This study focuses on a non-destructive methodology for the elastic characterization of fiber-reinforced composites. The methodology uses the surface skimming longitudinal wave (SSLW) generated by an ultrasonic probe and detected via laser interferometry. Conventional mechanical and ultrasonic techniques frequently necessitate the use of multiple samples and intricate configurations to estimate the complete elasticity matrix, particularly in the case of anisotropic materials. To address these limitations, we propose a laser-based approach that enables precise measurement of group velocities across a 180° angular sector of a single specimen. The method was validated on isotropic PMMA and applied to two transversely isotropic composites: a unidirectional glass fiber-reinforced epoxy and a short-fiber bone-mimetic composite. A polar scanning scheme illustrated in B-scan, in conjunction with high-resolution time-of-flight analysis, enabled the extraction of SSLW velocities with a high degree of accuracy. These experimental velocities were then used in an inverse optimization algorithm based on Christoffel equations to retrieve four out of five independent elastic constants. The results showed strong agreement with contact-mode ultrasonic measurements and theoretical models. Furthermore, the method enabled the estimation of the principal anisotropy direction in a composite with unknown fiber orientation, thereby demonstrating the robustness and versatility of laser interferometry for comprehensive elastic characterization of composite materials.

In Pressurized Water Reactor (PWR) cores, turbulent flows can induce vibrations leading to grid-to-rod fretting. A nuclear reactor core being an opaque medium, displacements induced by vibration measurement are not easy with classical approaches, optics for instance. In this framework, ultrasonic methods could constitute an interesting way of investigation. Nevertheless, ultrasonic displacement measurement in turbulent flows remains scarcely documented. This study investigates ultrasonic wave propagation in a test section generating vortices at various Reynolds numbers, replicating conditions in a PWR cores. Measurements were conducted in both transmission and reflection modes, and local fluctuations in acoustic velocity caused by vortices were interpreted as errors in the measured distance. Results indicate that under frozen flow conditions, vortices do not affect reflection measurements, whereas in transmission, measurement dispersion increases with Reynolds number. These findings validate the use of ultrasonic reflection measurements for displacement monitoring in turbulent PWR flows and suggest further investigation into the limits of the frozen flow assumption.

In the realm of nuclear waste management, an ultrasonic investigation of radiolysis bubbles in bitumen has been carried out. Mechanical waves are very sensitive to gas cavities in matter, therefore ultrasonic velocity was measured in a straight-run distillation bitumen labelled AZALT 70/100 irradiated with 60Co (gamma irradiation) at dose rates between 5 and 1200 Gy/h and total integrated doses ranging from 2 to 100 kGy in IRMA and PAGURE French irradiation facilities. A comparative study of ultrasonic velocity and X-Ray microtomography measurements shows that ultrasonic velocity is linked to the concentration of bubbles within the material. A first attempt to deduce the volume fraction of hydrogen bubbles created by irradiation at ambient conditions with ultrasonic velocity measurements are proposed and discussed. This method constitutes an interesting approach dedicated to the monitoring of radiolysis bubbles formation and their evacuation mechanisms. It is particularly promising as ultrasonic sensors can operate effectively in high radiative and high temperature environments. Thus, real time application can be envisaged during irradiation and temperature increase for future experiments.

The ARISE project, supported by the National French Research Center (CNRS) and the Nuclear Safety and Radiation Protection Authority (ASNR), began in 2023 to explore the feasibility of innovative ultrasonic methods to detect the appearance and growth of radiolysis bubbles in bituminized waste products (BWPs). More generally, the subject can cover the investigation of any opaque medium. In this communication, we present results on bitumen samples irradiated at the IRMA French facility, as part of the ASNR BOREE experimental platform. The samples were subjected to total absorbed doses of 6, 50 and 100 kGy with dose rates ranging from 155 to 1230 Gy/h. By using the velocity and attenuation of ultrasonic signals at around 500 kHz, combined with Foldy’s model applied to polydisperse bubble clouds and X-Ray microtomography as validation technique, we demonstrate that relevant parameters can be estimated in a non-destructive manner in irradiated bitumen, namely: the void fraction, bubble radius and the polydispersity of the bubble size distribution. These results pave the way for non-destructive real time monitoring of bubble formation and growth under gamma irradiation in bitumen, as a part of the next phases of this extensive research program.

