Thin Liquid Wall Behavior under IFE Cyclic Operation

1
Thin Liquid Wall Behavior under IFE Cyclic
Operation

• A. R. Raffray1, S. I. Abdel-Khalik2, D. Haynes3,
  F. Najmabadi4, J. P. Sharpe5 and the ARIES Team
• 1Mechanical and Aerospace Engineering Department
  and Center for Energy Research, University of
  California, San Diego, EBU-II, Room 460, La
  Jolla, CA 92093-0417
• 2School of Mechanical Engineering, Georgia
  Institute of Technology, Atlanta, GA 30332-0405
• 3University of Wisconsin, Fusion Technology
  Institute, 1500 Engineering Drive, Madison, WI
  53706-1687
• 4Electrical and Computer Engineering Department
  and Center for Energy Research, University of
  California, San Diego, EBU-II, Room 460, La
  Jolla, CA 92093-0417
• 5Fusion Safety Program, EROB E-3 MS 3860, INEEL,
  Idaho Falls, Idaho 83415-3860
• 15th Topical Meeting on the Technology of Fusion
  Energy
• Washington, D.C.November 20, 2002

2
Outline

• IFE chamber operating conditions
• Thin Liquid Wall Configuration
• Attractiveness and key issues
• Film Establishment and Coverage
• Wetted wall
• Forced film flow
• Film Condensation
• Aerosol formation and behavior
• Aerosol source term (including explosive boiling
  estimate)
• Aerosol formation and transport analysis
• Design windows (including driver and target
  constraints)
• Concluding Remarks

3
IFE Operating Conditions

• Cyclic with repetition rate of 1-10 Hz
• Target injection (direct drive or indirect
  drive)
• Driver firing (laser or heavy ion beam)
• Microexplosion
• Large fluxes of photons, neutrons, fast ions,
  debris ions toward the wall
• - possible attenuation by chamber gas

4
Energy Partitioning and Photon Spectra for
Example Direct Drive and Indirect Drive Targets
Energy Partitions for Example Direct Drive and
Indirect Drive Targets
Photon Spectra for Example Direct Drive and
Indirect Drive Targets
(25)
(1)

• Much higher X-ray energy for indirect drive
  target case (but with softer spectrum)
• Basis for example wetted wall analysis presented
  here
• (More details on target spectra available on
  ARIES Web site http//aries.ucsd.edu/ARIES/)

5
IFE Thin Liquid Wall Configuration

• Advantages of decoupling functions
• Armor function to accommodate X-ray and ion
  threat spectra provided by renewable liquid film
  for longer lifetime
• Structural and energy recovery functions provided
  by solid blanket at the back for high efficiency

• Major issues
• Film establishment and coverage
• Film dynamics
• Injection method
• Geometry effects
• Recondensation
• Ablated material and chamber clearing
  requirements
• Ablation processes
• Film condensation
• Aerosol formation and behavior
• Driver and target requirements

• Key processes
• Thin film dynamics
• Condensation
• Aerosol formation and behavior
• These are assessed here with Pb and flibe as
  example fluids

6
Film Dynamics

• Two Injection Methods Considered
• - Radial injection through a porous first wall
  ( wetted wall design)
• - Forced flow of a thin liquid film
  tangential to a solid first wall (forced
  film design)
• Critical Questions Include
• (1) Can a stable liquid film be maintained on
  the upper section of the chamber?
• (2) Can the film be re-established over the
  entire cavity surface prior to the next
  target explosion?
• (3) Can a minimum film thickness be maintained
  to prevent dry patch formation and provide
  adequate protection during the next target
  explosion.
• These Questions are Being Addressed through
  Complementary Modeling and Experimental
  Investigations
• - Example results illustrated here

7
Example of Wetted Wall Investigation

• Modeling simulation of 3-D evolution of
  liquid film surface based on
• - Liquid injection velocity through porous
  wall
• - Surface disturbance amplitude,
  configuration and mode number
• - Surface inclination angle
• - Liquid properties
• - Effect of film evaporation and/or
  condensation
• Results used to develop generalized
  charts, showing effects of these
  variables on
• - Frequency of liquid drop formation and
  detachment,
• - Size of detached droplets
• - Minimum film thickness prior to
  droplet detachment

• Example results for 700 K Pb with initial
  thickness of 1.0 mm and injection velocity of 1.0
  mm/s
• Random initial perturbation with maximum
  amplitude of 1.0 mm applied beginning of the
  transient
• In this case, droplet detachment occurs 0.38 s
  after initial perturbation

• Poster presented during Tue. afternoon session
  (1.27)

