ITER measurements on

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• ITER measurements on
• retained H/D/T
• 10th ITPA on SOL/divertor physics, Jan 2008

Philip Andrew Diagnostics Division ITER
International Organization Cadarache, France
philip.andrew_at_iter.org
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• Outline
• ITER T inventory control strategy
• T phase
• Gas accounting
• Tritium burn-up
• Local measurements
• H phase
• Status of retention measurements
• What could be proposed?
• Summary

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• ITER T inventory control strategy
• Strategy in formulation
• Design Change Request, DCR131
• driven by safety
• License to construct
• License to operate
• Elements of T control strategy
• Measurement
• Removal

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Gas Accounting

• Tritium Handling system can measure available
  tritium inventory to 0.5-1 (measure of T decay
  heat)
• Measurement done outside operation (eg.
  overnight)
• Tritium deficit T retention T burn up

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• Amount of T
• 10 error in neutron fluence (T burn up)
  measurement over 10 years results in 0.5kg error
  in T measurement
• DT ITER pulse
• 50g T fuelling (fuelling rate 5?1022 DT/s)
• 0.35g T burned (3.5?1020 DT/s)
• 0.035g T error in burn (0.35?1020 DT/s)
• Retention gt 0.14g T (gt1.4?1020 DT/s)
• Modelled retention 0.02-2g T (0.2-20?1020
  DT/s)
• Existing (all carbon) tokamaks (0.05-6?1020
  DT/s)
• Be wall, W divertor, presented by J. Roth at
  this meeting
• ITER physics basis

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• Local measurements
• Need a direct measurement of inventory
• deal with accumulated error in T burned
• Traditional method remove wall tiles
• remotely detachable wall/divertor samples
• probably still need to vent
• In-situ methods
• Laser ablation of wall target with spectroscopic
  measurement of ablation cloud

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Laser based surface probe (E.E. Mukhin)
Sensitive to H, D T
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• Local measurement ? vessel inventory
• Large uncertainty when extrapolating
• T distribution very non-uniform
• gt x 10 error possible
• Need to benchmark measurement
• Against gas balance
• Against analysis of components removed in
  shutdown
• i.e. gradually learn how to interpret measurement
  

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• H phase retention Status
• In T phase,
• Inventory evaluated by difference in tritium
  plant (TP) inventory at different times
• pVT-c pressure, volume, temperature,
  concentration (variety of ways of measuring
  concentration)
• In H phase (3 years?)
• Tritium plant unavailable (still being
  commissioned for T usage) but ready for D
• DCR 136 non-active gas supply during H-phase
• Any criteria requirement of H tracking could be
  incorporated into DCR 136

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• H phase retention
• what could be done?
• Inventory derived from
• Intergrated Flow in - Integrated Flow out
• Flow in flow meters available from beginning
  of H-phase, 1-5 accuracy
• Flow out asdf
• Pressure x conductance, 50 accuracy
• PVT-c measurement of integrated exhaust, 5
• Modelled retention (for C/Be/W) 4
• Requirements for H retention measurements could
  be folded into the H gas handling DCR

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• Summary
• Main T retention measurement
• Tritium Plant deficit Tritium burn-up
• Direct measurements of inventory
• Deal with T burn-up error (if retention small)
• to indicated where T is being held up
• not presently part of ITER design
• Hydrogen phase
• does not have T plant available for gas
  accounting
• H gas balance challenging, even with C in divertor