Institute for Radiation Protection and Nuclear Safety (IRSN)
Not a member yet
7928 research outputs found
Sort by
Analysis of Embedded Numerical Programs in the Presence of Numerical Filters
No full textInternational audienceThis chapter presents how Frama-C verifies some complex loop invariant for numerical embedded code and how to produce such invariants. Numerical embedded code usually defines an endless loop that takes inputs from sensors and that emits outputs for actuators. Moreover, such a code commonly uses some floating-point global memories to keep track of the input or output values from the previous loop cycles. These memories store a summary of previous values to filter the input or the output over time. Hence, recursive linear or Infinite Impulse Response (IIR) filters are very common in such code. Among such filters, low-pass filters are challenging for Frama-C since finding a loop invariant with complex relationships between the variables is never an evident task for the engineer. Hence, this chapter presents different approaches to find and organize inductive invariants for such numerical reactive systems and shows how Frama-C can prove them with its Eva and Wp plug-ins. It also exposes optimal theoretical results for first-order and higher-order filters to compare the quality of results of the different solutions. Several examples and several concrete solutions illustrate the generation/writing of such inductive invariants and their formal verification
Role of fluids in the triggering of swarms and mainshock–aftershocks sequences: example from complex earthquake crisis in the Ubaye Region (Western Alps)
No full textInternational audienc
Electromagnetical and ultrasonic characterizations of concretes subjected to internal swelling reactions
No full textInternational audienceAmong pathologies of reinforced concrete structures, internal swelling reactions (ISR), including alkali-aggregate reaction and delayed ettringite formation, are at the origin of cracks and major disorders due to rebar corrosion. Visual evaluation of crack density combined to non-destructive testing techniques can be used to characterize the global swelling and then give some structural diagnosis. For the last ones, an intermediate step (assimilated to a calibration step) can be performed at laboratory to evaluate the sensitivity of electromagnetic, electrical and ultrasonic properties of concretes subject to ISR.This present study focuses on such characterizations of concrete samples presenting different levels of ISR and for several water content. Numerous samples have been extracted from mock-ups representative of two massive concrete structures, affected one by alkali-aggregate reaction and the other by delayed ettringite formation, and conditioned in homogeneous and controlled conditions. After describing the experimental campaign, results are shown and commented
Heterogeneity of absorbed dose distribution in kidney tissues and dose–response modelling of nephrotoxicity in radiopharmaceutical therapy with beta-particle emitters: A review
No full textInternational audienceAbsorbed dose heterogeneity in kidney tissues is an important issue in radiopharmaceutical therapy. The effect of absorbed dose heterogeneity in nephrotoxicity is, however, not fully understood yet, which hampers the implementation of treatment optimization by obscuring the interpretation of clinical response data and the selection of optimal treatment options. Although some dosimetry methods have been developed for kidney dosimetry to the level of microscopic renal substructures, the clinical assessment of the microscopic distribution of radiopharmaceuticals in kidney tissues currently remains a challenge. This restricts the anatomical resolution of clinical dosimetry, which hinders a thorough clinical investigation of the impact of absorbed dose heterogeneity. The potential of absorbed dose–response modelling to support individual treatment optimization in radiopharmaceutical therapy is recognized and gaining attraction. However, biophysical modelling is currently underexplored for the kidney, where particular modelling challenges arise from the convolution of a complex functional organization of renal tissues with the function-mediated dose distribution of radiopharmaceuticals. This article reviews and discusses the heterogeneity of absorbed dose distribution in kidney tissues and the absorbed dose–response modelling of nephrotoxicity in radiopharmaceutical therapy. The review focuses mainly on the peptide receptor radionuclide therapy with beta-particle emitting somatostatin analogues, for which the scientific literature reflects over two decades of clinical experience. Additionally, detailed research perspectives are proposed to address various identified challenges to progress in this field
Variability Due to Nuclear Data Applied to the Watts Bar Unit 1 Benchmark with CASMO5/SIMULATE5 Code Sequence
