Institute for Radiation Protection and Nuclear Safety (IRSN)
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Nouvelles normes IEC et EN dans le domaine de l'instrumentation pour la radioprotection
No full textNational audienceLe sous-comité (SC) 45B de l’IEC « Instrumentation pour la radioprotection » prépare les normes internationales IEC dans ce domaine alors que le comité miroir européen CENELEC/TC 45B transpose ces normes en normes européennes EN pouvant faire des modifications techniques. Cette communication présentera les points importants de quelques normes IEC issues du SC 45B et publiées récemment, ainsi que des nouveaux projets qui viennent de démarrer.La norme IEC 62387 Ed. 2 « Instrumentation pour la radioprotection - Systèmes dosimétriques avec détecteurs passifs intégrés pour la surveillance de l'individu, du lieu de travail et de l'environnement des rayonnements photoniques et bêta » a été publiée début 2020 et a subi d’importantes modifications techniques lors de sa transposition européenne parue en octobre 2022 :-modification du titre ;-ajout d'exigences de performance pour que les dosimètres mesurent H'(3) pour les rayonnements photoniques et bêta ; -adoption du fantôme cylindre en lieu et place du fantôme plaque pour la grandeur Hp(3) ; -correction et clarification de plusieurs paragraphes pour obtenir une meilleure applicabilité.Dans le domaine de l‘instrumentation pour la détection et l'identification du trafic illicite des matières radioactives, 3 révisions de normes ont été publiées en 2020 et en 2022 : -IEC 62484 Ed. 2 « Moniteurs spectroscopiques pour portiques d'accès utilisés pour la détection et l'identification du trafic illicite des matières radioactives » ;-IEC 62618 Ed. 2 « Dispositifs individuels spectroscopiques d’alarme aux rayonnements pour la détection du trafic illicite des matières radioactives » ;-IEC 62694 Ed. 2 « Détecteur de rayonnement de type sac-à-dos (BRD) pour la détection du trafic illicite des matières radioactives ».Lors de ces révisions, les 3 normes ont été harmonisées avec l’ensemble d’une dizaine de normes dans ce domaine. Un test de fonctionnalité a été créé pour tous les essais environnementaux, électromagnétiques et mécaniques avec référence à l’IEC 62706 pour les performances climatiques, électromagnétiques et mécaniques. Une exigence pour le coefficient de variation de chaque lecture moyenne nominale a été également introduite.La deuxième édition de l’IEC 62706 Ed. 2 « Exigences recommandées en matière de performances climatiques, électromagnétiques et mécaniques et méthodes d'essai » est parue fin 2019 avec les modifications techniques majeures suivantes par rapport à l'édition précédente :-modification du titre ;-ajout d'informations supplémentaires sur les méthodes d'essai choisies ;-exigences révisées en matière d'essais de radiofréquence, sur la base de mesures effectuées à divers emplacements ;-guide et recommandations de configuration concernant les équipements et instruments ajoutés. Concernant les nouveaux projets, il faut citer :-IEC 61577-6 « Instruments de mesure du radon et des descendants du radon - Partie 6: Systèmes de mesure du radon à intégration passive utilisant des détecteurs solides de traces nucléaires » (publication prévue en 2025) ;-IEC 60761-2 Ed. 3 « Équipements de surveillance en continu de la radioactivité dans les effluents gazeux - Partie 2 : Exigences particulières aux moniteurs d'aérosols radioactifs, y compris les aérosols transuraniens » (publication prévue en 2025) menée par l’IRSN ;-IEC 63391 « Exigences techniques générales pour les systèmes actifs à ondes millimétriques pour le contrôle de sécurité des personnes » (publication prévue en 2024)
Accounting for organ dose uncertainties on childhood cancer risk estimates in the French CT cohort
No full textInternational audienceBackground: Computed tomography (CT) has been used increasingly worldwide over the last decades. However, concerns have been raised about potential radiation-related cancer risks, particularly after exposure to CT in childhood, due to the greater radiation sensitivity of children and to their longer life expectancy allowing to develop radiation associated late health effects. Several CT cohort studies aim at understanding the relationship between CT organ dose and cancer incidence. However, several sources of uncertainty coming from CT acquisition parameters and patient’s morphology exist but have sparsely been accounted for in risk estimates. This may lead to biased risk estimates and misleading conclusions. In this work, the aim is to study the impact of CT organ dose uncertainties on the risk of central nervous system (CNS) tumors and leukemia in the French CT cohort. Methods: The French CT cohort includes almost 100,000 children who received at least one CTbetween 2000 and 2011 in one of the 21 participating university hospitals. Patients were followed until the first diagnosis of cancer, the