Institute for Radiation Protection and Nuclear Safety (IRSN)
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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
Radiological dose from seafood ingestion; a global summary from 40 years of study
No full textInternational audienceSeafood is an important source for meeting future global nutrient demands. However, it alsocontributes disproportionately to the radiological ingestion dose of more than five billionworld consumers– up to ~70%–80% of the total-foods dose in some countries. Althoughnumerous studies report seafood doses in specific populations, there is still no comprehensiveevaluation answering basic questions such as “what is the ingestion dose to the averageglobal seafood consumer?” Analysis of 238 worldwide seafood dose estimates suggests thattypical adult consumers receive from 0.13 to 0.21 mSv, with a likely best estimate of 0.15mSv per annual seafood intake. Those consuming large amounts of seafood, particularlybivalves, may experience ingestion doses exceeding 1 mSv per annual intake, surpassing other routinebackground dose sources. The published studies suggest that doses of 3 mSv or greater aresurpassed in about 150 million adult seafood consumers worldwide. Almost all this dose comes fromthe natural radionuclides that are prevalent in marine systems–especially 210 Po. While trace levels ofanthropogenic radionuclides are ubiquitous in seafoods (e.g.,137 Cs and 239 Pu), the added dose from these is typically orders of magnitude lower. Even following the large-scale releases from theFukushima accident, with food safety controls in place, the additional dose to consumers in Japanwas small relative to routine dose from natural background radionuclides. However, the worldwideseafood dose estimates span seven orders of magnitude, indicating a need for an assessment thatintegrates global seafood radionuclide data as well as incorporating changes in seafood consumption and production patterns
Cone beam CT dose optimisation: A review and expert consensus by the 2022 ESTRO Physics Workshop IGRT working group
No full textInternational audienceImage guided radiotherapy (IGRT) using kilovoltage cone-beam CT (CBCT) has become an indispensable tool to ensure the geometric accuracy of radiotherapy treatment delivery. Although significant technical advances have been made in reducing imaging dose, the repeated imaging procedures can still accumulate significant dose to healthy tissues. Despite the widespread use, we still lack clear guidance for optimisation and widely accepted frameworks for evaluating the quality and suitability of CBCT imaging protocols. To address this gap, the 2022 European Society for Radiotherapy and Oncology (ESTRO) Physics Workshop focused on image-quality and imaging-dose optimisation for IGRT using CBCT. This publication represents a review and an expert consensus of the 2022 ESTRO Physics Workshop IGRT working group. Here we aim to provide practical advice for optimising and maintaining CBCT imaging protocols to meet the needs of local procedures and patient populations. The review includes summaries of the current status of CBCT use and optimisation for IGRT in adults and paediatrics, an overview of currently available guidelines, and finally practical guidance on optimising and implementing CBCT imaging protocols for local IGRT treatments and patient populations
Gamma irradiation accelerates alkaline degradation of cellulosic materials in radioactive waste
No full textCorrigendum to “Gamma irradiation accelerates alkaline degradation of cellulosic materials in radioactive waste” [Radiat. Phys. Chem. 229 (2025) 112464] (Radiation Physics and Chemistry (2025) 229, (S0969806X24009563), (10.1016/j.radphyschem.2024.112464))International audienceCellulosic materials make up a significant fraction of the current low-and intermediate-level radioactive waste. During storage and disposal, radiolytic degradation of such materials is inevitable and can occur under both oxic and anoxic conditions. In addition, the highly alkaline cementitious environment of a disposal system promotes the alkaline degradation of cellulosic materials, producing radionuclide-complexing agents, such as isosaccharinic acid (ISA). As radiolytic degradation changes the physicochemical properties of cellulose, it could also affect its alkaline degradation and thus the production of ISA during disposal. Hence, in the present work, we investigated the alkaline degradation of pre-irradiated cellulosic tissues, which are representative of real radioactive waste. Pre-irradiation occurred by exposing tissues to γ-irradiation under oxic or anoxic conditions at absorbed doses up to 1.4 MGy and at two different dose rates. These irradiated tissues were then submerged in artificially prepared cement water (initial pH of 13.3) and monitored over 2.5 years. The results show a significantly faster production and release of dissolved organic carbon and ISA with an increasing absorbed dose during pre-irradiation, and even more so when oxygen is present during irradiation. The irradiation dose rate did not affect the subsequent alkaline degradation rate. Taken together, this work demonstrates that irradiation of cellulosic materials in radioactive waste during storage and disposal will accelerate their alkaline degradation under disposal conditions. Consequently, radionuclide-complexing agents such as ISA will form at rates far exceeding those anticipated from alkaline degradation alone. These findings are therefore pivotal for improving long-term predictions of the ISA production in radioactive waste
