Institute for Radiation Protection and Nuclear Safety (IRSN)
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Full numerical approach to demonstrate compliance with safety standards
No full textInternational audiencePara. 701 of lAEA's Régulations for the Safe Transport of Radioactive Material (No. SSR 6 Rev. 1, 2018 edition) provides various methods which shall be used to demonstrate the compliance of radioactive materials, packagings and packages with the performance standards required in Section VI of SSR-6: experimental testing with specimens or scale models, reference to previous satisfactory safety demonstrations of sufficiently similar nature, calculation or reasoned argument when the calculation procedures and parameters are generally agreed to be reliable or conservative, or the combination of those methods. Concerning mechanical safety performance in accident conditions of transport required for type B, type C and fissile packages, the conventional demonstration used to be primarily based on experimental testing which could be completed with numerical calculations (justification of the tests' parameters, extrapolation of the tests for the limit parameters of the regulations...). Lately, along with the increasing performance of numerical modeling and calculation, many applicants favor the calculation approach as an alternative for experimental testing, for new package designs. Some limited experimental tests continue to be carried out in order to justify reliability or conservatisms of the numerical approach. In some cases now, the mechanical demonstrations are exclusively numerical. This paper presents IRSN's expectations, feedbacks and issues regarding this full numerical approach, as a technical support organization (TSO), especially concerning:■ the relevance of the numerical model, behavior law, mesh size and qualification of the code toreproduce the physical phenomena of interest. These points are very important given thecomplexity of the modeling of all components having an impact on the package performance;■ the definition of criteria to assess the performance of the package designs;■ the validity domain of the numerical calculations and associated parameters, through sensitivitystudies;■ the determination and assessment of the global uncertainties associated with the results of thenumerical calculations for studied package designs.The paper discusses areas where the current regulations could be adapted to address all theaforementioned issues
PROJET DOCTORAL SUR L'EVALUATION DES EFFETS DES RAYONNEMENTS IONISANTS SUR APIS MELLIFERA : PREMIERES EXPERIMENTATIONS DU PROJET BEERAD
No full textInternational audienceLa radiocontamination de l'environnement est un enjeu écologique majeur. Afin, d'avoir une meilleure anticipation des conséquences d'accidents tels que Tchernobyl ou Fukushima, il est nécessaire d'améliorer les connaissances sur les impacts et les risques environnementaux de l'irradiation et de la contamination liées aux éléments radioactifs. Dans le contexte de ma thèse, l'abeille domestique, Apis mellifera, a été choisie comme modèle pour étudier les effets des rayonnements ionisants aux niveaux moléculaire, cellulaire et tissulaire, mais également aux niveaux de l'individu et de la population. L'abeille rend de nombreux services aux écosystèmes, de ce fait, elle est essentielle pour l'environnement et la société. En effet, les abeilles sont des insectes d'importance économique, agro-environnementale, sociétale et scientifique. L'objectif de ma thèse est d'approfondir la connaissance des effets et des mécanismes d'action des rayonnements ionisants sur les abeilles, puisque très peu de données existent sur ce sujet. Mon projet doctoral fait partie du projet ANR BEERAD piloté par le LECO de l'IRSN à Cadarache et le LTE de l'INRAE d'Avignon. Le projet général est détaillé dans le résumé " Evaluation des effets de la contamination radioactive sur les abeilles : projets BEERAD et BEECONECT" présenté par Béatrice Gagnaire. Dans la partie détaillée ici, les premières expérimentations de laboratoire seront présentées. Des irradiations externes sont réalisées sur des abeilles lors d'expériences en conditions contrôlées, en utilisant des débits de doses pour certains proches de la contamination environnementale de Fukushima. Le but de la première expérimentation est de déterminer les effets toxicopathologiques des rayonnements ionisants, en utilisant le pathogène Nosema ceranae, afin d’identifier les possibles conséquences de l’interaction entre ce pathogène et l’exposition aux rayonnements ionisants. Pour cela, des analyses physiologiques (enzymes de lutte contre le stress oxydant, enzyme de l’activité neurale, enzymes de l'immunité, enzymes du métabolisme, protéines), de survie, de consommation de nourriture et de charges