Pressurized Water Reactor (PWR) fuel rods are made of ceramic pellets (UO2, (U,Pu)O2 or gadolinium fuel) assembled in a zirconium alloy cladding tube. By design, an initial gap exists between these two elements. During irradiation, they both undergo transformations leading progressively to the closure of this gap. A local and non-destructive examination of the pellet/cladding interface could constitute a useful help to identify the zones where the two materials are in contact, particularly at high burnups when a strong chemical bonding occurs under nominal operating conditions in PWR fuel rods. The evolution of the pellet/cladding bonding during irradiation is also an area of interest. In this context, the Institute of Electronic and Systems (IES UMR CNRS 5214), in collaboration with the Alternative Energies and Atomic Energy Commission (CEA), is developing a high frequency acoustic microscope adapted to the control and imaging of the pellet/cladding interface. Because the geometrical, chemical and mechanical nature of the contact interface is neither axially nor radially homogeneous, the ultrasonic system must allow the acquisition of 2D images of this interface by means of controlled displacements of the sample rod along both its axis and its circumference. In the present communication, the first prototype of this microscope will be presented and the first results of the pellet/cladding interface examinations will be analyzed in order to highlight the potentials of the system, whose final objective is to be introduced in hot cells of the LECA-STAR facility in CEA-Cadarache.

With a specific ultrasonic device adapted to small volumes analysis, we carried out a pilot study of cell by cell honey ultrasonic velocity in a beehive. In this context, we followed, cell by cell, the evolution of ultrasonic velocity in honey throughout its elaboration, from fresh liquid just deposited into cells, to the capping. The results, averaged over the whole honeycomb correlated rather well with moisture content (in the range 14-64%) even if, for the same moisture content, the values of velocities significantly varied suggesting differences in sugar composition. Concerning cell by cell analysis, data collected showed that ultrasonic velocity significantly differs from one cell to another, versus time and versus location in the honeycomb. These first results demonstrate that ultrasonic velocity measured cell by cell could be precious data if it would be correlated to other physicochemical parameters such as water activity. Our ultrasonic method is not, in its present form, directly applicable for real time non-destructive monitoring of the hive. Nevertheless, our first results prove that ultrasonic methods could be interesting for honey evaluation during the ripening process at the cell level, using volumes inferior to the millilitre and not in a macroscopic way.

In the realm of radioactive waste management, the impact of radiolysis on bitumen and bituminized radioactive waste also called bituminized waste product (BWP) is considered one of the most significant factors influencing structural changes and the generation of radiolysis gas bubbles. This review provides a comprehensive overview of several studies that have explored the intricate interaction between radiation and various types of bitumen, to gain a better understanding of how such waste ages when exposed to radiation. While these studies provide insights into the diverse effects of radiolysis on bitumen, they also highlight numerous unanswered questions. The absence of gas bubbles does not necessarily indicate an absence of gas production, leaving further research to be undertaken. The complexities of bitumen radiolysis offer multiple avenues for future investigation, aiming to enhance our understanding and provide comprehensive solutions for bituminous radioactive waste management. Among the studied types of bitumen, blown R85/40 bitumen and straight-run distilled bitumen with a penetration grade of 70/100 stands out due to their widespread use in immobilizing co-precipitated radioactive sludges. These bituminous matrices play an essential role in understanding the broader implications of radiolysis within the context of bituminous waste management. This review underscores the significance of further research into radiolysis and bitumen ageing, emphasizing the need for a more in-depth exploration of these complex phenomena and their implications for the long-term safety and efficacy of repositories and disposal facilities.