death, the 18th birthday or the 31st December 2016. Examinations and radiological protocols were retrieved to estimate cumulative absorbed doses to the brain and the red bone marrow (RBM) with NCICT 1.2. Sensitivity analysis indices were computed to identify the most influential input parameters in the estimation of organ doses. A first submodel was proposed to describe the discrepancy between the CT values provided by the French radiological protocols for these input parameters and their “true” values. A second submodel was proposed to describe the discrepancy between the NCICT estimated organ doses and “true” dose values accounting for patients’ morphology. Cox and excess hazard ratio survival models were considered as two alternative doseresponse models. The submodels were combined into a unique framework and fitted simultaneously using a Bayesian learning algorithm to estimate cancer risks. PACS data (Picture archiving and communication system) were used to learn about dosimetric uncertainties.Results and discussion: When not accounting for dosimetric uncertainties, a Cox model-basedfrequentist estimation, with asymptotic 95% confidence intervals,showed statistically significant doseresponse relationships for CNS tumors and leukemia. Bayesian risk estimates were similar but with wider credible intervals which seems to call into question the use of any statistical estimation approach based on asymptotic assumptions, in this context of weak signal data. Moreover, we will show how dose uncertainties impact cancer risk estimates and compare the fitting abilities of several model
Constructing and using an experimental space for resolving crisis: A case study of a chemical leak following an industrial accident
No full textInternational audienceThis article argues that space plays an active role in shaping collective responses to crisis situations. While it is well known that the physical features of a place affect the way industrial accidents can be managed by response and rescue teams, this article will examine another important aspect of space: its role in helping to resolve crises. We present a case study involving a French complex where a chemical cloud, emitting an odor reminiscent of household natural gas, was accidentally released. Based on interviews with key participants, as well as a variety of documents, we will explain how the physical and material features of the accident site can be used to transform a situation of great uncertainty and chaos into a well‐designed and controlled experiment, thereby aiding in crisis resolution. This article contributes to crisis literature by shedding new light on the role of space in crisis resolution using the concepts of boundaries, movement, and distance, and by contrasting the case with the Fukushima Daiichi accident. By conceptualizing space not only as a reservoir of information and evidence, but also as a tangible foundation, it becomes feasible to utilize it as a valuable resource for managing and resolving future crises
Convergence of the fully discrete incremental projection scheme for incompressible flows
No full textInternational audienceThe present paper addresses the convergence of a first order in time incremental projection scheme for the time-dependent incompressible Navier-Stokes equations to a weak solution, without any assumption of existence or regularity assumptions on the exact solution. We prove the convergence of the approximate solutions obtained by the semi-discrete scheme and a fully discrete scheme using a staggered finite volume scheme on non uniform rectangular meshes. Some first a priori estimates on the approximate solutions yield the existence. Compactness arguments, relying on these estimates, together with some estimates on the translates of the discrete time derivatives, are then developed to obtain convergence (up to the extraction of a subsequence), when the time step tends to zero in the semi-discrete scheme and when the space and time steps tend to zero in the fully discrete scheme; the approximate solutions are thus shown to converge to a limit function which is then shown to be a weak solution to the continuous problem by passing to the limit in these schemes
Experimental study of a travelling fire along a cable tray assembly in a mechanically ventilated enclosure
