1. 10th ITPA on SOL/divertor physics, Jan 2008
ITER measurements on
retained H/D/T
10th ITPA on SOL/divertor physics, Jan 2008
Philip Andrew
Diagnostics Division
ITER International Organization
Cadarache, France

2. ITER T inventory control strategy T phase
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

3. ITER T inventory control strategy
Strategy in formulation
Design Change Request, DCR#131
driven by safety
License to construct
License to operate
Elements of T control strategy
Measurement
Removal

4. 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

5. 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 D+T/s)
0.35g T burned (3.51020 D+T/s)
0.035g T error in burn (0.351020 D+T/s)
Retention*: > 0.14g T (>1.41020 D+T/s)
Modelled retention**: g T (0.2-201020 D+T/s)
Existing (all carbon) tokamaks**: (0.05-61020 D+T/s)
*Be wall, W divertor, presented by J. Roth at this meeting
**[ITER physics basis]

6. Need a direct measurement of inventory
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

7. Laser based surface probe (E.E. Mukhin)
Sensitive to H, D & T

8. Local measurement  vessel inventory
Large uncertainty when extrapolating
T distribution very non-uniform
> 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

9. 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

10. Inventory derived from
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

11. Main T retention measurement Direct measurements of inventory
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