Institute for Radiation Protection and Nuclear Safety (IRSN)
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Natural convection through and over a heating porous medium: Towards high fidelity simulations of nuclear spent fuel pools
No full textInternational audienceThis paper presents a numerical investigation involving Direct Numerical Simulations (DNS) of natural convection occurring within mixed domains of porous and pure fluids, featuring an internally heated solid matrix. Our study does not aim to replicate 1:1 scale of Spent Fuel Pool (SFP) scenarios during Loss of Cooling Accidents (LOCA), but rather focuses on a reduced scale mock-up of such pool while keeping essential phenomena. By doing such, this study does provide valuable insights into the intricate dynamics of fluid flow and heat transfer in such prototypical configuration. We conduct a sensitivity analysis on the parameters driving the physical modeling of the porous medium, revealing the substantial influence of the drag on key features of the heat and mass transfers such as the Large-Scale Circulation (LSC), mass flow rates, temperatures within the porous medium, and overall heat transfer process. In a domain scaled to represent a reduced-scale SFP (1:200), we explore the effects of varying rack heights relative to the bottom wall. This variation significantly affects temperature distribution within both the bottom layer and the porous medium. Notably, when the racks make contact with the bottom wall, a dual-roll LSC pattern emerges. Additionally, we examine the consequences of non-uniform heat load distribution within the racks. This distribution leads to larger maximum temperatures within the most heated region of the porous medium. However, it also results in lower area-averaged temperatures due to increased horizontal diffusion and Postprint submitted to International Journal of Heat and Mass Transfer Nov. 2024 mixing. Consequently, the Nusselt number within the pure-fluid region is reduced compared to a scenario with uniform heat load distribution
Joint Clustering With Alignment for Temporal Data in a One-Point-per-Experiment Setting
No full textInternational audienceTemporal data, obtained in the setting where it is only possible to observe one time point per experiment, is widely used in different research fields, yet remains insufficiently addressed from the statistical point of view. Such data often contain observations of a large number of entities, in which case it is of interest to identify a small number of representative behavior types. In this paper, we propose a new method that simultaneously performs clustering and alignment of temporal objects inferred from these data, providing insight into the relationships between entities. Simulations confirm the ability of the proposed approach to leverage multiple properties of the complex data we target such as accessible uncertainties, correlations and a small number of time points. We illustrate it on real data encoding cellular response to a radiation treatment with high energy, supported with the results of an enrichment analysis. Supplementary materials for this article are available online
Updated Results of the Nuclear Accident Dosimetry Intercomparison at the Armed Forces Radiobiology Research Institute's TRIGA Reactor
No full textUranium et cancer du rein : étude de la tumorigénèse et de l’angiogenèse chez des souris génétiquement modifiées
No full textLe supplément de résumés est publié sous le titre The Toxicologist, « Supplement to Toxicological Sciences »International audienceExposure to uranium compounds is prevalent in various situations such as nuclear fuel processing, military activities, and environmental context. Uranium has a propensity to accumulate in the kidneys, yet its potential carcinogenic effect remains controversial. The UKCAN project (Uranium Kidney CANcerous effects in rodents) is dedicated to investigating the potential carcinogenic effects of low-dose uranium on the kidneys.Our study has the following objectives: -Evaluate the development of benign and malignant renal tumor lesions over time and dose following uranium repeated exposure -Elucidate the underlying biological mechanisms in renal oncogenesis and carcinogenesis associated with human exposureTo simulate the development of kidney cancer, we employ two genetically engineered mouse (GEMs) models with mutation in key kidney cancer predisposition genes (Vhl and Pbrm1, or Tsc2). The Pax8-cre, Vhlf/f, Pbrm1f/f model enables us to study more specifically the ccRCC form (clear cell Renal Cell Carcinoma, HIF