Institute for Radiation Protection and Nuclear Safety (IRSN)
Not a member yet
7928 research outputs found
Sort by
The CRISTAL critically package: From 2.0 Towards 2.1 version
No full textInternational audienceThe version 2 of the CRISTAL package, devoted to criticality safety calculations for safetyenhancement and criticality risk prevention, was first released in 2014. Since then, fourupgrades of its components led to the 2.0.3patch version. The development, verificationand validation processes have been carried out in a joint project between the IRSN(Institut de Radioprotection et de Sûreté Nucléaire), the CEA/DES (Direction desEnergieS du Commissariat à l’Énergie Atomique et aux Énergies Alternatives), incollaboration with Orano group, EDF (Électricité de France) and Framatome. TheCRISTAL V2.0.3 experimental validation database contains more than 3100configurations representing the various configurations encountered in the fuel cycle. TheCRISTAL2.0.3 package is available at the OECD Database.In all its 2.0 versions, the CRISTAL package relies on the following extensively validatedneutron transport codes and package key components: APOLLO2.8-3.C, MORET 5.B.1and TRIPOLI-4.8. Each code uses the CEAV5.1.2 library based on the JEFF-3.1.1nuclear data evaluation, for multigroup and continuous-energy calculations.The link between the CRISTAL calculation codes is ensured by the LATEC workbenchthat allows users to generate all CRISTAL package input files, to launch calculations andto post-process outputs. The use of validated calculation options with the support ofAPOLLO2’s dedicated procedures ensures high quality results and reproducibility.The purpose of this paper is firstly to present the improvements brought by the latest 2.0.3version.Secondly, a presentation of the major upgrades of the future 2.1 version with a specificfocus on experimental validation, new calculation tools, nuclear data libraries andfunctionalities, is made
Datation archéomagnétique de bas-fourneaux du pays Bassar (Togo) : une étude de faisabilité
No full textInternational audienc
Brain cancEr risk in a pooled Case-cOntrol study of MEdical workers exposed to ionizing radiation in France, South Korea and the United States (the BECOME study)
No full textInternational audienceContextAmong medical professionals, there is some evidence that protracted exposure to ionizing radiation (IR) is associated with risk of certain cancers. Some publications have reported an excess of brain tumor in interventional cardiologists. However, few epidemiological studies have been performed to examine brain cancer risk with organ dose assessment in cohort of medical radiation workers.ObjectivesThe objective of the BECOME (Brain CancEr risk in joint cOhort of MEdical workers exposed to Ionizing radiation in France, USA and Korea) project is to conduct an international nested case-control study to quantify the radiation-induced risk of death from central nervous system (CNS) cancer, using estimated cumulative IR occupational doses in 3 cohorts of medical professionals exposed to IR in France, USA and Korea.MethodsThe study is based on 3 national cohorts, aiming at analyzing the risk of radiation-induced diseases in medical professionals: the French O'RICAMs (Occupational Radiation-Induced Cancer in Medical Staff) cohort, which follows 227,000 individuals since 2002, the USRT (U.S. radiological technologists) cohort, which includes about 110 000 medical workers exposed from 1920 to through the 2020s, and the Korean cohort, which includes 94,394 individuals followed since 1996.At the end of follow-up, 193, 67 and 25 deaths by CNS tumors were reported in the US, French and Korean cohorts, respectively. For each case, five controls will be randomly selected in the country-specific cohort and matched according to year of birth and sex.Organ doses for individuals of the USRT cohort have already been calculated and published. Organ doses for French and Korean cohorts will be estimated based on passive dosimetry, accounting for uncertainties.Conditional logistic regression models will be used to estimate the dose response relationship, taking into account potential confounding factors. Expected results and conclusionThe inclusion of 285 cases and 1425 matched controls will allow detecting at least an odds ratio of 1.66 for a statistical power of 80% (alpha significance level 5%). The study will quantify the relationship between occupational exposure to low doses of IR and CNS tumor mortality risk in medical workers. Our joint approach could be extended to assess the dose-response for other type of cancers and non-cancer outcomes, andit will increase the knowledge on health effects of protracted low-dose exposures to IR
DECORHONE - Définir les fonctions écologiques du fleuve Rhône, première étape vers les services écosystémiques
No full textNational audienc
Quantizing rare random maps: application to flooding visualization