No full textInternational audienceThe variability of nuclear data is of main interest for the Verification, Validation and Uncertainty Quantification (VVUQ) of reactor physics computational tools, as these data can be a major source of uncertainty. Based on the Watts Bar Unit 1 benchmark, this paper focuses on the impact of nuclear data on neutronic core behavior for the first reactor operating cycle. The CASMO5/SIMULATE5 code sequence is used to evaluate neutron parameters such as critical eigenvalues, rod worths, isothermal temperature coefficients, critical boron concentration, radial power distributions and peak powers. The results obtained using different nuclear data libraries (JEF-2.2, JEFF-3.1.1, JEFF-3.2, ENDF/B-VII.1 and ENDF/B-VIII.0) show good agreement with available measurements. The calculation biases on the main neutron parameters are lower than the criteria from the General Operating Rules usually used on French PWR reactors during start-up tests and over the operating cycle. However, differences between nuclear data libraries show that nuclear data may account for a significant part of the errors made on safety-relevant neutron parameters such as peak pin power (FQ) and critical boron concentration. Obviously, these conclusions cannot be generalized at this stage, given the limited number of studied configurations. Thus, in a VVUQ context, a more robust approach based on a rigorous uncertainty propagation would be the most accurate way to assess the effect of nuclear data on core neutronic parameters. Nevertheless, this approach is technically challenging and time consuming, which implies that it should be limited to the cases with the most significant safety implications
Systematic review of statistical methods for the identification of buildings and areas with high radon levels
No full textInternational audienceRadon is a natural and radioactive noble gas, which may accumulate indoors and cause lung cancers after long term-exposure. Being a decay product of Uranium 238, it originates from the ground and is spatially variable. Many environmental (i.e., geology, tectonic, soils) and architectural factors (i.e., building age, floor) influence its presence indoors, which make it difficult to predict. However, different methods have been developed and applied to identify radon prone areas and buildings. This paper presents the results of a systematic literature review of suitable statistical methods willing to identify buildings and areas where high indoor radon concentrations might be found. The application of these methods is particularly useful to improve the knowledge of the factors most likely to be connected to high radon concentrations. These types of methods are not so commonly used, since generally statistical methods that study factors predictive of radon concentration are focused on the average concentration and aim to identify factors that influence the average radon level. In this paper, an attempt has been made to classify the methods found, to make their description clearer. Four main classes of methods have been identified: descriptive methods, regression methods, geostatistical methods, and machine learning methods. For each presented method, advantages and disadvantages are presented while some applications examples are given. The ultimate purpose of this overview is to provide researchers with a synthesis paper to optimize the selection of the method to identify radon prone areas and buildings
Aerosol deposition in bends: sensitivity studies of various parameters in a lagrangian stochastic model
No full textInternational audienceIndoor air is a topic of interest for the safety and health of industrial workers as well as more recently for the population, enhanced by pollution concerns and the Covid pandemy. Many applied studies have investigated the risk assessment of aerosol dispersion and its consequences on air quality using CFD commercial codes, which are easy to handle and produce fast results in complex geometries (ventilated rooms, buildings, schools, hospitals, ...) For the particle phase, the easiest and fastest way to implement a two-phase flow in such codes is to use the one-way coupling lagrangian approach. As a result, many applied papers have been written on aerosol dispersion. In the dispersion of aerosol, wall deposition is one important component and over the past 20 years, many studies ([1.], [3.], [4.], [6.], [7.], [9.]) have been performed with different versions of commercial codes to investigate this phenomenon, on the basis of test-cases. For aerosol deposition studies, the Pui’s experiments on deposition in bends have been widely used. The Piu correlation has been revisited recently [8.] leading to a new correlation obtained over a wider range of parameters. The objective of this work is to simulate this test case with the Fluent code and compare it with the original and the newest correlation, including a sensitivity study on several parameters, including the so-called Cl stochastic constant, that has, to our knowledge, never been explicitly mentioned in previous studies. The Pui case [5.] concerns the deposition of 900 kg/m3 aerosol in a bend for two duct radii, two curvature ratios and two Reynolds