Institute for Radiation Protection and Nuclear Safety (IRSN)
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IVMR modelling with transient effects during molten pool formation and stabilization outcomes from models’ comparison performed in the IAEA CRP J46002
No full textInternational 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. IVMR is already implemented in several nuclear power plants of generation II and III (VVER440, AP1000, HPR1000…) and under consideration for implementation in existing VVER-1000 reactors and future Small Modular Reactor (SMR) for examples. 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, several analytical benchmarks were performed focusing on different reactor designs: a generic 1000 MWe PWR design, the Russian VVER-1000 design, the Chinese CAP1400 design and the Canadian CANDU design. This paper focuses on work done and achievements obtained within the generic 1000 MWe PWR design benchmark. This benchmark is a follow up and an extension of the one developed in the scope of the European H2020 IVMR project. Compared to the other benchmarks dedicated to a specific reactor design, this benchmark is called “generic” because its objective is not to simulate expected corium configuration for a given scenario and reactor but to allow detailed comparison of models between codes based on prescribed and simplified configurations. It intends to cover generic models to be implemented in capable codes (either integral SA code or dedicated code) which may be used for IVMR simulations. Several cases are defined with increasing complexity to allow step by step comparison of the code models. Such an approach is useful for code developers but also for code users in order to better understand results and code capabilities or limitations. Specific attention is paid to molten pool formation and transient effects until reaching steady state configuration. Eight different benchmarks have been developed 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. State of codes performance and remaining issues are discussed in this paper, focusing on configurations involving progressive molten material arrival in the lower plenum
Hydrodynamic modelling for simulating nearshore waves and sea levels: classification of extreme events from the English Channel to the Normandy coasts
No full text(IF 3.3;Q2)International audienceAssessing the vulnerability of coastal systems to storms often rely on an accurate modelling of extreme events and the identification of their impacts that depend on their physical characteristics. This requires the development of an exhaustive numerical downscaling of extreme hydrodynamics from deep to shallow areas to enhance our ability to predict the risks induced by these events, which is of fundamental importance for coastal managers. This work aims at investigating the nearshore dynamics of extreme events and their evolution from the shelf seas of the English Channel to the Normandy Coasts by developing a new numerical field of wave and sea level simulations during a period of 40 years. This dataset has been explored for the classification of extreme events considering their severity, direction, and duration. The overall results highlighted that more than 90% of the storms are coming from the Atlantic Ocean with a substantial change in their amplitude and their duration along the Channel: storms with Northern component are more severe while those coming from the South last longer with higher energy. A detailed monitoring of three different storm events exhibited that their impact depends on their travelling direction, being more significant for hydrodynamic events propagating following the orientation of the Channel, of about 70 degrees to the North, with lower diffraction. Extreme events coming from South Atlantic experience a stronger wave modulation when they arrive nearshore
Dose conversion in retrospective dosimetry: Results and implications from an inter-laboratory comparison featuring a realistic exposure scenario
No full textInternational audienceDose conversion coefficients attempt to harmonize the material-, location-, and exposure-dependent results from retrospective dosemeters. The issues and uncertainties arising from dose conversion are explored within the framework of an interlaboratory comparison exercise in which mobile phones were positioned around anthropomorphic phantoms and exposed to non-uniform photon fields, with the glass and resistors they contain employed as fortuitous dosemeters. The difficulties of adopting pre-calculated tables of generic conversion coefficients are evaluated first, and then compared against those arising through the use of bespoke data derived by Monte Carlo modelling, and also against not converting the doses measured by the phones. It is seen that the different subjective choices that users might make when selecting 'optimal' generic data can lead to a significant source of uncertainty (up to around 70 %), though may be improved (to around 30 %) by appropriate quality controls. Use of generic coefficients typically led to over-estimates of the organ doses: an average discrepancy of ca. a factor of 2 was found, but this is still better than the factor of around 3 observed when no conversion coefficients were applied. Use of bespoke conversion factors led to the best estimates of organ doses, although they still over-estimated by approximately 1.5 on average, and an uncertainty of around 20 % was associated with generating their values. Overall, applying bespoke conversion data improves but does not guarantee correct dose categorization of individuals, with the inconsistences in the measured results found generally to be the limiting factor in obtaining accurate dose assessments
