Institute for Radiation Protection and Nuclear Safety (IRSN)
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Les coefficients de dose interne de la CIPR
No full textNational audienceLa dose efficace engagée à la suite de l’incorporation de radionucléides n’est pas directement mesurable. Elle est évaluée à partir de la radioactivité ambiante ou corporelle à l’aide d’un coefficient de dose spécifique à un radionucléide, une forme physicochimique, une voie de contamination interne (inhalation, ingestion ou passage transcutané) et à une classe d’âge.Les valeurs des coefficients de dose sont fixées par la réglementation à partir des publications de la Commission internationale de protection radiologique (CIPR). La CIPR a récemment complété une révision de l’ensemble des coefficients de dose applicables aux travailleurs exposés. Elle s’emploie désormais à mettre à jour les coefficients destinés au reste de la population, adultes et enfants, pour une prochaine série de publications. La tutoriale présentera les nouvelles hypothèses et les nouveaux outils de la CIPR qui motivent une mise à jour des coefficients de dose existants : données nucléaires de base, modèles biocinétiques respiratoire, alimentaire et systémique, fantômes anthropomorphes homme et femme, facteurs de pondération radiologiques et tissulaires. Les résultats numériques obtenus pour les travailleurs seront discutés, ainsi que la façon de choisir la valeur appropriée à une situation d’exposition professionnelle. Le travail en cours sur les coefficients de dose interne applicables au public, notamment dans les situations d’exposition environnementale, sera ensuite présenté
Deliverable 9.7: ROUTES – Review of radioanalytical characterisation of selected radioactive wastes and wastes with complex chemical and toxic properties
No full textRadioanalytical characterisation is a vital part of the waste management route for radioactive wastes. It ensures the compliance with waste acceptance criteria for interim storage, long-term storage and final disposal and therefore contributes to the safe handling of radioactive waste. The objective of this deliverable is a comprehensive description of radioanalytical characterisation, including • the identification of characterisation techniques, • the comparison of characterisation methods applied for the same waste in different countries, • the analysis of existing approaches and identification of knowledge gaps, as well as • to give recommendations both for future research and development (R&D) tackling the identified knowledge gaps and for characterisation approaches for countries with non-developed waste management concepts.The first part of this deliverable describes the motivation and criteria for radioanalytical characterisation of waste by analysing the countries regulations, the distribution of responsibilities, as well as the motivation and techniques for characterisation. This section shows, that the majority of the participating member states (MS) of this deliverable have individual national regulations in place or have regulations based on Council Directive 2011/70/Euratom. In approx. 2/3 of the countries the respective waste owner is responsible for the characterisation of waste, while approx. 1/3 of the countries have assigned this task to national organisations. In general, the motivation for characterisation cited by the participating MS with implemented regulations is the verification of compliance with legal regulations or waste acceptance criteria (WAC), utilising a combination of non-destructive and destructive methods, as well as numerical models and scaling factors.The second part of this deliverable presents identified radioanalytical characterisation approaches for six selected waste types: graphite, sludge, organic waste, spent ion exchange resins (SIERs), U/Ra/Th bearing waste and decommissioning waste. The radionuclide inventory of waste is highly dependent on waste type, such as graphite or spent ion exchange resins (SIERs), but also on the waste history or generation. Relevant for the selection of radioanalytical characterisation methods is moreover the physical and chemical form of the waste, such as liquid or solid, untreated or treated, or, non-conditioned or conditioned. This part identifies applied characterisation techniques specific for the selected waste types. Additionally, for the selected waste types, different characterisation approaches currently applied in different countries contributing to this deliverable are outlined.In the third part, the different radioanalytical characterisation approaches and common issues are analysed waste type specific. Amalgamated, common