In order to design thin backing materials, for high-frequency ultrasonic probes (1MHz-10MHz), dedicated to high-temperature applications, aluminium powders containing a small amount of Acrawax (2-4%V/V) were uniaxially pressed before sintering. Transversely isotropic lamellar pellets with a high longitudinal acoustic attenuation (>100dB/cm) were obtained. Their acoustical impedance, close to 5 MRayl, represents a good compromise between bandwidth and sensitivity when these backing materials are coupled to a piezoelectric element such as PZ27, PZ46 or LiBiO3 for non-destructive ultrasonic testing up to 500°C. Thanks to its simplicity, the experimental protocol proposed in this communication enables the rapid in-lab conception of thin backing materials for ultrasonic applications in high technology domains such as nuclear industry.

In the context of bituminized radioactive waste storage and disposal, nucleation monitoring at room temperature and radiolysis bubbles migration at elevated temperature is crucial particularly in fire scenarios where bubble may impact thermal properties. Traditional methods are limited by the opacity of bitumen. To gain a deeper insight into bitumen rheology and ultrasonic wave propagation, we conducted a pilot study using ultrasonic testing cells spanning temperatures from 10°C to 60°C. Ultrasonic velocities and attenuations were measured at around 500 kHz in a 70/100 grade bitumen. Rheological information was deduced with the Time-Temperature Superposition principle and a behaviour model was proposed to describe bitumen across a wide frequency range. Notably, our study reveals a transition point around 50°C to 60°C, where bitumen’s liquid behaviour becomes dominant. The shear-thinning characteristics gradually give way to a more Newtonian response. Using the proposed model, ultrasonic attenuation and viscosity were estimated at 110°C. Acceptable ultrasonic frequencies for monitoring the nucleation and migration of radiolysis bubbles are discussed for future investigations. These findings have significant implications for safety measures and a deeper understanding of bitumen response within the realm of radioactive waste management.

PMMA is often considered as a calibration material for experimental benches dedicated to viscoelasticity investigation. Nevertheless, regarding literature, data concerning attenuation coefficients and quality factors are essentially available in the MHz frequency range and results in the low-frequency range are scarce and scattered. In this communication, thanks to the use of high-frequency ultrasonic spectroscopy between 2 and 8 MHz in the range 6 & DEG;C - 45 & DEG;C, Time-Temperature Superposition principle and Resonant Ultrasonic Spectroscopy (RUS), we show that both longitudinal and shear quality factors of PMMA decrease considerably for low frequencies (<MHz), and that the classically accepted linear laws describing attenuation as a function of frequency are valid only beyond several MHz. This variation is attributed to secondary relaxation processes such as & gamma; relaxation considering the activation energy deduced from experimental data. Power laws are proposed to describe the evolution of quality factors and attenuation coefficients versus frequency in the 20 kHz - 12 MHz range.

Spinal cord injury (SCI) induces severe losses of trabecular and cortical volumetric bone mineral density (vBMD), which cannot be discriminated with conventional dual-energy X-ray absorptiometry (DXA) analysis. The objectives were to: (i) determine the effects of SCI on areal BMD (aBMD) and vBMD determined by advanced 3D-DXA-based methods at various femoral regions and (ii) model the profiles of 3D-DXA-derived parameters with the time since injury. Eighty adult males with SCI and 25 age-matched able-bodied (AB) controls were enrolled in this study. Trabecular and cortical vBMD, cortical thickness and derived strength parameters were assessed by 3D-SHAPER® software at various femoral subregions. Individuals with SCI had significantly lower integral vBMD, trabecular vBMD, cortical vBMD, cortical thickness and derived bone strength parameters ( p < 0.001 for all) in total proximal femur compared with AB controls. These alterations were approximately to the same degree for all three femoral subregions, and the difference between the two groups tended to be greater for cortical vBMD than trabecular vBMD. There were minor differences according to the lesion level (paraplegics vs tetraplegics) for all 3D-DXA-derived parameters. For total proximal femur, the decreasing bone parameters tended to reach a new steady state after 5.1 years for integral vBMD, 7.4 years for trabecular vBMD and 9.2 years for cortical vBMD following SCI. At proximal femur, lower vBMD (integral, cortical and trabecular) and cortical thickness resulted in low estimated bone strength in individuals with SCI. It remains to be demonstrated whether these new parameters are more closely associated with fragility fracture than aBMD.

