Institute for Radiation Protection and Nuclear Safety (IRSN)
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Analyse des particules produites par explosion au contact d'éprouvettes en béton
No full textNational audienceThe physical protection of nuclear facilities requires taking into account malicious acts, in particular explosions that could lead to radiological consequences. These scenarios are poorly documented in terms of aerosol release, and to date we have no precise knowledge of the mass of dust generated by explosions in contact with specimens containing radioelements. The aim of this work is to gain a better knowledge of generated dusts, particularly those with an aerodynamic diameter of less than 10 µm, by developing an experimental protocol for analysing the particles dispersed by explosions in contact with concrete specimens: weighing, sieving and optical counting are used.La protection physique des installations nucléaires impose la prise en compte des actes de malveillance, notamment les explosions pouvant engendrer des conséquences radiologiques. Ces scénarios sont peu documentés sur le plan des aérosols émis et nous ne connaissons pas, à ce jour, de manière précise, la masse des poussières dispersées par des explosions au contact de cibles incluant des radioéléments. Ce travail cherche à apporter des connaissances sur les poussières générées, notamment celles dont le diamètre aérodynamique est inférieur à 10 µm, en développant un protocole expérimental d'analyse des particules dispersées par des explosions au contact d'éprouvettes de béton : pesée, tamisage et comptage optique sont utilisés
Effects of salinity on the water retention properties and microstructure of the Opalinus Clay from the lower sandy facies (LSF) of Mont Terri
No full textInternational audienceIn this study, the impact of salinity on the water retention properties and microstructure of the Opalinus Clay from the lower sandy facies (LSF) of Mont Terri site was investigated by exposing a series of unsaturated Opalinus Clay samples to two sodium nitrate NaNO3 solutions of controlled osmotic suctions ( p ¼ 15 and 34MPa) nd to a synthetic water (same salinity as the natural pore water) p ¼ 1MPaÞ at different water contents. The water retention curves were determined along wetting path for the three osmotic suctions, and microstructural analyses were conducted at different saturation states. While the total suction increased with salinity, the porosity decreased, suggesting the decrease in the swelling potential. Exposing the Opalinus Clay to a highly saline solution at low water contents increased the specific surface area and the peak of the dominant mesopore population. This is due to the dispersion of the Na-clay fraction and to the swelling of the initially unsaturated clay fraction. At higher water content, the water transfer from the meso to the macropores prevails and a decrease in specific surface area, peak and density of the mesopores were observed. The higher the osmotic suction, the lower the water content at which the shrinkage of the mesopores is initiate
Active faulting of the southern segment of the Rhine River Fault, southern Germany: Geomorphological and paleoseismological evidence
No full textInternational audienceOur study focuses on the southern segment of the Rhine River Fault, located in one of the most seismically active regions in intraplate Europe, at the southern end of the Upper Rhine Graben and forming part of the eastern Rhine Graben Boundary Fault. It stands out due to its impressive geomorphological expression in the landscape near the village of Tunsel, in southwestern Germany. We present details about the timing of fault activity and the contribution of earthquakes to the morphology, as this information is crucial for seismic hazard assessment, considering its location 8 km from the Fessenheim Nuclear Power Plant. Through the integration of the sedimentary sequences, morphotectonic observations, shallow geophysics, and paleoseismological trenching, our findings demonstrate that several earthquakes along the RRF have ruptured the surface (M6.7 ± 0.5). The youngest surface rupturing earthquake occurred during medieval times (EZ) and the penultimate event (EY) is constrained by stratigraphic correlation with reworked Loess deposits dated to the Younger Dryas (ca. 13 kyr BP). Three older earthquake events have also been unearthed (EX, EW and EV) occurring prior to the Late Glacial Maximum, where event EX led to considerable lateral spread at the banks of the Pleistocene Rhine river. Vertical displacements reach up to 0.5 m and lateral offsets up to max. 1.5 m per earthquake event, consistently with a 15 - 30 km-long rupture of this segment of the Rhine River Fault
A step toward flow simulation through cracks in beam-particle models
