Institute for Radiation Protection and Nuclear Safety (IRSN)
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Recommendation of RILEM TC 256-SPF on fire spalling assessment during standardised fire resistance tests: complementary guidance and requirements
No full textInternational audienceThe recommendation is based on the co-authors’ work organized by the RILEM TC 256-SPF “Spalling of concrete due to fire: testing and modelling”. It aims to provide useful information, guidance and best practices in fire spalling assessment to laboratories that perform large-scale tests based on fire resistance test standards. It provides guidance on the spalling observation techniques during testing, as well as post-test spalling quantification/assessment methods. This document is intended to be used in conjunction with the fire resistance test standards, e.g. EN 1363-1 and ISO 834-1
Simultaneous measurement of labile U(VI) concentration and (234U/238U) activity ratio using a Monophos®-based Diffusive Gradients in Thin-films sampler.
No full textInternational audienceBackgroundIn a context of environmental monitoring around installations related to the nuclear fuel cycle, the Diffusive Gradient in Thin-films (DGT) technique captures the integrated concentration of U isotopes in their native environment, yielding comprehensive data on U origin (anthropogenic vs natural), total concentration, and mobility. However, for common deployment times (4-5 days) in moderately basic waters, none of the commercially available binding gels is adapted to measure the total U concentration. So, the development of novel DGT binding gels is timely.ResultsA new DGT sampler, using the Monophos® resin, as well as a new model for the interpretation of the DGT flux, has been successfully developed to measure the labile U concentration (which was also its total concentration) in moderately basic waters (pH ≈ 8). The model accounts for the penetration of uranyl carbonate complexes into the binding gel. Monophos-DGT samplers were able to quantify the total U concentration (accuracy >90 %) in three different mineral basic waters and in a synthetic seawater in laboratory experiments, as well as in situ in the rivers Essonne and Œuf, France. Ion interferences (e.g., Ca2+, Mg2+ and HCO3-), critical when using Chelex and Metsorb resins as binding agents, were overcome by using the new DGT sampler, thus allowing for a longer linear accumulation of U in the tested matrices and, above all, a better detection of U minor isotopes improving the potential of using DGT samplers for water source tracing through isotopic measurements.SignificanceThe use of the new DGT sampler and the new model for the interpretation of DGT flux is recommended to improve the accuracy of total U concentration determinations in field applications. Moreover, simultaneous elemental and isotopic measurements were successfully performed during field application, confirming new perspectives for environmental applications such as identification of U pollution sources by using isotopic signatures
Développement et utilisation de normes internationales pour les appareils de mesure de l'équivalent de dose ambiant neutron
No full textInternational audienceMeasurements of neutron ambient dose equivalent rates are challenging because there are no perfect instruments that cover the entire 9 orders of magnitude neutron energy range (thermal to 20 MeV). Hence quantifying performance requirements with the international standard IEC 61005 for neutron ambient dose equivalent rate meters presents unique challenges. This paper discusses the requirements of this standard, which have been refined and improved over the last 20 years. Examples of type testing results for the constancy of ambient dose rate response, variation of the response due to neutron energy, response time, and various environmental disturbances are examined. IEC 61005 provides manufacturers with internationally acceptable requirements and provides consistent test methods for compliance with stated performance requirements.Les mesures des débits d'équivalent de dose ambiants de neutrons sont difficiles car il n'existe pas d'instruments parfaits couvrant l'ensemble de la gamme d'énergie des neutrons de 9 ordres de grandeur (thermique à 20 MeV). Par conséquent, la quantification des exigences de performance avec la norme internationale IEC 61005 pour les appareils de mesure du débit d'équivalent de dose ambiant de neutrons présente des défis uniques. Cet article traite des exigences de cette norme, qui ont été affinées et améliorées au cours des 20 dernières années. Des exemples de résultats d'essais de type pour la constance de la réponse du débit de dose ambiant, la variation de la réponse due à l'énergie des neutrons, le temps de réponse et diverses perturbations environnementales sont examinés. La norme IEC 61005 fournit aux fabricants des exigences acceptables au niveau international et fournit des méthodes d'essai cohérentes pour la conformité aux exigences de performance énoncées