No full textInternational audienceVisualization is an essential operation when assessing the risk of rare events such as coastal or river floodings. The goal is to display a few prototype events that best represent the probability law of the observed phenomenon, a task known as quantization. It becomes a challenge when data is expensive to generate and critical events are scarce, like extreme natural hazard. In the case of floodings, each event relies on an expensive-to-evaluate hydraulic simulator which takes as inputs offshore meteo-oceanic conditions and dyke breach parameters to compute the water level map. In this article, Lloyd's algorithm, which classically serves to quantize data, is adapted to the context of rare and costly-to-observe events. Low probability is treated through importance sampling, while Functional Principal Component Analysis combined with a Gaussian process deal with the costly hydraulic simulations. The calculated prototype maps represent the probability distribution of the flooding events in a minimal expected distance sense, and each is associated to a probability mass. The method is first validated using a 2D analytical model and then applied to a real coastal flooding scenario. The two sources of error, the metamodel and the importance sampling, are evaluated to quantify the precision of the method
Distribution and accumulation of metals and metalloids in planktonic food webs of the Mediterranean Sea (MERITE-HIPPOCAMPE campaign)
No full textInternational audienceParticle-size classes (7 fractions from 0.8 to 2000 µm) were collected in the deep chlorophyll maximum along a Mediterranean transect including the northern coastal zone (bays of Toulon and Marseilles, France), the offshore zone (near the North Balearic Thermal Front), and the southern coastal zone (Gulf of Gabès, Tunisia). Concentrations of biotic metals and metalloids (As, Cd, Cr, Cu, Fe, Mn, Ni, Sb, V, Zn) bound to living or dead organisms and faecal pellets were assessed by phosphorus normalisation. Biotic metals and metalloids concentrations (except Cr, Mn, and V) were higher in the offshore zone than in the coastal zones. In addition, biotic Sb and V concentrations appeared to be affected by atmospheric deposition, and biotic Cr concentrations appeared to be affected by local anthropogenic inputs. Essential elements (Cd, Cu, Fe, Mn, Ni, V, Zn) were very likely controlled both by the metabolic activity of certain organisms (nanoeukaryotes, copepods) and trophic structure. In the northern coastal zone, biomagnification of essential elements was controlled by copepods activities. In the offshore zone, metals and metalloids were not biomagnified probably due to homeostasis regulatory processes in organisms. In the southern coastal zone, biomagnification of As, Cu, Cr, Sb could probably induce specific effects within the planktonic network
Ionizing radiation affects the demography and the evolution of Caenorhabditis elegans populations
No full textInternational audienceIonizing radiation can reduce survival, reproduction and affect development, and lead to the extinction of populations if their evolutionary response is insufficient. However, demographic and evolutionary studies on the effects of ionizing radiation are still scarce. Using an experimental evolution approach, we analyzed population growth rate and associated change in life history traits across generations in Caenorhabditis elegans populations exposed to 0, 1.4, and 50.0 mGy.h−1 of ionizing radiation (gamma external irradiation). We found a higher population growth rate in the 1.4 mGy.h−1 treatment and a lower in the 50.0 mGy.h−1 treatment compared to the control. Realized fecundity was lower in both 1.4 and 50.0 mGy.h−1 than control treatment. High irradiation levels decreased brood size from self-fertilized hermaphrodites, specifically early brood size. Finally, high irradiation levels decreased hatching success compared to the control condition. In reciprocal-transplant experiments, we found that life in low irradiation conditions led to the evolution of higher hatching success and late brood size. These changes could provide better tolerance against ionizing radiation, investing more in self-maintenance than in reproduction. These evolutionary changes were with some costs of adaptation. This study shows that ionizing radiation has both demographic and evolutionary consequences on populations
Numerical simulations of a PVC cable fire on long cable-trays in a mechanically ventilated large scale facility
No full textInternational audienceElectrical cable-tray fires pose a known safety risk at nuclear power plants. As part of the OECD funded PRISME-3 experimental programme, IRSN aims to improve understanding of cable-tray fires in confined and ventilated environments. In this study, a PVC cable fire in horizontally stacked long cable-trays is simulated using the CALIF3S-Isis CFD code. A FLASH-CAT approach approximates the heat release rate profile and allows for flame front tracking, a potentially important characteristic for fires involving long cable-trays. A further equivalent simulation without flame-front tracking is also carried out, injecting the same total mass but this time over the combined upper surface areas of the cable trays. Comparisons suggest that the flame-front tracking approach reduces the maximum error seen in the CFD predictions of temperatures in the near-fire zone. A similar result is found for gas product concentrations. However, a quantitative analysis suggests that, in its current state, the implemented FLASH-CAT approach requires further improvements if it is to realise its potential to reduce errors in long cable-tray fire simulations. Suggested improvements relate to the mass loss rate per unit area profile implemented in the FLASH-CAT approach to improve the predictive capabilities of flame-front tracking methods