Experimental contribution to the determination of the In-Zr system for severe nuclear accident assessment
No full textInternational audienceA revised In-Zr phase diagram is proposed on the basis of detailed metallographic observations, XRD, DTA and bi-TA, calorimetric techniques and literature data. The new version of the phase diagram will serve as a basis for a future CALPHAD reassessment of the system in the NUCLEA database which will also allow the internal consistency of the experimental results to be tested.The existence of the intermetallic compounds (In3Zr, In2Zr, InZr, InZr2 and InZr3) previously reported by Schubert et al. [1, 2, 3] has been confirmed. An additional phase of In3Zr2 composition was found by SEM examination of 20-40 at.%Zr alloys after DTA. Existence of this phase is also supported by DFT calculations [4] but we have not been able to confirm it by XRD.Using bi-DTA investigation, we showed that there is peritectic reaction (In) αIn3Zr + Liquid at low temperature (156.8 ± 0.3 °C). The peritectic decomposition of all the In-rich phases has been evidenced: In3Zr In2Zr + L at 591.6 ± 2.4 °C, In2Zr In3Zr2 + L at 1132.9 ± 1.8 °C and In3Zr2 InZr + L at 1279 ± 6°C. However, it was impossible to determine the phase transition temperature of αIn3Zr to βIn3Zr by DTA due to the quasi athermal character of the transition.No information is available on the melting and invariant temperature of the compounds in the central region of the system.On the Zr-rich side, the peritectoid reaction reported by Betterton and Noyce [5] was adopted. However, metallographic investigations on few alloys in this compositional range after DTA have surprisingly shown lamellar eutectoid-like microstructures. Future studies need to be done in order to draw a definite conclusion about the type of invariant reaction.The experimental standard enthalpy of formation of In3Zr and In2Zr compounds have been determined by dissolution calorimetry at 1173 K. For In2Zr, the enthalpy value obtained by dissolution calorimetry was further complemented by drop calorimetry at 1273 K. The values obtained for In2Zr are consistent with the NUCLEA database, -38.3 kJ.mol-1.at-1 while the value obtained for In3Zr is more exothermic than NUCLEA, -32.5 kJ.mol-1.at-1 [6]. The standard enthalpy of formation of In2Zr determined by both direct reaction and dissolution calorimetry are consistent. The results obtained for In2Zr are also in agreement with the experimental data [7, 8].[1]:Schubert, K., Meissner H.G., Raman A., Rossteutscher W., Einige Strukturdaten Metallischer Phasen (9). Die Naturwissenschaften. 51 (12): 287–287 (1964).[2]:Schubert K., Frank K., Gohle R., Maldonado A., Meissner H.G., Raman A., et al.,Einige Strukturdaten Metallischer Phasen (8). Die Naturwissenschaften. 50 (2): 41–41 (1963).[3]:Schubert K., Meissner H.G., Potzschke M., Rossteutscher W., Stolz E., Einige Strukturdaten Metallischer Phasen (7). Die Naturwissenschaften. 49 (3): 57–57 (1962).[4]:Colinet C. “Private communication (2019)”.[5]:Betterton J.O., Noyce W.K. The Equilibrium Diagram of Indium-Zirconium in the Region 0-26 At. Pct In. Trans. Metall. Soc. AIME. 212 (6): 340–342 (1958).[6]:Fischer E., Thermodynamic database NUCLEA (IRSN) (2014).[7]:Gajavalli J., Experimental Contribution to Thermodynamics of the Ag-Cd-In, In-Zr and In2O3-ZrO2 Systems. PhD Thesis, Aix Marseille University (2019).[8]:Meschel S.V., Kleppa O.J., Standard Enthalpies of Formation of Some Transition Metal Indium Compounds by High Temperature Direct Synthesis Calorimetry. J. Alloys Compd. 333:91–98 (2002)
Creating a comprehensive framework for design, construction and management of healthy buildings