No full textInternational audienceCrack characterization in reinforced concrete structures, such as the containment walls of 1300 MWe nuclear power plants, is critical for accurately estimating air leakage. Traditional modeling strategies, such as Poiseuille's law applied to a simplified geometry, rely on indirect parameters like a tortuosity coefficient, which is difficult to predict and has limited validity, leading to increased uncertainty. This study presents a novel post-processing tool based on the Beam-Particle simulation approach, capable of detecting micro-crack paths and constructing macro-crack geometries using graph theory. The generated macro-crack geometry can be integrated into computational fluid dynamics (CFD) simulations for more accurate airflow predictions or by calibrating simplified approaches like Poiseuille's law based on numerically obtained crack characteristics. Validation against optical measurements from Brazilian splitting tests demonstrates the tool's potential to advance simplified modeling and enhance detailed crack characterization, opening new possibilities for improved air leakage predictions
Results of a Geant4 benchmarking study for bio‐medical applications, performed with the G4‐Med system
No full textInternational audienceBackgroundGeant4, a Monte Carlo Simulation Toolkit extensively used in bio‐medical physics, is in continuous evolution to include newest research findings to improve its accuracy and to respond to the evolving needs of a very diverse user community. In 2014, the G4‐Med benchmarking system was born from the effort of the Geant4 Medical Simulation Benchmarking Group, to benchmark and monitor the evolution of Geant4 for medical physics applications. The G4‐Med system was first described in our Medical Physics Special Report published in 2021. Results of the tests were reported for Geant4 10.5. PurposeIn this work, we describe the evolution of the G4‐Med benchmarking system.Methods The G4‐Med benchmarking suite currently includes 23 tests, which benchmark Geant4 from the calculation of basic physical quantities to the simulation of more clinically relevant set‐ups. New tests concern the benchmarking of Geant4‐DNA physics and chemistry components for regression testing purposes, dosimetry for brachytherapy with a source, dosimetry for external x‐ray and electron FLASH radiotherapy, experimental microdosimetry for proton therapy, and in vivo PET for carbon and oxygen beams. Regression testing has been performed between Geant4 10.5 and 11.1. Finally, a simple Geant4 simulation has been developed and used to compare Geant4 EM physics constructors and physics lists in terms of execution times. ResultsIn summary, our EM tests show that the parameters of the multiple scattering in the Geant4 EM constructor G4EmStandardPhysics_option3 in Geant4 11.1, while improving the modeling of the electron backscattering in high atomic number targets, are not adequate for dosimetry for clinical x‐ray and electron beams. Therefore, these parameters have been reverted back to those of Geant4 10.5 in Geant4 11.2.1. The x‐ray radiotherapy test shows significant differences in the modeling of the bremsstrahlung process, especially between G4EmPenelopePhysics and the other constructors under study ( G4EmLivermorePhysics , G4EmStandardPhysics_option3 , and G4EmStandardPhysics_option4 ). These differences will be studied in an in‐depth investigation within our Group. Improvement in Geant4 11.1 has been observed for the modeling of the proton and carbon ion Bragg peak with energies of clinical interest, thanks to the adoption of ICRU90 to calculate the low energy proton stopping powers in water and of the Linhard–Sorensen ion model, available in Geant4 since version 11.0. Nuclear fragmentation tests of interest for carbon ion therapy show differences between Geant4 10.5 and 11.1 in terms of fragment yields. In particular, a higher production of boron fragments is observed with Geant4 11.1, leading to a better agreement with reference data for this fragment.ConclusionsBased on the overall results of our tests, we recommend to use G4EmStandardPhysics_option4 as EM constructor and QGSP_BIC_HP with G4EmStandardPhysics_option4 , for hadrontherapy applications. The Geant4‐DNA physics lists report differences in modeling electron interactions in water, however, the tests have a pure regression testing purpose so no recommendation can be formulated
IVMR modelling with transient effects during molten pool formation and stabilization – Outcomes from models’ comparison performed in the IAEA CRP J46002
No full textArticle published as part of the Special Issue “ERMSAR 2024 – 11th European Review Meeting on Severe Accident Research”.International audienceIn 2020, the International Atomic Energy Agency (IAEA) has started the 4-year Coordinated Research Project (CRP) on In-Vessel Melt Retention (IVMR) with the main objective to harmonize the international understanding of the scientific and technological bases underpinning crucial parts of the safety demonstration of this Severe Accident (SA) management strategy. This strategy consists in maintaining the degraded reactor core (corium) within the vessel by ensuring its cooling thanks to cavity flooding and power extraction through the vessel wall. In the scope of this CRP, analytical benchmarks were performed focusing on different reactor designs. Among them, a generic 1000MWe PWR design benchmark was set up with a different objective compared to those dedicated to a given scenario and reactor. Its main purpose was to allow detailed comparison of models implemented in capable codes (either integral SA code