Discrimination entre les particules érodées et resuspendues: OSR6 | Axe B - Action B1.4 | Rapport scientifique final
No full textEtudier l’origine des particules transportées par le Rhône est un des objectifs clefs de l’Observatoire des Sédiments du Rhône (OSR). Dans cette action exploratoire, nous proposons d’appliquer une méthode de traçage pour déterminer si les matières en suspension transportées lors des crues sont issues de sols fraichement érodés ou de sédiments remis en suspension. Les travaux ont principalement porté sur le bassin versant de l’Ardèche car de taille modeste et à proximité du laboratoire IRSN ; et la méthode a également été appliquée sur quelques échantillons des autres stations de l’OSR. Cette méthode se base sur la mesure de trois radionucléides, le césium-137 (137Cs), le berrylium-7 (7Be) et le plomb-210 en excès (210xPb), traceurs de l’origine des particules. Si les résultats de cette action ne permettent pas de quantifier l’origine des MES, ils montrent que l’origine de celles-ci est multiple et généralement issues d’un mélange de source : sols fraichement érodés, sols préalablement érodés et/ou sédiments remis en suspension et sols de sub-surface ou de berges. Les premières mesures de ces radionucléides dans les MES des autres affluents du Rhône confirment cette observation, et il serait intéressant de comparer ces résultats avec l’approche de modélisation développé dans l’axe D (action D3)
Une dialectique récurrente : des dangers aux risques des expositions aux rayonnements ionisants
No full textNational audienceThe notions of danger and risk are often confused. Although they are closely related, they cover different realities, whether in the field of natural and technological hazards or in other areas. This is also true in the field of radiation protection. What's more, these two concepts evolve over time in line with changes in society and social perceptions of risk. These developments have consequences for the radiation protection system, which need to be taken into account in risk studies and in the current reflections on the evolution of the ICRP's general recommendations.Les notions de danger et de risque sont très souvent confondues. Bien qu’étant proches, elles recouvrent des réalités différentes, que ce soit dans le domaine des risques naturels et technologiques ou dans d’autres domaines. Ceci est vrai également dans le domaine de la radioprotection. De plus ces deux notions évoluent dans le temps avec les évolutions de la société et la perception sociale du risque. Ces évolutions entraînent des conséquences sur le système de radioprotection qui devront être prises en compte dans les études de risque et les réflexions en cours sur l’évolution des recommandations générales de la CIPR
Presentation and first outcomes of the FIGARO research program that aims at assessing the airborne release fraction of plutonium dioxide during glove box fires in nuclear fuel fabrication and reprocessing plants
No full textInternational audienceFires in nuclear fuel fabrication and reprocessing plants can cause the rupture of the glove box (GB) containment with a risk of dispersion of plutonium dioxide (PuO) within the facility. Fire safety analyses need to assess the resulting radiological consequences to strengthen the appropriate prevention and protection measures in these plants. To this end, the French institute for radiological protection and nuclear safety (IRSN), in partnership with the Japanese nuclear regulation authority (NRA), has carried out since 2019 a research project that aims at assessing the airborne release fraction (ARF) of PuO involved in GB fires. This project, named FIGARO (Fires Involving Glove boxes with Aerosol Release Occurrences) follows a progressive approach, that has started with small and medium-scale analytical tests to study separately the various mechanisms involved in the GB fires and the PuO airborne release and will end with large-scale GB fire tests to transpose and validate the analytical works for realistic assessments of the ARF of PuO both in open and confined conditions. This project also includes the development of a GB fire model in the IRSN SYLVIA and CALIF3S-ISIS softwares and its validation. In addition to presenting the FIGARO program, this paper provides its first outcomes
Analytical solutions for long-time steady state Boussinesq gravity currents flowing along a horizontal boundary of finite length
