Study of concrete radiation ageing

International audienceConcrete is a durable material which is a vital part of engineering barrier for radioactive waste disposal. In many concepts of low and intermediate level waste (e.g. the French concept) and in some cases even of high level waste, concrete is planned to be used for construction of containers carrying the primary packages of the immobilized waste. Therefore, it is needed to understand the effect of gamma irradiation on concrete with respect to its durability. A joint experimental program of Czech and French research organizations CVR and CEA respectively was started in order to study the changes in the properties of cementitious composites after their exposition to gamma irradiation. Samples of cement mortars, manufactured in CVR, were divided into two sets, each of them irradiated and characterized with both CVR and CEA facilities. Samples tested in CVR were exposed to cumulative doses of 1.6 to 1.8 et61655;106 Gy with doses from 0.5 to 4.5 kGy/h, while samples in Saclay were exposed to cumulative doses of 0.72 to 3.1et61655;106 Gy with doses 0.6, 1.6 and 2.6 kGy/h, respectively. Mechanical properties of irradiated mortars were then defined by ultrasonic measurement to obtain changes in Young modulus of elasticity and by classical loading to obtain changes of flexural and compressive strength. A comparison with non-irradiated samples maintained in same environment was done. Moreover, investigation of microscopic changes in the concrete structure was executed by scanning electron microscope.Comparison of all the results can be seen in the paper

Calculation to Experiment Comparison of SPND Signals in Various Nuclear Reactor Environments

International audienceIn the perspective of irradiation experiments in the future Jules Horowitz Reactor (JHR), the Instrumentation Sensors and Dosimetry Laboratory of CEA Cadarache (France) is developing a numerical tool for SPND design, simulation and operation. In the frame of the SPND numerical tool qualification, dedicated experiments have been performed both in the Slovenian TRIGA Mark II reactor (JSI) and very recently in the French CEA Saclay OSIRIS reactor, as well as a test of two detectors in the core of the Polish MARIA reactor (NCBJ). A full description of experimental set-ups and neutron-gamma calculations schemes are provided in the first part of the paper. Calculation to experiment comparison of the various SPNDs in the different reactors is thoroughly described and discussed in the second part. Presented comparisons show promising final results

Experimental validation of a Monte Carlo based toolbox for self-powered neutron and gamma detector simulation in the OSIRIS MTR

International audienceA numerical toolbox based on Monte Carlo calculations for self-powered neutron and gamma detector design, simulation and operation has been developed in order to save operators numerous and fastidious calibration tests. The experimental validation of this numerical toolbox, called MATiSSe', in the OSIRIS Material Testing Reactor is fully detailed in the paper. C/E comparisons presuppose promising future application for the numerical toolbox

Creep and shrinkage of Intermediate Level Long Life containers concrete comparison between gamma-irradiated and non-irradiated material

International audienceMany of the facilities and structures involved in the radioactive waste repository call for reinforced concrete (RC) in their construction. RC is used for containers as well as for surface and deep geological structures. In this paper we will focus on concrete containers (about 2 cubic meter) which would receive 1 to 4 waste containers (steel or concrete waste packages) of Intermediate Level Waste Long Lived (ILW-LL). With regards to the present disposal concept these containers would be placed one above the others up to 4 levels in the repository cells. In such context, Andra has to demonstrate the continuous mechanical integrity of the structure all over the operating / reversibility period.Classical mechanical properties of this concrete, as compressive strength, tensile limit and Young modulus are well known in classical non irradiated environment and must be confirmed in irradiated environment. This present study deals with the assessment of creep, shrinkage and others physical properties both under and out gamma irradiation, the samples being at the same thermal and hydric conditions.Specific experiment has been developed to address these parameters using cylindrical concrete dedicated to creep measurement and prisms dedicated to shrinkage.Samples are split in two groups, half irradiated and half non-irradiated. Gamma-irradiation has been carried out at the dose level representative of such ILW-LL wastes ($\approx$30 Gy/h) during 8 months to reach a total dose near to 180 kGy in average.The results show only a very small dimensional differences between irradiated and non-irradiated concrete samples in the same order of magnitude both for creep and shrinkage samples. Irradiation at such dose does not induced significate mechanical deterioration of the cementitious material