pathway), and Tsc2+/- model enables to study the benign and malignant tumors development with a phenotype similar to pRCC (papillary Renal Cell Carcinoma, PI3K/Akt/mTOR pathway). In this experimental study, each of these two GEM models is exposed to repeated uranium intranasal instillation and monitored for 10 or 12 months. Three different doses- 0; 125 or 250 µg/kg/d (n=20/dose/genotype) are being tested.To evaluate the development of renal tumor lesions over time, ultrasonography is used throughout the animal’s lifespan. In a second stage, postmortem analyses using histological and immunohistological methods provide details characterization of tumor lesions. To study the biological mechanisms from kidney tissue, urine or plasma samples, we used protein array, RTqPCR and multiplex immuno-assay.Histological analyses performed are intended to assess tubular, glomerular and interstitial kidney injuries in a semi-quantitative approach, according to criteria defined by Frazier et al. 2012. The anatomopathological scoring of each of these criteria highlights the development of cysts, adenomas and carcinomas depending on the age and genotype of GEMs. In order to characterize more precisely the tumor subtype, immunostaining of 3 clinically relevant proteins (carbonic anhydrase 9, cytokeratin-7, vimentin) are performed on renal tissue sections. Thus, we differentiate ccRCC, pRCC and chRCC (the three most common Renal Cell Carcinoma in human) from oncocytomas (benign tumors): for example although they have a similar cellular phenotype, in humans ccRCC is CA-IX(+) VIM(+) while oncocytoma is CA-IX(-) VIM(-). pRCC is characterized by the presence of septa in the lesion’s lumen, but at more advances stages, tumor cells display polymorphism: it’s necessary to differentiate pRCC who is CK-7(+) VIM(+) from chRCC CK-7(+) VIM(-). Secondly, this approach facilitates the correlation of histological findings with ultrasound imaging data, enabling the tracking of endogenous renal tumors exceeding 200 µm, and characterizing their type, number, and volume. Analyses of Pax8-cre, Vhlf/f, Pbrm1f/f model show, as expected, a development over the time: tumoral incidence reach 50% after 10 months and 90% after 12 months. In addition, we observed a doubling of incidence of adenomas, and carcinomas only in mice exposed to uranium at 10 months. In Tsc2+/- GEM model, the tumor incidence reaches 85% at 12 months, and exposure to uranium does alter the number or type of lesions developed according to histological and immunohistological analyses.In a second step, hallmarks of kidney cancer were assessed through the screening of genes involved in renal carcinogenesis (initiation, promotion, and proliferation) and mechanisms of uranium toxicity (oxidative stress, DNA damages) by RTqPCR. Proteins levels were measured by protein-array (AKT pathway or cytokines) on a small number of animals (n=4/condition). For the Tsc2+/- model, the expression of this panel of markers were not significantly altered by uranium, either on gene expression or proteins of PI3K/Akt pathway. By contrast, the Pax8-cre, Vhlf/f, Pbrm1f/f GEM model highlighted an effect of uranium exposure on 14 of the 44 targets evaluated by RTqPCR. For example, Lcn2, Nqo1 or Cdkn1a have a 3 to 4-fold increase expression compared to unexposed animals at 10 months of age (p<0.05). On the full cohort of animals, targets such as osteopontin (Spp1) or PAI-1 (Serpine1) implicated in inflammation and angiogenic mechanisms, are 2-fold overexpressed (p<0.05) in kidney tissue after uranium exposure. One of the main prospects is then to focus on these tumorigeneses’ mechanisms. Vascular system could be characterized by immunohistochemistry (CD31, αSMA, VE-cadherin, Coll-IV), and molecular makers such as VegfA, Angpt2 might be quantified in plasma and tissue.Thanks to the use of GEM models of different types of renal cancer, the results obtained suggest that uranium influences the development of ccRCC tumors (the most common subtype in humans) through modifications of mechanisms of angiogenesis or inflammation but the development of benign or pRCC lesions were not altered by this uranium exposure.These findings will contribute to identifying the most relevant parameters for the experimental evaluation of the potential link between uranium exposure and the development of kidney cancer in our GEM models
Dose Heterogeneity Reduces Radiation Oxygen Dependence in Both Tumor and Healthy Tissues: The Case of Proton Minibeam Radiation Therapy
