Institute for Radiation Protection and Nuclear Safety (IRSN)
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Evolution of Air Permeability of Concrete due to Expansion Caused by Internal Swelling Reactions (ISR)
No full textInternational audiencePredicting and evaluating the transfer properties of concrete affected by Internal Swelling Reactions (ISR) is a main challenge for experts involved in concrete durability testing. The aim of this study is to measure the evolution of air permeability with the development of ISR, for different levels of expansion and various degrees of concrete saturation. In this work, two ISR were studied: the Alkali-Silica Reaction (ASR) where the origin of the swelling is located in the aggregates, and the Delayed Ettringite Formation (DEF) where the origin is located in the cement matrix. The first results obtained show that the development of ISR and induced cracks leads to an increase in the air permeability of concrete, especially in highly saturated concrete. The data of this study make it possible to evaluate the evolution of the transfer properties according to the generated expansion and induced cracking and the degree of saturation of the concrete
Integration of heterogeneous data to understand the effect of low doses of HTO on intestinal tumorigenesis in the APCmin/+ mouse model
No full textInternational audienceBiological mechanisms of low-dose radiation (LDR) induced health effects are very complex. Analytical methods using systems biology approaches to analyze complex multimodal and/or multiomics data have shown great potential for revealing networks of causally related biological changes spanning molecular, cellular, tissue and organism levels. We present here our systems biology approach using data collected in a recently completed study wherein the effects of low doses of tritiated water (HTO) on intestinal tumorigenesis were examined in the APCmin/+ mouse model of human colon cancer. The data comprised of RNA-seq transcriptomes, DNA-seq methylomes, blood cellularity and biochemistry, blood cytokine profiles, and tumor formation. In this work, we focused especially on three types of data sets: blood (blood cellularity and biochemistry and blood cytokine profiles), tumors and RNAseq. The major challenge related to the data structure was that not all data sets were obtained from the same individual animal, whic
Comparison Between HEC-RAS and TELEMAC-2D Hydrodynamic Models of the Loire River, Integrating Levee Breaches
No full textInternational audienceThroughout history and in the present era, flooding has represented a significant challenge, resulting in substantialproperty damage and a noteworthy loss of lives, despite extensive risk mitigation measures and billions invested in flooddefenses globally. The Loire river, the longest in France, has a rich history of flooding. To mitigate floods, levees havebeen built since the Middle Ages. For this study, a 2D hydraulic model was built using HEC-RAS, covering a 50-kilometerstrech of the river from Gien to Jargeau. Building upon a previously developed numerical model of the study area byIRSN using TELEMAC-2D, the HEC-RAS model was created based on its data and assumptions. The objective was toassess the performance of both software by comparing the obtained results. The HEC-RAS numerical model has beencalibrated for the largest recorded flood event, which occurred in 2003, and validated on two other major floods. Thisallowed us to estimate the impacts of flooding, with a particular focus on the simulation of an estimated 1000-year returnperiod flood and incorporating the analysis of multiple levee breach scenarios. Furthermore, the results obtained withthe hydrodynamic models implemented using HEC-RAS and the existing TELEMAC-2D model were summarized,encompassing their performance, capabilities, limitations, and the analysis of levee breaches scenarios testing variousbreach parameters. This analysis provides a robust set of criteria to guide to selection of the most suitable tool for furtherstudies based on the objectives of each project
Chemical composition of aerosols generated by heating prototypic fuel debris samples
