Institute for Radiation Protection and Nuclear Safety (IRSN)
Not a member yet
7928 research outputs found
Sort by
Outcome of the VIKING project: status and perspectives of numerical modeling of flow-induced vibrations of nuclear power plant components
No full textInternational audienceCrucial nuclear power plant (NPP) components, such as fuel assemblies and steam generators, are exposed to flow-induced vibrations (FIV), potentially leading to fatigue problems and fretting wear of the material. Damage or failure of these components may lead to safety issues, thereby potentially necessitating unplanned outages of the reactor, resulting in substantial repair and standstill costs. With FIV being one of the leading causes of damage to these components, it is important to assess its impact on the integrity of fuel rods and steam generator tubes during the early design phase. While such an assessment has historically been done using semi-empirical models, due to the rise in computing power and capabilities, numerical tools are used more frequently, in particular in the last 10-15 years. To assess and further advance the current state-of-the-art of studying FIV in NPPs, the joint industry VIKING (Vibration ImpaKt In Nuclear power Generation) project was launched at the beginning of 2020. In this project, nine organizations collaborated for almost four years on FIV of configurations representative of steam generators and fuel rods and assemblies. This was done by performing numerical benchmark studies on five different experimental facilities. The current paper describes the main results and conclusions obtained from each numerical benchmark. Based on the individual findings, the status and perspectives of numerically simulating FIV of the aforementioned NPP components are presented
Numerical modelling of creep, agin and leakage of the prestressed reinforced concrete structure. Application to concrete containment building
No full textInternational audienceThe concrete containment building (CCB) is the third and last safety barrier to protect the environment from diffusion of radioactive products. In 2014, Électricité de France (EDF) launched the VERCORS project to improve the knowledge of leak-tightness in the CCB under air pressure loading and aging effects. VERCORS is in a 1:3 scaled CCB mock-up of a 1,300 MWe French pressurized water reactor (PWR). This paper presents a numerical methodology applied on VERCORS mock-up and numerical results focus on the gusset only, which is the lower part of the containment wall casted right after the base slab. Concrete is modeled through 3D elements while rebars and tendons are modeled by 1D elements. The simulation includes THM analysis of the gusset, prestressing phase and pressurization phase, and is conducted through a finite element code, Cast3M. The delayed strains including creep and shrinkage are especially considered. The instantaneous prestress losses, which result from friction; relaxation and pull-in at wedge, are taken into account. Regarding the long-term prestress loss due to the delayed strains, it is achieved by a kinematic relationship at interface of concrete-tendons. To describe cracks in concrete, an elastic damage model is used for the concrete elements, and the post-processing of leak-tightness is based on through crack leakage only. Those cracks appear usually at the early age phase given the restrained strains that the gusset undergoes during the hydration and hardening phase
Characterization of a high lateral resolution and high sensitivity dosimeter for proton beams using inorganic scintillator detector
No full textInternational audienceIn the context of proton dosimetry, detectors with high sensitivity and spatial resolution are needed to ensure the accurate monitoring of the deposited dose. The aim of this work is to study the response of a fiber-integrated inorganic scintillator detector under proton irradiation and to evaluate the effect of efficient volume on light collection. The results show that for a same incident energy flux, a larger volume results in a decrease of light collection. Mathematical modelling of the detection system is used to calculate dead times of the detection system elements and the scintillator’s light yield. The insertion of the optical fiber into the scintillator appears to be a critical parameter in the characterization of the detector, because its value has a major impact on light collection. These results help us to define the specifications for this dosimeter optimization, particularly for specific irradiation conditions such as FLASH-protontherapy or microdosimetry
Effets de l'exposition interne au 90Sr sur le stress oxydant et l'induction de senescence dans le tissus osseux et la moelle osseuse.
No full textAfter nuclear disasters, large amounts of radionuclides can be released into the environment.Strontium 90 ( 90 Sr) is a bone-seeking element and is part of these persistent radionuclides in the environment. Our previous studies in mice demonstrated that the chronic ingestion of 90 Sr at low doses leads to a decreased immune response and a modification of the bone physiology. Moreover, using an in vitro assay we showed that such an effect could be explained by the induction of the senescence in the mesenchymal stem cells that support the hematopoietic differentiation. In the present study, to better understand the effects of 90 Sr on both immune system and bone physiology, the expression of genes and the levels of proteins involved in bone and bone marrow homeostasis were measured in Balb/c mice exposed to 90 Sr during fetal life until the age of 24 weeks. The parent mice and offspring were exposed chronically via drinking water containing 90 Sr at 4, 20 or 100 kBq.L -1 . Results indicated a decrease in gene expression of bone formation markers and an increase in antioxydative enzymes. In addition, an increase in p21 expression, a potential marker of senescence, and a decrease in IL-6 were also observed in bone of contaminated mice.</p
Sources naturelles et artificielles de rayonnements ionisants : quelle exposition des personnes ?
