Institute for Radiation Protection and Nuclear Safety (IRSN)
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En quête d'archives : Les archives de l'IRSN éclairent la naissance de la sûreté nucléaire en France
No full textAu début de l’année 1960, le Commissariat à l’énergie atomique (CEA) crée la Commission de sûreté des installations atomiques (CSIA) dont l’objectif est de centraliser l’examen des problématiques de sûreté des installations nucléaires françaises. La création de la CSIA et ses différentes sous-commissions2 marquent les débuts de la formalisation de la sûreté en France autour de pratiques et d’outils encore en vigueur aujourd’hui (dialogue technique, rapport de sûreté…). La CSIA et ses différentes sous-commissions sont l’ancêtre conjoint de l’ASN, de l’IRSN et des groupes permanents d’experts.Accompagné de l’archiviste Camille Bouchain, Michaël Mangeon s’est plongé dans quatre documents d’archives gardés précieusement à l’IRSN, permettant de comprendre la formalisation, en quelques mois, d’un embryon de système de contrôle et d’expertise et de quelques principes fondateurs de la sûreté nucléaire en France.Les documents mobilisés sont les suivants :- CEA, note de service n°C 278, Création d’une commission de sûreté des installations atomiques du CEA, 27 janvier 1960. Archive IRSN/FAR 314592- CEA, compte-rendu de la réunion du 11 février 1960 de la commission de sûreté des installations atomiques. Archive IRSN/FAR 327047- CEA, note de service HC N°38, Commission de sûreté des installations. Documents à fournir concernant la sûreté des piles, 14 mars 1960. Archive IRSN/FAR 314592- CEA, compte-rendu de la réunion du 7 avril 1960 de la sous-commission de sûreté des piles, 8 avril 1960. Archive IRSN/FAR 314592Pour analyser ces documents d’archive, nous reviendrons dans un premier temps sur l’origine de la création de la CSIA. Dans une seconde partie, nous analyserons la création et les principes de fonctionnement de la CSIA. Dans une troisième partie, nous éclairerons le rôle du rapport de sûreté, outil central dans le processus de dialogue technique avec l’exploitant. Dans une quatrième partie, nous tenterons de cerner la philosophie de cet embryon de système de contrôle et d’expertise, tourné vers la proximité entre acteurs et le développement industriel. Enfin, nous conclurons sur les héritages de ces premiers mois de fondations de la sûreté nucléaire en France
Sources, Transport, and accumulation of Mercury in the northwestern Mediterranean margin sediments during the Industrial Era and influence of turbiditic events
No full textInternational audienceSources and pathways of the Hg accumulated in the sediments of the Gulf of Lion (GoL) and its adjacent marine areas (Northwestern Mediterranean) have been explored using sediment grab samples, sediment cores, and sediment trap samples. The main source of Hg along this margin is the Rhône River, whose suspended sediments settle mainly in the prodelta area but also along the mid-shelf, then reaching the continental rise via wave resuspension and cascading of dense shelf waters. Seaward, these riverine particles are mixed with carbonated ooze conveyed to the bottom by the biological pump. The Hg is enriched in surface sediments of the GoL with decreasing concentrations westward and seaward from the Rhône prodelta to the continental rise. Dated cores from the Rhône prodelta give access to riverine sediments deposited over the last 400 years and show that the Hg concentration time trend resembles the evolution of coal consumption in France, peaking during in the 1960s. Similar trends were observed in sediment cores collected along the GoL slope and submarine canyons along with the preservation of traces of erosion and sediment instability events. Seaward, on the continental rise, the Hg concentration distribution suggests the deposition of fine planktonic-derived material and particles episodically advected from the shelf during deep cascading pulses. Anthropogenic Hg accumulated in GoL and continental rise sediments during the Industrialized Era is ∼ 150 Mg (tons), two-thirds of which are buried in the Rhône prodelta area. Significant correlations are found between Hg and organic matter in GoL sediments, but the relationships differ between areas and are disrupted by the inputs of anthropogenic Hg and by the Hg availability in the Rhône River watershed during the pre-industrial period. The HgT availability in waters appears to be the limiting factor to the Hg enrichment of the particulate organic matter. Monomethyl mercury (MMHg), which represents on average 0.3 % of the total Hg, was positively correlated to total Hg. Their distributions suggest in situ MMHg formation and a more effective net Hg methylation for surface sediment or particles collected in traps compared with particles buried in the sedimentary column
Forward and Backward Lagrangian Probability Density Properties