issues for all addressed waste types are representative sampling and legislative challenges, such as missing WAC. For graphite, additional challenges in identifying disposal options arise from the 36Cl content. For sludge, additional challenges arise from chemical properties such as reactivity, inflammability or gas generation, as well as big volumes of this waste type from oil- and gas-industries. A SIERs specific challenge is the gas generation due to radiolysis, as well as the determination of 226Ra and 232Th inventory of non-conditioned mixed waste containing SIERs. For U/Ra/Th bearing wastes, the variety of waste types containing is one of the challenges associated with it. Another issue is the large volume of U/Ra/Th bearing wastes, especially from non-nuclear facilities and the monitoring of 222Rn release, especially for open pit storage of uranium mining tailings. As waste from decommissioning is a broad category, only general issues have been mentioned by participating countries. One specific challenge for decommissioning waste is the reduction of waste volume classified as low-level waste (LLW) and very low-level waste (VLLW) and increase the volume classified as exempted waste.From the analysed issues, still existing knowledge gaps are derived and recommendations for future R&D to close identified knowledge gaps given. The origin of most identified characterisation issues are of financial or legislative nature, but also characterisation issues based on missing input from research and development have been identified. Regarding the recommendations for future R&D activities, a common similarity of most waste addressed types is the representative sampling and improvement as well as validation of scaling factors.In the last part, means of providing an efficient transfer of knowledge and experience to countries without mature waste disposal concepts and recommendations for the selection of applicable radioanalytical characterisation methods, e.g., for small inventory member states (SIMS) are given. For these countries, recommended non-destructive methods are the dosimetry and the gamma spectrometry. As destructive method, only liquid scintillation counters are recommended by task participants. Stated reasons for not recommending a specific technology are based on the costs of equipment, maintenance, specific knowhow needed to operate the equipment, as well as limited applicability of the technology. The obstacles for SIMS on radioanalytical characterisation can be condensed to two main reasons: Availability of know-how and availability of equipment. Therefore, three actions will be recommended:• Development of a guide on radioanalytical characterisation dedicated to SIMS• Knowledge transfer program on technology application• Research project on the development of a mobile facility for characterisatio
Coolability of a corium pool in a debris bed – Critical heat flux (CHF) dependency with tilting angle, debris size and steam flowrate
No full textInternational audienceIn case of severe accident in a light water reactor, large debris beds may form inside the core. If, in some part of the debris bed, the temperature increases up to thefuel melting point, it will lead to the formation and expansion of a molten pool which becomes more and more difficult to cool down as it grows. Therefore, it is ofprimary interest to determine the maximum size of a molten pool surrounded by debris which may be stabilized under water either after reflooding the vessel (as inTMI-2) or in case of a debris bed formed in a flooded reactor pit. One of the key parameters for that issue is the maximum heat flux (CHF) that may be extracted fromthe pool by water flowing within the debris bed. To determine that CHF, a series of tests have been conducted at IRSN. A heated copper cylinder generates a heat fluxat one of its ends which simulates the boundary of the pool and is placed in contact with a debris bed made of monodisperse steel balls. Temperature measurementsalong the cylinder allow to calculate the heat flux transmitted to the debris bed through the cylinder tip.Several experimental parameters have been investigated:- The tilting angle of the heated surface, to take into account the shape of the molten pool.- The diameter of the balls.- The upwards steam flowrate simulating the steam coming from the part of the core located below the molten pool.- The upwards liquid flowrate simulating the natural circulation of water along the debris bed.As it is usual for CHF experiments, a significant dispersion of the measurements was observed, due to unavoidable evolutions of the contact zone between thecopper surface and the balls. However, the impact of that random dispersion could be reduced by performing a large number of tests. This allows to identify cleartendencies on the CHF for the 3 studied parameters, with a rather good degree of confidence.From those tendencies, it was possible to derive a general CHF correlation with the tilting angle and the steam flowrate. When the liquid velocity increases, theCHF increases in most cases, except for some cases with low velocity. However it is more difficult to find a clear correlation with the liquid velocity or flow rate
