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 philip.andrew@iter.org

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

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

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

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**: 0.02-2g 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]

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

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

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

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

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

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