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

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

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

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.

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

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

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

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 : 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

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

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

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

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

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

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.

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

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.

Thank you for your attention : 2013/05/22 LE MANS – 13 th NDCM| PAGE 17