Opportunities and Issues for IFE Chamber Science

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Opportunities and Issues for IFE Chamber Science

• Jeff Latkowksi, Wayne Meier
• Fusion Energy Program, LLNL
• Per F. Peterson, Philippe Bardet, Haihua
  ZhaoDepartment of Nuclear Engineering
• University of California, Berkeley

Heavy Ion Fusion Science VNL Program Advisory
Committee Meeting Aug. 9-10, 2006 Livermore, CA
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Outline

• Thick liquid wall chambers for IFE
• Near-term opportunities
• Preparing for an experimental test facility
• Connecting to NIF

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Thick liquid wall (TLW) chambers have beenthe
focus of chamber research for HIF

• Potential advantages are well known
• Chamber structures experience a much lower rate
  of damage ? may last for plant lifetime (gt30
  years)
• 14 MeV neutron source (1B) not required ?
  existing or slightly modified steels can be used
• Chambers can be much more compact ? improves HI
  focusing
• TLW also protects from short range target
  emission and shock due to first surface ablation
• Most fusion energy deposited directly in the
  coolant ? efficient heat transport
• Have high tritium breeding efficiency

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The key issues can be summarizedin three primary
categories

• Issues related to repetitive nature of IFE,
  including liquid wall response and recovery of
  chamber conditions between pulses (reformation of
  protective liquid configuration, clearing of
  drops and vapor that could interfere with next
  shot).
• Issues related to shock mitigation, including
  ability of multi-layer thick liquid wall
  configurations to attenuate shocks and thus
  protect the structural wall from possible
  damaging effects of shocks.
• Issues related to use of molten salt (preferred
  liquid), including material compatibility
  (corrosion), target debris transport and removal,
  tritium recovery, heat transport and power
  conversion.

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Recent past RD has focused on fundamental
understanding and key issues

• Hydrodynamic scaling
• High quality jets needed along beam paths
• Disruption and re-establishment of liquid
  protection
• Condensation and vacuum recovery
• Shock propagation through jet array
• New schemes, e.g., vortex flow, that may permit
  higher rep-rate
• Interface issues and integrated design studies,
  e.g., Robust Point Design

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Near-term opportunities

• Re-engage Universities for small scale
  experiments
• Focus on schemes compatible with lower cost
  development path
• Small effort on system integration to assure
  coupling of development in targets, driver, and
  focusing schemes

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Scaled water experiments have demonstrated
multiple liquid configurations of interest for HIF
UCB
Re 100,000
High-Re Cylindrical Jets
Vortex Layers for Beam Tubes
Oscillating Voided Liquid Slabs
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Large liquid vortices could enable thick-liquid,
high-rep-rate, lower yield HIF options
Example Chamber volume 80m3 Liquid volume
28m3 Open fraction of solid angle 2.4
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UCB has performed detailed measurements of
turbulence and surface topology in vortex beam
tubes
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A series of scaled experiments were constructed
at UCB to provide proof of principle for large
vortex generation

• A first-generation test device was fabricated
  from a short segment of cylindrical pipe (22.5-cm
  diameter)
• Eight pressurized plenums provided blowing flow
• Perforations between injection plenums provided
  suction
• Asuction 2Ainjection
• End walls produced modest non-ideality

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Liquid accumulated during startup was cleared in
the first-generation device
t 2.0 sec
t 7.0 sec

• The first viability issue for large-vortex flows
  is removing excess liquid during startup
• UCB experiments demonstrate that this can be done
  by providing sufficient suction area
• After startup, flow dumps on suction drains can
  be closed, and pressure recovery can be achieved
• Reduce pumping power
• Increase layer thickness

t 14.0 sec
stable layer established
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A large variable recirculation flow loop was
constructed
Flow meter

• Pump is rated for 500-gpm at 300-ft of head
• Thanks to the frequency controller,the flow rate
  can be accurately controlledat any flow rates up
  to 800-gpm

Manifold
Nozzle
Frequency controller
1000 liter tank
50 hp pump
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Larger scale facilities will be needed prior to
ETF (could begin prior to ignition if funding
available)

