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Validation of predicted path of thermally deflected ultrasonic waves (phD work on acoustic thermometry in SFR) Nicolas Massacret (PhD Student ) Directors: Joseph Moysan*, Marie-Aude Ploix* CEA tutor: Jean-Philippe Jeannot** * LMA-LCND -FRANCE- (Laboratory of Mechanics and Acoustics - Non Destructive Characterization Laboratory) ** CEA (Atomic Energy Commission) Cadarache -FRANCE-DEN/DTN/STPA/LIET 2013/05/22LE MANS – 13 th NDCM| PAGE 1

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Outline I- Context II- Ultrasonic measurement advantages and issues III- Acoustic model and implementation for simulation IV- Experimental validation V- Further experimentation 2013/05/22LE MANS – 13 th NDCM| PAGE 2

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French option for the 4 th generation of nuclear reactor: SFR project: Sodium-cooled Fast Reactor In the past: Rapsodie – Phénix – Superphénix (French SFR) In the future (plan to be built in 2023): ASTRID prototype Need to develop several innovative and specific instrumentations based on feedbacks: For this kind of reactor, To diversify and enhance current instrumentation, For the liquid sodium, an opaque fluid banning optical technique. I- Context Rapsodie Phénix Superphénix 2013/05/22LE MANS – 13 th NDCM| PAGE 3 ASTRID

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2013/05/22LE MANS – 13 th NDCM| PAGE 42013/05/22LE MANS – 13 th NDCM| PAGE 4 METHOD PATENTED IN 1989 BY UKAEA An Ultrasonic Technique for the Remote Measurement of Breeder Subassembly Outlet Temperature, Instrumentation for the Supervision of Core Cooling in LMFBR's. [Macleod and al. 1989]. THERMOMETRY ISSUES USING THERMOCOUPLE: (possible influence of neighboring subassemblies, long response time, important volume of instrumentation,…) Thermometry at the subassemblies outlet: turbulent area. I- Context Context: Thermometry of sodium at the subassemblies outlet : ≈350 thimbles, each one containing 2 thermocouples.

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Acoustic instrumentation advantages : Opacity of sodium is not an issue any more. It is non-invasive: Acoustic transducer can be away from the measured area. There is no more thermal inertia of thimble containing thermocouples : so response-time is improved for thermometry. It is possible to realize a measurement in different areas with only one transducer. Temperature: Inhomogeneities of sodium temperature above the core (ΔTmax=50°C) Speed flow field at the subassemblies outlet: Turbulent flow (Re=60 000), High speed flow (about. 4 m.s -1 ), Important speed gradient (1.5m.s -1.cm -1 ). Deflection and diffusion of ultrasonic waves However, ultrasonic propagation depends on: 2013/05/22LE MANS – 13 th NDCM| PAGE 5 II- Ultrasonic measurement advantages and issues

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Objective : Define an appropriate model for ultrasonic propagation in turbulent fluid, dealing with influence of temperature and flow speed. Considering the thermo-hydraulics characteristics of the medium (characteristic length of the inhomogeneities, Mach number, …) and thanks to the application of the frozen fluid hypothesis: Model using the acoustic ray theory and a refractive index based on temperature and flow speed field. Numerical simulation of transit-time ultrasonic flowmeters: uncertainties due to flow profile and fluid. [B. Iooss and al. 2000] 2013/05/22LE MANS – 13 th NDCM| PAGE 6 II- Acoustic model and implementation

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Numerical Calculation Acoustic ray equation: Prediction of ray deflections and delays Gaussian beam approach (in development) Thermo-hydraulics data (from experiment, simulation, …) 2013/05/22LE MANS – 13 th NDCM| PAGE 7 II- Acoustic model and implementation Where : r(x,z) is the 2D ray position vector, s is the arc length, t(r) is the unit vector tangent to the ray, (r) is the travel time of the wave on the ray, c(r) is the acoustic celerity, v(r) the fluid velocity vector, S = t/(c+ t.v) is the acoustic slowness vector, = 1-v.S

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Principle of the experiment UPSilon (Ultrasonic Path in Silicone oil): Creation of thermal inhomogeneities in fluid Propagation of ultrasonic waves across thermal inhomogeneities Observation of delays and deflections of ultrasonic waves Comparison with acoustic ray simulation Fluid properties : Silicone Oil Very viscous fluid (viscosity : 10 000 cSt) to avoid convection movement. High dependence of ultrasonic celerity with the temperature in this medium. As the sodium (and unlike water), this dependence is linear and the celerity decreases with the temperature. 2013/05/22LE MANS – 13 th NDCM| PAGE 8 III- Experimental validation

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Experimental setup: Vertical cross-section views 2013/05/22LE MANS – 13 th NDCM| PAGE 9 III- Experimental validation Y X X Y 2.25 MHz

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Acoustic scan along 5 cm. Step : 0.2 mm. Temperature : 20.5 °C. Ultrasonic celerity ≈ 1000 m.s -1. Experimental result: « B-Scan » without heating. Planar wavefront. Weak influence of wires. Amplitude (Volt) III- Experimental validation 2013/05/22LE MANS – 13 th NDCM| PAGE 10 Bscan: local extrema

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Experimental result: « B-Scan » with heating. Delayed wavefront Deflected wavefrontNon disturbed wavefront Amplitude (Volt) 2013/05/22LE MANS – 13 th NDCM| PAGE 11 III- Experimental validation

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Thermal map for simulation X Y Simulation: definition of the UPSilon thermal map Temperature (°C) Strioscopic view of the experimental thermal gradient Determination of thermal gradient area with strioscopy 2013/05/22LE MANS – 13 th NDCM| PAGE 12 III- Experimental validation Measurement of the thermal gradient amplitude with 4 thermocouples at different depths

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Simulation : Propagation of acoustic rays Temperature (°C) Propagation of 52 acoustic rays through the thermal inhomogeneities Selection of one time => Determination of the corresponding wavefront 2013/05/22LE MANS – 13 th NDCM| PAGE 13 III- Experimental validation Delayed wavefront Deflected wavefront Non disturbed wavefront

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Comparison between experiment and simulation For delayed waves: Relative difference < 1% Very good agreement. For delayed and deflected waves: Relative difference < 3% Good agreement 2013/05/22LE MANS – 13 th NDCM| PAGE 14 III- Experimental validation Comparison of experimental and numerical wavefront ● experimental wavefront + numerical wavefront Rescaling of data.

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Effect of speed flow inhomogeneities on acoustic waves propagation. Coming experimentation for validation: IKHAR (in June 2013). IKHAR: Instabilities of Kelvin-Helmholtz for Acoustic Research Kelvin-Helmholtz Instabilities: -well-known -periodic Ultrasonic transducer 2013/05/22LE MANS – 13 th NDCM| PAGE 15 IV- Further works Overview of IKHAR

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2013/05/22LE MANS – 13 th NDCM| PAGE 16 IV- Conclusion and perspectives Simulation of acoustic rays through thermal inhomogeneities. Validation with experiment UPSiIon (in silicon oil at 20-30°C). Simulation of acoustic rays through speed flow inhomogeneities. Coming experiment: IKHAR. Full term perspectives: Utilization of this simulation code as a tool to define possibilities and limits of acoustic technique in reactor. Simulation code will allow us to: Estimate influence of thermal inhomogeneities and speed flows on ultrasonic propagation, Design optimal transducers for applications in reactor, Help to analyze different configurations of acoustic instrumentation. Optimize the signal processing methods.

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Thank you for your attention ! @ : nicolas.massacret@cea.fr 2013/05/22 LE MANS – 13 th NDCM| PAGE 17

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