Institute for Radiation Protection and Nuclear Safety (IRSN)
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Techniques de modélisation multi-échelle de l'interface acier-béton pour le calcul de structures en béton armé à grande échelle
No full textInternational audienceLa caractérisation du comportement des structures en béton armé est un défi majeur, en particulier lorsque des sollicitations au-delà du niveau de dimensionnement sont considérées. Dans ce cas, des informations locales sur le comportement de fissuration du béton sont indispensables pour évaluer la performance structurale. Cela est particulièrement observé dans le cas où les ouvrages de génie civil présentent des exigences d'étanchéité. La prise en compte de l'interaction entre le béton et les armatures en acier dans les simulations numériques joue un rôle important dans l'estimation réaliste de la fissuration. Les approches existantes de modélisation numérique de cette interface acier-béton restent peu satisfaisantes principalement car elles demandent des temps de calcul élevés. Leur mise en oeuvre à l'échelle d'un bâtiment industriel reste fastidieuse (Phan et al., 2015). L'objectif de ce travail est de proposer une approche multi-échelle pour la modélisation de l'interface. Cette approche consiste à définir un macro élément capable de reproduire le comportement de l'acier et de l'interface acier-béton reliés au moyen d'une densité de forces d'interface. La formulation de macro-éléments est fournie dans ce travail. Des études de cas sont également présentées pour démontrer la robustesse du modèle et sa capacité à reproduire le comportement expérimental d'un élément structural en béton armé
Effectiveness of staff radiation protection devices for interventional cardiology procedures
No full textInternational audienceTo evaluate the effectiveness of currently available radioprotective (RP) devices in reducing the dose to interventional cardiology staff, especially to the eye lens and brain. Methods: The performances of five RP devices (masks, caps, patient drapes, staff lead and lead-free aprons and Zero-Gravity (ZG) suspended radiation protection system) were assessed by means of Monte Carlo (MC) simu lations. A geometry representative of an interventional cardiology setup was modelled and several configura tions, including beam projections and staff distance from the source, were investigated. In addition, measurements on phantoms were performed for masks and drapes. Results: An average dose reduction of 65% and 25% to the eyes and the brain respectively was obtained for the masks by MC simulations but a strong influence of the design was observed. The cap effectiveness for the brain ranges on average between 13% and 37%. Nevertheless, it was shown that only some upper parts of the brain were protected. There was no significant difference between the effectiveness of lead and lead-free aprons. Of all the devices, the ZG system offered the highest protection to the brain and eye lens and a protection level comparable to the apron for the organs normally covered. Conclusion: All investigated devices showed potential for dose reduction to specific organs. However, for masks, caps and drapes, it strongly depends on the design, exposure conditions and staff position. Therefore, for a clinical use, it is recommended to evaluate their effectiveness in the planned conditions of use
Tritiated thymidine internalization in zebrafish early life stages: joint use of experimental procedures and microdosimetry
No full textInternational audienceTritium is found in the environment under three forms: free in the water, gaseous, and bound to organic matter. Once internalized in living organisms, it can be found in two forms: tissue free water tritium (TFWT) and organically bound tritium (OBT). This study aims to better understand OBT internalization in living organisms and to show the complementarity between experimental procedures and microdosimetry simulations that have often been used to obtain more information on imparted energy to cell nuclei. To do so, tritiated thymidine, an organic form of tritium, was chosen and zebrafish embryos [3.5 h post fertilization (hpf)] were exposed to a range of activity concentrations (2.21 × 103 to 5.95 × 105 Bq/mL). First, individual zebrafish embryos were sampled after different exposure times (1 to 96 h) to qualify the internalization kinetics. Then, the barrier role of the chorion was assessed after 2 days of exposure. Lastly, individual zebrafish embryos were sampled after 1 and 4 days of exposure to measure the internalization in the whole fish and its DNA, but also to highlight a possible link between the internal dose rate and the external activity concentration. Microdosimetry simulations were also made to quantify the imparted energy that could occur in the zebrafish cells after exposure to tritium. Results showed that when bound to thymidine, tritium rapidly incorporates in zebrafish early life stages, with the internalization being almost complete after 24 h. Results also showed that while the chorion acted as a barrier to prevent thymidine from entering the embryos, significant levels could still be measured in the whole organisms as well as in DNA. This study also highlighted that when the external activity concentration increased, the internal dose rate increased as well, following a sigmoidal trend. Microdosimetry simulations highlighted that the size and shape of the cell matters, and that the smallest cells seem to be at the greater risk, with only low-energy electrons inducing energy depositions. A linear fit was also found between the mean energy deposited and the logarithm of the radius of the cell, thus showing that the quantity of deposited energy is proportional to the radius of the cell. While this study highlighted important internalization pattern, it will also be used as the starting point of a study focusing on the toxic effects of tritiated thymidine on zebrafish in its early life stages
