Influence of the thermophoresis on aerosol deposition on warm urban surfaces

International audienceIn the case of an accidental or chronic atmospheric pollution by a nuclear plant, aerosols' deposition transfer coefficients must be known. A major issue is to determine the impact of aerosols contained in the radioactive plume on urban areas with the smallest uncertainties

Combining short-range dispersion simulations with fine-scale meteorological ensembles: probabilistic indicators and evaluation during a 85Kr field campaign

Numerical atmospheric dispersion models (ADMs) are used for predicting the health and environmental consequences of nuclear accidents in order to anticipate countermeasures necessary to protect the populations. However, these simulations suffer from significant uncertainties, arising in particular from input data: weather conditions and source term. Meteorological ensembles are already used operationally to characterize uncertainties in weather predictions. Combined with dispersion models, these ensembles produce different scenarios of radionuclide dispersion, called “members”, representative of the variety of possible forecasts. In this study, the fine-scale operational weather ensemble AROME-EPS (Applications of Research to Operations at Mesoscale-Ensemble Prediction System) from Météo-France is coupled with the Gaussian puff model pX developed by the IRSN (French Institute for Radiation Protection and Nuclear Safety). The source term data are provided at 10 min resolution by the Orano La Hague reprocessing plant (RP) that regularly discharges 85Kr during the spent nuclear fuel reprocessing process. In addition, a continuous measurement campaign of 85Kr air concentration was recently conducted by the Laboratory of Radioecology in Cherbourg (LRC) of the IRSN, within 20 km of the RP in the North-Cotentin peninsula, and is used for model evaluation. This paper presents a probabilistic approach to study the meteorological uncertainties in dispersion simulations at local and medium distances (2–20 km). First, the quality of AROME-EPS forecasts is confirmed by comparison with observations from both Météo-France and the IRSN. Then, the probabilistic performance of the atmospheric dispersion simulations was evaluated by comparison to the 85Kr measurements carried out during a period of 2 months, using two probabilistic scores: relative operating characteristic (ROC) curves and Peirce skill score (PSS). The sensitivity of dispersion results to the method used for the calculation of atmospheric stability and associated Gaussian dispersion standard deviations is also discussed. A desirable feature for a model used in emergency response is the ability to correctly predict exceedance of a given value (for instance, a dose guide level). When using an ensemble of simulations, the “decision threshold” is the number of members predicting an event above which this event should be considered probable. In the case of the 16-member dispersion ensemble used here, the optimal decision threshold was found to be 3 members, above which the ensemble better predicts the observed peaks than the deterministic simulation. These results highlight the added value of ensemble forecasts compared to a single deterministic one and their potential interest in the decision process during crisis situations.</p

Combining short-range dispersion simulations with fine-scale meteorological ensembles: probabilistic indicators and evaluation during a 85Kr field campaign

Numerical atmospheric dispersion models (ADMs) are used for predicting the health and environmental consequences of nuclear accidents in order to anticipate countermeasures necessary to protect the populations. However, these simulations suffer from significant uncertainties, arising in particular from input data: weather conditions and source term. Meteorological ensembles are already used operationally to characterize uncertainties in weather predictions. Combined with dispersion models, these ensembles produce different scenarios of radionuclide dispersion, called “members”, representative of the variety of possible forecasts. In this study, the fine-scale operational weather ensemble AROME-EPS (Applications of Research to Operations at Mesoscale-Ensemble Prediction System) from Météo-France is coupled with the Gaussian puff model pX developed by the IRSN (French Institute for Radiation Protection and Nuclear Safety). The source term data are provided at 10 min resolution by the Orano La Hague reprocessing plant (RP) that regularly discharges 85Kr during the spent nuclear fuel reprocessing process. In addition, a continuous measurement campaign of 85Kr air concentration was recently conducted by the Laboratory of Radioecology in Cherbourg (LRC) of the IRSN, within 20 km of the RP in the North-Cotentin peninsula, and is used for model evaluation. This paper presents a probabilistic approach to study the meteorological uncertainties in dispersion simulations at local and medium distances (2–20 km). First, the quality of AROME-EPS forecasts is confirmed by comparison with observations from both Météo-France and the IRSN. Then, the probabilistic performance of the atmospheric dispersion simulations was evaluated by comparison to the 85Kr measurements carried out during a period of 2 months, using two probabilistic scores: relative operating characteristic (ROC) curves and Peirce skill score (PSS). The sensitivity of dispersion results to the method used for the calculation of atmospheric stability and associated Gaussian dispersion standard deviations is also discussed. A desirable feature for a model used in emergency response is the ability to correctly predict exceedance of a given value (for instance, a dose guide level). When using an ensemble of simulations, the “decision threshold” is the number of members predicting an event above which this event should be considered probable. In the case of the 16-member dispersion ensemble used here, the optimal decision threshold was found to be 3 members, above which the ensemble better predicts the observed peaks than the deterministic simulation. These results highlight the added value of ensemble forecasts compared to a single deterministic one and their potential interest in the decision process during crisis situations.</p

