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Chemistry aspects of the ITER cooling water : impact on the experiments in the CEA loops

DEN/CAD/DTN. Chemistry aspects of the ITER cooling water : impact on the experiments in the CEA loops. ITER CHEMISTRY and THERMODYNAMICS. The ACP migration (release and deposit) in ITER circuits is : 1 ) driven by thermodynamics. Thermodynamics in ITER conditions is governed by :

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Chemistry aspects of the ITER cooling water : impact on the experiments in the CEA loops

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  1. DEN/CAD/DTN Chemistry aspects of the ITER cooling water : impact on the experiments in the CEA loops

  2. ITER CHEMISTRY and THERMODYNAMICS The ACP migration (release and deposit) in ITER circuits is : 1) driven by thermodynamics. Thermodynamics in ITER conditions is governed by : the « bulk » basic fluid conditions : • Pressure and temperature which are measured • pH, which is known by validated codes (or can be measured by industrial dedicated probes) • Redox is expected to be monitored by existing H2 probe • Chemical bulk composition of the fluid which is estimated by sampling (and cooling) and by the solid composition of the material in contact with the coolant (initially known).

  3. ITER CHEMISTRY and THERMODYNAMICS • 2) kinetically limited by (physico)chemical mechanisms (mass/thermal diffusion, physico-chemical reactions, surface interactions….) • These limitationscan be measured through : • the corrosion potential of the material which can be monitored by existing probes (Ag/AgCl by A. Molanders or by SCK-CEN via the LIRES-EU project) • the composition of deposited oxydes which may be monitored by Raman spectrometry • else …. These measurements need to be adapted to the reference PACTITER V3 formalism

  4. APPLICATION TO ACP TRANSFER EXPERIMENTS Experiments must cover the range of ITER conditions: • Chemical conditioning (pH20°C=7.0, [H2]=25 cm3/kg), OK • Fluid temperature (50°C  240°C), OK • Velocity (static water 12m/s), < 5 m/s • Materials (stainless steel, copper alloy). OK Chemical conditioning : For ensuring a neutral pH, Li can be added at low concentrations. Li (as LiOH) is also a convenient way to « buffer » the conductivity (i.e the redox) of the fluid. The ionic strength of the fluid may also have some influence and is buffered through the redox Extension to ITER operating conditions ? Behaviour vs Cu ?

  5. APPLICATION TO ACP TRANSFER EXPERIMENTS Chemical conditioning : • copper colloids formation and stability ? • if colloidal formation, redox (and ionic strength) will play a major (?) role • Temperature and velocity of the cooling fluid : • temperature of the bulk or temperature of the walls ? • Velocity or reynolds (magnitude of erosion ?) ? • kinetics of the warm up of the circuit ? (competition between thermodynamics and diffusional limitations as in SS release ?)

  6. APPLICATION TO ACP TRANSFER EXPERIMENTS Materials • metallurgy (surface potential, stresses…) • Surface roughness (magnitude of erosion ?) Application to copper net release rate measurement Input data for PACTITER V3 (corrosion rate not taken into account) Temp, Velocity ? CuCrZr Chemical method

  7. Resin bed n° Day Bed Release Time Material Release Time 1 1 2 hour T0 + 2 hour 2 2 hour T0 + 4 hours 3 3 hour T0 + 7 hours 4 2 17 hours T0 + 24 hours 5 3 24 hours T0 + 48 hours 6 4 24 hours T0 + 72 hours 7 5 24 hours T0 + 96 hours COPPER net release rate measurement Table 1 : Sampling Frequency of the copper release measurements for a set of 7 beds.

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