In the framework of in vitro osteoporosis investigation with ultrasound on rat model, we propose a study of axisymmetric modes guided in small cylindrical structures such as rat tibias. The main objective is to analyze how an ultrasonic pulse (with a frequency close to the MHz) transmitted through the cortical bone diaphysis can be used to obtain a rapid estimation of the axial Young's modulus. Thanks to a numerical approach and experimentations on bone phantoms we show that the velocity of the first arrival signal (VFAS) measured with a simple time of flight method corresponds to the maximum of the group velocity of the axisymmetric L0,2 mode. Considering the geometry of the cylinders analyzed, we show that it is possible to use this velocity to estimate the axial Young's modulus. The ratio (internal radius / thickness) is an important parameter for small tubes such as rat tibias and has to be considered for results analysis. In this framework, µCT measurements are of first interest. At the end of this communication, preliminary experiments on rat tibias are presented and discussed.

This study investigated the potential role of quantitative ultrasound (QUS) to assess low bone mass in anorexia nervosa patients (AN). Bone parameters from QUS and DXA were positively correlated and significantly reduced in AN compared with controls, suggesting that QUS is a pertinent technique to assess low bone mass in these patients. Purpose The aim of this study was to investigate the potential role of an alternative technique, quantitative ultrasound (QUS), to assess low bone mass in patients with anorexia nervosa (AN). Methods Two hundred seven young women (134 patients with AN and 73 healthy controls) with ages ranging from 14.4 to 38.4 years participated in this observational cross-sectional study. Bone mass was concomitantly evaluated by DXA to determine areal bone mineral density (aBMD; g/cm(2)) at hip, lumbar spine, and radius and by QUS to determine broadband ultrasound attenuation (BUA; dB/MHz) at the heel. Results BUA (66.5 +/- 4.6 dB/MHz vs 61.0 +/- 5.0 dB/MHz) and aBMD at the hip (0.916 +/- 0.013 g/cm(2) vs 0.806 +/- 0.010 g/cm(2)), lumbar spine (0.966 +/- 0.012 g/cm(2) vs 0.886 +/- 0.010 g/cm(2)), and radius (0.545 +/- 0.005 g/cm(2) vs 0.526 +/- 0.04 g/cm(2)) were significantly decreased (p < 0.01) in patients with AN compared with controls. When patient and control data were pooled, BUA was significantly correlated with aBMD at the hip (r = 0.60, p < 0.001), lumbar spine (r = 0.48, p < 0.001), and radius (r = 0.40, p<0.001). In patients with AN, BUA and aBMD were mainly and positively correlated with weight, lean tissue mass, body mass index (BMI), and minimal BMI life and negatively with the duration of both disease and amenorrhea. Better concordance between the two techniques was obtained when absolute BUA and aBMD values were used according to the WHO T score classification. Conclusion BUA measurement at the heel by QUS appears to be a pertinent nonionizing technique to assess low bone mass in patients with AN.

The decommissioning of nuclear power plants subjected to a nuclear accident is a crucial activity for post-accident recovery and remediation of the affected areas. To achieve this objective, safe and successful removal of the fuel debris is required, but the accomplishment of this task needs the conception, design and construction of adequate tools and new procedures. The Three Mile Island Unit 2 (TMI-2) experience has taught that the success of such operations is related to adequate knowledge of the fuel debris’ physical and mechanical properties; hence these properties must be accurately investigated. The present work focuses on the determination of corium’s elastic properties by using acoustic methods. The Young’s modulus was determined for prototypic corium produced during the FARO experiments at the Joint Research Centre Ispra and for compounds synthesised at the Joint Research Centre Karlsruhe; the acoustic microscopy was also applied to corium samples extracted from the TMI-2 nuclear reactor, and to “lava” sampled at the Chernobyl Nuclear Power Plant. The study shows a slight decrease in Young’s modulus caused by the increase in zirconia content for the prototypic corium and comparable values in the case of TMI-2 core rocks. In this scenario, the specimen of Chernobyl brown lava constitutes an exception due to its lower Young’s modulus, in comparison with prototypical corium or the In-Vessel accident corium.