RENEB Inter-Laboratory Comparison 2021: The FISH-Based Translocation Assay
No full textInternational audienceTranslocation analysis using fluorescence in situ hybridization (FISH) is the method of choice for dose assessment in case of chronic or past exposures to ionizing radiation. Although it is a widespread technique, unlike dicentrics, the number of FISH-based inter-laboratory comparisons is small. For this reason, although the current Running the European Network of Biological and Physical retrospective Dosimetry (RENEB) inter-laboratory comparison 2021 was designed as a fast response to a real emergency scenario, it was considered a good opportunity to perform an inter-laboratory comparison using the FISH technique to gain further experience. The Bundeswehr Institute of Radiobiology provided peripheral blood samples from one healthy human volunteer. Three test samples were irradiated with blinded doses of 0, 1.2, and 3.5 Gy, respectively. Samples were then sent to the seven participating laboratories. The FISH technique was applied according to the standard procedure of each laboratory. Both, the frequency of translocations and the estimated dose for each sample were sent to the coordinator using a special scoring sheet for FISH. All participants sent their results in due time. However, although it was initially requested to send the results based on the full analysis, evaluating 500 equivalent cells, most laboratories only sent the results based on triage, with a smaller number of analyzed cells. In the triage analysis, there was great heterogeneity in the number of equivalent cells scored. On the contrary, for the full analysis, this number was more homogeneous. For all three samples, one laboratory showed outlier yields compared to the other laboratories. Excluding these results, in the triage analysis, the frequency of translocations in sample no. 1 ranged from 0 to 0.013 translocations per cell, and for samples no. 2 and no. 3 the genomic mean frequency were 0.27 6 0.03 and 1.47 6 0.14, with a coefficient of variation of 0.29 and 0.23 respectively. Considering only results obtained in the triage analysis for sample no. 1, all laboratories, except one, classified this sample as the non-irradiated one. For sample no. 2, excluding the outlier value, the mean reported dose was 1.74 6 0.16 Gy indicating a mean deviation of about 0.5 Gy to the delivered dose of 1.2 Gy. For sample no. 3 the mean dose estimated was 4.21 6 0.21 Gy indicating a mean deviation of about 0.7 Gy to the delivered dose of 3.5 Gy. In the frame ofRENEB, this is the second FISH-based inter-laboratory comparison. The whole exercise was planned as a response to an emergency, therefore, a triage analysis was requested for all the biomarkers except for FISH. Although a full analysis was initially requested for FISH, most of the laboratories reported only a triage-based result. The main reason is that it was not clearly stated what was required before starting the exercise. Results show that most of the laboratories successfully discriminated unexposed and irradiated samples from each other without any overlap. A good agreement in the observed frequencies of transloca- tions was observed but there was a tendency to overestimate the delivered doses. Efforts to improve the harmonization of this technique and subsequent exercises to elucidate the reason for this trend should be promoted
Medieval demise of a Himalayan giant summit induced by mega-landslide
No full textInternational audienceDespite numerous studies on Himalayan erosion, it is not known how the very high Himalayan peaks erode. Although valley floors are efficiently eroded by glaciers, the intensity of periglacial processes, which erode the headwalls extending from glacial cirques to crest lines, seems to decrease sharply with altitude. This contrast suggests that erosion is muted and much lower than regional rock uplift rates for the highest Himalayan peaks, raising questions about their long-term evolution. Here we report geological evidence for a giant rockslide that occurred around 1190 ad in the Annapurna massif (central Nepal), involving a total rock volume of about 23 km. This event collapsed a palaeo-summit, probably culminating above 8,000 m in altitude. Our data suggest that a mode of high-altitude erosion could be mega-rockslides, leading to the sudden reduction of ridge-crest elevation by several hundred metres and ultimately preventing the disproportionate growth of the Himalayan peaks. This erosion mode, associated with steep slopes and high relief, arises from a greater mechanical strength of the peak substratum, probably because of the presence of permafrost at high altitude. Giant rockslides also have implications for landscape evolution and natural hazards: the massive supply of finely crushed sediments can fill valleys more than 150 km farther downstream and overwhelm the sediment load in Himalayan rivers for a century or more
Les archives des déchets bitumés : un rassemblement thématique pour répondre à l’expertise et à la recherche en sûreté nucléaire
