Institute for Radiation Protection and Nuclear Safety (IRSN)
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Modeling Two-Phase Flow with Hysteresis: Comparative Study of Hysteresis Models and Application
No full textInternational audienceDrainage (drying) and imbibition (wetting) cycles are expected in many applications involving subsurface flows, such as underground CO2 storage, hydrocarbon extraction and production, and deep geological disposal of radioactive waste (particularly in the potential production of hydrogen due to corrosion and radiolysis). In the presence of imbibition/drainage cycles, the two-phase constitutive relations between water saturation, capillary pressure and relative permeability to liquid and gas, cannot be represented by simple one-to-one functions: they depend on the history of wetting/drying processes. Recent numerical and experimental studies highlight the importance of hysteresis and its effect on two-phase flows in porous media. In this study, an extensive critical review of conceptual hysteretic models is first presented. The performance of these models is evaluated and tested from a theoretical point of view based on their assumptions, and by confronting them with measured data for various porous materials extracted from the literature (cement, sands, Bentonite MX80). The advantages and disadvantages of the different hysteretic constitutive models are discussed. Finally, we implement the five hysteresis models in the iTOUGH2 code, and we develop a numerical simulation of a two-phase flow experiment with immiscible Modeling two-phase flow with hysteresis fluids at the laboratory scale (meters), in order to compare the flow results obtained with or without hysteresis, and also, with or without capillary entrapment. The results highlight the need to take into account hysteresis in the modeling of multiphase porous media flows, especially when they are subjected to drying-wetting cycles. It is suggested that the model of Beriozkin and Mualem 2018 should be preferred both from a theoretical standpoint and for its computational advantages. Highlights • Quantitative assessment of several significant and representative conceptual models for hysteretic two-phase flow in porous media. • Identification of best hysteresis model in terms of physical parametrization, accuracy, and ease of implementation. • Gas entrapment in hysteresis models is found to be essential for accurate simulations of gas-liquid flow in porous media
Comprehensive framework for overcoming scientific challenges related to assessing radioactive ultra-fine (nano/micro) particles transfer at the atmosphere-leaf interface
No full textInternational audienceFood products are prone into contamination after a nuclear emission of radionuclides. While the mechanisms of emission and deposition of ultrafine radioactive particles are well documented, the transfer of these species from the atmosphere into plants is poorly assessed. This is evident in the lack of quantification of particles distributed within plants, especially regarding particles physical-chemical criteria to plant of different properties. Such knowledge gaps raise the concern about the representativeness of risk assessment tools designed for the transfer evaluation of ionic/soluble species to be qualified for simulating insoluble species exposure and proposes a possible underestimation. This highlights the possible need for special particle codes development to be implemented in models for future emissions. In addition, the later tools utilize transfer factors aggregating relevant sub-processes, suggesting another weak point in their overall reliability. As researchers specialized in the nuclear safety and protection, we intend in this perspective, to develop a compressive analysis of the interaction of ultrafine particles with plants of different specificities at different level processes starting from particles retention and gradual translocation to sink organs. This analysis is leveraged in providing insights for possible improvements in the current modeling tools for better real-life scenarios representation
Near-field (R<200m) atmospheric dispersion simulation and sensitivity analysis following a full scale atmospheric tracer experiment: Projet DIFLU : DIspersion du FLuor 18 en milieu Urbain
No full textInternational audienceEvaluating the risks associated with chronic or accidental industrial releases requires precise simulation and analysis of near-field atmospheric dispersion and associated uncertainties. The aim of this study was, firstly, to assess the effectiveness of an atmospheric simulation tool, SLAM (Safety Lagrangian Atmospheric Model), through comparison with a comprehensive full-scale atmospheric tracer experiment conducted in the near field, then to characterize the sensitive parameters affecting the near-field simulations. SLAM is a Lagrangian stochastic particles dispersion model, coupled with a wind and turbulence field database computed from the CFD code, ANSYS Fluent. This case study includes 19 trials involving various meteorological conditions. We used both statistical and graphical indicators to perform the model-to-data comparison. Results indicate that SLAM performs better under neutral or slightly unstable meteorological conditions. SLAM demonstrated a better accuracy in simulating the near-field dispersion (within 100 m) compared to Gaussian models. A global Sobol sensitivity analysis was also performed for a challenging low wind speed case under unstable atmospheric conditions. This sensitivity analysis focused on analysing how the meteorological parameters affect the output variance, represented by the statistical score FAC2. The results showed that the wind speed and wind direction are the first two primary factors impacting the near-field atmospheric dispersion. SLAM exceeded the acceptance threshold (FAC2≥0.5) in all trials by slightly adjusting these sensitive input parameters. This study confirms SLAM's effectiveness in accurately predicting near-field atmospheric dispersion and its potential for improving safety assessments in industrial contexts. It highlights the primary importance of meteorological inputs in atmospheric simulations, especially in the very near-field area, and some limits of the models in the immediate vicinity of the buildings
