Wayne R. Meier Lawrence Livermore National Lab Per Peterson UC Berkeley Introduction to Thick-Liquid-Wall Chambers* ARIES Meeting April 22-23, 2002 * This work was performed under the auspices of the U.S. Department of Energy by the University of California, Lawrence Livermore National Laboratory under Contract No. W-7405-Eng-48.
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Wayne R. Meier Lawrence Livermore National Lab Per Peterson UC Berkeley Introduction to Thick-Liquid-Wall Chambers* ARIES Meeting April 22-23, 2002 * This.
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Wayne R. MeierLawrence Livermore National Lab
Per PetersonUC Berkeley
Introduction to Thick-Liquid-Wall Chambers*
ARIES MeetingApril 22-23, 2002
* This work was performed under the auspices of the U.S. Department of Energy by the University of California, Lawrence Livermore National Laboratory under Contract No. W-7405-Eng-48.
ARIES HIF Modeling - WRM 4/22/022
Thick-liquid-wall chambers: Key features and issues
HYLIFE-II
• Thick liquid “pocket” shields chamber structures from neutron damage and reduces activation
• Oscillating jets dynamically clear droplets near target
• No blanket replacement required, increases chamber availability
• Suited for indirect-drive targets
Key Issue: Chamber Clearing. Can the liquid pocket and beam port protection jets be made repetitively without interfering with beams? Will vapor condensation, droplet clearing and flow recovery occur fast enough to allow pulse rates of ~ 6 Hz?
ARIES HIF Modeling - WRM 4/22/023
Why Thick Liquids?
• Replace fusion materials questions with fluid mechanics questions
– These are questions that can be answered without a $1 billion test facility
• Maximize fusion power density
– Bring final focus/transport elements close to target
– Improve economics
UC Berkeley
ARIES HIF Modeling - WRM 4/22/024
Liquid-protection parameter space provides multiple options for target chambers
The use of thick-liquid protection reduces the first wallneutron flux as well as the average neutron energy.
Dry Wall
Thick-Liquid Protection
Neu
tro
n F
lux
(n/c
m2 -s
)
Neutron Energy (MeV)
Casen,tot
(n/cm2-s)
En,avg (MeV)
Dry Wall 2.7 1015 3.25
Thick-Liquid
3.9 1014 0.47
Approximately 58 cm of flibe is needed to protect the wall against neutron damage and ensure that it would meet Class C requirements.
10-1
100
101
45 50 55 60 65
WDRWDR goal
Was
te d
isp
osa
l rat
ing
Thickness (cm)
100
101
102
0 10 20 30 40 50 60
dpa goalFirst wall dose (dpa/year)
DP
A/f
ull-
po
wer
-yea
r
Thickness (cm)
55 cm of flibe reduces the first wall damage rate to <3.3 dpa/fpy (100 dpa in 30 fpy).
58 cm of flibe is required to reduce the SS304 first wall waste disposal rating to <1.
ARIES HIF Modeling - WRM 4/22/027
Top/Bottom Mid-Plane
Several potential liquid pocket geometries can be assembled from existing single-jet nozzles
High amplitudejet oscillation
Low amplitudejet oscillation
Porous liquid structuresuppresses shock
transmission (> 0.125 secshock transit time)
All porous jets mergeat pocket top
and bottom to fullyenclose target
and shield structures
Use of cylindrical jets for beamgrid allows flow control to
correct pointing errors
Large dimensionpocket opening:• reduces effects of liquid motion on venting,• provides directed debris jet to a separate condenser,• smoothness of oscillating jet surface now less important
Several variants of the HYLIFE-II pocket will be examined.
Asymmetric venting reducespocket symmetry and
debris jetting up beam lines
UC Berkeley
ARIES HIF Modeling - WRM 4/22/028
ARIES HIF Modeling - WRM 4/22/029
Driver/chamber interface
Credit: K. Springer & R. Holmes, LLNL
Key Issue: Self-consistent design. Can super-conducting final focusing magnet arrays be designed consistent with chamber and target solid angle limits for the required number of beams, standoff distance to the target, magnet dimensions and neutron shielding thickness?
ARIES HIF Modeling - WRM 4/22/0210
Cut-away view shows beam and target injection paths
ARIES HIF Modeling - WRM 4/22/0211
Work has progressed to detailed 3D neutronics models - predicting >30 year magnet lifetime
12
34
56 1
23
45
60.00E+00
5.00E+18
1.00E+19
1.50E+19
2.00E+19
2.50E+19
• There is a strong peaking of the fast neutron fluence at the center of the magnet array due to neutron scattering between neighboring penetrations.