No full textPart of special issueNuMat2022: The Nuclear Materials Conference, Edited by Milan Konstantinovic - Institute of Nuclear Materials Science, Belgian Nuclear Research Centre (SCK-CEN), Boeretang 200, Mol, B-2400, BelgiumOne of the important challenges for the decommissioning of the damaged reactors of the Fukushima Daiichi Nuclear Power Station (1F) is the fuel debris retrieval. In this context, the URASOL (URAnium and aeroSOL) project has been undertaken by the French consortium laboratories consisting of ONET, CEA, and IRSN for JAEA/CLADS. It aims at acquiring basic data on the generation and characteristics of radioactive aerosols from the thermal or mechanical processing of fuel debris simulant. Prototypic fuel debris samples were fabricated at VULCANO facility based on the average of the lower head compositions computed in the OECD/BSAF benchmark. Samples were heated in the VITAE (Aerosols configuration of the VITI facility) induction furnace to simulate thermal cutting (e.g. by laser) and released aerosols were collected during three temperature ramps using impactors. The collected aerosols were chemically analyzed by ICP-AES and ICP-MS. Overall, iron and tin are the major elements found in these aerosols, followed by chromium and silicon. Uranium contributes to 1.8 wt% of the measured elements. Significant releases of tellurium, barium and cerium were observed, mainly in ramp 1 (20-1800 °C). A significant variation of releases with temperature and with aerosol size class were also observed. Finally, comparison with a simulant fuel debris, in which hafnium replaced uranium mole by mole, confirmed that uranium is significantly more released than the simulant, emphasizing the interest of carrying out experiments with prototypic materials
Convergence of the MAC scheme for the incompressible Navier-Stokes equations with variable density and viscosity
No full textInternational audienceThe present paper addresses the convergence of the implicit Marker-and-Cell scheme for time-dependent Navier–Stokes equations with variable density and density-dependent viscosity and forcing term. A priori estimates on the unknowns are obtained, and thanks to a topological degree argument, they lead to the existence of an approximate solution at each time step. Then, by compactness arguments relying on these same estimates, we obtain the convergence (up to the extraction of a subsequence), when the space and time steps tend to zero, of the numerical solutions to a limit; this latter is shown to be a weak solution to the continuous problem by passing to the limit in the scheme
Caractérisation dosimétrique et évaluation des lésions radio-induites après irradiation dans les conditions de la radiologie interventionnelle
No full textAt the end of the 19th century, following the discovery of X-rays by Wilhelm Röntgen, the use of ionizing radiation developed in various fields, particularly in medicine. Indeed, the appearance of interventional radiology in 1953 revolutionized patient treatment. This technique, guided by low-energy X-ray imaging (70 to 120 kV), is used for the diagnosis and treatment of various pathologies. Over the past 60 years, it has become an indispensable tool, covering more than 600 types of procedures, notably in cardiology and neurology. In France, more than 600,000 procedures are performed every year, and this number is constantly rising. Although this technique, which is less invasive than conventional surgery, is an undeniable asset for the patient and is largely under control, accidental overexposures can occur. Such accidents are rare but can lead to deterministic effects, ranging from erythema to necrosis when doses higher than 10 Gy are delivered locally to the tissue. Although the side effects most often observed with overexposure are cutaneous, the specificity of low-energy X-rays, where dose deposition is highly dependent on the composition and density of the tissue traversed, can lead to strong dose gradients. Thus, doses in dense media (bone) or adjacent to dense media can be much higher than the cutaneous dose. The lack of knowledge about the consequences and radiobiological effects of this type of exposure (low energy), where the heterogeneity of dose deposition can be significant, makes patient prognosis uncertain. This project aimed to is to contribute to the development of a new preclinical irradiation model capable of reproducing accidental overexposures in interventional radiology, to better understand the radiobiological consequences and specificities of this type of exposure through dosimetric and radiopathological characterization. To achieve this, a new model of localized low-energy (80 kV) irradiation of the paw in mice was set up on the SARRP with 5 exposure protocols (single dose: 15, 30, and 45 Gy or repeated: 2 and 3x15 Gy with 1-week intervals) and 6 post-irradiation euthanasia time points (D0 to D84). Dosimetric measurements by Electron Paramagnetic Resonance (EPR) spectroscopy on the