pathogènes ont été réalisées sur des abeilles irradiées. La deuxième expérimentation se concentre sur les effets populationnels : des colonies d'abeilles contenues dans des ruchettes sont placées dans des cages de vol et irradiées intégralement. Comme la première expérimentation, les paramètres physiologiques sont analysés ; l'émergence des abeilles est également étudiée. Puisque les abeilles vont se déplacer dans la cage de vol, le débit de dose externe réellement absorbé par les abeilles sera détecté puis calculé à l'aide de microdosimètres collés sur les thorax des butineuses. Ce projet contribuera à améliorer les connaissances sur les effets et les mécanismes d'action des RI sur les abeilles domestiques et pourrait permettre de prévoir des conséquences plus globales sur les pollinisateurs responsables d'une grande partie de la biodiversité végétale
Flux of tritium from the sea to the atmosphere around a nuclear reprocessing plant: Experimental measurements and modelling for the Western English channel
No full textInternational audienceTritium is released to the environment by nuclear industries in various forms, mainly HTO. In impact studies leading to estimated doses for the population, atmospheric discharges are mainly taken into consideration because they generally lead to values higher than those related to liquid discharges. However, the tritium released in liquid environments can be transferred to the atmosphere by evaporation and then be transported to terrestrial ecosystems by wind. This study was carried out in France near a fuel reprocessing plant (RP) which discharges tritium into the western English Channel. We highlighted the influence of a mass of water enriched with tritium on the HTO levels in atmospheric water vapour downwind through 18 field campaigns. A hydrodynamic model able to simulate tritium activity in the water was coupled with an evaporation an atmospheric transport model. It allows to reconstitute variations in atmospheric tritium on the coast, depending on liquid discharges of tritium from the reprocessing plant. On this basis, when seawater containing 20-100 Bq.L − 1 of tritium flows between 0 and 10 km off the coast, variations in atmospheric activity onshore can increase of 2-15 Bq.L − 1. Mean tritium quantities released by the sea into the atmosphere in the Western English Channel reached 130 TBq.y − 1 over the 2017-2020 period. Emissions were estimated at 0.9-11.3 GBq km − 2 .y − 1 and depends principally on the distance from the liquid discharge point. If we compare the "marine" source term, in HTO form, with the direct source term for gaseous discharges, the marine source term is one order of magnitude greater for the marine region affected by liquid discharges. Finally, we estimate that approximately 1.1% of tritium stock discharged at sea (regulated and controlled) return to the atmosphere each year at the scale of the Western English Channel
Comparison of calculated and measured spent nuclear fuel decay heat with CASMO5, SNF and standard methods
No full textInternational audienceIn this paper, we present a comparison between measured and calculated decay values for spent nuclearfuel assemblies from the Clab, GE-Morris EMAD facilities. Two codes are applied: CASMO5 and SNF, usingdifferent nuclear data libraries (JEF-2.2, JEFF-3.1.1, JEFF-3.2, ENDF/B-VII.1 and ENDF/B-VIII.0) and differentcode versions. Additionally values from four standard and guides for calculation of decay heats (ANS 2014,DIN 2014, ISO 2022 and RG-3.54 2018) were also compared with the measurements. All simulations withdifferent codes, code versions and methods are based on the same geometry and irradiation descriptions fora single assembly, providing more convenient comparisons of results. The impact of nuclear data librariesand computational methods are shown, compared to the spread of C/E (Calculations over Experiment) valuesbetween the 256 considered measurements. Finally, a comparison of the most important nuclides contributingto the decay heat is presented between measured assemblies and more recent cases corresponding to higherburnup, initial enrichment and longer cooling time
Tools for harmonized data collection at exposure situations with naturally occurring radioactive materials (NORM)