No full textInternational audienceWhile healthy buildings are investigated in academic research, practice, and policy, they often fail to address the needs and gaps due to insufficient knowledge transfer between them. Moreover, there is no general definition of healthy buildings that could act as a reference for different stakeholders of the building sector. Therefore, this paper presents a novel framework for healthy buildings and a definition for compiling existing knowledge and addressing the needs and gaps. The holistic approach of the framework was developed through an extensive literature review and tested with 12 building case studies in the major European climate zones. The framework outlines five different dimensions (improving mental and physical health, designed for human needs, sustainably built and managed, resilient and adaptive, empowering people), including 24 indicators and sub-indicators. The validation of the framework revealed that it is possible to assess different building projects against different indicators under each dimension. However, challenges remain due to issues such as lack of time, cost of data collection, or lack of documentation. The developed framework provides a balanced approach that promotes both individual well-being and broader sustainability goals. It provides necessary guidance to inform practitioners and policy makers as well as other building sector stakeholders to integrate healthy buildings thinking into their project development, assessment, and decision making
Cancer therapy-related cardiac dysfunction (CTRCD) after radiation therapy for breast cancer: Results of the French BACCARAT study
No full textInternational audienceIntroductionRadiation therapy (RT) for breast cancer (BC) can result in a broad spectrum of cardiotoxicity including subtle cardiac dysfunction that can occur early after treatment. In 2022, the first European Society of Cardiology (ESC) guidelines in cardio-oncology defined asymptomatic cancer therapy-related cardiac dysfunction (CTRCD). This newly defined event has never been studied in BC patients treated with RT.ObjectiveTo evaluate early to mid-term asymptomatic CTRCD occurrence and to analyze the association with radiation-induced cardiac exposure.MethodThe prospective monocentric BACCARAT study included BC patients treated with RT without chemotherapy, aged 40–75 years. Conventional and 2D Speckle tracking echocardiography was performed before, 6 and 24 months after RT. The present analysis included all patients with left ventricle ejection fraction (LVEF) and global longitudinal strain (GLS) measurements available for the three-time points. Asymptomatic CTRCD, as defined in the latest ESC guidelines, combines information on LVEF and GLS decrease from baseline occurring 6 or 24 months after RT. Whole heart, left ventricle (LV), and coronary arteries dose-volume parameters were considered to evaluate the impact of cardiac exposure on CTRCD.ResultsThe study included 72 BC (of 59 left-sided BC) patients with a mean age of 58 ± 8.2 years. A total of 32 (44%) patients developed any grade CTRCD during follow-up: 22 (31%) developed early dysfunction, and 14 (19%) developed midterm dysfunction with or without previous early dysfunction only in left BC patients. The cardiac doses were generally higher among patients with CTRCD rather than non-CTRCD. Significant dose-response relationships were observed between the risk of CTRCD and cardiac exposure, in particular LV exposure (OR for V2 LV dose = 1.03 (1.00–1.06) P = 0.01 and circumflex CX artery's mean dose OR = 2.44 (1.26–4.74) P = 0.008, D2 OR = 1.79 (1.13–2.85) P = 0.01 and V2 OR = 1.02 (1.01–1.04) P = 0.01. The results for the CX artery exposure were robust and significant after adjustment for classic cardiac risk factors (CVRF) and analyses according to the CTRCD grade; however, it did not remain significant for LV.ConclusionOur study suggests an association between specific cardiac structures and CTRCD 2 years after BC RT. considering CVRF. However, given the limited number of patients, further research is needed to understand the early mechanisms of radiation-induced CTRCD
Comparaison inter-laboratoires dédiée aux mesures de distributions granulométriques d'aérosols au moyen de compteurs optiques
No full textInternational audienceDans le cadre de la mise au point et de la validation de méthodes pour la mesure des aérosols, un exercice d’intercomparaison portant sur la mesure de la distribution granulométrique des aérosols solides impliquant des granulomètres optiques a été organisé à l’échelle nationale. Cet essai inter-laboratoires s’est déroulé sur une durée de 18 mois et a porté sur trois échantillons. Seize partenaires ont été impliqués avec 35 appareils de mesure. Les mesures ont été normalisées par rapport à une mesure réalisée simultanément avec un spectromètre commun de contrôle lors des expérimentations menées chez chaque partenaire
Generational Variance Reduction in Monte Carlo Criticality Simulations as a Way of Mitigating Unwanted Correlations