numbers. The method used is a fluorescence method where particles collected on the walls are washed to determine the deposited amount. Results are given in terms of deposited fractions and Stokes numbers. We will consider here 10% uncertainty on the Stokes number and the deposition efficiency, i.e. much higher than the announced 3% uncertainty of the original paper, a realistic assumption considering our experience on fluorescent aerosols. All calculations are performed up to y+=1 at walls, with 10 to 20 cells in the refinement zone and double precision. The sensitivity study concerns the bulk mesh density (M1, M2, M3), the type of mesh (tetra/hexa), the turbulence model (RSM-based on epsilon, SST-k- without Matida [2.]’s correction of the kinetic energy near the wall), the drag coefficient and the Cl constant of the lagrangian stochastic model. Example of results are presented in Figure 1. None of the studied parameters recover the new Wang correlation [8.]. The type of mesh, hexa or tetra has no influence when a refined mesh is used. The turbulence model has an influence over all the size range. The mesh density and the Cl parameter have mainly an influence on the smallest particles (1 to 3 µm). There is a need of discussions on the modelling choices of Cl in commercial codes especially since the 1-3 µm particles are the ones considered in a lot of aerosol dispersion studies linked to COVID applications. One step before is also to verify if flows in bends, especially the secondary flows and the recirculation zone, are well recovered with the choices performed. Detailed best-practice guidelines including flow and particle validations steps and sensitivity studies for the use of aerosol stochastic modelling for dispersion studies need to be enhanced
Host defense alteration in Caenorhabditis elegans after evolution under ionizing radiation
No full textInternational audienceAbstract Background Adaptation to a stressor can lead to costs on other traits. These costs play an unavoidable role on fitness and influence the evolutionary trajectory of a population. Host defense seems highly subject to these costs, possibly because its maintenance is energetically costly but essential to the survival. When assessing the ecological risk related to pollution, it is therefore relevant to consider these costs to evaluate the evolutionary consequences of stressors on populations. However, to the best of our knowledge, the effects of evolution in irradiate environment on host defense have never been studied. Using an experimental evolution approach, we analyzed fitness across 20 transfers (about 20 generations) in Caenorhabditis elegans populations exposed to 0, 1.4, and 50.0 mGy.h − 1 of 137 Cs gamma radiation. Then, populations from transfer 17 were placed in the same environmental conditions without irradiation (i.e., common garden) for about 10 generations before being exposed to the bacterial parasite Serratia marcescens and their survival was estimated to study host defense. Finally, we studied the presence of an evolutionary trade-off between fitness of irradiated populations and host defense. Results We found a lower fitness in both irradiated treatments compared to the control ones, but fitness increased over time in the 50.0 mGy.h − 1 , suggesting a local adaptation of the populations. Then, the survival rate of C. elegans to S. marcescens was lower for common garden populations that had previously evolved under both irradiation treatments, indicating that evolution in gamma-irradiated environment had a cost on host defense of C. elegans . Furthermore, we showed a trade-off between standardized fitness at the end of the multigenerational experiment and survival of C. elegans to S. marcescens in the control treatment, but a positive correlation between the two traits for the two irradiated treatments. These results indicate that among irradiated populations, those most sensitive to ionizing radiation are also the most susceptible to the pathogen. On the other hand, other irradiated populations appear to have evolved cross-resistance to both stress factors. Conclusions Our study shows that adaptation to an environmental stressor can be associated with an evolutionary cost when a new stressor appears, even several generations after the end of the first stressor. Among irradiated populations, we observed an evolution of resistance to ionizing radiation, which also appeared to provide an advantage against the pathogen. On the other hand, some of the irradiated populations seemed to accumulate sensitivities to stressors. This work provides a new argument to show the importance of considering evolutionary changes in ecotoxicology and for ecological risk assessment
Ensembling Unets for rare chromosal aberration detection in metaphase images, uncertainty quantification, and ionizing radiation dose estimation
