Institute for Radiation Protection and Nuclear Safety (IRSN)
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Batch Effect Correction in a Confounded Scenario: a Case Study on Gene Expression of Chornobyl Tree Frogs
No full textInternational audienceWhen large omics datasets present unwanted latent variability, a critical analysis step is to control these so-called batch effects properly. However, most batch effect-correction algorithms (BECAs) face limitations when the source of unwanted variation and the variable of interest are confounded. In this paper, we use RNA-seq data to study the effects of radiation contamination on tree frogs (Hyla orientalis) collected in the Chornobyl Exclusion Zone. We identify the site of collection of the frogs as a confounding factor in the transcriptomics analysis. We present our strategy to correct this confounding effect using the following BECAs: ComBat-seq, linear residualization, and Surrogate Variable Analysis. We show that the severe confounding between the site and radiocontamination level makes the correction step challenging. Instead, we investigate the site-to-site variability and successfully deconvolute the batch variable from the radiation level by adjusting for the population genetic structure. Our strategy allowed us to reveal the effects of low-dose radiation on the gene expression of Chornobyl tree frogs and appropriately preprocess the RNA-seq dataset for future multimodal integrative analyses
Main lessons learnt from 40 years of R&D on iodine source term prediction: Identification of the main parameters governing iodine volatility in PHEBUS FP tests
No full textInternational audienceIodine chemistry and phenomenology in the containment has been studied for several decades. The main phenomena leading to the formation of volatile iodine have been identified step by step and their kinetics has been modeled and capitalized over the years in ASTEC-SOPHAEROS IRSN Severe Accident (S.A) code. Recently, the uncertainties for each phenomenon have been quantified and uncertainty propagation calculations have been performed on PHEBUS FPT-0/1/2/3 tests within the objective to identify which phenomena govern iodine volatility. The main highlights from PHEBUS studies are that (1) the sump reactions do not contribute to iodine volatility and (2) the gaseous phase chemical reactions are the main contributor to iodine volatility and (3) only a few gaseous reactions govern iodine volatility in PHEBUS containment. Another objective was to narrow the estimated range of %I2_RCS (gaseous iodine fraction coming from the RCS). The results show that, considering 43 uncertain parameters, the iodine volatility plume is compatible with the experimental data whatever 2% < %I2_RCS < 50% that mostly govern iodine volatility in the first days. It also indicates that, as soon as the FP release from the core is stopped and whatever 2% < %I2_RCS < 50%, the influence of %I2_RCS decreases over time so that the main processes leading to iodine volatility are slowly switched from %I2_RCS (short term) to other gaseous phenomena (long term). The influence of %I2_RCS on iodine volatility is thus important in the short term but becomes less and less significant in the long term (after several days). A more complete analysis is necessary for reactor applications to identify if the same conclusions can be drawn
Morphologie des canyons messiniens du Rhône et de l'Ardèche : apport de nouveaux profils sismiques
No full textInternational audienceTwelve available two-way time high-resolution seismic reflection profiles located in the central part of the middle Rhône valley are interpreted. In addition, one of the profiles was reprocessed to determine the P-wave velocities of the main geological units and to convert this profile into a depth cross section. The Lower and Upper Cretaceous units are clearly identifiable on all the profiles, along with the Messinian Erosion Surface (MES) carved out during the Messinian Salinity Crisis (MSC) by the paleo-Rhône and its western tributaries, the Ardèche and Cèze paleo-canyons. The Plio-Quaternary fill of these paleo-canyons shows at least 4 main units with an overall transgression. The combination of geological data from geological maps, geological field surveys and borehole data made it possible to model the MES in 3D at the scale of the region, and to produce depth/elevation model. From a geological point of view, the interpretation of the seismic profiles enabled us to reconstruct the stages in the sub-aquatic filling of the Messinian-Pliocene aggradation of the paleo-river. Several Mass Transport Deposits (MTDs) were identified both during the drop and during the rise in the Mediterranean Sea level. From a geomorphological point of view, this study provides new insights in