Le modèle murin inductible KPC:APC pour l'étude de la carcinogenèse du côlon in vivo et ex vivo
No full textInternational audienceIntroductionThe B6.Cg-Krastm4Tyj Apctm1Tno Tg(CDX2-cre/ERT2)752Erf/MaraJ mouse model (referred to as KPC:APC) recapitulates colon carcinogenesis through the chromosomal instability pathway via inducible Apc and Kras mutations in Cdx2-expressing intestinal cells (Maitra et al., 2019). Following induction with tamoxifen, KPC:APC mice develop tumors resembling human colon cancer. However, further investigations are needed to better characterize the time course and characteristics of tumor development. Furthermore, we developed an ex vivo inducible colorectal cancer model derived from the KPC:APC mouse to study cellular and molecular pathways involved in Apc-Kras-driven colon carcinogenesis.Material and MethodsApc and/or Kras mutations were induced in adult KPC:APC mice via single or repeated 10 to 20 mg/kg intraperitoneal tamoxifen administration. Tumor development was histologically assessed between 4 and 12 weeks post induction. Using intestinal crypts extracted from KPC:APC mice, we developed 3D organoids to perform cellular and molecular characterizations.Results and DiscussionsTumor development was highly dependent on tamoxifen administration regimen and mouse genotype (mutations in Kras and/or Apc genes). Apc mutation induction alone resulted in hyperplasia and dysplastic lesions, while the co-induction of Apc and Kras mutations accelerated adenoma development. Regardless of the genotype, lesions remained primarily restricted to the colon.KPC:APC mouse organoids were treated with tamoxifen to induce tumorigenesis.ConclusionHere we show that the KPC:APC mouse model is a relevant model for colon cancer research with its inducibility allowing for the coexistence of Apc and Kras mutation and its lesions mainly contained to the colon. Enhanced knowledge on tumor development will allow investigations on the effects of stressors (such as medical diagnostic exposures to low dose radiation) on colon carcinogenesis. The establishment of an ex vivo model combined with the fully characterized in vivo model provides the opportunity to conduct parallel histopathologic and mechanistic studies to advance colon cancer research
Du prélèvement à la mesure des iodes, une métrologie à géométrie variable
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Gas-entry pressure impact on the evaluation of hydrogen migration at different scales of a deep geological disposal of radioactive waste
No full textInternational audienceAlthough the importance of gas-entry pressure in simulating two-phase liquid–gas flow in porous media has been studied at the column and borehole scales, its impact on the simulation of transient hydraulic-gas at different scales of a deep geological repository of radioactive waste (DGR) in low permeability clay rock during the post-closure phase has not yet been studied. The purpose of this work is to show that neglecting this phenomenon can lead to underestimation of the maximum gas pressure and water–gas fluxes simulated within the host rock and backfilled drift network. This could impact the performance of the engineered barrier system of a DGR. Simulations performed for a high-level waste disposal cell and for a simplified repository composed of hundreds of disposal cells situated in a clay host rock, show that gas preferentially migrates through the DGR components with low capillary entry pressures, such as the excavation damaged zone (Refers to the zone where fractures develop due to failure of the rock mass around galleries after tunneling) (EDZ), the engineered barriers materials (backfill, bentonite-plug…) and interfaces between the EDZ and these materials. Such a result could have significant consequences on the performance of a repository, due to the accumulation of gas in the drift network and high increase of gas pressure, which could lead to the host rock hydraulic fracturing
En quête d’archives : Intervenir à toute vitesse en cas d’accident nucléaire. Une histoire de la voiture rail du SCPRI
No full textCrée en 1956, le Service central de protection contre les rayonnements ionisants (SCPRI) dispose dès sa création de moyens mobiles d’intervention en cas d’accident nucléaire. Au début des années 1980, le SCPRI commande une voiture rail à la SCNF dans l’optique de réaliser des mesures spectrométriques à très grande échelle et avec une cadence de contrôle de 5000 personnes par jour. Inaugurée après l’accident nucléaire de Tchernobyl, dont les suites ont fortement impacté l’image du SCPRI, la voiture rail devient un enjeu de communication, symbole des moyens importants mis en oeuvre pour intervenir en cas d’accident et ainsi rassurer les populations.Accompagné de l’archiviste Camille Bouchain, Michaël Mangeon s’est plongé dans les archives de l’IRSN pour en savoir plus sur l’histoire de cette voiture rail. Raphaël Bô, du Laboratoire d'évaluation de la dose interne (LEDI) de l’IRSN, a permis de retrouver de nombreux documents et photos et a fourni une aide précieuse pour appréhender techniquement ce sujet.Pour analyser ces documents d’archive, nous réaliserons dans un premier temps un récit de la genèse de cette voiture rail, en mobilisant le contexte et les enjeux liés aux moyens mobiles d’intervention du SCPRI. Dans un second temps, nous mettrons en lumière la communication autour d’elle dans le contexte de l’après Tchernobyl. Enfin, nous proposerons une description de la vie de cette voiture rail, de son exploitation jusqu’à sa réforme en 2017, avant de conclure sur les héritages de cette histoire et les moyens mobiles actuels de l’IRSN
