Institute for Radiation Protection and Nuclear Safety (IRSN)
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La construction de la nef de Notre-Dame de Paris : nouvelles données chronologiques
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New correlations for focusing effect evaluation of the light metal layer in the lower head of a nuclear reactor in case of severe accident
No full textInternational audienceIn case of a severe accident (SA) in a nuclear reactor, the core heats up and materials melt and relocate to the lower head of the vessel. In such configuration, stratification occurs between the oxide and metal phases present in the melt. When the metal phase is lighter than the oxide phase, the maximum heat flux applied to the vesselwall is concentrated at the location of this top metal layer, creating the so-called “focusing effect”. The modelling of the focusing effect is essential for SA codes to properly evaluate the vessel failure time or to demonstrate the vessel integrity, when In Vessel Retention (IVR) strategy is implemented. However, existing correlations used inSA codes for focusing effect modelling have some limitations: if the thickness of the metal layer becomes verysmall, they predict an extremely high heat flux. Moreover, they were validated with tests using water, whereas the Prandtl number was found to play a significant role in this heat transfer.In this paper, the focusing effect is studied based on 3D Direct Numerical Simulations (DNS) of a cylindrical metal layer, covering all possible metal layer characteristics in terms of geometry and boundary conditions, especially for its top surface where the intensity of radiative heat transfer may vary. The analysis of the fluid behavior and the quantitative results obtained allow to derive new correlations and a new model based on the radial profile of the mean temperature of the system and on the radial profile at the top surface. Results at reactor scale confirm the overestimation of existing 0D model used in SA codes for a thin metal layer and highlight the relevance of the proposed model for focusing effect evaluation during transient situations
Evaluation of Air Permeability of Alkali-Aggregate Reaction (AAR)-Affected Concrete
No full textInternational audienceIn the context of Alkali-Aggregate Reaction (AAR), the presence of water has a significant impact on the chemical reactions involved, making it challenging to predict and evaluate the transport properties of affected concrete. Air permeability is a particularly sensitive indicator of damage induced by AAR, and the characterization of this property is crucial for reducing the risk of interaction between the fluid, the cement paste, and the new products formed during AAR.This paper demonstrates that specimens subjected to AAR undergo swelling in three phases: a latent phase, an acceleration phase, and a deceleration phase. Early swelling leads to significant crack opening, rendering the material permeable to air flow despite its high moisture content. As the expansion continues, permeability increases and is primarily driven by the crack network created, although a small portion is filled by hydration products. This is further highlighted by drying kinetics, which slow down at high expansion rates
Employee eXperience Representation for Personalization within Digital Business Ecosystems
No full textInternational audienceIn the interconnected world of Digital Business Ecosystems (DBE), employees of organizations use different endpoints to search for information, access data, and interact with other users. However, navigating the supporting platforms can often be challenging for users due to a lack of intuitive design and difficulty finding relevant information. This results in a stressful and unsatisfactory experience. In this paper, we report on the definition of a conceptual model of Employee eXperience (EX) we establish in a scientific network to improve the Employee eXperience. We validate the model by applying it to the case of a scientific network. The obtained results could be generalized to define the data structure, including users’ profiles, intentions, and behavior, together with the contextual data to improve User eXperience (UX) within Digital Business Ecosystems and platforms of different sectors
Leukaemia, lymphoma, and multiple myeloma mortality after low-level exposure to ionising radiation in nuclear workers (INWORKS): updated findings from an international cohort study
No full textInternational audienceBackground A major update to the International Nuclear Workers Study (INWORKS) was undertaken to strengthen understanding of associations between low-dose exposure to penetrating forms of ionising radiation and mortality. Here, we report on associations between radiation dose and mortality due to haematological malignancies.Methods We assembled a cohort of 309 932 radiation-monitored workers (269 487 [87%] males and 40 445 [13%] females) employed for at least 1 year by a nuclear facility in France (60 697 workers), the UK (147 872 workers), and the USA (101 363 workers). Workers were individually monitored for external radiation exposure and followed-up from Jan 1, 1944, to Dec 31, 2016, accruing 10·72 million person-years of follow-up. Radiation-mortality associations were quantified in terms of the excess relative rate (ERR) per Gy of radiation dose to red bone marrow for leukaemia excluding chronic lymphocytic leukaemia (CLL), as well as subtypes of leukaemia, myelodysplastic syndromes, non-Hodgkin and Hodgkin lymphomas, and multiple myeloma. Estimates of association were obtained using Poisson regression methods.Findings The association between cumulative dose to red bone marrow, lagged 2 years, and leukaemia (excluding CLL) mortality was well described by a linear model (ERR per Gy 2·68, 90% CI 