No full textIn biological dosimetry a radiation dose is estimated using the average number of chromosomal aberrations per peripheral blood lymphocytes. This analysis is still manually performed on 2D metaphase images depicting the 23 pairs of chromosomes because the false discovery rate of current automated detection systems is too high and variable because of sensitivity to small variations in image quality (chromosome spread, illumination variations ...). Therefore, the current systems are only used to assist human experts. Designing more performant automatic and reliable chromosomal aberration detection systems has become of paramount importance to improve diagnosis speed and reduce human expertise time. Here, we propose a novel deep-learning method for automatic rare chromosomal aberration detection and uncertainty quantification. We formulate the problem as a unique regression problem requiring the minimization of a sparsity-promoting loss to reduce the false alarm rate. Furthermore, we select checkpoints at the end of each epoch during training to form a model ensemble. The resulting artificial experts are further analyzed to derive a consensus voting, similar to an agreement of human annotator rating, to provide trustworthy aberration detections and confidence intervals. A radiation dose curve is finally derived from deep learning-assisted counting of dicentrics and fragments in metaphase images, in high agreement with the reference hand-crafted curve in biological dosimetry
Ionizing radiation of Gammarus fossarum affect their reproduction but not their food consumption
No full textInternational audienceIn the environment, wildlife is chronically exposed to various sources and levels of ionizing radiation. For an ecological risk assessment issue, a thorough knowledge of the chronic effects of radioactive contamination on the ecosystems is crucial to define relevant reference levels of protection and then minimise impacts. To date, several reference levels have been proposed for different ecosystems, i.e. generic , terrestrial-, aquatic- one, ranging from 10 μGy.h-1(Garnier-Laplace et al., 2010) to 400 μGy.h-1 (UNSCEAR 2008). In addition, ‘Derived Consideration Reference Levels’ (DCRLs) have been defined by International Commission of Radiological Protection (ICRP) for ‘reference animals and plants’ (RAPs) (ICRP 2008). However, the available RAPs do not represent consistently the diversity of the species in the ecosystems (Spurgeon, Lahive et al. 2020). In particular, the crustacean radio-sensitivity is currently considered as insufficiently described and characterized, particularly for the ones which reproductive strategy differs from parthenogenesis. Gammarids (Gammarus sp.) are amphipod crustaceans, often abundant in the aquatic ecosystems (Europe: G. fossarum and G. pulex, Asia: G. nipponensis...), with sexual reproduction. They have an important ecological role as detritivores, significantly contributing to the degradation of leaf litter in watercourses and therefore to the nutrient cycle. They are used as sentinel organisms in ecotoxicology, recognised for their sensitivity to the quality of the environment and characterised in their biological response to numerous chemical compounds (metallic and organic traces) (Chaumot, Geffard et al. 2015). Thus, they could constitute a relevant model to increase the knowledge for radiological protection and to complete data on a freshwater crustacean with a sexual reproductive strategy.A dose-response study in controlled laboratory conditions was performed with five irradiation levels (0.005, 0.054, 0.57, 5.01, 51mGy.h-1) and a control condition. The dose rates ranged from low levels framing the threshold value of 10 µGy.h-1 to 51 mGy.h-1, close to those found in post-accidental situations (e.g. immediately after the Chernobyl nuclear accident. This study aims at assessing phenotypical responses after continuous γ irradiation of either males or females Gammarus fossarum. In particular life history traits, such as survival, feeding behaviour, molt and reproductive ability, were assessed after exposure during a reproductive cycle (14 days).We found that ionizing radiation of Gammarus fossarum affect their reproduction, critical for population dynamic, but not their food consumption, linked to general health status of gammarids.In addition, radio-induced reprotoxicity is more severe for male gammarids than for female after chronic exposure and is significant from 5 mGy.h-1, that is much lower than for other crustaceans such as Daphnia magna (35 mGy.h-1). Per se, these radio-induced phenotypical effects observed for parental generation exposed 14d don’t question the ICRP DCRLs for crustaceans defined as between 0.4 and 4 mGy.h 1, but with our experimental design the threshold dose rate of reprotoxicity significancy belongs to the range [0,5 - 5 mGy.h-1], so likely to be lower than 4 mGy.h 1. In addition, these results let suppose higher effects at much lower dose rates if irradiation occurs over several generations (Parisot, Bourdineaud et al. 2015) like in situ. To go further, sub-individual endpoints will be analyzed to decipher mechanisms relative to the observed effects and fuel database such as adverse outcome pathway framework that constitutes ERA interesting perspectives