Noisy radioactivity data analysis using parametric Poisson models
No full textInternational audienceIn metrology, the use of decision threshold and detection limit concepts often creates manyproblems for metrologists in radioactivity analysis laboratories. It is usual to censor data whenit becomes difficult to discern the presence or absence of the activity, due to noise in the measurement data. This implies that if the measurement results are non significant which are belowcritical value of the test statistic which is called the decision threshold (DT) in metrology. Theanalysis simply states that the true value (signal) of the radioactivity is below a certain limitcalled the detection limit (DL). These problems are frequently related to the incorrect understanding of the DT formulas or the wrong choice between several formulas whose numericalresults are significantly different. Moreover, it is often unclear how to generate an appropriate and justified DT. In the current research paper, we elaborate a statistical method of DTdetermination, capable of providing DT with a high statistical power, using a smaller numberof repeated measurements. The method is then applied to a real test case. Next, statisticalapproaches methods are adopted to estimate the density, the expectation and the variance ofthe radioactivity. Some of its asymptotic properties are also discussed. Efficiency and feasibilityof these approaches are corroborated through applications on simulated real data sets
Consideration of hereditary effects in the radiological protection system: evolution and current status
No full textInternational audiencePurpose: The purpose of this paper is to provide an overview of the methodology used to estimate radiation genetic risks and quantify the risk of hereditary effects as outlined in the ICRP Publication 103. It aims to highlight the historical background and development of the doubling dose method for estimating radiation-related genetic risks and its continued use in radiological protection frameworks.Results: This article emphasizes the complexity associated with quantifying the risk of hereditary effects caused by radiation exposure and highlights the need for further clarification and explanation of the calculation method. As scientific knowledge in radiation sciences and human genetics continues to advance in relation to a number of factors including stability of disease frequency, selection pressures, and epigenetic changes, the characterization and quantification of genetic effects still remains a major issue for the radiological protection system of the International Commission on Radiological Protection.Conclusion: Further research and advancements in this field are crucial for enhancing our understanding and addressing the complexities involved in assessing and managing the risks associated with hereditary effects of radiation
Liposomal formulations of bisphosphonate molecules for the treatment of internal strontium/cobalt contamination
No full textInternational audienceIn the event of nuclear/radiological incidents or accidents involving internal contaminations with radioactive cobalt or strontium compounds, the current recommended therapeutic options (calcium salts of DTPA and calcium gluconate respectively) have shown low specificity and efficacy. The main health risk resulting from internal contamination is irradiation of the organs accumulating the radionuclides considered (skeleton, liver, kidney), which can cause long-term deleterious effects that can lead to the development of malignant diseases. There is therefore a crucial need to develop new decorporation agents to improve the medical care of patients exposed to such events. To address this question, the experimental strategy adopted was to use a class of pharmaceutical molecules (Biphosphonates or BPs) that already have regulatory approval and whose complexation properties towards divalent cations have been already shown. The first step of this work consisted of assessing the affinity of BP molecules with the cations of interest (cobalt and strontium). To this end, we set up an analytical method based on capillary electrophoresis. Several charged metal-ligand complexes were identified between cobalt and EHBP. We then developed new liposomal formulations to target these potential chelating molecules to the main radionuclide retention organs (bone, liver, and kidneys). In vivo evaluation of the decorporation efficiencies of both free and liposome-encapsulated molecules were performed in a rodent model. The results showed a clear interaction between the radionuclides and the ligand and unexpected data concerning reference treatments. For now, BP-based treatments do not fulfil all the necessary conditions to constitute a decorporating agent. Thus, our results highlight the need to continue efforts to find an efficient chelating treatment and the importance of starting the treatment as soon as possible after exposure