Concrete radiolysis effect on steels corrosion and comparison with non-irradiated material

International audienc

Câbles-capteurs à fibres optiques pour les mesures réparties Brillouin, Raman et Rayleigh dédiées à la surveillance des structures

International audienceCes dernières années, les avancées technologiques dans le domaine de la mesure ont conduit à rendre progressivement disponibles sur le marché des instrumentations optoélectroniques performantes, fondées sur les phénomènes de rétrodiffusion Raman, Brillouin et Rayleigh dans la silice constituant les fibres. Ces phénomènes physiques, exploités dans des systèmes réflectométriques (en anglais : OTDR – Optical Time-Domain Reflectometry), permettent de mesurer le profil des paramètres (température, déformations, courbure, fuite, pression, …) le long de la fibre déployée, sur des portées le plus souvent multi-kilométriques.Dans cette publication, nous décrivons le développement, la qualification métrologique, la fabrication industrielle en très grandes longueurs (10 km) de plusieurs câbles optiques de mesure dédiés. Les contraintes du déploiement de ces câbles en situation réelle (conditionnement, transport, installation, raccordement optique en conditions de terrain) sont détaillées de même que la mise en oeuvre des instrumentations optoélectroniques disponibles (dites aussi "systèmes de mesure" ou "interrogateurs")

Les capteurs à réseaux de Bragg fibrés, au cœur des matériaux, structures et procédés industriels

The advantages of the Optical Fiber Sensors (OFS) were stated 20 years ago. During the eighties, many techniques were studied but they did not succeed from the industrial point-of-view, for many reasons: low reliability, high cost, conservatism of end users... Then, in 1989, a new approach based on Fiber Bragg Gratings was proposed. To date, metrological performances and good behaviour of FBG-based instrumentations in harsh environments were verified in laboratory and through many field testing. Some industrial sectors even start to make profit with such kind of instrumentation, through the monitoring of key parameters (strain, displacements, temperature, pressure, force, slope, effects of the impacts, refractive index...). Today, the main applications deal with Structure Monitoring, as well as industrial processes (geology, civil engineering, public works, oil and gas, aeronautics, marine, railway…).Il y a désormais 20 ans que les avantages des Capteurs à Fibres Optiques (CFO) ont été énoncés. Pendant la décennie 80 de nombreuses techniques furent étudiées mais elles ne réussirent pas à s’imposer, pour des raisons de fiabilité, de coût, de conservatisme ... Puis, en 1989, une nouvelle approche fondée sur les réseaux de Bragg, a été proposée. A ce jour, les qualités métrologiques et la tenue aux environnements sévères des CFO à réseaux de Bragg ont été vérifiées, en laboratoire et via des démonstrations de terrain. Certains secteurs industriels commencent même à tirer profit de ce type d’instrumentation, et ce pour de nombreuses grandeurs d’intérêt (déformations, déplacements, température, pression, force, inclinaison, effets des impacts, indice de réfraction, ...). Les principales applications concernent la surveillance des structures et des processus industriels (géologie, génie civil, travaux publics, pétrole, aéronautique, marine, ferroviaire, …)

Impact damage detection in radome sandwich structures by traditional non destructive evaluation and fiber optic integrated health monitoring systems

Communication to : 10th international conference on adaptive structures and technologies - ICAST'99, Paris (France), October 11-13, 1999SIGLEAvailable from INIST (FR), Document Supply Service, under shelf-number : 22419, issue : a.1999 n.189 / INIST-CNRS - Institut de l'Information Scientifique et TechniqueFRFranc