No full textInternational audienceLa journée d’étude « Archives et nucléaire » s’articule autour des enjeux archivistiques et des supports documentaires liés à la gestion du nucléaire, ainsi que de l’usage, voire la manipulation qu’il est possible de faire de ces enjeux et de ces supports. Le débat et les discussions que la rencontre mulhousienne souhaite promouvoir se placent donc dans un cadre d’échanges universitaires qui se veut indépendant des débats politiques animant l’actualité, bien que ces mêmes débats interviennent dans les dynamiques archivistiques sur lesquelles la journée d’étude entend s’attarder. Le passage de la science à l’archive, les notions de gestion, d’oubli et de mémoire documentaires dans le contexte (du) nucléaire, l’appropriation et l’utilisation d’un langage intérsémiotique qui peut également représenter une approche identitaire au nucléaire sont au cœur de la journée d’étude : ainsi, les thématiques abordées souhaitent mettre en exergue les questions liées à la gestion et à la communicabilité de ces archives, l’appropriation et la réélaboration de certains thèmes dans la culture populaire, la gestion de l’environnement et les voies possibles pour la construction d’une identité nucléaire aussi bien affichée que soupçonnée ou imaginée
Modelling the atmospheric chlorine 36 dry deposition on grass using micrometeorology
No full textInternational audienceChlorine 36 (36Cl, T1/2 = 301,000 years) is a radionuclide with natural and anthropogenic origin that can be rejected during decommissioning of nuclear power plants or chronically during recycling of used nuclear fuels. Once emitted into the atmosphere, chlorine 36 (gas and particles) can be transferred to the soil and vegetation cover by dry and wet deposition. However, quantitative constraints of these deposits are very scarce. Because of its relatively high mobility in the geosphere and its high bioavailability, chlorine 36 fate in the environment should be studied for environmental and human impact assessments. The aim of this study is therefore to develop dry depositional models for the gaseous and particulate fractions of chlorine 36. The model used for the parameterization of gaseous chlorine 36 dry deposition on grass is the > model based on the electrical analogy (Seinfield 1985). It was adapted from the Bah (2020) model developed for iodine. For particulate chlorine 36, the Damay Pellerin (2017) model was used. This model requiring the diameter of particulate chlorine 36 to be known, a sample of aerosol was taken in the chlorine 36 plume to determine on which particle size it is fixed. The sampling was performed on a low pressure impinger (LPI, DEKATI) of 13 levels for particles with diameters between 30nm and 10μm. In order to obtain model input data, meteorological and micrometeorological parameters were measured continuously at the IRSN La Hague technical platform (PTILH, France). The PTILH is located 2 km north of Orano La-Hague plant which emits small quantities of chlorine 36. An ultrasonic anemometer (Young 81000V) installed at a height of 4,5 m from the ground measured the direction (°), the velocity u (m/s) and the air friction velocity u* (m/s), the sensible heat flux H, the Monin-Obukhov length (L) and the atmospheric stability (1/L). A weather station (Spectrum Watchdog, series 2000) measured temperature Ts (°C), relative humidity RH (%), dew point (°C), global radiation SR (Wat/m^2) and photosynthetic active radiation PAR (μM/m^2.s). Sampling campaigns of 2 weeks were also conducted at the PTILH site to determine experimental depositional rates of chlorine 36. Chlorine 36 measurements were carried out by acceleration mass spectrometry at CEREGE-LN2C (France).The particle size distribution of the aerosol sample from chlorine 36 plume shows two peaks, a main one at 2μm and a second one at 10μm, typical distribution of marine aerosol. The modelsyield chlorine 36 depositional velocities between 6,7.10-3 and 10-2 m/s for the particulate fraction,and between 5.10-3 and 1,3.10-2 m/s for the gaseous one. The total dry depositional velocities(particles and gas) calculated from the model are less than one order of magnitude than the onesobtained experimentally
Mitigation of particle resuspension by aqueous foam during explosive detonation experiment
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Chemo-mechanical modeling of cement pastes swelling and cracking subjected to external weak sulfate attacks
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Preliminary results of geotechnical and geophysical investigations on sites with liquefaction occurrences in the greater Petrinja area after the 2020 earthquake
No full textVoir aussi : https://irsn.hal.science/hal-04414348vInternational audienceThe occurrence of extensive liquefaction during the 2020 Petrinja earthquake in the epicentral area raises many questions, notably the geometries of sedimentary bodies in depth. In the fluvial plains of the Kupa, Glina and Sava rivers, many lines of sand ejecta and cracks at the surface are subparallel to the riverbanks in convex meanders and would reveal buried sand point bars below a thick layer of silts. In order to highlight the different structures and estimate their mechanical properties, geotechnical and geophysical investigations were carried out at different sites along the Kupa river in the Petrinja epicentral area. This work presents the approach adopted for both the site selection and the study methods. Then, we show some preliminary results as well as the perspectives of further studies on liquefied layers