Advancing the Prediction of Evaporation Rate of Liquid Pool Fires in Mechanically Ventilated Compartments Using Computational Fluid Dynamics
No full textInternational audienceThe propagation of smoke and hot gases in mechanically ventilated nuclear compartmentshas been highlighted as one of the main issues of significance. It may lead to the failure ofseveral systems such as clogging of filters located in the ventilation network or electricaldevices. To address this issue, the continuous improvement of the predictive capability ofexisting models with regards to liquid pool fires is of high importance. Computational fluiddynamics (CFD) is widely used for fire simulations. It is worth noting that most pool firesimulations in open atmosphere, under-ventilated and mechanically ventilated compartments have relied on pre-defined/prescribed fuel mass loss rate (MLR) or heat release rates(HRR) from correlations or experimental data when available. Therefore, the predictionof fuel MLR and HRR based on the specific actual fire conditions rather than prescribeddata, remains a key development area for the fire community. The present work aims toprovide some contribution and advances on this issue. Building on existing liquid evaporation models, the study develops an approach which in then implemented in an in-houseversion of the CFD code FireFOAM in which a mechanical ventilation model has beenembedded, to predict the fuel MLR in both open atmosphere and mechanically ventilatedcompartments. Validations of the implemented model includes comparison with experimental fuel MLR and previous studies that made use of correlations and experimental data.The results show acceptable fuel MLR predictions with reasonable accuracy and providefurther insights into fire behaviour in mechanically ventilated compartments
Iron in Cambodia: Archaeometallurgy and Direct Radiocarbon Dating for Heritage and Technology
No full textInternational audienceIron is a fundamental element, present in various forms: naturally as mineral oxides, as oxidized residues from metallurgical activity, and as metallic iron, widely exploited to produce tools, objects, and support diverse activities. It constitutes an essential material that underpins both technological and social practices in ancient societies, shaping daily life as well as large-scale projects.In the Khmer Empire (9th–14th c.), iron was used for temple clamps, bronze reinforcements, weapons, tools, and domestic objects, reflecting its central role in technology, labor organization, and social networks. Understanding its production—what resources were exploited, which technologies were employed, and who transformed and produced?—is key to reconstructing ancient metallurgical systems and social relationships, a task addressed by Archaeometallurgy, which allows us to trace the different stages of transformation of resources, both mineral and forest-based. To relate these practices to historical dynamics and avoid misinterpretations, it is crucial to place them accurately in time. While radiocarbon dating was traditionally applied to organic materials, recent advances allow extraction of residual carbon directly from the metal itself, originating from the transformation of wood or charcoal and the ore during smelting. Accelerator mass spectrometry (AMS) thus provides direct dating of iron objects, producing robust chronological sequences that contextualize production and usage. This approach has been applied to iron objects from Angkor temples (clamps) and museum collections (clamps, armatures, others), providing insights into construction phases, production networks, and the circulation of iron, and enhancing our understanding of ancient metallurgical practices and their social significance. Here, we present key observations, methods, and historical results derived from this approach
Adaptive adjoint-based population-control methods for kinetic simulations in TRIPOLI-4
No full textInternational audienceTime-dependent Monte Carlo simulations for reactor kinetics applications require special variance-reduction and population-control techniques in order to efficiently cope with the typically huge imbalance between the respective time scales and population sizes of neutrons and precursors. Building upon the legacy implementation of the algorithms devoted to kinetics in the Monte Carlo code TRIPOLI-4, in this work we propose an adaptive adjoint-based population-control method that considerably improves the behaviour of time-dependent simulations. Thanks to a time-dependent importance-sampling scheme, based on the solution of the adjoint point-kinetics equations, neutron and precursor weights are continuously adjusted, which paves the way towards the simulation of previously unattainable reactor transients involving long times and large reactivity excursions. The computational effectiveness of the newly developed method is evaluated in terms of Figure of Merit (FoM) over a set of time-dependent scenarios encompassing the Flattop-Pu, SPERT III E-core and CROCUS benchmarks
