DEVELOPMENT OF ELECTROMAGNETIC ACOUSTIC TRANSDUCER (EMAT) PHASED ARRAYS FOR SFR INSPECTION

Transcription

1 DEVELOPMENT OF ELECTROMAGNETIC ACOUSTIC TRANSDUCER (EMAT) PHASED ARRAYS FOR SFR INSPECTION QNDE 2013 Florian LE BOURDAIS and Benoit MARCHAND CEA LIST, Centre de Saclay F Gif-sur-Yvette, France

2 OUTLINE OF PRESENTATION Context: inspection needs within the ASTRID project Evaluation of an L-wave 8 elements probe through an experimental and simulation approach Application of the L-wave phased array to under-sodium inspection Conclusions QNDE 2013 EMAT Phased arrays for SFR inspection Le Bourdais et al. 2

3 CONTEXT

4 CONTEXT French nuclear program: development of the Advanced Sodium Technical Reactor for Industrial Demonstration (ASTRID) project Strong focus on in-service inspection methods for improved safety Probe operating conditions Probe immersed into liquid sodium at 200 C during inspection shutdown Reduced sodium flow Gamma irradiation Short service time (2 weeks) Inspection needs Detection - Telemetry Surface metrology - Imaging Enhancement of existing piezoelectric probes and development of new R&D techniques Development of EMAT probes since QNDE 2013 EMAT Phased arrays for SFR inspection Le Bourdais et al. 4

5 EVALUATION OF AN L-WAVE 8 ELEMENTS PROBE THROUGH AN EXPERIMENTAL AND SIMULATION APPROACH

6 PRESENTATION OF L-WAVE PHASED ARRAY MANUFACTURED BY INNERSPEC TECHNOLOGIES Characteristics Longitudinal wave custom phased array probe Joint design with CEA-LIST 8 elements into a row Kapton coils Strong permanent magnets NdFeB to withstand temperature Stainless housing (70x70x70mm3) Operation at 1 MHz in liquid sodium N Magnets S stainless steel tube casing SST housing Active surface (stainless steel) S N Coils Eddy currents Tangential magnetic field Lorentz force distribution QNDE 2013 EMAT Phased arrays for SFR inspection Le Bourdais et al. 6

7 FIRST LABORATORY TESTS ON ALUMINIUM BLOCK AT 2 MHZ Field measurement setup A-scan for each (x, y) position Maximum over time for each (x,y) No delay law 15 degree deviation 30 degree deviation Experimental field measurements show The ultrasonic beam is deflected as expected from the applied delay laws Secondary wavefront contributions Change in shape of the focal spot and appearance of grating lobes Analysis of the measurements using simulation tools Measure magnetic field Simulate Lorentz force and elastic propagation QNDE 2013 EMAT Phased arrays for SFR inspection Le Bourdais et al. 7

8 EMAT PROBE MAGNETIC FIELD MEASUREMENT Goal: determine magnetic field created by the EMAT probe Hall effect probe used to map the magnetic field underneath the probe Experiment Maximum intensity 0.26 T at 1 mm Bx By Bz Simulation of equivalent magnet configuration for comparison Simulation The simulated field matches the experimental data QNDE 2013 EMAT Phased arrays for SFR inspection Le Bourdais et al. 8

9 SIMULATION OF LORENTZ FORCE DISTRIBUTION Lorentz force is product of eddy current density and magnetic field Simulation of coils with excitation signal at 2 MHz σ xz σ yz σ zz Main component is along z direction (as expected), with secondary contribution due to coil layout Secondary longitudinal contributions Secondary shear contributions Also, unequal amplitude in the center region Secondary sources Module of stress QNDE 2013 EMAT Phased arrays for SFR inspection Le Bourdais et al. 9

10 COMPARISON OF ELASTIC WAVE PROPAGATION SIMULATION WITH EXPERIMENTAL DATA Comparison for 0 degree case Experimental Simulation y x Comparison for 30 degree case Experimental Simulation QNDE 2013 EMAT Phased arrays for SFR inspection Le Bourdais et al. 10

11 WAVE FRONT AND BEAM ANALYSIS BY SIMULATION Comparison for 0 degree case t = 1 µs t = 3 µs t = 5 µs secondary secondary Secondary wavefronts perturbate the main field with low amplitude (-10 db) Comparison for 30 degree case t = 1 µs t = 3 µs t = 5 µs secondary secondary Secondary source wavefronts are steered to -30 degrees Need to block the propagation of the secondary waves QNDE 2013 EMAT Phased arrays for SFR inspection Le Bourdais et al. 11

12 EXPERIMENTAL TESTING OF SOLUTION TO SECONDARY SOURCE WAVE PROPAGATION Solution: use adapted front surface on probe to block the secondary force generation by shielding Test on aluminium block as previously Lower thickness Secondary contributions have been reduced Focal spot shape now adequate for telemetric measurements QNDE 2013 EMAT Phased arrays for SFR inspection Le Bourdais et al. 12

13 APPLICATION TO UNDER-SODIUM INSPECTION

14 SODIUM TESTING SIMULATION 0 Simulation with different phased array delay laws 0 angle 5 angle 10 angle 15 angle 50 mm z mm x Target working distance: 130 mm Focal spot loses shape with steering angle Due to uneven amplitude contributions from coils For angles larger than 10 QNDE 2013 EMAT Phased arrays for SFR inspection Le Bourdais et al. 14

15 SODIUM PLANE PLATE TESTING Probe was immersed 18 hours with a maximum temperature of 180 C Surface echo present from the beginning of immersion Signals on plane plate improved during immersion (+3 db after 2 hours) t G = 43 db SNR = 25 db A = 135% Target: plate SST, 30mm Distance EMAT/target = 127mm t 0 + 2H 180 G = 41 db SNR = 28 db A = 177% QNDE 2013 EMAT Phased arrays for SFR inspection Le Bourdais et al. 15

16 150mm 170mm SODIUM BEAM STEERING A custom target was developed for beam steering in sodium Goal: show that the probe can steer ultrasound beam Three 6 mm rods at different heights Good detection of rod at normal incidence SNR of 13 db 45mm 35mm 23mm Without target Backwall With target Middle rod A = 24% QNDE 2013 EMAT Phased arrays for SFR inspection Le Bourdais et al. 16

17 SODIUM BEAM STEERING Delay laws were applied to steer the ultrasonic beam Returned energy: weak Large focal spot (middle rod detected) SNR too low to distinguish rod at 14 incidence angle Need to improve the custom target for further sodium testing QNDE 2013 EMAT Phased arrays for SFR inspection Le Bourdais et al. 17

18 CONCLUSIONS

19 CONCLUSIONS An 8 elements Phased Array EMAT probe has been developed for under sodium testing at 200 C Testing on Aluminum plate revealed Good steering of the focal spot (delay laws) Large focal spot Secondary contributions Simulation used for the analysis of the data Lead to the enhancement of the probe by reducing the secondary contributions Testing in liquid sodium at 180 C showed Good SNR under normal incidence Good beam steering capability but target too small compared to the focal spot Work in progress Improvement of the sodium beam steering target Bigger diameter for rods Reduction of the focal spot QNDE 2013 EMAT Phased arrays for SFR inspection Le Bourdais et al. 19

20 THANK YOU FOR LISTENING! QUESTIONS?