m
• CHAMBER • R 6.5 m • T ~1500 C
• ACCELERATOR • 8 m • 1000 g • Capsule velocity out 400 m/sec
• INJECTOR • ACCURACY
• TRACKING • ACCURACY
• GIMM R 30 m
Laser-Final Optics Threat Spectra
Final Optic Threat Nominal Goal
Optical damage by laser >5 J/cm2 threshold (normal to beam)
Nonuniform ablation by x-rays Wavefront distortion <λ/3 (~100 nm)Nonuniform sputtering by ions 6x108 pulses in 2 FPY:
2.5x106 pulses/atom layer removed
Defects and swelling induced Absorption loss of <1%by γ-rays and neutrons Wavefront distortion of < λ/3
Contamination from condensable Absorption loss of <1%materials (aerosol, dust, etc.) >5 J/cm2 threshold
Two main concerns:∗ Damage that increases absorption (<1%)∗ Damage that modifies the wavefront –
spot size/position (200µm/20µm) and spatial uniformity (1%)
85Þ
stiff, lightweight, actively cooled, neutron transparent substrate
1 m
11.5 m
Safety and Environmental Activities in ARIES-IFE Chamber Assessment
In-vesselActivation
Ex-vesselActivation
WasteAssessment
Waste Metrics
Energy Source Radiological and Toxic Release
Metrics
Evaluation
Decay Heat
Calculation
Tritium andActivationProduct
Mobilization
Debris or Dust
ChemicalReactivity
ToxicMaterial
(Performed jointly by INEEL, UW, LLNL)
• Several causes have been identified for rogue shots: imperfect targets; or incorrect target injection, laser pulse actuation control, laser energy deposition– Imperfect targets remain in fueling stream, ~ 10 to 50/day
based on 1-5% defect rate in factory (current electronic mfg data) and 0.1% failed to be rejected
– Improper target velocity/trajectory in IFE chamber, ~ 1E-03/year based on high reliability gas injection system
– Laser pulse actuation control fault, ~ 1E-05/year based on modern fly by wire digital control systems
– Lasers deliver inadequate energy to target, ~ 1E-03/year based on critical nature of the component in the system
Preliminary Initiator Frequency for IFE Rogue Shots
Ø Rogue shots should be considered “operational occurrences” until more is determined about quality control procedures and approaches for the approximately 1M targets produced per day.
Ø Impact on the chamber of such a shot
Ø Initiator of an accident (shrapnel possibly leading to a loss of
coolant event)
Ø Overall reliability of the facility
Understanding the Impact of Rogue Shots On IFE Power Plant Operation is Essential
Accident Initiators - Rogue Pellets
1
0.1
0.01
1E-03
1E-04
1E-05
1E-06
1E-07
1E-08
1E-09
Operational occurences
Unlikely event
Extremely unlikely event
Beyond design basis events/severeaccidents
Failure probability per year
Nuclear valve andpump failure rate
Passive pipingfailure rate
Electronic components andcomputer chips
1 shot per 10 10
1 shot per 100 millionFrequency of rogue shot
1 shot per 10 12
1 shot per 10 14
Anticipated event
Crane load drop
"Fly by wire" controlsystems in jets
Initial Results from ARIES-IFE have Removed Major Feasibility Issues of Dry Wall Chambers
Ø Research is now focused on Optimization And Attractiveness
Ø Trade-off studies are continuing to fully characterize the design window. We are analyzing response of the chamber to∗ Higher target yields∗ Smaller chamber sizes∗ Different chamber wall armor
Ø Un-going activities in:∗ Engineered Material,∗ Effect of chamber environment on target trajectory∗ Final optics∗ Safety