bone at D0 and simulations highlight the high heterogeneity of dose deposition and the strong dependence on low-energy material composition. EPR measurements on the bone over time, carried out for the very first time on a preclinical in vivo model, show a loss of signal probably due to bone turnover. In the context of retrospective dosimetry following a radiological accident, dose underestimation is possible if the sample is taken several months after irradiation. Macroscopic assessment of radiation-induced lesions, using lesion scoring, weighing, and Doppler laser images to characterize blood flow, enabled us to classify irradiation protocols. Histological and microCT analyses of bone and muscle tissues showed a change in the density of irradiated muscles and a loss of trabecular bone volume at late stages. In conclusion, in this work, the new model of localized irradiation using low-energy X-rays was characterized dosimetrically and radiopathologically. It has enabled us to highlight the specific features of this type of exposure, improve our knowledge of the consequences of such exposures, and improve the prediction of the risk of complications linked to exposures in interventional radiology.À la fin du XIXème siècle, suite à la découverte des rayons-X par Wilhelm Röntgen, l'utilisation des rayonnements ionisants se développe dans différents domaines notamment dans le domaine médical. En effet, l'apparition de la radiologie interventionnelle en 1953 révolutionne le traitement des patients. Cette technique, guidée par une imagerie de rayons-X de basse énergie (70 à 120 kV), est utilisée aussi bien pour le diagnostic que le traitement de diverses pathologies. En 60 ans, elle est devenue incontournable, regroupant plus de 600 types d'actes notamment en cardiologie ou neurologie. En France, on compte plus de 600 000 actes par an et ce nombre est en constante augmentation. Bien que cette technique, moins invasive que de la chirurgie classique, soit un atout indéniable pour le patient et majoritairement maitrisée, des surexpositions accidentelles peuvent se produire. Ces accidents restent rares mais peuvent entrainer l'apparition d'effets déterministes, allant de l'érythème à la nécrose lorsque des doses supérieures à 10 Gy sont délivrées localement aux tissus. Même si les effets secondaires les plus souvent observés lors de ces surexpositions sont cutanés, la spécificité des rayons-X de basse énergie où le dépôt de dose dépend beaucoup de la composition et de la densité du tissu traversé, peut conduire à de forts gradients de dose. Ainsi, les doses dans des milieux denses (os) ou adjacents aux milieux denses peuvent être beaucoup plus élevées que la dose cutanée. Le manque de connaissances sur les conséquences et les effets radiobiologiques de ce type d'exposition (basse énergie) où l'hétérogénéité du dépôt de dose peut être importante, rend le pronostic du patient incertain. L'objectif de ce projet est de contribuer au développement d'un nouveau modèle d'irradiation préclinique capable de reproduire des surexpositions accidentelles en radiologie interventionnelle, afin de mieux comprendre les conséquences radiobiologiques et les spécificités de ce type d'exposition à travers une caractérisation dosimétrique et radiopathologique. Pour cela, un nouveau modèle d'irradiation localisée de la patte chez la souris à basse énergie (80 kV) a été mis en place sur le SARRP avec 5 protocoles d'exposition (dose unique : 15, 30 et 45 Gy ou répétée : 2 et 3x15 Gy avec 1 semaine d'intervalle) et 6 temps d'euthanasie post-irradiation (J0 à J84). Les mesures dosimétriques par spectroscopie par Résonance Paramagnétique Electronique (RPE) sur l'os, à J0 et les simulations mettent en évidence la forte hétérogénéité du dépôt de dose et la forte dépendance de la composition des matériaux à basse énergie. Les mesures RPE sur l'os au cours du temps, réalisées pour la toute première fois sur un modèle préclinique in vivo, montrent une perte de signal probablement dû au renouvèlement osseux. Dans un contexte de dosimétrie rétrospective lors d'un accident radiologique, une sous-estimation de la dose est possible si le prélèvement est réalisé plusieurs mois après l'irradiation. L'évaluation macroscopique des lésions radio-induites, via du scoring lésionnel, des pesées et des mesures au laser Doppler caractérisant le flux sanguin a permis de classer les protocoles d'irradiation. Des analyses histologiques et microCT sur les tissus osseux et musculaires ont montré une modification de la densité des muscles irradiés et une perte du volume d'os trabéculaire aux temps tardifs. Pour conclure, dans ce travail, le nouveau modèle d'irradiation localisé, utilisant des rayons-X de basse énergie a été caractérisé dosimétriquement et radiopathologiquement. Il a permis de mettre en évidence les spécificités de ce type d'exposition, améliorer les connaissances sur les conséquences de ces expositions et améliorer la prédiction du risque des complications liées aux expositions en radiologie interventionnelle