1·13 to 4·55, n=771) and was not modified by neutron exposure, internal contamination monitoring status, or period of hire. Positive associations were also observed for chronic myeloid leukaemia (9·57, 4·00 to 17·91, n=122) and myelodysplastic syndromes alone (3·19, 0·35 to 7·33, n=163) or combined with acute myeloid leukaemia (1·55, 0·05 to 3·42, n=598). No significant association was observed for acute lymphoblastic leukaemia (4·25, –4·19 to 19·32, n=49) or CLL (0·20, –1·81 to 2·21, n=242). A positive association was observed between radiation dose and multiple myeloma (1·62, 0·06 to 3·64, n=527) whereas minimal evidence of association was observed between radiation dose and non-Hodgkin lymphoma (0·27, –0·61 to 1·39, n=1146) or Hodgkin lymphoma (0·60, –3·64 to 4·83, n=122) mortality.Interpretation This study reports a positive association between protracted low dose exposure to ionising radiation and mortality due to some haematological malignancies. Given the relatively low doses typically accrued by workers in this study (16 mGy average cumulative red bone marrow dose) the radiation attributable absolute risk of leukaemia mortality in this population is low (one excess death in 10 000 workers over a 35-year period). These results can inform radiation protection standards and will provide input for discussions on the radiation protection system.Contexte Une mise à jour importante de l'étude internationale INWORKS sur les travailleurs du nucléaire a été menée pour améliorer la compréhension de la relation entre l'exposition à de faibles doses de rayonnements ionisants pénétrants et le risque de décès. Nous rapportons ici les résultats pour la mortalité due aux hémopathies malignes.Méthodes Une cohorte de 309 932 travailleurs du nucléaire (269 487 [87 %] hommes et 40 445 [13 %] de femmes) employés au moins un an en France (60 697 travailleurs), au Royaume-Uni (147 872 travailleurs) ou aux États-Unis (101 363 travailleurs) a été constituée. Les travailleurs ont fait l'objet d'une surveillance individuelle de l'exposition professionnelle aux rayonnements ionisants et ont été suivis du 1er janvier 1944 au 31 décembre 2016, cumulant 10,72 million de personnes-années de suivi. Des relations dose-risque ont été quantifiées en termes d'excès de risque relatif (ERR) par gray (Gy) de dose à la moelle osseuse pour la leucémie non lymphoïde chronique, différents sous-types de leucémie, les syndromes myélodysplasiques, les lymphomes non hodgkiniens et hodgkiniens, et le myélome multiple. Ces associations ont été estimées à l'aide de régressions de Poisson.Résultats L'association entre la dose cumulée à la moelle osseuse, avec un délai de latence de 2 ans, et la mortalité par leucémie non lymphoïde chronique était bien décrite par un modèle linéaire (ERR par Gy = 2,68 ; intervalle de confiance (IC) à 90 % : 1,13 à 4,55) et n’était pas modifiée par le fait d’avoir été exposé aux neutrons ou surveillé vis-à-vis du risque de contamination interne, ni par la période d'embauche. Des associations positives ont également été observées pour la leucémie myéloïde chronique (ERR par Gy = 9,57 ; 90%CI : 4,00 à 17,91) et les syndromes myélodysplasiques seuls (ERR par Gy = 3,19 ; 90%CI : 0,35 à 7,33) ou combinés à la leucémie myéloïde aiguë (ERR par Gy = 1,55 ; 90%CI : 0,05 à 3,42). Aucune association significative n'a été observée pour la leucémie lymphoblastique aiguë (ERR par Gy = 4,25 ; 90%CI : -4,19 à 19,32) ou la leucémie lymphoïde chronique (ERR par Gy = 0,20 ; 90%CI : -1,81 à 2,21). Une association positive a été observée entre la dose de rayonnements ionisants et le risque de décès par myélome multiple (ERR par Gy = 1,62 ; 90%CI : 0,06 à 3,64), mais peu d’arguments supportaient une association entre la dose et la mortalité par lymphome non hodgkinien (ERR par Gy = 0,27 ; 90%CI : -0,61 à 1,39) ou hodgkinien (ERR par Gy = 0,60 ; 90%CI : -3,64 à 4,83).Interprétation Cette étude rapporte des associations positives entre une exposition prolongée à de faibles doses et faibles débits de dose de rayonnements ionisants et la mortalité dueplusieurs types d’hémopathies malignes. Étant donné les doses relativement faibles généralement cumulées par les travailleurs de cette étude (16 mGy de dose cumulée à la moelle osseuse en moyenne), le risque absolu de décès par leucémie attribuable aux rayonnements dans cette population est faible (1 décès supplémentaire parmi 10 000 travailleurs sur une période de 35 ans). Ces résultats apportent de l’information aux comités qui examinent les normes de radioprotection et contribueront aux discussions sur le système de radioprotection
Etude de différents moyens de mitigation aerosol pour le retrait du corium à Fukushima Daiichi
No full textInternational audienceThe general context of the article is to evaluate strategies that can be used to mitigate aerosol dispersion during the fuel debris or corium retrieval from Fukushima damaged reactors. We propose to study various mitigation means, such as the spray scrubbing technology used to collect airborne particles, resin coating and local collection
Effects of confounding and effect-modifying lifestyle, environmental and medical factors on risk of radiation-associated cardiovascular disease