No full textA basic relationship between forward and backward lagrangian probability density functions (pdfs.) is derived for any continuous medium if mass conservation is postulated. For an incompressible medium these pdfs are identical: see equation (45). This identity is used to generalize some previous results obtained under more restrictive hypotheses. It is shown:1.Identity of forward and backward variances for dispersion was established under the condition of unstrained stationary flow [1]. The same identity is obtained hereafter under homogeneity condition only.2.Identity of Eulerian and Lagrangian velocity moments was established under homogeneous and stationary flow conditions [2]. This identity and the equality of the lagrangian and eulerian velocity pdfs are established here for homogeneous and unsteady conditions.These results were published first year 1981 in French in the “comptes-rendus” of the French Science Academy [3]. Such an issue imposes a very concise paper limiting additional developments and explanations. We propose herewith such additions providing an opportunity for longer explanations of how such results are obtained.Chapter two is devoted to the description of deterministic random displacement of a continuous medium, e.g. a turbulent fluid flow. In addition, elementary elements of probability tools are provided in connection with the developments of the chapter three. This one addresses the question of forward and backward displacements and their respective lagrangian pdfs and proves their equality. Finally, chapter four establishes the results 1 and 2 mentioned above in this introduction using forward and backward pdfs. equality
Experimental study of secondary hydriding during a LOCA transient
No full textInternational audienceDuring the oxidation phase of a Loss of Coolant Accident (LOCA), significant hydrogen absorption can occur at the inner side of the fuel rod, between the pellet and the cladding. This phenomenon, known as secondary hydriding, has been investigated through semi -integral tests. To better understand this phenomenon, a new protocol was developed to simulate and conduct separate effects tests (SETs). The results of these separate effects tests are valuable for supporting codes aimed at simulating secondary hydriding. In this study, separate effects tests were carried out to characterize the influence of pellet positioning inside the cladding on the azimuthal distribution of hydrogen within the cladding after the transient. Hydrogen measurements have revealed a correlation between the azimuthal hydrogen distribution and the non -coaxial positioning of pellets during the transient
Comparison of simulated and inferred structural damage caused by historical earthquakes
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In-situ measurements of fog microphysics: Visibility parameterization and estimation of fog droplet sedimentation velocity
No full textInternational audienceMeasurements of fog microphysics were conducted during the winter season of 2021 -2022 at the BarakahNuclear Power Plant (BNPP), located in the Western coastal region of the United Arab Emirates. Twelve fogevents were observed during this period. The primary objective of this study is to detail the microphysicalcharacteristics of these events and refine current visibility parameterization schemes based on in-situ measurements of fog microphysical properties.All observed fog events are found to share a common feature of a bimodal distribution in droplet numberconcentration (Nd), with modes at 4.5 μm and 23.2 μm. Despite the high proportion of smaller fog dropletsassociated with the fine mode, the greatest contribution to the liquid water content (LWC) comes essentially from medium to large droplets between 10 and 35 μm. The recalibration of existing visibility parameterizationschemes revealed that the increase in horizontal visibility with increasing FI (fog index) tends to be more gradualfor the studied cases compared to standard visibility parameterization schemes.Additionally, the fog droplet sedimentation velocity, estimated to be at a maximum of 1.85 cm s-1, occurspredominantly in the LWC range of 100–200 mg m-3, corresponding to a median volume diameter 24.8 μm. Ourfindings shed new light on the complexity of fog microphysics and its impact on visibility, underscoring theirimportance in refining weather models for accurate fog forecasting
Subdivision scheme for discrete probability measure-valued data
No full textInternational audienceThis paper deals with the approximation of discrete probability measure-valued data by a new subdivision scheme. Its construction relies on a coupling between linear subdivision and optimal transport. A mathematical analysis is performed to study its convergence. Two test cases are finally described to emphasize its capability: the first one is related to point cloud interpolation while the second one is a first attempt in the framework of image approximation
International fuel performance study of fresh fuel experiments for PCMI effects during RIA experiments