No full textInternational audienceThis paper presents analytical solutions for a steady turbulent miscible gravity current flowingalong a horizontal rigid boundary of finite length into a quiescent uniform environment. Thesesolutions are obtained from the governing equations (mass, momentum and buoyancy) originallyproposed by Ellison & Turner [J. Fluid. Mech., 6, 423 (1959)] for a buoyant layer of fluid in theBoussinesq approximation. For a constant drag coefficient Cd and the specific entrainment lawE ∝ Ri^{-1}, Ri being the local Richardson number, we first derived a system of coupled ordinary differentialequations describing the longitudinal evolution of the velocity u, the height h, the densitydeficit η and the Richardson number Ri of the current. For an initially supercritical flow (Ri0 < 1),explicit relations are found for u(x), h(x) and η(x) solely as a function of the Richardson numberRi(x). The longitudinal evolution of the Richardson number is then theoretically obtained froma universal function F which can be tabulated and, as in the present paper, also plotted. Thefunction F allows us to determine (and only from the knowledge of the boundary conditions atthe source) whether the flow remains supercritical over the whole length of the rigid boundary, ormight transit towards a subcritical state (Ri > 1). In this latter case, the mathematical resolutionis modified by including a discontinuity similar to a hydraulic jump. The location and amplitudeof this discontinuity are calculated from an additional universal function G and the injection conditions.The method is finally extended to provide analytical solutions for other classical entrainmentlaws
Simulation de la propagation de fissure lors d'essais de rupture de type mini-C(T) dans le domaine de transition ductile-fragile à partir d'une approche cohésive : application aux aciers de cuves de réacteurs
No full textNational audienceLe but de cette étude est de simuler la propagation de fissure lors d’essais de rupture réaliséssur des éprouvettes mini-C(T) afin d’estimer la ténacité d’acier de cuve de réacteur nucléaire dans ledomaine de transition ductile-fragile. Un modèle de zones cohésives est utilisé pour modéliser la propagation de fissure. L’évolution des paramètres cohésifs avec la probabilité de rupture et la températureest calibrée à partir d’essais à basse température et à température proche de la température de référencede la courbe maîtresse. Une très bonne concordance est observée entre les résultats des simulations etl’approche par la courbe maîtresse
Microstructure, water permeability and micromechanical properties of alkali activated slag subjected to accelerated leaching
No full textInternational audienceThis study investigated the leaching resistance of alkali activated slag mortars (AAS) under immersion in a 6 M NH4NO3 solution for a duration of up to 28 days, taking into consideration the effect of water-to-binder (w/b) ratio. SEM-EDS analysis revealed decalcification, desodiumization, and dealumination in AASs during leaching, leading to changes in the microstructure and micro-mechanical properties of the materials. A combination of N2-adsorption and MIP analysis demonstrated that there was a coarsening of the structure and an increase in porosity along the depth of degradation in the leached AAS. The predominant pore framework in the leached materials was found to be capillary pores. Furthermore, the elastic modulus and micro-hardness of AAS decreased after 28 days of leaching, as evidenced by micro-indentation. The water permeability of AASs exhibited an exponential rise with the increase in porosity, both before and after leaching, as a consequence of the changes in microstructure. Notably, the w/b ratio significantly influenced the leaching rate, microstructure, and water permeability of the AAS
Structural evolutions of MX80 bentonite pellet/powder mixtures under wetting and suction-controlled oedometer loading
No full textInternational audienceThe compression behaviour of MX80 bentonite pellet/powder mixture was investigated by performing suction-controlled oedometer tests. The suction from 113 to 4.2 MPa was imposed by vapour equilibrium technique (VET), and zero suction by water circulation (WC). After instantaneously unloaded from various target vertical stresses, the structural observation was conducted by mercury intrusion porosimetry and micro-computed tomography. Results showed that during wetting, the intra-grain micro- and macro-pores increased due to the swelling of pellets and powder grains. During loading, the variation of intra-grain micro-pores was characterised by the loading effect, while that of intra-grain micro-pores was controlled by the suction and loading effects. The inter-grain pores, for the VET samples, were reduced by the swelling of pellets and powder grains during wetting on one hand, and by the movement of pellets and powder grains during loading on the other hand. For the WC samples, most inter-grain pores were closed during wetting, with a few pores in the top closed by further loading. The global compression of bentonite mixture samples during loading was mainly governed by the filling of inter-grain pores for the VET samples, but controlled by the compression of intra-grain pores for the WC samples