No full textInternational audienceNaturally occurring radioactive materials (NORM) contribute to the dose arising from radiation exposure for workers, public and non-human biota in different working and environmental conditions. Within the EURATOM Horizon 2020 RadoNorm project, work is ongoing to identify NORM exposure situations and scenarios in European countries and to collect qualitative and quantitative data of relevance for radiation protection. The data obtained will contribute to improved understanding of the extent of activities involving NORM, radionuclide behaviours and the associated radiation exposure, and will provide an insight into related scientific, practical and regulatory challenges.The development of a tiered methodology for identification of NORM exposure situations and complementary tools to support uniform data collection were the first activities in the mentioned project NORM work. While NORM identification methodology is given in Michalik et al., 2023, in this paper, the main details of tools for NORM data collection are presented and they are made publicly available.The tools are a series of NORM registers in Microsoft Excel form, that have been comprehensively designed to help (a) identify the main NORM issues of radiation protection concern at given exposure situations, (b) gain an overview of materials involved (i.e., raw materials, products, by-products, residues, effluents), c) collect qualitative and quantitative data on NORM, and (d) characterise multiple hazards exposure scenarios and make further steps towards development of an integrated risk and exposure dose assessment for workers, public and non-human biota.Furthermore, the NORM registers ensure standardised and unified characterisation of NORM situations in a manner that supports and complements the effective management and regulatory control of NORM processes, products and wastes, and related exposures to natural radiation worldwide
Numerical methodology on prestressed reinforced concrete containment building: Creep, aging and leakage. Application to VERCORS mock-up
No full textInternational audienceThe containment building (CB) is known as 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 CB under air pressure loading and aging effects. VERCORS consists in a 1/3 scaled containment mock-up representing a 1300 MWe CB of a typical French pressurized water reactor (PWR). This paper presents the results of a numerical methodology applied on VERCORS mock-up. The simulation includes THM analysis in gusset, prestressing phase and pressurization phase, and is conducted through a finite element code, Cast3M. Concrete is modeled through 3D elements while rebars and tendons are modeled by 1D elements. Moreover, 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 the internal variable of the damage model and a hydric analysis. The mechanical results reveal different damage zones on the CB, which are distributed at gusset, hatch and dome
Do transient hydrological processes explain the variability of strontium-90 activity in groundwater downstream of a radioactive trench near Chernobyl ?
No full textInternational audienceThe Chernobyl Pilot Site (CPS) was created in 2000 in order to study radionuclide migration processes to the geosphere from radioactive material of the Red forest buried in a trench. In this article, the data collected in the CPS up to 2015 are analyzed to identify the links between hydrological conditions and release of strontium-90 (90 Sr) from the trench. Then, a flow-and-transport model is used for simulating distribution of 90 Sr both in the unsaturated and saturated zones downstream of the trench. The results show that the 90 Sr activity in groundwater is strongly transient in time, due to the high inter-annual variability of both the recharge rate and the groundwater level (some particularly wet winters resulted in saturation of the bottom part of the trench). In addition, the parameters that govern the sorption of 90 Sr in trench material appear to vary significantly in space (the retardation factor ranges from 10 to 50 depending on the location). This spatiotemporal variability could hide some critical processes, e.g., related to a long-term trend, and needs to be characterized through an appropriate sampling frequency
Ultrafine Particles Issued from Gasoline-Fuels and Biofuel Surrogates Combustion: A Comparative Study of the Physicochemical and In Vitro Toxicological Effects
No full textInternational audienceGasoline emissions contain high levels of pollutants, including particulate matter (PM), which are associated with several health outcomes. Moreover, due to the depletion of fossil fuels, biofuels represent an attractive alternative, particularly second-generation biofuels (B2G) derived from lignocellulosic biomass. Unfortunately, compared to the abundant literature on diesel and gasoline emissions, relatively few studies are devoted to alternative fuels and their health effects. This study aimed to compare the adverse effects of gasoline and B2G emissions on human bronchial epithelial cells. We characterized the emissions generated by propane combustion (CAST1), gasoline Surrogate, and B2G consisting of Surrogate blended with anisole (10%) (S+10A) or ethanol (10%) (S+10E). To study the cellular effects, BEAS-2B cells were cultured at air-liquid interface for seven days and exposed to different emissions. Cell viability, oxidative stress, inflammation, and xenobiotic metabolism were measured. mRNA expression analysis was significantly modified by the Surrogate S+10A and S+10E emissions, especially CYP1A1 and CYP1B1. Inflammation markers, IL-6 and IL-8, were mainly downregulated doubtless due to the PAHs content on PM. Overall, these results demonstrated that ultrafine particles generated from biofuels Surrogates had a toxic effect at least similar to that observed with a gasoline substitute (Surrogate), involving probably different toxicity pathways