In this work, we have investigated the estimation of particles size, to prove the feasibility of a simplified acoustic system for continuous characterization of turbid water during underwater cave exploration with autonomous vehicles. Because of the nature and concentration level of sediments in natural water networks, we have identified the most suitable models for suspended sediments. They were proposed by Urick [1] and Sheng & Hay [2] assuming that particles are movable, rigid and at low concentration. These models have the advantage to provide a simple analytical expression with a limited number of input parameters. In order to test a very simplified prediction tool, these models are used to calculate attenuation only for monodisperse particle size distributions Experimentally, we used clay powder sifted to 40 μm, to create turbid water similar to cave water. This mixture characterised using laser diffraction spectroscopy shows a large and non-uniform particle distribution. From the measurement of the echo amplitude in reflexion mode, we deduce the attenuation coefficient in a frequency range from 1.5 MHz to 16 MHz. We used several transducers for different travel distances (3.5 cm to 7.5 cm) and different clay concentrations in volume (0.3 to 1.7 %). We obtained a linear dependence between attenuation coefficient and concentration for any tested frequency in total agreement with the selected model. Fitting experimental attenuation data with this model, the best agreement was obtained with a particle diameter of 70 μm. This value is in agreement with the standard Dv90 parameter provided by laser diffraction analysis. This is an encouraging result to validate our minimalist experimental setup and the selected model for a simplified implementable system for in situ characterization of turbid water.

H. Saikouka, D. Lauxa, E. Le Cléziob, B. Lacroixc, K. Audicd, R. Largentond, E. Federicic et G. Despauxb aUniversité de Montpellier IES, 860 rue de St Priest CC 05003, 34095 Montpellier, France bUniversité de Montpellier IES, 860 rue de saint priest, 34095 Montpellier, France cCEA CADARACHE, Cadarache, 13108 St Paul, 13108 St Paul, France dEDF R&D Dept MMC/T25, Avenue des Renardières Ecuelles 77818 MORET SUR LOING, 77818 Moret Sur Loing, France hajar.saikouk@umontpellier.fr CFA 2018 Le Havre

Dans cet article, une vision d’ensemble de la methode de pulse-echo, tres utilisee dans le domaine du controle non destructif pour caracteriser mecaniquement les solides ou les liquides, est presentee. Les principes de base ainsi que les ondes utilisees sont communs au domaine medical, meme si dans ce cas le transducteur ultrasonore est multi-elements. Si a priori la methode semble tres simple, car elle repose sur une relation elementaire (distance = vitesse x temps), un certain savoir-faire est necessaire pour obtenir des caracterisations precises. Apres une presentation du transducteur mono-element et du banc de mesure classique couramment employe, les approches experimentales les plus repandues sont detaillees et illustrees au travers de divers exemples.

We propose in this paper to use a simple and robust experimental protocol based on longitudinal ultrasonic velocity measurement in order to evaluate the viscosity of coconut water in a cylindrical stainless-steel pipe. Seven samples with Soluble Solids Content (SSC) ranging from 6.7 to 44.2 degrees Brix were studied using conventional Couette viscometry and high-frequency ultrasonic methods. Calibration laws linking the ultrasonic velocity measured at 5 MHz to the shear viscosity and to the SSC are proposed. These laws are in very good agreement with previous measurements carried out several years ago using a plane 25 MHz transducer directly introduced into the coconut water with SSC of up to 60 Brix. (C) 2018 Elsevier Ltd. All rights reserved.