the route and longitudinal profile of paleo-rivers and, in particular, it deepens the profile of the Paleo-Rhône at the latitude of the Tricastin region (up to 700 m b.s.l.) and significantly modifies the course and depth of the Ardèche proposed in previous studies. The N-Ardèche river, known to develop a karstic system during the MSC, is connected to a deep canyon, most likely through a karstic pocket valley, as suggested by the very steep longitudinal profile of the MES. Finally, from a structural point of view, our interpretation of the seismic profiles shows a broad ENE-trending anticline structure associated with a normal fault which apparently did not affect the Mio-Pliocene fill. In the southern part of the area, near the Uchaux anticline, the imaged structures suggest the presence of a recent (syn- to post-Pliocene) fold propagation fault. In addition to all the new information on the geology, morphology and methods of excavation and filling of the Messinian paleo-canyon, the proposed topographic model of the paleo-canyon is crucial for modelling seismic movement in the context of a basin with a complex geometry and, in particular, for the numerical assessment of site effects in a context of low seismicity.12 profils de sismique-réflexion à haute résolution situés dans la partie centrale de la moyenne vallée du Rhône ont été interprétés. Un des profils a été retraité pour déterminer les vitesses des ondes P des principales unités géologiques et pour convertir cette ligne en une coupe en profondeur. Sur tous ces profils, les unités du Crétacé inférieur et supérieur sont clairement identifiables, de même que la surface d'érosion messinienne (MES) creusée pendant la crise de salinité messinienne (CSM) par le paléo-Rhône et ses affluents de rive droite, les paléo-canyons de l'Ardèche et de la Cèze. Le remplissage Plio-Quaternaire de ces paléo-canyons montre au moins 4 unités principales témoignant d'une transgression globale. La combinaison des données issues des cartes géologiques, des études de terrain et des données de forages a permis de modéliser la MES à l'échelle de la région. D'un point de vue géologique, l'interprétation des lignes sismiques a permis de proposer une reconstruction des étapes du remplissage sub-aquatique de l'aggradation messino-pliocène des paléo-rivières. Plusieurs épisodes de dépôts de transport de masse (MTD) ont été interprétées comme résultant de différents cycles eustatiques. D'un point de vue géomorphologique, cette étude fournit de nouvelles informations sur le tracé et le profil longitudinal des paléo-rivières et, en particulier, elle approfondit le profil du Paléo-Rhône à la latitude de la région du Tricastin (jusqu'à 700m sous le niveau de la mer) et modifie de manière significative le cours et la profondeur de l'Ardèche tel qu'il a été proposé dans des études antérieures. La Paléo-Ardèche, connue pour développer un système karstique pendant la MSC, est connectée à un profond canyon, très probablement par le biais d'une reculée karstique, comme le suggère le profil longitudinal très abrupt de la MES. Enfin, d'un point de vue structural, l'interprétation des lignes sismiques montre une large structure anticlinale orientée ENE associée à une faille normale d’extrados qui n'affecte apparemment pas le remplissage mio-pliocène. Dans la partie sud de la zone, près de l'anticlinal d'Uchaux, les structures imagées suggèrent la présence de failles ayant eu une activité récente (syn à post-pliocène) associée au rejeu de cet anticlinal. Les nouvelles informations apportées par cette étude sur la géologie, la morphologie et les processus de creusement et de remplissage du paléo-canyon messinien ont permis de proposer un modèle topographique du paléo-canyon. Concernant l’évaluation de l’aléa sismique, l’utilisation d’un tel modèle est cruciale pour modéliser les effets de site dans un bassin à géométrie complexe dans un contexte de faible sismicité
CIDRRE : Evaluer l'impact de vos rejets liquides dans le système d'assainissement
No full textInternational audienceAvec l’autorisation des maires ou de leurs délégataires, les services de médecine nucléaire et les laboratoires de recherche peuvent déverser dans le réseau d’assainissement des eaux usées contenant des radionucléides à période courte, après une décroissance au moins partielle de leur activité. Cette radioactivité est susceptible d’exposer des travailleurs dans les égouts et dans les stations de traitement des eaux usées. Ces travailleurs n’étant pas professionnellement exposés aux rayonnements ionisants, au sens de la réglementation, leur exposition annuelle ne doit pas dépasser la limite de 1 mSv/an applicable aux membres du public. L’établissement à l’origine du déversement doit contrôler et minimiser son impact ; cependant que l’employeur