No full textInternational audienceNous sommes tous exposés au rayonnement cosmique et aux radionucléides présents dans notre environnement, qu’il s’agisse de radionucléides naturels (cosmogéniques ou telluriques) ou de radionucléides artificiels rémanents des retombées anciennes des essais atmosphériques d’armes nucléaires ou de l’accident de Tchernobyl, ou encore de radionucléides rejetés par l’industrie nucléaire. Nous pouvons être également exposés à des rayonnements ionisants utilisés en imagerie médicale et pour le traitement de certaines pathologies. Enfin, les travailleurs de certains secteurs professionnels (travailleurs du domaine médical et de l’industrie nucléaire, personnels navigants de l’aéronautique…) sont soumis à des expositions spécifiques. La dose moyenne reçue par la population française pendant la période 2015-2019 a été estimée à 6,5 mSv/an, cette moyenne cachant une importante variabilité liée au lieu de résidence, au mode de vie ou encore aux actes médicaux
La radioprotection : enjeu majeur pour la vie dans l’espace
No full textInternational audienceLes astronautes sont exposés au rayonnement cosmique, constitué essentiellement de particules chargées de haute énergie, pouvant induire des niveaux de doses significatifs en fonction des situations rencontrées. En effet, les situations d’exposition peuvent être très différentes suivant le profil de la mission : en orbite basse ou au-delà, présence de protection par l’environnement, durée… Les risques en orbite basse, comme pour la station spatiale internationale, sont considérés comme acceptables et globalement sous contrôle. En contrepartie, les missions spatiales prolongées, au-delà des orbites basses, présentent de véritables enjeux en termes de radioprotection, en particulier du fait de l’exposition potentielle à de fortes éruptions solaires qui peuvent induire des niveaux de doses significatifs et conduire à des effets sur la santé à court et long terme
Convention OSPAR et travaux du Comité des Substances Radioactives (RSC)
No full textInternational audienceLa convention OSPAR a pour objectif la protection du milieu marin de l’Atlantique Nord-Est. Par l’intermédiaire de son comité dédié aux substances radioactives, OSPAR s’intéresse aux rejets des substances radioactives dans le milieu marin, la stratégie d’OSPAR visant à les prévenir, les réduire, voire les supprimer, notamment par le recours aux meilleures techniques disponibles. À ce titre, la France présentera son prochain rapport périodique sur le sujet en 202
Evaluating SMD resistors in electronic devices as accident dosimeters using red thermoluminescence
No full textInternational audienceTraditional protocols utilizing optically stimulated luminescence (OSL) and thermoluminescence (TL) of surfacemounted devices (SMDs) for retrospective dosimetry have demonstrated promising results, but limitations in sensitivity, especially for a limited number of SMD components, and small sample sizes, have prompted the exploration of alternative methods. The red thermoluminescence (RTL) protocol has emerged as a promising alternative, taking advantage of the strong TL emission of SMD components in the near-infrared spectral range.The present study investigates the dosimetric performance of red thermoluminescence (TL) emission from surface-mounted devices (SMDs) and its potential for use in accident dosimetry. Key characteristics, such as intrinsic zero-dose signal, signal reproducibility, dose-response relationship, signal stability, and a dose recovery test, were systematically analysed. An irradiation experiment was conducted in which SMDs were exposed to 6 MV X-rays using LINAC, and subsequent dose reconstruction was carried out employing the RTL protocol. The experiments demonstrated that a new RTL protocol yields promising signal intensities, and successful dose reconstruction was achieved even after delayed readout, with fading corrections applied. Dose estimates obtained from single SMD resistors, both reference components and those extracted from a smartwatch, showed good agreement with reference dosimeters, with overestimations between 5 % and 24 %. These findings confirm that the RTL method includes sufficient sensitivity and the ability to analyse very limited sample quantities, particularly in scenarios where signal sensitivity is critical.</p
Numerical simulation of solute transport in argillaceous rock under thermal gradient with a coupled THM-solute transport model
No full textInternational audienceArgillaceous rocks have many favourable characteristics for deep geological disposal of high-level radioactive waste (HLW) such as low permeability resulting in slow solute transport dominated by diffusion processes. However, waste-generated heat can increase pore pressure through Thermal-Hydraulic-Mechanical (THM) coupled processes, potentially enhancing advective transport. In this study, the authors developed a mathematical model to simulate a laboratory and a large-scale in situ experiment at an underground research facility (URF), to investigate (1) T-solute transport coupling (via the Soret effect and temperature-dependent diffusion coefficient) and ( 2) THM-solute transport coupling in argillaceous rock. The findings suggest that the Soret effect is significant in the laboratory experiments with relatively high thermal gradient, but negligible in the URF experiment where the thermal gradient is much smaller. Instead, the effect of temperature on the diffusion coefficient appears to play a more crucial role for the URF experiment. In addition, the advection enhancement due to thermal pressurization as a result of THM processes shows an insignificant effect on solute transport. The modelling of the URF experiment, as confirmed by observational evidence, shows the importance of anisotropy of the THM-transport properties as well as the effects of the excavation damage zone (EDZ). Finally, the model captures the key features of both experiments, highlighting its capability in enhancing comprehension of transport processes from a deep geological repository (DGR) built in argillaceous rocks. This improved understanding is valuable for safety assessments of DGRs in such rock types
Performance of the MORA Apparatus for Testing Time-Reversal Invariance in Nuclear Beta Decay
No full textInternational audienceThe MORA experimental setup is designed to measure the triple-correlation D parameter in nuclear beta decay. The D coefficient is sensitive to possible violations of time-reversal invariance. The experimental configuration consists of a transparent Paul trap surrounded by a detection setup with alternating beta and recoil-ion detectors. The octagonal symmetry of the detection setup optimizes the sensitivity of positron-recoil-ion coincidence rates to the D correlation, while reducing systematic effects. MORA utilizes an innovative in-trap laser polarization technique. The design and performance of the ion trap, associated beamline elements, lasers and beta and recoil-ion detectors, are presented. Recent progress towards the polarization proof-of-principle is described