No full textInternational audiencePurpose: Proton minibeam radiation therapy (pMBRT) is an innovative delivery technique characterized by spatially modulated radiation. It was shown to increase the therapeutic index in preclinical glioma models by reducing toxicities while maintaining or even increasing tumor control. Moreover, pMBRT leads to differential immunomodulatory effects. Both dosimetry and radiobiology diverge from classical concepts. We hypothesize that the distinct mechanisms and characteristics of pMBRT could reduce the oxygen dependence of radiation tissue response.Methods and Materials: To address this question, in this study, glioblastoma-bearing and naïve animals were irradiated with different oxygen supplementation concentrations with a single fraction of pMBRT or conventional proton therapy (CPT) at an average dose of 25 Gy. The differential effects of blood oxygenation were assessed by analyzing immune response, survival capability, and histopathological changes in brain and bone tissues. The tumor’s hypoxic nature was confirmed by hypoxia inducible factor-1α staining before irradiation.Results: Our results revealed no significant influence of oxygen supplementation on survival outcomes or immune infiltration after pMBRT. These findings contrast with CPT, where oxygen supplementation was detrimental to immune infiltration but improved survival probability. Also, no significant brain or bone tissue alterations have been observed after pMBRT, regardless of blood oxygenation levels during irradiation. These differences highlight the distinct radiobiological effects of pMBRT and its potential to bypass the classical oxygen dependency observed in CPT and conventional radiation therapy.Conclusions: The distinct radiobiological effects of pMBRT have the potential to bypass the classical oxygen dependency. Thus, pMBRT could be beneficial for the treatment of hypoxic tumors
Author Correction: Risk of hematological malignancies from CT radiation exposure in children, adolescents and young adults
No full textInternational audienceIn the version of the article initially published, Magda Bosch de Basea’s surname appeared incorrectly (as Bosch de Basea Gomez) and has now been amended in the HTML and PDF versions of the article
Quantification of particles generated by explosions in contact with concrete specimen
No full textInternational audienceQuantifying inhalable particles generated by explosions is a key factor in defining the target to be protected from such an event in the context of radioactive material. This study focuses on the particles generated by explosions in contact of concrete radioactive waste packages. The main objective is to quantify the mass of particles smaller than 10 µm in terms of aerodynamic diameter. For that purpose, we developed a protocol and measured a reasonable envelope of the mass of particles collected after concrete specimen explosions, at middle-scale
Analyzing structural changes induced by gas migration in heterogeneous pellet/powder bentonite mixtures through X-ray computed micro-tomography
No full textInternational audienceUnderstanding the mechanisms of gas transport and the resulting preferential pathways formation through bentonite-based barriers is essential for their performance evaluation. In this experimental study, gas migration within a heterogenous mixture of MX80 bentonite pellets and powder with a ratio of 80/20 in dry mass was investigated. A novel X-ray transparent constant volume cell has been developed to assess the effect of gas pressure, material heterogeneities, and water vapor gas saturation on breakthrough pressure and gas pathways. The new cell allows to perform high-resolution X-ray computed micro-tomography (X-ray μCT) scans to track microstructural changes during different phases of saturation and gas injection. Experimental results showed that the gas breakthrough occurred when the pressure was raised to 3 MPa. This is slightly higher than the expected swelling pressure (2.9 MPa) of the bentonite sample. Each gas injection was followed by a long resaturation phase restoring material homogeneity at μCT resolution scale (16 μm). However, the elapsed time needed for gas to breakthrough at 3 MPa diminished at each subsequent injection test. X-ray μCT results also revealed the opening of the specimen/cell wall interface during gas passage. This opening expanded as the injection pressure increased. The gas flow along the interface was associated with the development of dilatant pathways inside the sample, although they did not reach the outlet surface. It was observed that the water vapor gas saturation had no effect on the breakthrough pressure. These findings enhance the understanding of the complex mechanisms underlying microstructural evolution and gas pathway development within the highly heterogeneous mixture. The experimental outcomes highlight the effectiveness of X-ray μCT to improve quality protocols for engineering design and safety assessments of engineered barriers