Metals in marine environment (mollusc Patella sp, fish Labrus bergylta, crustacean Cancer pagurus, beach sand) in a nuclear area, the North Cotentin (France)

International audienceThe results of a 1-year long survey of trace metals concentrations (Al, Cd, Cr, Co, Cu, Fe, Mn, Hg, Ni, Pb, Zn) measured in beach sand, limpets and, occasionally, in fish and shellfish from the North Cotentin area (France), where nuclear industries are implanted, are presented. The objective of these study was to provide useful data for the validation of models predicting the impact of these industries on the marine environment. Even if differences were noted between sites for various metals, the levels are consistent with existing data published for similar site and do not appear to give evidence of contamination by industrial sites

Dispersion and deposition of gas and aerosol particles in urban environment: examples of in situ experiments for predictive model validation

International audienceIn terms of chronic or accidental release of radioactive particles into the atmosphere, knowing atmospheric gas and particle dispersion, as well as particle-bound radionuclide deposition flux on ground surfaces is essential to assess risks on both populations and environments. Protecting urban environments and populations living in the vicinity is a major issue. However, urban areas are among the least studied environments due to their complexity in terms of dynamics, thermal properties and spatial heterogeneity. Our work focus on how in situ experiments help constraining predictive models of atmospheric gas and particle dispersion, and particle-bound radionuclide deposition flux on various spatiotemporal scales in urban environments. Examples of past and ongoing studies will be presented. Our in situ experiments use tracing gas (SF6 and He), tracing particles (fluorescein) or natural radionuclides already present in environment such as 7Be. Results will be discussed during the conference

Tissues from equine cadaver ligaments up to 72 hours of post-mortem: a promising reservoir of stem cells

BACKGROUND: Mesenchymal stem cells (MSCs) harvested from cadaveric tissues represent a promising approach for regenerative medicine. To date, no study has investigated whether viable MSCs could survive in cadaveric tissues from tendon or ligament up to 72 hours of post-mortem. The purpose of the present work was to find out if viable MSCs could survive in cadaveric tissues from adult equine ligaments up to 72 hours of post-mortem, and to assess their ability (i) to remain in an undifferentiated state and (ii) to divide and proliferate in the absence of any specific stimulus. METHODS: MSCs were isolated from equine cadaver (EC) suspensory ligaments within 48–72 hours of post-mortem. They were evaluated for viability, proliferation, capacity for tri-lineage differentiation, expression of cell surface markers (CD90, CD105, CD73, CD45), pluripotent transcription factor (OCT-4), stage-specific embryonic antigen-1 (SSEA-1), neuron-specific class III beta-tubulin (TUJ-1), and glial fibrillary acidic protein (GFAP). As well, they were characterized by transmission electron microscope (TEM). RESULTS: EC-MSCs were successfully isolated and maintained for 20 passages with high cell viability and proliferation. Phase contrast microscopy revealed that cells with fibroblast-like appearance were predominant in the culture. Differentiation assays proved that EC-MSCs are able to differentiate towards mesodermal lineages (osteogenic, adipogenic, chondrogenic). Flow cytometry analysis demonstrated that EC-MSCs expressed CD90, CD105, and CD73, while being negative for the leukocyte common antigen CD45. Immunofluorescence analysis showed a high percentage of positive cells for OCT-4 and SSEA-1. Surprisingly, in absence of any stimuli, some adherent cells closely resembling neuronal and glial morphology were also observed. Interestingly, our results revealed that approximately 15 % of the cell populations were TUJ-1 positive, whereas GFAP expression was detected in only a few cells. Furthermore, TEM analysis confirmed the stemness of EC-MSCs and identified some cells with a typical neuronal morphology. CONCLUSIONS: Our findings raise the prospect that the tissues harvested from equine ligaments up to 72 hours of post-mortem represent an available reservoir of specific stem cells. EC-MSCs could be a promising alternative source for tissue engineering and stem cell therapy in equine medicine