No full textInternational audienceThis paper presents the results of High-burnup Experiments for Reactivity-initiated Accident (HERA) Modeling & Simulation (M&S) exercise. The HERA project under the Nuclear Energy Agency (NEA) Second Framework for Irradiation Experiments (FIDES-II) program is focused on studying Light Water Reactor (LWR) fuel behavior during Reactivity-Initiated Accident (RIA) conditions. The Part I M&S cases are based on a series of tests in the Transient Reactor Test (TREAT) facility in the United States and the Nuclear Safety Research Reactor (NSRR) in Japan. The purpose of this work is to evaluate the test design to accomplish its goals in establishing clearer understanding of the effects of power pulse width during RIA conditions. The blind predictions using various computational tools have been performed and compared amongst to interpret the behaviors of high burnup fuels during RIA. While many international participants evaluate the thermal–mechanical behavior of fuel rod under different conditions, a considerable scatter of outputs comes out for the cases due to the disparity between codes in predicting mechanical behaviors. In general, however, the results of thermal–mechanical analysis elaborate that nominal design conditions the shorter pulse width tests in NSRR should cause cladding failures while the TREAT tests appear to have more split prediction of failure or not. Furthermore, the sensitivity analysis varying key testing parameters reveals the considerable effect of power pulse width and total energy deposition on prediction of fuel rod failure
Development of a methodology for dose assessment and estimate of amount of NORM residues disposable in a conventional landfill
No full textInternational audienceThe final disposal of NORM wastes in conventional landfill generally determines problems of acceptance by the landfill operators, since their willingness to accept Naturally Occurring Radioactive Material (NORM) is often limited due to their concern about the radiological risks and reluctance of the local community to have at local landfills material that despite being cleared is still perceived as 'radioactive'. In order to raise awareness among landfill operators, and also among other stakeholders on the actual radiological risk of exempted or cleared NORM wastes, it is of interest to estimate the mass of annual wastes containing NORM that can be disposed of in a landfill for conventional waste complying with the annual dose criterion of 1 mSv.A methodology was developed considering a hypothetical homogeneous large landfill and assuming that NORM wastes are delivered with an initial activity concentration of 1 kBq kg -1 . The methodology uses exposure scenarios and assumptions from Radiation Protection 122 Part 2, the codes RESRAD-ONSITE and OFFSITE, and the most recent dose coefficients from ICRP. The exposure scenarios considered are the "worker handling NORM at an active landfill" and "members of the public living near an active landfill", For these scenarios, screening levels (called Operational Levels in this work) in terms of activity concentration fulfilling the annual dose criterion of 1 mSv, for members of the public (including all ICRP age groups) and workers at a landfill, have been calculated for each decay chain segments using a generic and conservative approach. The Operational Levels evaluated in this work are almost independent from the landfill size and are relevant to the landfills complying the EU directive 1999/31 requirements.The obtained Operational Levels (OL) are all higher than 1 kBq kg -1 , for U-238 and Th-232 series radionuclides and 10 Bq g -1 for K-40, which are the general clearance levels adopted in the European Union. The estimated OLs range between 2 kBq kg -1 (for Th-232sec) and about 150 kBq kg -1 (for Po-210). For the U-238 decay chain, the segments with the smallest OLs values are U-238sec (OL = 2.5 kBq kg -1 ) and Ra-226+ (OL = 3.7 kBq kg -1 ). For Th-232 chain, the most critical segments are Th-232sec and Th-228+ (OL = 3.8 kBq kg -1 ). As regards the mass of annual NORM wastes that can be disposed of in a conventional landfill, the levels obtained for Po-210, Pb-210+ and K-40 indicate that from the radiological point of view limitations to the annual admissible mass may occur only for large activity concentrations (i.e. 40 kBq kg -1 and above). For the other segments, instead, limitations can occur for activity concentration levels in residues above 2 kBq kg -1 .</p
Relevance of the steady laminar flamelet model for the large-eddy simulation of a reactive plume
No full textInternational audienceThe relevance of the steady laminar flamelet model (SLFM) is analyzed and discussed on the basis of computational results issued from the large-eddy simulation (LES) of a 30 cm diameter methanol pool fire. In a first step of the analysis, the computational results are assessed versus available experimental data: a satisfactory level of agreement is obtained. Then, the computational database is used to analyze the combustion regimes and model response