• Hydraulics Test Facility Demonstrate the type
  of flow configurations needed for TLW chambers at
  1/4 scale. Simulant fluid (e.g., water) used to
  minimize costs. Facility would simulate (e.g., by
  using chemical detonations) flow disruption by
  fusion energy pulses to study chamber clearing.
  Also used to study/validate shock mitigation
  techniques.
• Chamber Dynamics Test Facility Study
  vaporization/condensation dynamics of molten
  salt. Focus on aspects unique to molten salt and
  cannot be simulated in the hydraulic test
  facility.
• Molten Salt Test Loop(s) Address issues related
  to use of molten salts in fusion applications
  corrosion, transport recovery of target debris,
  transport and recovery of tritium.
• Heat Transfer Component Facilities
  Develop/demonstrate compact, efficient heat
  exchangers and power cycle components using
  molten salt coolants. Applicable to IFE, MFE and
  fission, including hydrogen production.

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NIF will benefit from chamber science work and
spin-backs are possible

• First opportunity for test with prototypical
  target emissions
• Experiments to validate chamber response models
• First opportunity for neutron isochoric heating
  experiment (disassembles jets in some TLW
  designs)
• IFE analyses tools will be improved and can be
  used for NIF experiment planning
• X-ray and debris transport and deposition
• Surface heating, ablation, shocks
• Liquid motion, condensation, etc.
• Neutron heating, neutron activation

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Neutron isochoric heating can be an important
issue for the NIF

• Neutron isochoric heating will first be
  experienced on NIF
• Can drive debris and shrapnel threats to the
  final optics(e.g., He-filled cryotubes was the
  original design)
• Understanding of the liquid response to isochoric
  heating is a critical issue for TLW IFE
• liquid break-up
• droplet formation
• chamber clearing

Can ion beams be used as near-term surrogate and
assist in these issues prior to high-yield shots
on NIF?
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Target drop experiment on the NIF?

• One could think about dropping a target rather
  than holding it on the target positioner
• Would greatly reduce the mass sitting near the
  target, and thus, debris and shrapnel issues
• Translates into reduced debris loading on
  diagnostics and final optics may lead to
  reduced maintenance needs
• Would benefit IFE along path of getting past the
  giggle factor regarding target injection
  tracking
• Can it be done?
• Is this also too many sigmas from the norm?

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Conclusions

• A good start has been made in TLW chamber science
  for HIF
• Opportunities exist for modest cost, near-term
  RD to continue progress
• A serious IFE effort will require larger scale
  facilities to address key issues
• Chamber science will benefit from experiments
  that can be fielded on NIF more work is needed
  to define in detail
• HIF chamber science can also benefit NIF operation

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• BACK-UP SLIDES

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An second-generation device was constructed,
based on the previous experiment

• A test device was fabricated from a segment of
  cylindrical pipe (25.4-cm diameter, 14-cm wide)
• Injection and suction holes were fabricated with
  precision
• Eight pressurized plenums provided blowing flow
• Perforations between injection plenums provided
  suction
• Asuction 2Ainjection
• End walls produced modest non-ideality

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Different layer thicknesses have been obtained
with Froude number as low as 3 in the
second-generation device

• d/R 5
• Fr U2/gR 13.6
• Re UR/d 5105

• the layer is inhomogeneous, due to sharp angle
  of injection Polygon shape layer

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Dye marking of injection jets revealed their
behavior in the layer - further work is required
Homogeneous Nozzle
Inline Nozzle
Rapid prototyping nozzles
Free Surface
Dye Marking
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Based on the 2nd generation, a new area of study
was commenced on concepts with modular nozzles

• To provide improved vortex layer control,
  distributed injection and suction are needed
• The investigation studied injection/suction
  modules to study the influence of the
  injection and suction angles the injection is
  homogeneously distributed over the circumference
• the modules can be built with rapid prototyping

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Two nozzles with different injection/extraction
patterns were built and tested in a ramp
experiment

• Inline Concept

• Homogeneous Concept

Ramp experiment allows testing of a modular
nozzle section (1/8th circumference).