Dispersion and deposition of gas and aerosol particles in urban environment: examples of in situ experiments for predictive model validation

International audienceIn terms of chronic or accidental release of radioactive particles into the atmosphere, knowing atmospheric gas and particle dispersion, as well as particle-bound radionuclide deposition flux on ground surfaces is essential to assess risks on both populations and environments. Protecting urban environments and populations living in the vicinity is a major issue. However, urban areas are among the least studied environments due to their complexity in terms of dynamics, thermal properties and spatial heterogeneity. Our work focus on how in situ experiments help constraining predictive models of atmospheric gas and particle dispersion, and particle-bound radionuclide deposition flux on various spatiotemporal scales in urban environments. Examples of past and ongoing studies will be presented. Our in situ experiments use tracing gas (SF6 and He), tracing particles (fluorescein) or natural radionuclides already present in environment such as 7Be. Results will be discussed during the conference

A gapless code-based hash proof system based on RQC and its applications

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Aerosol Particle Dry Deposition Velocities above Grassland According to the Diameter and the Micrometeorological Parameters: The "V" Curve between 1.5 nm and 1 µm with Three Different Methods

Nuclear facilities introduce different types of radionuclides into the atmosphere in the form of gases and aerosols during chronic or accidental releases. These particles may be submitted to atmospheric dispersion, dry and wet deposition. The study of dry deposition based on the dry deposition velocity (dry deposition flux divided by an atmospheric concentration above the substrates) concept is a major issue concerning the impact of radionuclides on the population and the environment. Uncertainties on the dry deposition velocity values of submicronic particles are up to several orders of magnitude discrepancies according to the model used (Petroff et al., 2008). Moreover there is no data for particle diameter under 10 nm. So, the aim of this study is to quantify dry deposition velocity according the particles diameter and the atmospheric stability. Dry deposition flux can be determinate with different devices. We used 3 different methods to quantify the dry deposition velocities according the particles diameter. (1): For particles around 1.5 nm we studied the dry deposition of free faction of alpha particles of Rn222 decay products by the gradient method (2) For particles between 2.5 nm and 1.2 µm we used the eddy correlation method with a cospectral analysis (Pellerin et al., 2017): the dry deposition flux is determinate thanks to covariance between fluctuations of the vertical wind velocity and fluctuations of the atmospheric aerosol particle concentration during 30-minutes periods at high frequency. The aerosol particle concentration was measured by coupling two Condensation Particles Counters (CPC 3788, TSI, Inc.) for particle sizes between 2.5 and 14 nm (Twin CPC method) and for particle sizes between 7 nm and 1 µm, an Electrical Low Pressure Impactor (ELPI, Dekati, Inc.) was used. The wind 3-component velocity was measured by an ultrasonic anemometer (Young 81000, Inc.). (3) The last method used is the direct deposition of fluorescein particles of 0.6 µm on synthetic grass and the measurement are carrying on by a fluorimeter. Four experimental campaigns were conducted above a grassland in western France (near Poitiers) april 2015 and September 2016. The first results of these campaigns show that the particles under 10 nm are influenced only by the mechanical turbulence (link with the friction velocity u*), while the particles over 10 nm are influenced by the mechanical turbulence and the thermic turbulence (link with the sensible heat flux H). The different results of dry deposition velocities with the three different methods allowed to obtain a “V” curve between 1.5 nm and 1.2 µm. In fact, if we look the curve of dry deposition velocities normalized by friction velocities according to particles diameter and for the four sampling campaign, even if the used different technics, all of the point are consistent. Moreover we can find the theoretical curve shape of dry deposition velocity with the effects of the three dry deposition mechanisms: Brownian diffusion, interception and impaction. We propose to present the all used methods and devices and then, to describe the result