or dedicated code) based on prescribed and simplified configurations. This paper presents the work done and achievements obtained within this benchmark. Different cases, corresponding to different corium configurations and boundary conditions, were developed with increasing complexity. In total, eight benchmarks are studied covering molten pool formation from solid particles, progressive corium relocation to the lower plenum, progressive molten steel incorporation, vessel wall ablation and possible stratification inversion. Together, they form an efficient and useful tool to better understand IVMR results and code capabilities or limitations. State of codes performance and remaining issues are discussed, focusing mainly on configurations involving progressive molten material arrival in the lower plenum
Geochemical analysis of overbank fine sediments of the Upper Rhine (Rhinau island, France): Evidence of metal (Pb, Zn, Cu & Sn) enrichments over the last century
No full textInternational audienceA geochemical analysis of a well-dated 1.2 m-thick sedimentary sequence collected on the Rhinau island at ~60km south of Strasbourg (France) has been performed in order to reconstruct the evolution of metal contents inoverbank fine sediments of the Upper Rhine over the last 150 years. Data indicate that most of the geochemicalvariations in major elements as well as in trace elements along the sedimentary profile can be related to variationsin the sediment mineralogical composition during deposition. Only Cu, Pb, Zn, and Sn highlight enrichmentin the sediments, interpreted as resulting from human releases into the fluvial hydrosystem. Enrichmentquantification is made by using diagrams of variation of element X normalized to silica as a function of Al2O3/SiO2. The results point out that each metal has its own enrichment pattern. The enrichment significances andorigins are discussed by comparing them with the knowledge of historical contaminant release and/or depositionin the Upper Rhine hydrosystem. Sn enrichment is thus linked to Sn releases by textile industries downstream ofBasel, whose activity peaked in ~1940/1950 CE before gradually declining. Pb enrichment, which started to decline in the mid-1980s and disappeared in the 2000s, is explained by the reduction and then cessation in the early 2000s of the two main sources of Pb pollution to the Rhine hydrosystem, namely (i) atmospheric fallout linked to the combustion of leaded gasoline and (ii) Pb flux associated to the Alsacian Potassium Mining rejects into the Rhine river. Cu and Zn enrichments are explained by diverse sources (e.g. agriculture, industries and wastewater treatment plants), whose emissions have reduced over the last decades but can still occur to a significant extent. Overall these results confirm potential and usefulness of our multi-method approach for assessing the effectiveness of public policies to reduce the impact of metal releases into continental hydrosystems, as well as their response time
Godiva-IV leakage dose characterization
No full textInternational audienceAs new nuclear accident dosimetrists are being trained by their respective institutions, there was a need for nuclear accident dosimeter (NAD) ntercomparison exercises. This required a reference neutron and photon dose for nuclear accident dosimetrists to test their dosimeters and analysis. The U.S. Department of Energy (DOE) Nuclear Criticality Safety Program (NCSP) supported an experimental campaign to characterize the Godiva-IV leakage dose in 2014 to support future exercises. A Passive Bonner Sphere Spectrometer (PBSS) was deployed by Atomic Weapons Establishment (AWE) to measure the neutron spectrum. CaF thermoluminescent dosimeters (TLDs) were used to measure the photon doses. The results were documented in a report at that time but this paper reanalyzed and updated those results with other measurements in the interim. This work established updated reference neutron and photon doses as a function of radial distance from the center of Godiva-IV, which will be used for future NAD intercomparison exercises
On the Necessity of Adopting Irradiation Protocols Recommended by the Compatibility in Irradiation Research Protocols Expert Roundtable (CIRPER) in Published Research and Why It Matters to Health Physicists
No full textInternational audienceThe National Nuclear Security Administration (NNSA) seeks to assist and support all partners in the fields of radiobiology, health physics, radiation physics, and related areas to transition from cesium-137 chloride-based technologies, which can potentially be used in an act of terrorism, to x-ray technologies. The absence of information on experimental procedures, equipment, and irradiation parameters directly and negatively impacts the reproducibility and translatability of a sizable portion of radiation biology studies. It also discourages researchers from adopting new tools that eliminate the risks of a radiological dispersal device.Ongoing discussions on reproducibility have not had a significant impact on publishing practices. The lack of agreement on minimum standards for disclosure of irradiation parameters results in the need to repeat costly studies, yielding uncertainty in