Coolability of a Corium Pool in a Debris Bed: Impact of Debris Size, Steam, and Liquid Flow Rate; Tilting Angle; and Pressure on Critical Heat Flux—First Numerical Evaluations
No full textSelected papers from the NURETH-20 special issueInternational audienceIn case of severe accident in a light water reactor, a debris bed may form in the core and possibly melt, as it happened in TMI-2. Knowledge about the coolability of such molten pool surrounded by debris is crucial to investigate the possibility of stabilizing a part of the fuel inside the vessel. In particular, it is of primary interest to determine the maximum size of a molten pool surrounded by debris which may be stabilized under water. The maximum heat flux (CHF) that may be extracted from the pool boundary by water flowing within the debris bed is a key parameter. A facility was built at IRSN to determine the CHF under various conditions. A heated copper surface simulates the boundary of the pool and is placed in contact with a debris bed (monodisperse steel balls), under water. In this article, we first complete previous experimental work with steam and liquid flowrate, ball diameter, tilting angle of the heated surface and pressure up to 2.5 bar abs. A general CHF correlation depending on the tilting angle and the steam flowrate is derived and an example of the use of this correlation to evaluate the maximum mass of corium pool that can be stabilized under water is given, for some typical reactor conditions. In the last part, the accuracy of the ASTEC code is evaluated based on first calculations intending to reproduce the experimental impact of liquid and steam flowrate
Analyse du risque radio-induit de décès chez les professionnels de santé exposés aux rayonnements ionisants
No full textStudies of workers exposed to ionizing radiation enable the characterization of health effects resulting from chronic low-dose exposure. Although extensive research has been carried out on the subject, there are still uncertainties surrounding the quantification of these effects. To date, medical workers represents the largest group of workers occupationally exposed to artificial sources of ionizing radiation. Their subsequent risk of various pathologies is therefore an important subject of study. Nevertheless, the conclusions of these studies are uncertain and debated, particularly regarding the risk of developing tumors of the central nervous system (CNS).Based on literature reviews supported by meta-analyses and on statistical analyses of data collected as part of the epidemiological follow-up of the ORICAMs (Occupational Radiation Induced Cancer in Medical staff) cohort, this thesis aims to improve knowledge of the effects of ionizing radiation on health in the context of low-dose exposure.A mortality analysis was carried out on the ORICAMs cohort, including 164 015 medical workers occupationally exposed to ionizing radiation in France, presenting at least one dosimetric record between 2002 and 2012. Mortality was significantly lower in the ORICAMs cohort than in the general population. However, these results based on a comparative analysis with national rates may be influenced by the healthy worker effect, and do not allow to conclude on the existence or not of a potential relationship between occupational exposure and the risk of death. To address this issue, a case-control study nested within the ORICAMs cohort was set up, including 33 cases and 160 controls. However, conditional logistic regression analyses showed no dose-response relationship between occupational exposure to ionizing radiation and death from CNS tumors. An extension of the cohort follow-up and the inclusion of the case-control study in the international BECOME project will increase the statistical power of the analyses, allowing the assessment of the long-term effects of chronic exposure to low doses of ionizing radiation.Les études portant sur les travailleurs exposés aux rayonnements ionisants permettent de caractériser les effets sanitaires résultant de l'exposition chronique aux faibles doses. Bien que de nombreuses recherches aient été réalisées