No full textInternational audienceMonte Carlo criticality simulations are widely used in nuclear safety demonstrations, as they offer an arbitrarily precise estimation of global and local tallies while making very few assumptions. However, since the inception of such numerical approaches, it is well known that bias might affect both the estimation of errors on these tallies and the tallies themselves. In particular, stochastic modeling approaches developed in the past decade have shed light on the prominent role played by spatial correlations through a phenomenon called neutron clustering. This effect is particularly of great significance when simulating loosely coupled systems (i.e., with a high dominance ratio). In order to tackle this problem, this paper proposes to recast the power iteration technique of Monte Carlo criticality codes into a variance reduction technique called Adaptative Multilevel Splitting. The central idea is that iterating over neutron generations can be seen as pushing a subpopulation of neutrons toward a generational detector (instead of a spatial detector as variance reduction techniques usually do). While both approaches allow for neutron population control, the former blindly removes or splits neutrons. In contrast, the latter optimizes the spatial, generational, and spectral attributes of neutrons when they are removed or split through an adjoint flux estimation, hence tempering both generational and spatial correlations. This is illustrated in the present paper with a simple case of a bare slab reactor in the one-speed theory on which the Adaptive Multilevel Splitting was applied and compared to variations of the Monte Carlo power iteration method used in neutron transport. Besides looking at the resulting efficiency of the methods, this work also aims to highlight the main mechanisms of the Adaptive Multilevel Splitting in criticality calculations
20 years of ams 14 c dating using the artemis facility at the lmc14 national laboratory: review of service and research activities
No full textConf paper : https://radiocarbon24.ethz.ch/International audienceIn 2001, five French public organizations (CNRS, CEA, IRD, IRSN, and the Ministère de la Culture) signed an agreement to purchase a new accelerator mass spectrometer to provide radiocarbon dating services at the national level. The Laboratoire de Mesure du Carbone 14 (LMC14) was set up in Saclay (France) around ARTEMIS, an AMS system based on a 3MV Pelletron from NEC and installed in early 2003. In 2015, the LMC14 joined the Laboratoire des Sciences du Climat et de l’Environnement, making it possible to develop research projects in addition to the service activity and since 2021, the LMC14 has been a member of the IAEA Collaborating Centre “Atoms for Heritage” at the Université Paris-Saclay. Since 2003, 70,000 samples have been measured. Two-thirds of the samples have been prepared on site and one-third in two associated laboratories in Paris and Lyon. Over the past years, the LMC14 has participated in several international inter-comparisons and has continuously improved its capabilities by developing new protocols for preparation and measurement. In this paper, the radiocarbon dating services of the last 20 years for research institutions, museums and environmental monitoring are reviewed and recent results from environmental and archaeological research programs are highlighted
Relationships between residential radon exposure during childhood and late health effects at adult age, in the Constances cohort
No full textInternational audienceIntroductionRadon exposure is an established risk factor for lung cancer. Over the recent decades, a growing number of epidemiological studies have investigated other possible health effects of radon exposure, but results are inconsistent. No study has focused on radon exposure during childhood and health outcomes at adult age. The objectives of this project are: 1/ to carry out a reconstruction of residential radon exposure from birth until 2019 in a large cohort; 2/ to estimate the risks of cancers and other chronic diseases at adult age potentially associated with radon exposure and doses to specific organs, especially during childhood.MethodsIndividuals were selected from the French CONSTANCES population-based adults cohort recruited between 2012 - 2017. We included in our study participants with a completed residential history since birth, and who gave their consent to the use of data concerning them from the French national health system (SNDS). Radon exposure was reconstructed by linking residential histories with a map of indoor radon concentrations by municipalities. Incident case of chronic diseases were identified over the period 2010-2021. Cancer and non-cancer risks will be estimated using survival models.Results Initially 58,697 participants provided a residential history since birth, and 57,571 (46% males) of them were identified in the SNDS. Mean age at recruitment was 48.8 years. The median annual radon exposure during childhood (0 -15 years) was 59 Bq/m3. At this stage, incident cases for the following diseases have been identified: 104 lung, 406 colorectal, 1251 breast and 735 prostate cancers, 612 strokes, 291 heart failures and 1703 coronary heart diseases.DiscussionStatistical analyses adjusting for potential confounders will be undertaken to investigate the relationships between these diseases and radon exposure as well as related organ doses, especially during childhood but also considering the influence of doses at later ages