Assessment of cfd codes capabilities to predict the risk of flammability or explosivity in the event of a hydrogen leak in nuclear facilities
No full textInternational audienceIn the context of nuclear safety, a 4 m3 experimental ventilated enclosure called CARDAMOMETTE has been implemented at IRSN to study the risk of explosion in the event of a hydrogen leakage from a duct in a nuclear facility. Different configurations of hydrogen leakage have been studied allowing to identify those that could potentially lead to explosivity conditions. For safety reason, helium was considered to simulate the behavior of hydrogen. Thanks to high level instrumentation (PIV, He mass spectrometry) and a well-equipped facility allowing local measurements inside the enclosure, a lot of data has been acquired, ensuring a very accurate validation of the CFD code ANSYS CFX. The objective of this validation is to evaluate the capabilities of the CFD code to predict the potential risk of explosivity depending on gas leakage and ventilation configurations.For this purpose, an experimental and numerical program has been launched to study the influence of ventilation (location of air inlets, renewal rates), gas leakage configurations (location and flowrate, impinging jet) and space clutter (cylindrical container, tubes network, suspended ceiling) on helium dispersion inside the experimental bench and to highlight those leading to hazardous situations.First, code-experiment comparisons of airflows inside the enclosure were led to ensure the capability of the CFD code to reproduce experimental airflows for some configurations. PIV velocity fields and experimental air renewal curves have been compared to those obtained with CFD calculations, showing a satisfactory agreement. Thanks to this first step, optimal numerical parameters (turbulence model, mesh, boundary conditions) have been chosen.Secondly, studies of helium dispersion were carried out according to the different configurations presented before. In this paper, only results for free helium jet and impinging helium jet on the wall are presented. Experimental and numerical results of local concentrations were compared, showing a very good agreement and hence the capability of the code to highlight the high concentration areas. Sensitivity studies about turbulent Schmidt number were also led, allowing to define the best numerical dataset depending on the helium injection configurations.Other experimental and numerical comparisons are currently in progress, especially for the configuration of an impinging helium jet on a cylindrical container
Mechanical tensile behaviour of cement paste/aggregate bond exposed to leaching
No full textInternational audienceAn experimental program is oriented to the mechanical behaviour of the Interfacial Transition Zone (ITZ) exposed to leaching, for a single mix. Leaching kinetics of the degraded depth, measured through grey level on cross sections, reveals a maximum gap of 10 % between ITZ and bulk cement paste. ITZ, with a main thickness of 15 µm suffers a significant decalcification, which is reflected on the mechanical properties of the bond. Grey level, Calcium/Silicon (Ca/Si) molar ratio and Young’s modulus in the degraded zone present similar evolution. Effect of ITZ causing cracking and then debonding is noticed, through chemical analysis, image observation and mechanical tests
The use of stable lead isotopes for the identification of the sources and transport processes leading to the release of radioactive contaminants downstream of former uranium mine sites