sur le sujet, des incertitudes persistent encore aujourd'hui quant à la quantification de ces effets. À ce jour, le corps médical représente le plus grand groupe de travailleurs exposés professionnellement à des sources artificielles de rayonnements ionisants. Leur risque subséquent de diverses pathologies est donc un sujet d'étude important. Néanmoins, les conclusions concernant ces études sont incertaines et font l'objet de débats, notamment en ce qui concerne le risque d'apparition de tumeurs du système nerveux central (SNC).Basés sur des revues de la littérature accompagnées de méta-analyses et sur des analyses statistiques menées à partir des données recueillies dans le cadre du suivi épidémiologique de la cohorte ORICAMs (Occupational Radiation Induced Cancer in Medical staff), ces travaux de thèse visent à améliorer les connaissances sur les effets sanitaires des rayonnements ionisants dans le cadre de l'exposition à de faibles doses.Une analyse de la mortalité a été réalisée au sein de la cohorte ORICAMs incluant 164 015 personnels médicaux exposés professionnellement aux rayonnements ionisants en France, présentant au moins un enregistrement dosimétrique entre 2002 et 2012. La mortalité était significativement diminuée dans la cohorte ORICAMs en comparaison à celle de la population générale. Cependant, ces résultats basés sur une analyse comparative avec des taux nationaux peuvent être influencés par l'effet du travailleur sain, et ne permettent pas de statuer sur l'existence ou non d'une relation potentielle entre l'exposition professionnelle et le risque de décès. Pour répondre à cette problématique, une étude cas-témoins nichée dans la cohorte ORICAMs a été mise en place, incluant 33 cas et 160 témoins. Néanmoins, les analyses par régressions logistiques conditionnelles n'ont pas permis de montrer de relation dose-réponse entre l'exposition professionnelle aux rayonnements ionisants et le décès par tumeur du SNC. Une prolongation du suivi de la cohorte et l'inclusion de l'étude cas-témoin dans le projet international BECOME permettront d'augmenter la puissance statistique des analyses ce qui permettra d'évaluer les effets à long terme d'une exposition chronique à des faibles doses de rayonnements ionisants
Radiation and CNS effects: summary of evidence from a recent symposium of the Radiation Research Society
No full textInternational audienceThis article summarizes a Symposium on 'Radiation risks of the central nervous system' held virtually at the 67th Annual Meeting of the Radiation Research Society, 3-6 October 2021. Repeated low-dose radiation exposure over a certain period could lead to reduced neuronal proliferation, altered neurogenesis, neuroinflammation and various neurological complications, including psychological consequences, necessitating further research in these areas. Four speakers from radi ation biology, genetics and epidemiology presented the latest data from their studies seeking insights into this important topic. This symposium highlighted new and important directions for further research on mental health disorders, neurodegenerative conditions and cognitive impairment. Future studies will examine risks of mental and behavioral disorders and neurodegenerative diseases following protracted radiation exposures to better understand risks of occupational exposures as well as provide insights into risks from exposures to galactic cosmic rays
Study of the stability of iodine oxides (IxOy) aerosols in severe accident conditions
No full textInternational audienceIodine oxide aerosol are formed during a nuclear severe accident in the containment due to oxidation of volatileiodine either molecular iodine or organic iodide. These oxides may exist under different chemical forms more orless stable (I2O4, I4O9 and I2O5). Decomposition rate has to be experimentally studied to better estimate theiodine cycle and thus the source term. Iodine oxide aerosols decompose under radiation, whatever the surfacedeposition and lead to mainly form again gaseous molecular iodine. Decomposition rates under irradiation weredetermined at 80 °C and 120 °C in presence of humidity and kinetics is rapid. It also appears that IxOy aerosolsare also not thermally stable and temperature effect promotes decomposition. The aerosols speciation seems toevolve in humid environment under irradiation towards less stable species. Such phenomena have to beconsidered in simulation severe accident software to model outside radioactive iodine releases and predict in thecourse of the accident the partition aerosol/gaseous iodine forms