Status of Thermal Heat Balance Analysis

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Status of Thermal Heat Balance Analysis
NSTX
Supported by
Art Brooks
College WM Colorado Sch Mines Columbia
U CompX General Atomics INEL Johns Hopkins
U LANL LLNL Lodestar MIT Nova Photonics New York
U Old Dominion U ORNL PPPL PSI Princeton U Purdue
U SNL Think Tank, Inc. UC Davis UC
Irvine UCLA UCSD U Colorado U Illinois U
Maryland U Rochester U Washington U Wisconsin
Culham Sci Ctr U St. Andrews York U Chubu U Fukui
U Hiroshima U Hyogo U Kyoto U Kyushu U Kyushu
Tokai U NIFS Niigata U U Tokyo JAEA Hebrew
U Ioffe Inst RRC Kurchatov Inst TRINITI KBSI KAIST
POSTECH ASIPP ENEA, Frascati CEA, Cadarache IPP,
Jülich IPP, Garching ASCR, Czech Rep U Quebec
NSTX Centerstack Upgrade Peer Review LSB,
B318 August 13, 2009
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Planned Scope of Analysis

• Assess Overall Heat Balance During Normal
  Operation
• Heating of CS FW, Divertor, PP VV from Plasma
  including
• RF Heating (High harmonic Fast Wave) max 4 MW
• Neutral Beam Injection max 2x 5 MW
• Total Power 14 MW for 5s at 1200s reprate
• Initial Power 9 MW for 5s at 2400s reprate
• For Reference, NSTX previously analyzed for 6 MW
  for 5s at 300s reprate
• Active Cooling of VV, PP and Divertor
• Heat Losses thru CS to OH1, PF1A,B and C
• Evaluate Max Temperature Excursions of CS (and
  other Components)
• Impact on Thermal Expansion of Center Stack
  Casing
• Impact on Adjacent Coils

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NSTX
August 13, 2009
NSTX Center Stack Upgrade Peer Review
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Comparison of Averaged Heating Power

• Total Power per Pulse has increased significantly
  while Pulse Duration has remained the same
• May lead to higher first pulse FW temperatures
• Mitigated in part by larger surface area of
  center stack
• Rep rate is significantly longer at full power
• Average heating (based on above??) is lower
• Thermal Ratcheting expected to be relatively less
  
• Pulse Power Distributed Assumed (based on prior
  analysis for natural divertor)
• 30 radiative from plasma, uniformly distributed
  over exposed surfaces
• 0.11 MW/m2
• half of non-radiative power (35) to CS, other
  half to outboard divertor
• GRD also specifies local Heat Flux and Power Flux
  width on PFCs (Table 3-2)
• Max 15.5, Avg 9.8 MW/m2 to IBDHS
• Max 6.3, Avg 4.0 MW/m2 to IBDAS IBDVS
• Max 0.2, Avg 0.1 MW/m2 to CSFW

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Power Distribution in Center Stack FW
14 MW

• GRD Specification shows larger fraction of total
  power being dumped on center stack tiles than
  assumed in baseline analysis

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Section Thru ProE Model of NSTX CSU
Areas of Concern
PF1C
PF1B
PF1A
OH (Not Shown)
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2D Axisymmetric Radiation Exchange ModelGeometry
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Heating, Cooling and Radiation Exchange
Plasma Heating of FW and exposed VV Radiation
Enclosure assumes emissivity of .7 for Graphite
tiles .27 for SS surfaces
Existing Active/Convectively Cooled Surfaces Need
to verify existing cooling parameters Cooling
to be added to new IBD
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ANSYS Model with Boundary Conditions
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Test Case

• Assume All Heating dumped into Center Stack
• 14 MW for 5 sec averaged over 1200 rep rate
• Center stack area 8 m2
• Steady State Average heat load 7291 w/m2
• Assume Cooling at VV, PP, Outboard Divertor and
  Horizontal Inboard Divertor Section
• Assume CS perfectly insulated from coils
• Results in higher averaged temperature

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Test Case SS Temperature Distribution
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Test Case SS Temperature Distribution
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Test Case - Overall Heat Balance
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Work has just begun

• Need to examine global transient behavior of
  Single and Double Null Divertor Plasmas as
  specified in GRD
• Need to evaluate local heating of tiles
• Need to confirm adequacy of existing cooling of
  VV, PP and Outboard Divertor