des travailleurs du système d’assainissement a la responsabilité du respect de la limite de dose réglementaire. Pour aider les services de médecine nucléaire, les laboratoires de recherche et les gestionnaires de système d’assainissement à estimer l’impact sur les travailleurs, l’IRSN met à disposition l’outil de calcul d’impact des déversements radioactifs dans les réseaux (CIDRRE, https://cidrre.irsn.fr/). CIDRRE permet d’évaluer la dose efficace annuelle potentiellement reçue par 6 catégories de travailleurs (égoutiers immergés ou non, travailleurs des files eaux et boues de la station de traitement des eaux usées, travailleurs en charge du transport et de l’épandage agricole des boues) par irradiation externe en provenance des eaux et des boues contaminées et par inhalation ou ingestion de gouttelettes et de poussières. Les modèles de calcul appliqués par CIDRRE sont simples pour permettre une utilisation facile avec un nombre limité de paramètres à renseigner : activité manipulée ou administrée des différents radionucléides, débit d’eau usée à l’émissaire de l’établissement et à l’entrée de la station de traitement. Pour les radionucléides les plus utilisés en médecine nucléaire, la biocinétique des médicaments radiopharmaceutiques et la présence de cuves de décroissance reliées aux sanitaires des chambres radioprotégées sont prises en compte.Puisqu’il doit garantir, à l’aide d’un modèle générique, le respect de la limite réglementaire de dose dans l’ensemble des situations particulières, CIDRRE applique des hypothèses volontairement majorantes qui conduisent à surestimer l’exposition réelle dans la plupart des cas. Si le résultat obtenu approche ou dépasse la limite, une évaluation plus réaliste devrait être conduite en intégrant des données spécifiques au site comme le délai minimum avant rejet imposé par les fosses toutes eaux, les temps de travail, les débits d’eau usée dans les collecteurs, la production annuelle de boue ou l’éloignement des patients traités en ambulatoire.L’atelier sera l’occasion d’une présentation, d’une démonstration et d’un échange autour de l’outil CIDRRE
A compact scintillator-based detector for high energy neutron spectrometry
No full textInternational audienceA compact neutron spectrometer consisting of a 6 mm × 6 mm × 120 mm prism of EJ-276 plastic scintillator capable of pulse shape discrimination coupled to a single silicon photomultiplier is described. In principle this device will be capable of spectroscopic measurements exceeding 100 MeV using unfolding analyses with detector response functions measured at neutron time-of-flight facilities. A characterisation of the device is described and illustrated with measurements of the detector response made at three fast neutron facilities with energies between 5.0 MeV and 63.5 MeV. Nearly mono-energetic detector response functions were used to produce neutron energy spectra by unfolding light output distributions measured with the detector in the energy range of interest
Risques des examens radiodiagnostiques chez l'enfant
No full textVol. 74, n° 1The question of cancer risk associated with diagnostic medical exposure during childhood is important in view of the sharp increase in the use of radiological examinations, particularly computed tomography (CT), since the 2000s. Moreover, children represent a population particularly sensitive to ionizing radiation. Although conventional radiology examinations do not seem to be associated with an increased risk of cancer, several epidemiological studies, including some with high statistical power, show an increased risk of leukemia and brain tumors in children exposed to CT scans. These results reinforce the importance of the principles of radiation protection already applied daily in radiology, based on the justification of procedures, substitution as far as possible by techniques that do not expose patients to ionizing radiations (ultrasound and magnetic resonance imaging) and, if the use of CT scanners remains essential, systematic optimization of the doses delivered.Le nombre d’actes d’imagerie réalisés en pédiatrie augmente en France. Les enfants sont une population particulièrement sensible aux rayonnements ionisants qui induisent un sur-risque carcinologique faible mais statistiquement significatif. Ce risque impose des mesures de radioprotection : optimisation des doses délivrées et nécessité de justifier les actes réalisés, voire de les substituer par des techniques non irradiantes
On the Possible use of Propagation of Resonance Parameters Uncertainties Using the R-Matrix Formalism