Circulating microvesicles correlate with radiation proctitis complication after radiotherapy
No full textInternational audienceIn a large retrospective study, we assessed the putative use of circulating microvesicles (MVs), as innovative biomarkers of radiation toxicity in a cohort of 208 patients with prostate adenocarcinoma overexposed to radiation. The level of platelet (P)-, monocyte (M)-and endothelial (E)-derived MVs were assessed by flow cytometry. Rectal bleeding toxicity scores were collected at the time of blood sampling and during the routine follow-up and were tested for association with MVs using a multivariate logistic regression. MVs dosimetric correlation was investigated using dose volume histograms information available for a subset of 36 patients. The number of PMVs was significantly increased in patients with highest toxicity grades compared to lower grades. Risk prediction analysis revealed that increased numbers of PMVs, and an increased amount of MMVs relative to EMVs, were associated with worst rectal bleeding grade compared to the time of blood sampling. Moreover, a significant correlation was found between PMV and MMV numbers, with the range of doses up to the median exposure (40 Gy) of bladder/rectum and anterior rectal wall, respectively. MVs could be considered as new biomarkers to improve the identification of patients with high toxicity grade and may be instrumental for the prognosis of radiation therapy complications
Validation of iTOUGH2-EOS5 against analytical solution of compressible gas flow in a porous medium
No full textInternational audienceIn deep geological disposal of radioactive waste, anaerobic metal corrosion, radioactive decay of the waste,radiolysis of organic materials and water, and other reactions lead to the formation of gaseous components,in particular hydrogen (H2) which is highly compressible (and explosive). The accumulated gas withpressure increase could develop dilatant pathways for gas migration, which can have adverse effects on thehost rock confinement properties and the long-term stability of engineered barriers. Pore pressure build-updue to gas production, fluid flow and the stresses evolution around the canister in the EDZ and sealings areinvestigated in a wide range of studies around the world. But inconsistencies in the gas pressure estimationof H2 production models (corrosion model, gas source term, pathways in the engineered system) can leadto a misunderstanding of the physical phenomena and to incorrect modeling hypotheses for flow and Hydro-Mechanical (HM) coupling. Even if dilatancy of fluids and host rock has been previously studied (Xu et al.2020, Tunnelling and Underground Space Technology), there is a need for enhancing the modeling ofsingle-phase gas flow (as a special case of two-phase water-gas flow) by considering gas compressibility,in order to make reliable predictions of the gas pressure build-up because hydrogen is a highly compressiblegas. So, despite the substantial physics incorporated into these tools, their results are sometimes restrictedby the incompressible fluids hypothesis. The iTOUGH2 code (Finsterle 2007: iTOUGH2 User's Guide.LBNL-40040) includes some built-in constitutive relationships for the compressibility of the fluid and alsothe porous media (pore compressibility). In this work, the Equation-of-State module EOS5 of iTOUGH2 isapplied to simulate a single-phase gas flow of hydrogen in a 1D configuration with Dirichlet boundaryconditions (fixed gas pressures upstream and downstream). The mass conservation equation for thecompressible H2 gas is expressed using the law of perfect gases, and an analytical solution is developed atsteady state. Pressure profiles obtained by iTOUGH2 from this gas “permeameter” simulation were fittedto the analytical solution to estimate a key parameter in compressible gas flows (the gas compressibilitycoefficient) using a least squares optimization method, with reasonably good results. This test may helpassess by the numerical model the gas pressure build-up phenomena in a radioactive waste repository. Weexpect to account for real gas law and to design similar numerical experiments to identify mechanical andhydro-mechanical coefficients