• Estimated magnet life is 40-90 years depending on beam-to-structure clearance.
3D Tart model for HYLIFE-IIFast neutron flux for 36 magnet array
ARIES HIF Modeling - WRM 4/22/0212
IFE system phenomena cluster into distinct time scales
• Nanosecond IFE Phenomena– Driver energy deposition and capsule drive (~30 ns)– Target x-ray/debris/neutron emission/deposition (~100 ns)
• Microsecond IFE Phenomena– X-ray ablation and impulse loading (~1 s)– Debris venting and impulse loading (~100 s)– Isochoric-heating pressure relaxation in liquid (~30 s)
• Millisecond IFE Phenomena– Liquid shock propagation and momentum redistribution (~50 ms)– Pocket regeneration and droplet clearing (~100 ms)– Debris condensation on droplet sprays (~100 ms)
• Quasi-steady IFE Phenomena– Structure response to startup heating (~1 to 104 s)– Chemistry-tritium control/target fabrication/safety (103-109 s)– Corrosion/erosion of chamber structures (108 sec)
Pri
nci
pal
foc
us
for
IFE
Tec
hn
olog
y R
&D
...
UC Berkeley
ARIES HIF Modeling - WRM 4/22/0213
All IFE scientific topics can be identified and characterized by time scale and spatial location
Time Scale (Phenomena Duration)Spatial Volume Nanosecond
(Target Gain)Microsecond Millisecond
(Rep. Rate)Quasi-Steady
(Safety/Reliab.)
Capsule Neutron/ion/x-ray emission
—
Hohlraum (if used) X-ray and debrisemission
—
Driver energy transport paths Beam transportand focusing
Volumetric Flow (m3/s) 0.84 0.01 0.16 4.76 8.58 75.00Oscillation Frequency (Hz) 6.0 27.1 12.2 9.1 9.5 6.0Nozzle Velocity U (m/s) 12.0 13.0 5.9 6.9 7.8 12.0Number of Jets 1 1 10 89 89 89Jet Dimensions D (cm) 7 1.68 1.68 various various variousJet Dimensions W (cm) 100 8.1 16 various various variousPumping Power (kW) 356 2 21 907 1,530 31,800
Storage Tank Size (m3) N/A 4 4 300 N/A N/AJet Reynolds Number Re 160,000 160,000 99,000 160,000 43,700 160,000Jet Weber Number We 103,000 21,000 7,900 15,200 18,100 103,000Froude Number Fr 7.3 19.4 7.3 7.3 7.3 7.3Working Fluid Flibe Water Water Water Flibe Flibe
Phase I
UC Berkeley
ARIES HIF Modeling - WRM 4/22/0221
Computational tools have provided new insights
Computation plays thekey role in predicting impulse
loads to jets
CFD provides importantinsights for jet response
Droplet formation
UCLA
Droplet ejectionfrom cylindrical
jet surface
Tsunami simulation of vapor venting through jet
array
Code/experimentcomparison for
shock propagationover tube array
U. Wisc.UCB
Regions flattened by interaction with neighboring jet
Simulations from UCLA
Flow Direction
CollidingHYLIFEslab jets
ARIES HIF Modeling - WRM 4/22/0222
The electro-thermal plasma source: a powerful and cost effective solution for pulsed vapor generation
• Based on existing knowledge from other experiments (NCSU)
• Capable of generating prototypical vapor density of flibe in a practical size chamber
• Discharge characteristics (fast rise time, short period) adequate to simulate IFE post-shot event
New plasma gun is being developed for liquid flibe high-T environment:
• ceramic insulator instead of plastic
• gun entirely inside the vacuum chamber
Technical issues:
• achieve unaided breakdown at 550 C flibe vapor pressure (0.2 mTorr)
• avoid chemical contamination from ablation of insulating materials and secondary discharges
ARIES HIF Modeling - WRM 4/22/0223
A number of alternatives have been considered for thick liquid concepts
• We have evaluated flibe, flinabe, LiPb, Li and LiSn for pumping power requirements and TBR
• Calculated thickness of the liquid pocket is such that FW damage is limited to 100 dpa after 30 FPY operation
• Pumping power considers velocity head, friction loses and lift power
• LiPb and LiSn pumping power requirements are excessive
• Li has a large tritium inventory and poses fire hazards
• Only flibe and flinabe stand as reasonable options
• Regenerate chamber conditions for target injection, driver beam propagation, and ignition at sufficiently high rates (i.e. 3 - 6 Hz)
• Protect chamber structures for several to many years or allow easy replacement of inexpensive modular components
• Extract fusion energy in high-temperature coolant, regenerate tritium
• Reduce radioactive waste generation, inventory, and possible release fractions low enough to meet no-public-evacuation standards.