observed effects and producing difficulty in validating characterized animal models. The lack of standard reporting measures also contributes to the confusion and reluctance that researchers may experience when considering whether they should transition to alternatives to gamma irradiation. This reluctance is despite the many advantages these alternatives provide, including technological innovations such as guided imaging that mirror clinical applications (which cesium-137 irradiators simply cannot accommodate), significantly decreased regulatory burdens, and eliminating potential terror threats, among others. Forty-one percent of researchers that transitioned to x-ray irradiators surveyed by Brookhaven National Laboratories (BNL) reported that the advantages of x-ray irradiators allowed them to pursue new lines of research.Both BNL’s recent Alternative Technologies Meta Study (Stern et al. 2022) and the work of Draeger et al. (2020), on which it builds, reaffirm that many radiation biology studies lack information on experimental procedures, equipment, and physics parameters that would allow other researchers to compare and reproduce the outcomes of the studies. These literature reviews demonstrate that, although source specifications (e.g., model, energy, and spectra) are well reported, experimental methodologies and irradiation protocols are not. For example, there are significant information gaps in reporting dosimetry, geometry, filtration, and experimental error of uncertainty. Thus, replication of reported values across studies and users is problematic. For studies where the critical biological endpoints measured have a narrow range (±5% or less), knowing the parameters that control the dosimetry is critical. However, most published studies do not provide enough information on experimental results to reproduce the study or experiment.Two recent initiatives have attempted to bring about consensus on minimum standards for disclosure of irradiation methods and protocols. The AAPM empowered Task Group No. 319 to work on creating guidelines for accurate dosimetry in radiation biology experiments, and its findings are eagerly awaited. A second initiative, the Compatibility in Irradiation Research Protocols Expert Roundtable (CIRPER), began in October 2022 on the margins of the Radiation Research Society’s annual conference. Sponsored by the NNSA through its Office of Radiological Security and BNL, the roundtable invited radiation biologists, medical physicists, health physicists, federal grant managers, and device manufacturers to agree on a standardized set of parameters that radiation biologists working with x-ray cabinet irradiators should include when publishing their work. Such inclusion of parameters would allow other researchers to determine their work’s comparability to similar studies using different irradiation modalities, as well as facilitate reproducibility of their experimental results.Over two days of discussion, CIRPER participants agreed that, at a minimum, the methods sections of radiation biology papers must reference irradiation protocols, providing details on device specifications, dosimetry, experimental setup, and calibration. The CIRPER Recommended Methodological Disclosure Requirements are listed in Table 1. Summarizing the minimum recommended methodological information following Table 1 would provide for consistent, efficient, and standardized submissions to peer-reviewed research journals and federal funding agencies
Modelling of wave run–up on a macrotidal beach for assessing coastal flooding
No full textInternational audienceThis work examines the impact of coastal storms on a macrotidal beach at Normandy (France), the beach of Villers-sur-Mer, with the aim of assessing coastal flooding. Extreme wave heights and water levels of four typical storms are simulated using the non-hydrostatic model SWASH to estimate the wave run-up. The numerical simulations have been compared to empirical formulations and validated with processed timestacks generated by video monitoring systems (VMS). The validation shows good agreements between observations and simulations with a mean RMSE of 16 cm, which emphasizes the accuracy of this methodological approach. In the light of the overall results, the water level has a predominant effect on the run-up compared to the wave height. However, the combination of high water levels and waves induces the biggest wave run-up, responsible for the most significant flooding on the coast. Additionally, limited changes in water levels during storm events increase the wave height effect on the run-up, meanwhile small waves with short periods cannot uprush the beach. Furthermore, the transfer of storms, integrating the regional scale of the English Channel and the local scale of the beach, is an important step for assessing coastal flooding in semi-open environments and basins, where the wave direction is the conditioning parameter of storm evolution. Storms from WSW within the English Channel generate the highest wave run-up. This research provides an excellent methodological approach and accurate estimations of coastal flooding in Normandy, which is useful for further works on coastal hazards in response to storms