No full textInternational audienceThis paper presents recent progress in the propagation of uncertainties in resonance parameters, crucial for precise neutron transport simulations. The IRSN nuclear data processing code, GAIA, has been enhanced with a new module named COP (COvariance Processing). Currently, this module handles the uncertainties in cross sections and neutron angular distributions. Efforts have been made to extend its capabilities to include the uncertainties in resonance parameters and their covariances. The performance of the COP module in propagating uncertainties is assessed using a set of chosen criticality benchmarks, with the findings being thoroughly examined
Controlling the Deformation of the Antagonistic Shape Memory Alloy System by LSTM Deep Learning
No full textInternational audienceThe antagonistic system of two shape memory alloy wires is a great inspiration for the robotics field where it is applied as a linear actuator due to its shape memory effect. However, its control is still a challenge due to its hysteresis behavior. For that reason, a new controller is proposed in this paper for the displacement of the system’s effector. It is based on a Long Short-Term Memory neural network model. The aim is achieved by combining temperature-deformation data from an analytical model with voltage-temperature-deformation data from real experiments. Hence, these datasets are studied to overcome the nonlinearity obstacle of this system in order to be able to integrate it into robotic applications
Efficiency of aerosol surface concentration measurement by fluorimetry
No full textInternational audienceIn aerosol science, many experiments use fluoresceinebecause it can be detected at low concentrations (Stoberand Flachsbart, 1973). It is then used as a tracer in liquiddroplets or as solid particles, and it can easily berecovered from locations where it is deposited,especially where the access to the collected mass is noteasy. Different protocols can be developed to collect andmeasure fluorescent aerosol. The objective of this studyis to evaluate the so-called effective extraction rate fromdifferent substrates such as filters, galvanised steel,silicon wafer, wipes, stainless steel tube, connectingtubes, etc., and to compare it with other techniques
Application of Machine Learning to MICADO Passive and Active Neutron Measurement System for the Characterization of Radioactive Waste Drums
No full textInternational audienceA passive and active neutron measurement system 1 has been developed within the Measurement and Instrumentation 2 for Cleaning and Decommissioning Operation (MICADO) H2020 3 project to estimate the nuclear material mass inside legacy waste 4 drums of low and intermediate radioactivity levels. Monte-Carlo 5 simulations were performed to design a transportable neutron 6 system allowing both passive neutron coincidence counting and 7 active interrogation with the differential die-away technique 8 (DDT). However, the calibration coefficients (CCs) representing 9 the signal of interest (due to nuclear material) in these two 10 measurement modes may vary by a large amount depending on 11 the properties of the matrix of the nuclear waste drum. Therefore, 12 this article investigates matrix effects based on 104 Monte-13 Carlo calculations with different waste drums, based on Taguchi 14 experimental design with a range of densities, material com-15 positions, filling levels, and nuclear material masses. A matrix 16 correction method is studied using machine learning algorithms. 17 The matrix effect on the neutron signal is deduced from the signal 18 of internal neutron monitors located inside the measurement 19 cavity and from a transmission measurement with an AmBe 20 neutron source. Those quantities can be assessed experimentally 21 and are used as explanatory variables for the definition of a 22 predictive model of the simulated CC, either in passive or in 23 active mode. A multilinear regression model of the CC based on 24 ordinary least square (OLS) is built and compared to the random 25 forest (RF) machine-learning algorithm and to the multilayer 26 perceptron (MLP) artificial neural network. In passive neutron 27 coincidence counting, the residual error of the regression is lower 28 for the MLP and RF than for OLS. The agreement between the 29 predicted CCs of four mockup drums used as test is better than 30 17% and 3%, respectively, with the MLP and RF methods, while 31 three predictions are out of the 95% confidence level range with 32 OLS. In active neutron interrogation, similar conclusions are 33 drawn. The prediction of the CC for the four mockup drums is better than 12%, 35%, and 72% for the respective MLP, RF, and OLS methods. In conclusion, the MLP and RF regression model demonstrates more accurate results of the quantities of interest than the traditional OLS method. The future steps will focus on matrix heterogeneities, experimental validation, improving our models and testing new regression approaches