Deep learning approach for airborne alpha radioactivity monitoring in atypical atmospheric conditions
No full textInternational audienceIn nuclear facilities, the mandatory monitoring of airborne alpha radioactivity contamination is carried out by dedicated instruments that collect aerosols on a filter, measure the deposited radioactivity and trigger an alarm when a predetermined activity threshold is exceeded. The radioactivity measurement is highly influenced by variations in aerosol size and concentration on the filter, leading to numerous false alarms. In order to overcome this difficulty, we are interested in using artificial intelligence to automatically compensate the background noise and hence obtain precise information on the presence of artificial alpha emitters based on the alpha-particle spectrum. The ultimate aim is to reduce the false alarm rate
Investigations sur l'origine du rejet de radioéléments artificiels de mai 2023 : le plus complet de la décennie en Europe du Nord
No full textInternational audienceThe detection of traces of radionuclides in Northern Europe has become more frequent in recent years, although the origin of these emissions has not been officially confirmed by any authorities. IRSN has undertaken investigations to determine the source of the past detections and to understand the origin and the mechanisms that may have led to these releases into the environment. Recently, in May 2023, a new detection event was recorded in the same part of Europe, but this is the first time that such a high number of isotopes has been reported. This paper presents the analysis carried out by IRSN to identify the origin of this new release, the most comprehensive one in the last ten years. Using inverse atmospheric dispersion modelling methods, the most likely geographical origin was identified between Estonia and the western part of the Russian Federation, in line with previous releases. The key feature of this event is the simultaneous detection of 46 Sc alongside low volatile fission products and actinides, which prompted further investigations. About the origin of 46 Sc, it has been shown that it is an activated corrosion product specifically produced in WWER reactors. Although there is no certainty with so few data, this finding reinforces the interpretation from previous studies assuming the release is likely to have originated from a spent primary ion exchange resin of a WWER reactor, possibly involving a fuel cladding failure leading to fuel dispersion within the primary circuit. Finally, a scenario is proposed to explain the atmospheric release which is consistent with all available detection data. However, this scenario is based on highly unlikely assumptions and remains speculative.La détection de traces de radionucléides artificiel est relativement fréquente au cours des dernières années en Europe du Nord, bien que l'origine de ces rejets ne soit officiellement confirmés par aucune autorité. L'IRSN a déjà réalisé des investigations pour déterminer l'origine de plusieurs détections passées et pour en comprendre l'origine et leur mécanisme de rejet dans l'environnement. Récemment, en mai 2023, un nouvel événement de détection a été enregistré dans la même région d'Europe, mais c'est la première fois qu'un nombre aussi élevé d'isotopes est signalé. Cet article présente l'analyse réalisée par l'IRSN pour identifier l'origine de ce nouveau rejet, le plus important de ces dix dernières années. À l'aide de méthodes de modélisation inverse de la dispersion atmosphérique, l'origine géographique la plus probable a été identifiée entre l'Estonie et la partie occidentale de la Fédération de Russie, conformément aux rejets précédents. La caractéristique principale de cet événement est la détection simultanée de 46Sc avec des produits de fission non-volatils et des actinides, ce qui a motivé des investigations supplémentaires. Concernant l'origine du 46Sc, il a été démontré qu'il s'agit d'un produit de corrosion et d'activation, spécifiquement produit dans les réacteurs VVER. Bien qu'il n'y ait aucune certitude avec si peu de données, ces éléments renforcent l'interprétation des études précédentes selon laquelle le rejet proviendrait probablement d'une résine échangeuse d'ions primaire usagée d'un réacteur VVER, impliquant probablement une défaillance de la gaine du combustible avec une dispersion du combustible dans le circuit primaire. Enfin, un scénario est proposé pour expliquer le rejet atmosphérique, qui est cohérent avec toutes les données de détection disponibles. Cependant, ce scénario repose sur des hypothèses hautement improbables et reste spéculatif