Opinion of the French Agency for Food, Environmental and Occupational Health & Safety (ANSES) on the risks to human health associated with the proliferation of Ostreopsis spp. on the Basque coast
No full textN/AInternational audienceIn France, the presence of marine microalgae of the genus Ostreopsis has been identified repeatedly on the Mediterranean coast for several years, whereas on the French Basque coasts its presence is much more recent. In the summers of 2021 and 2022, major Ostreopsis flowering episodes were reported on the Basque coast, resulting in several hundred cases of intoxication among holidaymakers and residents. The main route of human exposure is inhalation of aerosols, although it is not yet known whether the agents responsible for poisoning are Ostreopsis cells, cell debris, known toxins produced by Ostreopsis, or other as yet unidentified compounds. Other routes of exposure (dermal contact, eye contact, ingestion of contaminated water or seafood) are also possible. Poisoning is manifested through various signs and symptoms, occurring within 48 hours of exposure (Neurosensory and neurological, respiratory, dermal and digestive). This document presents the opinion of the French Agency for Food, Environmental and Occupational Health & Safety (ANSES), established from the work of its WATER and ERCA Expert Committees. ANSES received a request from the Directorate General for Health (DGS) and the Directorate General for Food (DGAL) to update knowledge about Ostreopsis that had been reported in the Agency's opinions from 2007 and 2008 (ANSES, 2007 and 2008), and draw up specific recommendations for managing Ostreopsis proliferation on the Basque coast. The literature review conducted as part of this expert appraisal revealed that knowledge about the genus Ostreopsis (diversity, biology, ecology, toxins produced) is still too fragmentary to characterise the hazard and risk to human health. Nevertheless to help local authorities affected by Ostreopsis blooms, Agency proposes a surveillance and quality monitoring strategy based on collaboration between site managers and the regional health agencies (ARSs), applicable to sites currently subject to bathing water quality monitoring and water sports sites that meet the conditions below
Advanced Distributed Optical Fiber Strain Sensing for Monitoring Radioactive Waste Package Degradation
No full textInternational audienceThe safe and effective deep geological disposal of nuclear waste depends on advanced technologies to monitor the degradation of radioactive waste packages. However, long-term monitoring of such facilities presents significant challenges, including restricted access to waste packages and the need to minimize intrusive equipment such as sensors that must pass through protective containment barriers.This study explores the feasibility and benefits of using high spatial resolution Distributed Optical Fiber Strain Sensing (DOFSS) for the remote detection of package strain evolution and cracks detection, both key indicators of radioactive waste package degradation. DOFSS, widely used in civil engineering for structural health monitoring applications, has been adapted with a novel approach: the integration of optical fiber sensing cables within the concrete walls surrounding nuclear waste packages. This is achieved using 3D additive-printed support structures, which ensure precise installation positioning of the cable and enable high-performance, direct strain measurements. Laboratory experiments simulated package degradation were carried out on reduced scale samples through applying external mechanical force, sulfate attack tests, and CO₂ injection tests. The results demonstrate that DOFSS can effectively map concrete strain and track the evolution of the package shape over time. Furthermore, it can detect concrete cracking, with data analysis providing precise information on the location and width of created fractures.DOFSS enables the monitoring of both localized and abrupt disruptions such as cracking, and diffuse effects caused by swelling, loading or temperature changes. These findings highlight DOFSS as a promising and effective method for the remote monitoring of radioactive waste package degradation