No full textInternational audienceRadioactive enriched materials generated by uranium mining activities potentially release radionuclides and associated heavy metals into the environment, leading to high uranium accumulation in soils and sediments around the former uranium mine. However, high uranium content comparable to that from mining activities, due to natural weathering and erosion of local bedrock was reported (up to 6000 mg.kg-1). Thus, highlighting the potential sources and mechanisms driving radioactive elements dissemination in the vicinity of former U mines is a key element for the decision-making process, effective management, and remediation of contaminated sediments and soils. This research aims to identify the sources of radioactive contaminants and their transport mechanism using stable Pb isotopes and radioactive disequilibrium of the 238U-decay series. The study area is a wetland located downstream of the former Rophin U mine (Zone atelier territoires uranifères, France). Soils and sediments were sampled in the wetland and radiological and chemical analyses were performed (platforms PATERSON and LUTECE, IRSN). The uranium content here reaches 16000 mg.kg-1 in the surface organic layer (34 mg.kg-1 in local bedrock). The radiogenic 206Pb/207Pb ratio (~1.73) and the alignments of samples in the three Pb isotopes (206Pb, 207Pb, 208Pb) plot point out the impact of mining activities. Uranium originates probably from three sources related to the mining history of the site: i) pitchblende UO2 due to mechanical and chemical processing from Bois Noirs ore ii) parsonsite Pb2(UO2)(PO4)2, the local dominant U mineralization and iii) U from the local geochemical background. The high content of common Pb in parsonsite hides its radiogenic Pb signature limiting thus the use of the Pb isotopes as a relevant fingerprint for this case. Additionally, observations of Pb-bearing phases associated with phosphate by SEM strengthen our hypothesis. The variation of activity ratio 230Th/238U measured by gamma spectrometry also indicates the mobility of uranium in the profile, probably due to the fluctuation of the water table in the wetland. Finally, a geostatistical approach was explored to highlight lateral radioelement mobility at the wetland scale based on the data of in situ and mobile gamma measurements. Preliminary findings will be shown during the presentation
Micron-sized dust and nanoparticles produced in the WEST tokamak
No full textInternational audienceHighlights : Tungsten nanoparticles produced in a tokamak of tungsten divertor • Micron-sized tungsten dust particles emitted during off normal events • Helium nanobubbles produced at the surface of tungsten dust particles of a tokamakAbstract: Two populations of dust particles were found during the first phase of operation of WEST. Theone that dominates by size and weight comes from the delamination of tungsten coatingscovering graphite tiles and the emission of droplets of molten materials during off-normalevents. Sizes vary from several microns to tens of microns. More generally, micron-sized dustparticles due to the erosion of all materials present in the vacuum vessel were collected. Inaddition, nanocavities were found at the surface of tungsten dust sampled after He plasmas andwere attributed to He trapping in the form of nanobubbles. Tungsten nanoparticles constitutethe second unexpected dust population. They are dominant by their number and were essentiallyfound at the surface of micron-sized particles. They may result either from the condensation ofan oversaturated vapor above molten tungsten or come from ion-neutral clusters growing inplasma regions of low temperature until the appearance of solid particles
Évolution spatio-temporelle de la sismicité de la zone Ubaye/Haute-Durance : apports pour la compréhension de la dynamique et de l'évolution des essaims de sismicité en domaine de faible déformation
No full textThe Ubaye region, located in the Alps at mid-distance between Grenoble and Nice, is one of the most seismically active areas in France. One of the strongest earthquakes recorded in mainland France occurred on April 5, 1959 (MLLDG 5.3). This region is characterized by a particular seismic activity composed of intertwined mainshock/aftershocks and seismic swarm sequences, involving the complex interaction of several driving processes (stress transfer, fluid-pressure, etc). Some swarms contained earthquakes of magnitude greater than 4, like the 2012-2015 swarm, which is characterized by two mainshocks: MLLDG 4.8 (26/02/2012) and MLLDG 5.2 (07/04/2014). This PhD aims at better understanding the processes that drive the seismicity and relate it to known structures in the region. The study of historical and instrumental seismicity allowed to highlight the most active areas than others (Le Lauzet, Larche, Barcelonnette, St-Paul-sur-Ubaye, Guillestre) since the 18th century. Unfortunately, the uncertainties of location and our lack of knowledge of deep structures make it very difficult to relate outcropping faults with seismicity. We then focused on the two months aftershocks that followed the April 7, 2014 earthquake. The aftershock locations distribute in a wide volume around the