8
Examples of Forced Film Investigation
9
Film Condensation Rate is Fast
Example Analysis of Pb Vapor Film Condensation in
a 10-m Diameter Chamber
Characteristic time to clear chamber, tchar,
based on condensation rates and Pb inventory
for given conditions For higher Pvap, tchar is
independent of Pvap - Probably more limited by
heat transfer effectiveness As Pvap
decreases and approaches Psat, tchar increases
substantially
Typically, IFE rep rate 110 Time between
shots 0.11 s Pvap prior to next shot
(1-10)Psat Can be controlled by setting Tfilm
Of more concern is aerosol generation
(in-flight condensation) and behavior
10
Processes Leading to Vapor/Liquid Ejection
Following High Energy Deposition Over Short Time
Scale
Surface Vaporization
Liquid Film
X-Rays
Impulse
Spall Fractures
Impulse
Phase Explosion Liquid/Vapor Mixture
11
High Photon Heating Rate Could Lead to Explosive
Boiling
12
Photon Energy Deposition Density Profile in Flibe
Film and Explosive Boiling Region
Posters on flibe properties presented during
Tue. Wed. afternoon sessions (1.38 2.36)
Bounding estimates of aerosol source
term (1)Upper bound the whole 2-phase region
(2)Lower bound explosive boiling region
13
Analysis of Aerosol Formation and Behavior

• Spherical chamber with a radius of 6.5 m
• Surrounded by liquid Pb wall
• Spectra from 458 MJ Indirect Drive Target
• Explosive boiling source term (2.5mm, lower bound)

Region 1

• Appreciable and size of aerosol particles
  present after 0.25 s
• 107-109 droplets/m3 with sizes of 0.05-5 mm in
  Region 1

• Preliminary estimate of constraints
• - Target tracking based on 90beam
  propagation
• - Heavy ion driver based on stripping with
  integrated line density of 1 mtorr for
  neutralized ballistic transport

• From the analysis, aerosol formation could be a
  key issue and need to be further addressed
• Driver and target constraint also need to be more
  accurately defined

14
Analysis of Aerosol Formation and Behavior for
Flibe

• Spherical chamber with a radius of 6.5 m
• Spectra from 458 MJ Indirect Drive Target
• Explosive boiling source term (5.5 mm)

Aerosol size and after 0.25 s - 107-109
droplets/m3 with sizes of 0.3-3 mm - Exceeds
driver limit Again, from this analysis, aerosol
formation could be a key issue Needs to be
addressed by future effort Oral presentation
during Thu. morning session
15
Concluding Remarks

• Wetted walls provide possibility of high
  efficiency and renewable armor
• Key issues are film establishment and chamber
  conditions prior to next shot
• Experimental and modeling effort under way to
  provide generalized charts for designing film
  injection system
• - Wetted wall (droplet detachment, minimum film
  thickness)
• - Forced film flow (film detachment, beam port
  obstacles...)
• High energy deposition rate of X-rays would
  lead to explosive boiling
• - Provide bounding estimates for aerosol source
  term
• Aerosol modeling analysis indicate substantial
  and size of droplets prior to next shot for
  both Pb and FLiBe
• - Preliminary estimates of constraints for
  indirect-drive target and heavy ion driver
• - Marginal design window (if any)

Future effort - Completing generalized charts
on film dynamics - Better understanding aerosol
source term and behavior - Confirmation of
target and driver constraints
16
Other ARIES-IFE Related Presentations at 15th
TOFE

• S. Shin, S. I. Abdel-Khalik, D. Juric and M.
  Yoda, Effects of surface evaporation and
  condensation on the dynamics of thin liquid
  films for the porous wetted wall protection
  scheme in IFE reactors, Tue. afternoon
  poster session, 1.27
• J. K. Anderson, M. Yoda, S. I. Abdel-Khalik and
  D. L. Sadowski, Experimental studies of
  high-speed liquid films on downward-facing
  surfaces, Tue. afternoon poster session, 1.31
• M. Zaghloul, D. K. Sze and R. Raffray,
  Thermo-physical properties and equilibrium
  vapor-composition of lithium
  fluoride-beryllium fluoride (LiF/BeF2) molten
  salt, Tue. afternoon poster session, 1.38
• L. El-Guebaly, P. Wilson, D. Henderson, L.
  Waganer, R. Raffray and the ARIES Team,
  Radiological issues for thin liquid walls
  of ARIES-IFE study, Tue. afternoon poster
  session, 1.51
• J. P. Sharpe, B. J. Merrill and D. A. Petti,
  Aerosol production in IFE chamber systems,
  Thu. Morning oral session
• L. El-Guebaly, P. Wilson, D. Henderson, A.
  Varuttamaseni and the ARIES Team,
  Feasibility of target material recycling
  as waste management alternative, Thu. Morning
  oral session
• M. Zaghloul, Ionization equilibrium and
  thermodynamic properties of high-temperature
  FLiBe vapor in wide range of densities, Wed.
  afternoon poster session, 2.36