Le flashing gravitaire d'eau métastable dans un bassin chauffé par le bas: Une étude expérimentale
No full textThe present research is focused on the gravity-driven flashing of metastable water, a phenomenon which may be encountered in any system being heated from below, where an uprising hot fluid experiences a significant decrease in hydrostatic pressure. For sufficiently large vertical systems, be they a deep pool or some long duct such as a geyser, the temperature of the flowing fluid may exceed its saturation value and reach a so-called superheated, metastable state. From that situation, the metastable liquid may spontaneously vaporize through the form of bubbles as a way to tend toward thermal saturation, a process referred to as flashing. Specifically in this research, the emphasis is put on the case of a water pool heated from below, motivated by the absence in the scientific literature of any known report of the phenomenon in this precise configuration. By means of an experimental device called Aquarius, specifically designed and constructed during this research, the phenomenon is first evidenced in a heated pool. Then, its main characteristics are highlighted: instead of observing a cyclic flashing as for geysers, the emergence of bubbles from the superheated liquid appears typically steady in the presented tests. In addition, those created bubbles do emerge within the liquid bulk itself, into the most superheated area of the pool: underneath the liquid free surface. The dependence of the bubble production process on the heating power, operating pressure, initial pool level and amount of dissolved gases in the pool is then investigated. At last, an experimental data reduction by means of a set of mathematical correlations is achieved and a simple thermodynamic modeling of the studied system is proposed.Étudier l’ébullition à basse pression au sein d’un bassin permet l’atteinte de conditions de nucléation spécifiques : le flashing d’eau métastable. Si ce phénomène peut apparaître dans d’autres configurations (geysers, réservoirs dépressurisés), le dispositif expérimental original Aquarius conçu pour ce besoin permet de révéler les spécificités d’une variation des conditions de saturation induite par la pression hydrostatique couplée avec un transport de chaleur et d’espèces gazeuses dissoutes par convection naturelle. Il s’agit ainsi de reproduire à petite échelle une situation à même de se produire lors d’un accident de perte de refroidissement au sein des piscines d’entreposage de combustible nucléaire des réacteurs de production électrique. Ces travaux de thèse déterminent les conditions d’existence d’eau métastable au sein du bassin, avec des surchauffes pouvant atteindre de 1 à 5°C, dans la zone située sous la surface libre. Une nucléation y est observée et le dispositif a permis d’étudier l’influence de plusieurs paramètres sur son occurrence : la puissance de chauffe, le niveau de pression, la hauteur d’eau, la quantité de gaz dissous. Une analyse théorique des mécanismes de nucléation est proposée et identifie la flottaison libre de nuclei gazeux comme un mécanisme probable, ce qu’il conviendrait de prouver par une instrumentation adéquate. En outre, une analyse quantitative de l’ensemble des mécanismes de transport de masse, de chaleur et d’espèces au sein du bassin permet de proposer un ensemble de coefficients d’échange et de corrélations. Une modélisation par une approche de type code à zone, incluant ces propositions de modèles permet enfin de reproduire avec une incertitude modérée l’ensemble du transitoire des tests considérés
Experimental investigations on rod bundle cooling by a water spray in spent fuel pool accident conditions
No full textInternational audienceIncreased attention has been paid in the last decade to the Spent Fuel Pools (SFP) accident phenomenology. TheDENOPI project is part of this approach with the aim to gain knowledge in the SFP under loss of cooling or lossof coolant accident conditions and to better evaluate the safety margins. Questions are still pending regardingthe physical phenomena involved during the uncovery phase of the accident. Besides, the capabilities of a spraysystem to cool down a partially or totally uncovered assembly must be assessed. To address these issues, the ASPICfacility has been set up at the scale of one full height 17x17 rod bundle which is electrically heated. In this study,the results of a reference test are presented and discussed. For instance, the rod and wall section temperatures areanalyzed and a comparison is undertaken for the time evolution of these temperatures with and without the activation of the spray during the test. Besides, the impact of the spray on the outlet steam characteristics is examined