Electrochemical Boron-Doped Diamond Film Microcells Micromachined with Femtosecond Laser: Application to the Determination of Water Framework Directive Metals

Planar electrochemical microcells were micromachined in a microcrystalline boron-doped diamond (BDD) thin layer using a femtosecond laser (Photo 1). The electrochemical performances of the new laser-machined BDD microcell were assessed by differential pulse anodic stripping voltammetry (DPASV) determinations, at nM level, of the four heavy metal ions of the European Water Framework Directive (WFD): Cd(II), Ni(II), Pb(II), Hg(II). The results are compared with those of previously published BDD electrodes [1]. The calculated detection limits are 0.4 nM, 6.8 nM and 5.5 nm 2.3 nM, and the linearities go up to 35nM, 97nM, 48nM and 5nM for respectively Cd(II), Ni(II) Pb(II) and Hg(II). The detection limits meet with the environmental quality standard of the WFD for three of the four metals. It was shown that the four heavy metals could be detected simultaneously, in the concentration ratio usually measured in sewage or runoff waters

Non Destructive Evaluation of Containment Walls in Nuclear Power Plants

Two functions are regularly tested on the containment walls in order to anticipate a possible accident. The first is mechanical to resist at a possible internal over-pressure and the second is to prevent leakage. The reference accident LLOCA (Large Loss of Coolant Accident) is the rupture of a pipe in the primary circuit of a nuclear plant. In this case, the pressure and temperature can reach 5 bar and 180°C in 20 seconds. The national project ‘Non-destructive testing of the containment structures of nuclear plants’ aims at studying the non-destructive techniques capable to evaluate the concrete properties and its damaging or progression of cracks. This 4-year-project is segmented into two parts. The first consists in developing and selecting the most relevant NDEs (Non Destructive Evaluations) in the laboratory to reach these goals. These evaluations are developed in conditions representing the real conditions of the stresses generated during ten-yearly visits of the plants or those related to an accident. The second part consists in applying the selected techniques to two containment structures under pressure. The first (technique) is proposed by the ONERA (National Office for Aerospace Studies and Research of France) and the second is a mock-up of a containment wall on a 1/3 scale made by EDF (Electricity of France) within the VeRCoRs program. Communication bears on the part of the project that concerns the damaging and cracking follow-up. The tests are done in bending on 3 or 4 points in order to study the cracks’ generation, their propagation, as well as their opening and closing. The mostly ultrasonic techniques developed concern linear or non-linear acoustic: acoustic emission [1], LOCADIFF (Locating with diffuse ultrasound) [2], energy diffusion, surface waves velocity and attenuation, DAET (Dynamic Acousto-Elasticity Testing) [3]. The data contribute to providing the mapping of the parameters searched for, either in volume, in surface or globally. Image correlation is an important additional asset to validate the coherence of the data. The spatial normalization of the data allows proposing algorithms on the combination of the experimental data. The tests results are presented and they show the capacity and the limits of the evaluation of the volume, surface or global data. A data fusion procedure is associated with these results

Probabilistic analysis of piled earth platform under concrete floor slab

International audienceThis paper proposes a two-dimensional axisymmetric numerical modelling of an earth platform over a clayey sand improved by stiff vertical piles using a finite-difference continuum approach. The study focuses on the surface settlements and the stress efficacy of the improvement system. Only the soil parameters are considered as random variables and two assumptions (normal distribution or nonnormal distribution) are used. The first-order reliability method (FORM) is applied to calculate the reliability index. Response surface methodology (RSM) allows for access to the Hasofer-Lind reliability index and is optimized by the use of a genetic algorithm. The Hasofer-Lind reliability index is calculated for two distinct cases. Firstly, only the geomechanical parameters of the clayey sand are considered as random variables; secondly, the parameters of both the clayey sand and the earth platform are considered. The results show that the reliability of a single soil layer is safer than the reliability of the whole syste

Reliability analysis of a mechanically stabilized earth wall using the surface response methodology optimized by a genetic algorithm

International audienc

Probabilistic analysis of ultimate seismic bearing capacity of strip foundations

International audienc

Leachate flow around a well in MSW landfill: Analysis of field tests using Richards model

International audienceDuring the lifespan of a Municipal Solid Waste landfill, its leachate drainage system may get clogged. Then, as a consequence of rainfall, leachate generation and possibly leachate injection, the moisture content in the landfill increases to the point that a leachate mound could be created. Therefore, pumping the leachate becomes a necessary solution. This paper presents an original analysis of leachate pumping and injection in an instrumented well. The water table level around the well is monitored by nine piezometers which allow the leachate flow behaviour to be captured. A numerical model based on Richards equation and an exponential relationship between saturated hydraulic conductivity and depth is used to analyze the landfill response to pumping and injection. Decreasing permeability with depth appears to have a major influence on the behaviour of the leachate flow. It could have a drastic negative impact on the pumping efficiency with a maximum quasi-stationary pumping rate limited to approximately 1 m3/h for the tested well and the radius of influence is less than 20 m. The numerical model provides a reasonable description of both pumping and injection tests. However, an anomalous behaviour observed at the transition between pumping and recovery phases is observed. This could be due to a limitation of the Richards model in that it neglects the gas phase behaviour and other double porosity heterogeneous effects

An aptasensor for ochratoxin A based on grafting of polyethylene glycol on a boron-doped diamond microcell

International audienceA novel strategy for the fabrication of an electrochemical label-free aptasensor for small-size molecules is proposed and demonstrated as an aptasensor for ochratoxin A (OTA). A long spacer chain of polyethylene glycol (PEG) was immobilized on a boron-doped diamond (BDD) microcell via electrochemical oxidation of its terminal amino groups. The amino-aptamer was then covalently linked to the carboxyl end of the immobilized PEG as a two-piece macromolecule, autoassembled at the BDD surface, forming a dense layer. Due to a change in conformation of the aptamer on the target analyte binding, a decrease of the electron transfer rate of the redox [Fe(CN)(6)](4-/3-) probe was observed. To quantify the amount of OTA, the decrease of the square wave voltammetry (SWV) peak maximum of this probe was monitored. The plot of the peak maximum against the logarithm of OTA concentration was linear along the range from 0.01 to 13.2 ng/L, with a detection limit of 0.01 ng/L. This concept was validated on spiked real samples of ric

Biotechnology Agroalimentary and Biomedical Analysis Group, Department of Biology, Faculty of sciences, Moulay Ismaïl University, B. P. 11201, Zitoune, Meknes, Morocco

An electronic microtongue using an electrochemical microcell was designed to monitor wastewater quality. The planar electrochemical microcells were micromachined in a microcrystalline Boron Doped Diamond (BDD) thin layer using a femtosecond laser. The electrochemical measurements with these BDD microcells were conducted using Differential Pulse Anodic Stripping Voltammetry (DPASV) for the major detection of heavy metal ions. Global signal obtained for raw wastewater (influent of Waste water Treatment Plant (WWTP)) and for water from Arve river were found much higher than those of treated wastewater (effluent of WWTP) and of treated wastewater from hospital. The DPASV signals have been processed by Principal Component Analysis (PCA) and K- Nearest Neighbours (K-NN). According to PCA results, waters were identified and discriminated with 99.75 % of the total variance of the dataset. Using K-NN with cross-validation approach, a good performance of the developed model was achieved for K=1 and 100 % of the samples were able to be classifiedin their original groups