No full textInternational audienceThis study investigates the behaviour of a fire propagating over a long length of electrical cables, in order to assess the maximum burning length and the associated heat release rate of the travelling fire. It is part of the research work conducted in the framework of the OECD/NEA PRISME 3 project for a better assessment of fire propagation over cable trays in nuclear installations. The fire scenario consists of a set of 3 horizontal cable trays 6 m long, positioned in the corridor of a mechanically ventilated large-scale compartment. The parameters of the study are the nature of the cables (thermoset or thermoplastic types) and the distance of the cable trays from the ceiling. The determination of the fire heat release rate (HRR), the total burning length, the velocity of the flame front, the heat release rate per unit area (HHRPUA) and the effective heat of combustion (EHC) of the cable fires are given. For the configuration studied (3 cable trays and a given load), fire HRRs of 160 kW and 520 kW corresponding to burning lengths of 2 m and 3 m and corresponding to velocities of 0.4 mm/s and 0.9 mm/s are obtained for thermoset cables. For thermoplastic type cables (made of polyvinyl chloride), a power of 730 kW corresponding to a burning length of 3.5 m and corresponding to a velocity of 1.9 mm/s is reported. The order of magnitude for HRRPUA and EHC were respectively ranged between 50 kW/m² and 150 kW/m² and 20 MJ/kg and 25 MJ/kg for the two cable types
Review of experimental database to support nuclear power plant safety analyses in SGTR and LOCA domains
No full textInternational audienceIn the framework of the EU R2CA project the available experimental databases were reviewed to support nuclear power plant safety analyses in SGTR and LOCA domains. The review focused on the phenomena related to fuel failure, fission products release from the fuel rods and activity transport up to the environment. Furthermore, it was shown that the phenomena were covered by different scale facilities and different experimental procedures for several reactor designs and materials. Among the tests several separate effect tests and integral tests are listed and some NPP measurements were also included. It was concluded that the reviewed database, which includes more than forty experimental programmes and measurement series can be considered as a reliable basis to support the development and validation of numerical models for SGTR and LOCA safety analyses
Investigating seismotectonic activity in northern France from LiDAR, palaeosismological trench and OSL/C-14 dating : new results along the Artois and Mélantois structures
No full textInternational audienceNorthern France presents mostly a low level of seismic hazard according to the French national seismic hazard map. Despite low instrumental seismicity rates, strong and unfrequent historical earthquakes occurred, with for instance the M~6, 1580 Strait of Dover earthquake, or the M~5, 1896 Lens-Arras earthquake, whose seismogenic sources are presumably the Sangatte and the Marqueffles Faults, respectively. Both belong to the NW-SE-directed Weald-Boulonnais-Artois structure. Moreover, the Haubourdin Fault (also named Lille-Hazebrouck Fault), at the hinge of the Mélantois anticline, and bordering the southern edge of the Lille Metropolis (1.2 millions inhabitants), is considered as potentially active during Quaternary times. All these above-mentioned faults are linked to deep Paleozoic structures in the basement that formed along the northern front of the Variscan orogeny, and that were regularly reactivated during the Mesozoic and Cenozoic. To investigate and document the possible neotectonic activity of the Artois structure and the Haubourdin Fault, and therefore improve seismic hazard assessment in northern France, we used a pluridisciplinary approach based on the analysis of 1) LiDAR dataset, 2) paleoseismological trenching, 3) OSL/14C dating, and 4) sub-surface geophysical survey.Along the Artois structure, we focused on the locality of Harnes within Lens city suburbs. A preventive archeological work unraveled a clear sub-surface deformation feature that we analyzed through several ~2m-deep trenches. Field investigations indicated that the fault presents a regular N130° strike, which is consistent with surface and subsurface regional structures, and a 25-30° southwestward dip. Reverse throw along the fault were measured to about 15-20 cm thanks to a clearly displaced coal-rich horizon, sampled for C-14 dating. Interpretation of the data is complex since the site is located in a region where glacio-tectonic processes, severe First World War bombing and subsidence due to underground mining are documented.Along the Haubourdin Fault, our analysis of high resolution LiDAR data highlighted two topographic scarps aligned along a N110°E trend, but that do not match with the fault trace extracted from the geological map. This new fault trace is confirmed by subsurface geophysical survey (electric resistivity tomography and mapping). Both scarps present contrasted uplifted blocks since the southern block is uplifted (by several meters) for the western branch, whereas the northern block is uplifted (by 1-2 m) for the eastern branch. All these new field mapping results call for a substantial revision of the fault trace in the region together with a consideration of its segmentation. Finally, two new OSL datings has been obtained from a sandy-clay layer unconformably sealing some Late Paleocene deformation in the southern Lille suburb (i.e., Villeneuve d’Ascq). It gives the first minimum age in the literature for the deformation of the Mélantois northern limb