main fault plane. The complex spatial organization of the seismicity was quantitatively analysed through the study of the geometry of the families that composed it and confirmed by the computation of 100 focal mechanisms. During the different crisis periods (2003-2004 & 2012-2015), the presence of fluids was highlighted as one of the main drivers to explain the behaviour of the seismicity. We then decided to calculate the fluid-overpressures required to trigger each event by inverting the focal mechanisms and the stress-state. Three main results emerge: 1) the majority of events (65%) requires between 15 and 40 MPa of fluid-overpressure; 2) the strongest earthquakes also require fluid-overpressures; 3) the temporal evolution of overpressure is an indicator of the type of seismic sequence. From these results, a conceptual model is proposed to conciliate fluid and the complex behaviour of the seismicity based on the fault-valve behaviour (Sibson, 1990). After concentrating only on the 2014 crisis, I focused on the 2010-2019 period to link the pre-existing structures of the region to the 2012-2015 crisis chronology. A new relocation of the seismicity is then performed on this period starting from the LDG catalogue. The full Ubaye region seems affected by swarms and more particularly the Ubaye Valley. Moreover, the alignment of the seismicity allows us to hypothesize two faults intersecting in the area of the 2012-2015 swarm. The statistical study of the magnitude distribution (b-value of the Gutenberg-Richter law) allowed the reconstruction of a generic time l behaviour of the b-value evolutions during the swarm, interpreted as related to fluid processes. The variation of b-value is more complex for mainshock/aftershock sequences, with no generic evolution before and after the mainshock. The analysis of these different results allowed us to better understand the sequence of seismic events (mainshock/aftershocks and swarms) and gave us information on the organization of active structures in the Ubaye region. This improved understanding of the complex processes at play might then help improving the risk analysis in this area.La région de l'Ubaye, située dans les Alpes à équidistance de Grenoble et Nice, est l'une des zones les plus sismiques de France. L'un des plus forts séismes enregistrés en France métropolitaine s'y est produit le 5 Avril 1959 (MLLDG5,3). Cette région est caractérisée par une activité sismique particulière composée d'un entremêlement de séismes principaux/répliques et d'essaims sismiques impliquant l'interaction de plusieurs processus moteurs (transfert de contraintes, pression de fluides, etc). Certains essaims sont caractérisés par des séismes de magnitude supérieure à 4 comme ce fût le cas pour la crise de 2012-2015, frappée par deux séismes de magnitude MLLDG4,8 (26/02/2012) et MLLDG5,2 (07/04/2014). Cette thèse a pour objectif de mieux comprendre les processus qui sont à l'origine de la sismicité et de faire le lien avec les structures connues de la région. L'étude de la sismicité historique et instrumentale a permis d'illuminer certaines zones plus actives que d'autres (Le Lauzet, Larche, Barcelonnette, St-Paul-sur-Ubaye, Guillestre) depuis le XVIIIe siècle. Malheureusement, les incertitudes de localisations et notre méconnaissance des structures profondes rendent très difficiles une association entre les failles visibles sur le terrain et la sismicité. Nous nous sommes concentrés par la suite sur les deux mois suivant le séisme du 7 Avril 2014. Les répliques montrent une organisation spatiale complexe, dans un volume autour de la faille principale. L'organisation de la sismicité pour cette crise a été quantifiée par une analyse de la géométrie des structures en jeux et par un calcul de 100 mécanismes au foyer. Durant les différentes périodes de crises, la présence de fluides a été mise en évidence et est l'un des principaux moteurs proposé pour expliquer le comportement de la sismicité. J'ai donc calculer les surpressions de fluides nécessaires pour activer la sismicité à partir de l'inversion des mécanismes au foyer et de l'état de contraintes. Trois résultats majeurs ressortent : 1) la majorité des événements (65%) requièrent entre 15 et 40 MPa de surpressions de fluides ; 2) les plus forts séismes ont également besoin de surpression de fluides ; 3) l'évolution temporelle des surpressions est un indicateur du type de séquence sismique. A partir de ces résultats, un modèle conceptuel est proposé, basé sur le principe que l'activation d'une faille va permettre la libération de pression de fluides (« fault-valve behaviour », Sibson, 1990). Après cette étude détaillée sur les répliques