Chamber will be 9-15% of total capital costDesign, not chamber cost, is the most important issue
UC Berkeley
ARIES HIF Modeling - WRM 4/22/0228
Experiments can take advantage of recent scaling advances
• In IFE strong phenomena decoupling occurs in both time and space– Spatial decoupling boundaries
• small or unidirectional mass and energy fluxes• large time scale differences—slow side sees integral effect of fast
– Temporal decoupling boundaries• large time scale differences —slower phenomena sees integral effect of
fast– Inside these boundaries, phenomena
interactions must be considered• Phenomena change differently with reduced
geometric scale, time scale ratios for important coupled phenomena must be preserved to study interactions
S. Levy, 1999
Liquid pocket formation and hydraulic response can be studiedseparately from ablation, venting and condensation, using asimulant fluid (water) at reduced geometric scale.Reduces experiment cost by factor of ~50 to not use molten salt
UC Berkeley
ARIES HIF Modeling - WRM 4/22/0229
Nanosecond phenomena control scientific viability
Time Scale (Phenomena Duration)Spatial Volume Nanosecond
(Target Gain)Microsecond Millisecond
(Rep. Rate)Quasi-Steady
(Safety/Reliab.)
Capsule Neutron/ion/x-ray emission
—
Hohlraum (if used) X-ray and debrisemission
—
Driver energy transport paths Beam transportand focusing
Accelerator/laser systems Driver physics — Driver rep. rate and reliability
Target injection — — Accel./heating —
Target fabrication — — — Safety/reliability
Balance of plant — — — Safety/reliability
Quasi-steady phenomena:
• Control safety > Must be understood to judge the engineering viability of IFE and of experimental facilities
• Control reliability > Must be understood to judge the attractiveness of IFE
UC Berkeley
ARIES HIF Modeling - WRM 4/22/0232
ARIES HIF Modeling - WRM 4/22/0233
Nanosecond Chamber Phenomena
• Driver energy transport– Shielding material standoff and gas density distribution– IRE will provide primary experimental test capability
• Target x-ray/debris/neutron emission– The most important questions are:
• partitioning of energy between x-rays, debris, and neutrons• effective x-ray black body temperature(s)• directional characteristics of x-rays/debris• control of emission by mass addition outside hohlraum
– High energy density/radiation dominates energy transport– Target design codes can model– Multidimensional effects likely important
in partition of energy between x-rays and debris kinetic energy
• Neutron shielding/energy deposition– 3-D codes (e.g. TART) can model
UCB has improved flibe vapor pressure predictions and identified a new salt composition allowing lower pressures
• Detailed activity coefficient data has allowed the vapor pressure of flibe to be accurately predicted at lower temperatures
• Ternary salt systems (“Flinabe,” LiF/NaF/BeF2) have been identified with very low melting temperatures (320°C)
– In beam tubes this low temperature molten salt creates a large reduction in the equilibrium vapor pressure (109/cc at 400°C)
Cooler
~350°C
RegenerativeHeat Exch.
Pump
ChamberFlibe
Pump VacuumDisengager
~600°C
Vortex Tube
.
1.00E+10
1.00E+11
1.00E+12
1.00E+13
1.00E+14
1.00E+15
460 500 540 580 620 660 700
temperature (C)
m o l e c u l e s / c ctheoretical modelORNL extrapolation
Recent flibe vapor pressureprediction
A degassing system may permitflinabe to be used for He/H2 pumping
UC Berkeley
ARIES HIF Modeling - WRM 4/22/0248
Conclusions
• IFE has strong temporal and spatial phenomena decoupling– Pulsed complex systems: sequence from fast to slow phenomena
• Fast phenomena provide initial conditions for slower phenomena• First-principles modeling appears possible• Large temporal and spatial decoupling of subgroups of phenomena