Aerosol Mitigation Means for Fukushima Daiichi Fuel Debris Removal
No full textInternational audienceThe general context of the article is to evaluate strategies that can be used to mitigate aerosols dispersion during the fuel debris or corium retrieval of Fukushima damaged reactors. IRSN is involved in several projects led by ONET Technologies along with CEA to provide relevant information to analyze the risk of aerosol resuspension induced by fuel debris retrieval. The knowledge of the aerosol source term emitted during fuel debris retrieval operations is one of the key issues for the assessment of aerosol dispersion that can lead to the release of radionuclides into the environment. Such information are also necessary to define an efficient strategy to mitigate this risk. Various mitigation means could be implemented during the decommissioning of Fukushima Daiichi damaged reactors, depending on the operations such as cutting of fuel debris or metallic structures or investigation in Primary Containment Vessel (PCV) by robots. It is also important to consider accidental scenarios such as earthquake event, to define countermeasures limiting the consequence in terms of safety and radioprotection. We propose to study various mitigation means such as the spray scrubbing technology used to collect airborne particles and therefore limit their dispersion during the cutting operations. Resuspension of deposited particles may also occur during the decommissioning operations due to various type of stress, such as aeraulic, mechanical, vibrational and also during underwater operations. To address these particle resuspension issues, another mitigation means made by coating of resins is introduced
An analysis of criticality safety "near misses"
No full textInternational audienceAmong the criticality safety events reported to the nuclear safety authorities, that have occurred in nuclear facilities around the world, some have been of particular concern and are usually referred to as "near misses". They can be classified in different categories: some actually came close to critical conditions, or these conditions remained remote but were narrowly avoided thanks to an emergency human intervention, others occurred in otherwise favorable situations (margins resulting from other variable parameters) but could have come close to critical conditions assuming other authorized or possible parameters. Finally, other events would have remained far from critical conditions even potentially, but are nevertheless also considered as "near misses" for other reasons, for example serious breaches of the rules, a significant impact on the activities (shutdown), etc. In addition to these different categories of consequences, "near misses" can also be classified according to the types of original deficiencies that caused them: physical phenomena that were not previously known, lack of awareness of the importance of certain safety measures and consequently of rigor in their application, lack of basic criticality safety training, differences between the conditions described in the safety documents and those actually encountered, or simply a "detail" that escaped the vigilance of the operators or safety teams.This paper presents a "double classification" of 25 "near misses" according to both the original deficiencies and the types of consequences explained above, by briefly presenting the elements leading to these choices of categories
Screening levels of TCS-172 NaI(Tl) survey meters used for direct thyroid measurements in nuclear disasters
No full textInternational audienceIt is a challenging task to establish a feasible and robust method for the population monitoring of individuals’ thyroid exposure following an accidental intake of radioiodines in a nuclear emergency, because of the time restriction. The authors previously proposed a method for such monitoring to obtain as many reliable human data as possible and one of the components is simplified measurements by conventional NaI(Tl) survey meters that are intended to be used for the initial triage to identify significantly exposed individuals and get an overall picture of the exposure levels in a target population in a timely manner. This study determined screening levels (SLs) for a conventional NaI(Tl) survey meter (model TCS-172, Hitachi, Japan) using the conversion factor (131I kBq in the thyroid per μSv h−1) that were obtained from experiments and simulations with age-specific phantoms. The results demonstrated that the derived SLs for 100 mSv thyroid equivalent dose were as follows: 0.2 μSv h−1 (SL1) for the age group ≤ 5-y-olds, 0.5 μSv h−1 (SL2) for the 10- and 15-y-old age groups and 1.0 μSv h−1 (SL3) for adults. These SLs would be reasonably available within 1 week after the intake of 131I on the safe side