du séisme de 2014, je me suis concentrée sur l'ensemble de la crise 2012-2015, en étudiant la période 2010-2019 pour faire le lien entre les structures préexistantes de la région et la chronologie de la crise. Une nouvelle relocalisation de la sismicité est alors réalisée sur cette période à partir du catalogue du LDG. L'ensemble de la région de l'Ubaye semble être touché par des essaims et plus particulièrement la Vallée de l'Ubaye. De plus, l'alignement de la sismicité permet d'émettre l'hypothèse de deux failles venant s'intersecter au niveau de la zone de l'essaim de 2012-2015. L'étude statistique de la distribution de magnitude (exposant b de la loi de Gutenberg-Richter) a permis d'identifier un comportement temporel générique pour les essaims, associé à un processus de pression de fluides. La variation de l'exposant b est plus complexe pour les chocs principaux/répliques, avec des variations non génériques avant et après le choc principal. L'association des résultats obtenus nous a permis de mieux comprendre le déroulement des séquences sismiques (choc principal/répliques et essaims) et nous a apporté des informations sur l'organisation des structures actives de la région de l'Ubaye. Cette meilleure compréhension des processus en jeux peut permettre, à terme, une meilleure prise en compte du risque sismique dans cette région
Radiation Risk Assessment Associated With Terrestrial Gamma Ray Flashes for Commercial Flights
No full textInternational audienceTerrestrial gamma ray flashes (TGFs) are bursts of high-energy photons produced in thunderstorms. Photons are produced by bremsstrahlung from high-energy electrons, gaining energy through the electric field in the thunderstorm. Both electrons and photons are ionizing radiation and could have an impact on the radiation exposure of commercial aircrews and passengers. Previous works from Dwyer et al. (2010) and Pallu et al. (2021) have quantified doses possibly delivered by TGFs. They showed that the photon doses are sufficiently low so as not to be taken into account in the calculation of the radiation doses received during flights. However, electrons could deliver high doses up to 1 Sv, though in a compact area around the TGF source. In this work, we estimate an upper bound of the probability for a commercial flight to find itself in the electron beam of a TGF. Using the first Fermi-Gamma ray Burst Monitor TGF catalog and both simulated routes between airports as a first step and real flight routes from Air France airline for 2.5 years as a second step, we show that the probability is lower than one aircraft hit every 2 years for the total air traffic. Knowing that we did not take into account altitudes and the fact that pilots usually avoid thunderstorms, it is likely that no aircraft would have been hit by the source of a TGF since the beginning of the commercial aviation
CHENILLE: Coupled Behavior Understanding of Faults: from the Laboratory to the Field
No full textInternational audienceThe understanding of coupled thermo-hydro-mechanical behaviour of fault zones or in naturally fractured reservoirs is essential both for fundamental and applied sciences and in particular for the safety assessment of radioactive waste disposal facilities. The overall objective of the CHENILLE project is to better understand the physical processes resulting from thermal and hydraulic loading in a small fault zone in a highly consolidated shale formation. Consequently, a thermally controlled in-situ fluid injection experiment is intended to be performed on a strike-slip fault zone outcropping at the Tournemire/France Underground Research Laboratory (URL). A heating system has been installed around the injection area to enable a precise and controlled incremental increase of the thermal load. Different monitoring systems are designed to measure the seismic and aseismic deformation induced either by thermal and/or by hydraulic loading. The seismic monitoring system is composed of Acoustic Emission (AE) and broadband seismic sensors enabling monitoring of seismic fracturing processes down to sub-decimetre scale as well as slow deformation processes. Furthermore, we are about to install an injection chamber allowing to perform a controlled gaz injection test. The injection borehole will also be partly equipped with fiber optics in order to measure temperature in a distributed manner in the borehole. Time-lapse active seismic surveys are scheduled for before and after the experiment to image the structural network but also to detect the appearance of new structures triggered from the hydro-thermal pressurization of the fault as well as eventual changes in the velocity field