No full textInternational audienceBackground Cardiovascular disease (CVD) is the leading cause of death worldwide. It has been known for some considerable time that radiation is associated with excess risk of CVD. A recent systematic review of radiation and CVD highlighted substantial inter-study heterogeneity in effect, possibly a result of confounding or modifications of radiation effect by non-radiation factors, in particular by the major lifestyle/environmental/medical risk factors and latent period. MethodsWe assessed effects of confounding by lifestyle/environmental/medical risk factors on radiation-associated CVD and investigated evidence for modifying effects of these variables on CVD radiation dose-response, using data assembled for a recent systematic review. ResultsThere are 43 epidemiologic studies which are informative on effects of adjustment for confounding or risk modifying factors on radiation-associated CVD. Of these 22 were studies of groups exposed to substantial doses of medical radiation for therapy or diagnosis. The remaining 21 studies were of groups exposed at much lower levels of dose and/or dose rate. Only four studies suggest substantial effects of adjustment for lifestyle/environmental/ medical risk factors on radiation risk of CVD; however, there were also substantial uncertainties in the estimates in all of these studies. There are fewer suggestions of effects that modify the radiation dose response; only two studies, both at lower levels of dose, report the most serious level of modifying effect. Conclusions There are still large uncertainties about confounding factors or lifestyle/environmental/medical variables that may influence radiation-associated CVD, although indications are that there are not many studies in which there are substantial confounding effects of these risk factors.</div
Dynamique du coin salé et dynamique sédimentaire à l’embouchure du Rhône: OSR6 | Axe A - Action A.4 | Rapport scientifique final
No full textL’action A4 de l’OSR 6 portait sur la zone de l’estuaire du Rhône, où elle avait pour objectif de tester le couplage de méthodes de mesures optiques et acoustiques pour mieux caractériser les flux de MES sortant, ainsi que d’acquérir de nouvelles données pour caractériser la structure du coin salé. La complémentarité des capteurs pour caractériser à la fois le spectre en classe de taille des agrégats en suspension, leur densité effective et la possible présence de sable en suspension est avérée. Ce couplage, particulièrement intéressant pour l’évaluation du sable au fond de la colonne d’eau, mériterait d’être testé sur une large gamme de débit, mais la mise en œuvre des instruments et moyens nautiques se révèle difficile et limitante pour le redéploiement d’un tel système. Pour le coin salé les données des campagnes 2021 et 2022 viennent étayer les performances du modèle numérique DRACAR pour reproduire ce phénomène d’intrusion, qui se met en place à l’embouchure pour des débits entre 1500 et 1600 m3/s
Physical properties variations in a shaly formation across a fault core
No full textInternational audienceSUMMARY Faults in general, and in clay materials in particular, have complex structures that can be linked to both a polyphased tectonic history and to the anisotropic nature of the intact rock. Drilling through faults in shaly materials allows measuring properties such as the structure, mineralogical composition, stress orientation and physical properties. We combine different petrophysical measurements on core samples retrieved from a borehole drilled perpendicularly to a fault zone affecting Toarcian shales from the Tournemire underground research laboratory (France). The borehole is cross-cutting the entire fault thickness which is of the order of 10 m. We perform several types of measurements: density, porosity, saturation directly in the field and P-wave velocities together with P-waves anisotropy on core samples taken at regular intervals. Special protocols were developed to preserve as much as possible the saturation state of the samples. From our measurements, we were able to track the increase of damage, characterized by a smooth decrease in elastic moduli from the intact zone to the fault core. We then calculated Thomsen's parameters to quantify the elastic anisotropy evolution across the fault. Our results show strong variations of the elastic anisotropy with the distance to the fault core as well as the occurrence of anisotropy reversal
A centered limited finite volume approximation of the momentum convection operator for low-order nonconforming face-centered discretizations
No full textInternational audienceWe propose in this paper a discretization of the momentum convection operator for fluid flow simulations on quadrangular or generalized hexahedral meshes. The space discretization is performed by the low-order nonconforming Rannacher-Turek finite element: the scalar unknowns are associated to the cells of the mesh while the velocities unknowns are associated to the edges or faces. The momentum convection operator is of finite volume type, and its expression is derived, as in MUSCL schemes, by a two-step technique: (i) computation of a tentative flux, here, with a centered approximation of the velocity, and (ii) limitation of this flux using monotonicity arguments. The limitation procedure is of algebraic type, in the sense that its does not invoke any slope reconstruction, and is independent from the geometry of the cells. The derived discrete convection operator applies both to constant or variable density flows and may thus be implemented in a scheme for incompressible or compressible flows. To achieve this goal, we derive a discrete analogue of the computation u_i (∂t(ρ u_i)+div(ρ u_i u) = 1/2 ∂t(ρ u_i/2)+ 1/2 div(ρ u_i/2 u) (with u the velocity, u_i one of its component, ρ the density, and assuming that the mass balance holds) and discuss two applications of this result: firstly, we obtain stability results for a semi-implicit in time scheme for incompressible and barotropic compressible flows; secondly, we build a consistent, semi-implicit in time scheme that is based on the discretization of the internal energy balance rather than the total energy. The performance of the proposed discrete convection operator is assessed by numerical tests on the incompressible Navier-Stokes equations, the barotropic and the full compressible Navier-Stokes equations and the compressible Euler equations